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
  • 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
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/06—Copolymers with styrene
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B14/02—Granular materials, e.g. microballoons
  • C04B14/04—Silica-rich materials; Silicates
  • C04B14/06—Quartz; Sand
  • C04B14/066—Precipitated or pyrogenic silica
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • 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
  • C09C1/3045—Treatment with inorganic compounds
• • 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
  • C09C1/3063—Treatment with low-molecular organic compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2509/00—Use of inorganic materials not provided for in groups B29K2503/00 - B29K2507/00, as filler
  • B29K2509/02—Ceramics
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/50—Solid solutions
  • C01P2002/52—Solid solutions containing elements as dopants
  • C01P2002/54—Solid solutions containing elements as dopants one element only
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/54—Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
• • 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
  • C01P2006/14—Pore volume
• • 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
  • C01P2006/90—Other properties not specified above
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/006—Additives being defined by their surface area
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group

Definitions

• the present invention relates to a new process for the preparation of precipitated silica, new precipitated silicas and their applications, such as the strengthening of polymers.
• the object of the present invention is to provide, in particular, an alternative filler for polymer compositions which advantageously provides them with a reduction in their viscosity and an improvement in their dynamic properties while retaining their mechanical properties. It thus advantageously allows an improvement of the hysteresis / reinforcement compromise.
• the present invention firstly proposes a new process for the preparation of precipitated silica using, during or after the disintegration operation, at least one polycarboxylic acid.
• the preparation of precipitated silica 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), and then separation filtration, obtaining a filter cake, precipitated silica obtained, then disintegration of said filter cake and finally drying (generally by atomization).
• a silicate such as an alkali metal silicate (sodium silicate for example)
• an acidifying agent sulfuric acid for example
• separation filtration obtaining a filter cake, precipitated silica obtained, then disintegration of said filter cake and finally drying (generally by atomization).
• the mode of precipitation of the silica may be arbitrary: in particular, addition of acidifying agent to a silicate base stock, total or partial simultaneous addition of acidifying agent and silicate on a base of water or silicate.
• One of the objects of the invention is a new process for the preparation of a precipitated silica of the type comprising the precipitation reaction between a silicate and an acidifying agent, whereby a suspension of precipitated silica is obtained, followed by separation. and drying this suspension, characterized in that it comprises the following successive steps:
• silicate and acidifying agent are added simultaneously to the reaction medium, so that the pH of the reaction medium is maintained between 7 and 10,
• the filtration cake obtained at the end of the filtration is subjected to a disintegration operation comprising the addition of at least one (generally one) composed of aluminum,
• said method being characterized in that at least one polycarboxylic acid (for example a mixture of at least one polycarboxylic acid) is added to the filter cake, either during the disintegration process or after the disintegration operation and before the drying step; of polycarboxylic acids).
• at least one polycarboxylic acid for example a mixture of at least one polycarboxylic acid
• the filter cake is subjected to a disintegration operation during which are introduced at least one compound of aluminum and at least one polycarboxylic acid, or after which is introduced at least one polycarboxylic acid.
• the mixture then obtained suspension of precipitated silica
• is then dried generally by atomization.
• the disintegration operation is a fluidification or liquefaction operation, in which the filter cake is made liquid, the precipitated silica being in suspension.
• this disintegration operation is carried out by subjecting the filter cake to a chemical action by addition of at least one aluminum compound, for example sodium aluminate, and at least one polycarboxylic acid, preferably coupled to a mechanical action (for example by passing through a continuous stirred tank or in a colloid mill) which usually induces a grain size reduction of the suspended silica.
• the suspension (in particular aqueous) obtained after disintegration has a relatively low viscosity.
• at least one aluminum compound and at least one polycarboxylic acid are simultaneously added (co-addition) to the filter cake.
• At least one aluminum compound is added to the filter cake prior to the addition of at least one polycarboxylic acid.
• this disintegration operation is carried out by subjecting the filter cake to a chemical action by addition of at least one compound of aluminum, for example sodium aluminate, preferably coupled to a mechanical action. (for example by passing through a continuous stirred tank or in a colloid mill) which usually induces a grain size reduction of the suspended silica.
• a chemical action by addition of at least one compound of aluminum, for example sodium aluminate, preferably coupled to a mechanical action. (for example by passing through a continuous stirred tank or in a colloid mill) which usually induces a grain size reduction of the suspended silica.
• At least one polycarboxylic acid is added after the disintegration operation, that is to say the silica cake disintegrated.
• the filter cake to be subjected to the disintegration operation may be composed of a mixture of several filter cakes, each of said cakes being obtained by filtration of a part of the silica suspension obtained at the end of the step ( v) (this suspension being, prior to filtration, divided into several parts).
• polycarboxylic acid means polycarboxylic acids comprising at least two carboxylic acid functional groups.
• carboxylic acid functional group is taken here in its usual sense and refers to the -COOH functional group.
• the polycarboxylic acid employed according to the invention may have two, three, four or more carboxylic acid functional groups.
• the polycarboxylic acid is preferably chosen from dicarboxylic acids and tricarboxylic acids.
• the polycarboxylic acid employed can be a linear or branched polycarboxylic acid, saturated or unsaturated, aliphatic having from 2 to 20 carbon atoms or aromatic.
• the polycarboxylic acid may optionally include hydroxyl groups and / or halogen atoms.
• the aliphatic polycarboxylic acid may optionally comprise heteroatoms on the main chain, for example N, S.
• the polycarboxylic acid used according to the invention is chosen from the group consisting of linear or branched, saturated or unsaturated aliphatic polycarboxylic acids. having from 2 to 16 carbon atoms and aromatic polycarboxylic acids.
• linear polycarboxylic acids saturated or unsaturated, having from 2 to 14 carbon atoms, preferably from 2 to 12 carbon atoms.
• the polycarboxylic acid employed may have 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms.
• the polycarboxylic acid employed may have 4, 5, 6, 7, 8, 9 or 10 carbon atoms, preferably 4, 5, 6, 7 or 8 carbon atoms.
• the polycarboxylic acid employed may have 4, 5 or 6 carbon atoms.
• linear aliphatic polycarboxylic acids used in the invention include the acids selected from the group consisting of oxalic acid, malonic acid, tricarballylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid.
• branched polycarboxylic acids that may be mentioned are methylsuccinic acid, ethylsuccinic acid, oxalosuccinic acid, methyladipic acid, methylglutaric acid and dimethylglutaric acid.
• methylglutaric acid is meant both 2-methylglutaric acid and 3-methylglutaric acid and the mixture of these two isomers in all proportions.
• 2-methylglutaric acid is used to indicate both the (S) and (R) forms of the compound and the racemic mixture.
• Unsaturated polycarboxylic acids include maleic acid, fumaric acid, itaconic acid, muconic acid, aconitic acid, traumatic acid and glutaconic acid.
• polycarboxylic acids comprising hydroxyl groups
• phthalic acids namely phthalic acid, orthophthalic acid and isophthalic acid, trimesic acid and trimellitic acid.
• the polycarboxylic acid employed in the process according to the invention is selected from the group consisting of oxalic acid, malonic acid, tricarballylic acid, succinic acid, glutaric acid, acid and the like. adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutaric acid, dimethylglutaric acid, malic, citric acid, isocitric acid, tartaric acid.
• the dicarboxylic and tricarboxylic acids are chosen from adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutaric acid, oxalic acid and citric acid.
• the polycarboxylic acid may also be selected from the group consisting of oxalic acid, malonic acid, tricarballylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutaric acid, dimethylglutaric acid, malic acid, citric acid, isocitric acid, tartaric acid.
• the polycarboxylic acid may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutaric acid, dimethylglutaric acid, malic acid, citric acid, isocitric acid, tartaric acid.
• the polycarboxylic acid may be selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, acid, and the like. sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutaric acid, dimethylglutaric acid, malic acid, citric acid, tartaric acid.
• a single polycarboxylic acid is added to the filter cake.
• the polycarboxylic acid is then succinic acid.
• the polycarboxylic acid is succinic acid
• it is added to the filter cake after the disintegration operation.
• a mixture of polycarboxylic acids is added to the filter cake, said mixture comprising at least two polycarboxylic acids as defined above.
• the mixture may comprise two, three, four or more than four polycarboxylic acids.
• the polycarboxylic acids of the mixture are then chosen from adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutaric acid, oxalic acid and citric acid.
• the polycarboxylic acid mixture is preferably a mixture of dicarboxylic and / or tricarboxylic acids, especially a mixture of at least two, preferably at least three dicarboxylic and / or tricarboxylic acids, in particular a mixture of three dicarboxylic and / or tricarboxylic acids.
• the mixture of polycarboxylic acids is a mixture of dicarboxylic acids, especially a mixture of at least three dicarboxylic acids, in particular a mixture of three dicarboxylic acids.
• the mixture consists of three dicarboxylic acids, although impurities may be present in an amount not generally greater than 2.00% by weight of the total mixture.
• the polycarboxylic acid mixture used in the invention comprises the following acids: adipic acid, glutaric acid and succinic acid.
• the mixture of polycarboxylic acids comprises 15.00 to 35.00% by weight of adipic acid, 40.00 to 60.00% by weight of glutaric acid and 15.00 to 25.00% by weight. of succinic acid.
• the mixture of polycarboxylic acids according to this first preferred variant of the invention may be derived from a process for the manufacture of adipic acid.
• the mixture of polycarboxylic acids used in the invention comprises the following acids: methylglutaric acid, ethylsuccinic acid and adipic acid.
• the three acids can be present in the mixture in all proportions.
• the mixture of polycarboxylic acids comprises 60.00 to 96.00% by weight of methylglutaric acid, 3.90 to 20.00% by weight of ethylsuccinic acid and 0.05 to 20.00% by weight. of adipic acid.
• the mixture of polycarboxylic acids according to this second preferred variant of the invention may be derived from a process for the manufacture of adipic acid.
• the mixture of polycarboxylic acids according to this second preferred variant of the invention can be obtained by acid hydrolysis, preferably by basic hydrolysis, of a mixture of methylglutaronitrile, ethylsuccinonitrile and adiponitrile derived from the process of manufacture of adiponitrile by hydrocyanation of butadiene, adiponitrile being an important intermediate for the synthesis of hexamethylenediamine.
• a part or all of the polycarboxylic acid (s), in particular dicarboxylic and / or tricarboxylic acids, employed according to the invention may be in the form of a carboxylic acid derivative, namely under the form of anhydride, ester, salt (carboxylate) alkali metal (eg sodium or potassium), salt (carboxylate) alkaline earth metal (eg calcium) or salt (carboxylate) ammonium.
• carboxylate will be used hereinafter to denote the derivatives of carboxylic acid functional groups as defined above.
• the mixture of polycarboxylic acids may be a mixture comprising:
• methylglutaric acid in particular from 60.00 to 96.00% by weight, for example from 90.00 to 95.50% by weight
• ethylsuccinic anhydride in particular from 3.90 to 20.00% by weight, for example from 3.90 to 9.70% by weight
• adipic acid in particular from 0.05 to 20.00% by weight, for example from 0.10 to 0.30% by weight.
• the polycarboxylic acid mixture may also be a mixture comprising:
• methylglutaric acid in particular from 10.00 to 50.00% by weight, for example from 25.00 to 40.00% by weight
• methylglutaric anhydride in particular from 40.00 to 80.00% by weight, for example from 55.00 to 70.00% by weight
• ethylsuccinic anhydride in particular from 3.90 to 20.00% by weight, for example from 3.90 to 9.70%)
• adipic acid in particular from 0.05 to 20.00% by weight, for example from 0.10 to 0.30% by weight.
• the mixtures used according to the invention may optionally contain impurities.
• the polycarboxylic acids used in the invention may optionally be preneutralized (in particular by pretreating them with a base, for example of the sodium or potassium hydroxide type) before being added to the filter cake. This makes it possible in particular to modify the pH of the silica obtained.
• the polycarboxylic acids may be employed as an aqueous solution.
• the aluminum compound is selected from alkali metal aluminates.
• the aluminum compound is sodium aluminate.
• the amount of aluminum compound (in particular sodium aluminate) used is generally such that the ratio of the aluminum compound / amount of silica expressed in S102 contained in the filter cake is between 0.20 and 0.50% by weight, preferably between 0.25 and 0.45% by weight.
• the amount of polycarboxylic acid (s) used is generally such that the ratio of polycarboxylic acid (s) to the amount of silica expressed in SiO 2 contained in the filter cake (at the time of addition of at least one acid polycarboxylic acid) is between 0.50 and 2.00% by weight, preferably between 0.60 and 2.00% by weight, in particular between 0.55 and 1.75% by weight, in particular between 0.60 and 1, 50% by weight, for example between 0.65 and 1, 25% by weight.
• the filter cake may optionally be washed.
• the implementation during or after the disintegration operation, of at least one polycarboxylic acid and the succession of particular steps, and in particular the presence of a first simultaneous addition of acidifying agent and silicate in acid medium at pH between 2.0 and 5.0 and a second simultaneous addition of acidifying agent and silicate in a basic medium at a pH of between 7.0 and 10.0, gives the products obtained their particular characteristics and properties. .
• a strong mineral acid such as sulfuric acid, nitric acid or hydrochloric acid or an organic acid such as acetic acid, formic acid or carbonic acid is generally used as the acidifying agent.
• the acidifying agent may be diluted or concentrated; its normality can be between 0.4 and 36 N, for example between 0.6 and 1.5 N.
• the acidifying agent is sulfuric acid
• its concentration may be between 40 and 180 g / l, for example between 60 and 130 g / l.
• silicates such as metasilicates, disilicates and, advantageously, an alkali metal silicate, in particular sodium or potassium silicate, may be used as silicate.
• the silicate may have a concentration (expressed as SiO 2 ) of between 40 and 330 g / l, for example between 60 and 300 g / l, in particular between 60 and 260 g / l.
• the acidifying agent used is sulfuric acid and, as silicate, sodium silicate.
• sodium silicate In the case where sodium silicate is used, it generally has an SiO 2 / Na 2 O weight ratio of between 2.0 and 4.0, in particular between 2.4 and 3.9, for example between 3, 1 and 3.8.
• step (i) an aqueous base having a pH of between 2.0 and 5.0 is formed.
• the stock formed has a pH between 2.5 and 5.0, especially between 3.0 and 4.5; this pH is for example between 3.5 and 4.5.
• This initial starter can be obtained by adding an acidifying agent to water so as to obtain a pH value of the base of the tank between 2.0 and 5.0. preferably between 2.5 and 5.0, especially between 3.0 and 4.5 and for example between 3.5 and 4.5.
• It can also be prepared by adding acidifying agent to a stock base containing silica particles previously formed at a pH below 7.0, so as to obtain a pH value between 2.0 and 5.0, of preferably between 2.5 and 5.0, especially between 3.0 and 4.5 and for example between 3.5 and 4.5.
• the stock stem formed in step (i) may comprise an electrolyte.
• the stock formed in step (i) contains an electrolyte.
• electrolyte is here understood in its normal acceptation, that is to say that it signifies any ionic or molecular substance which, when in solution, decomposes or dissociates to form ions or charged particles.
• a salt of the group of alkali and alkaline earth metal salts in particular the salt of the starting silicate metal and of the acidifying agent, for example sodium chloride in the case of the reaction of a sodium silicate with hydrochloric acid or, preferably, sodium sulfate in the case of the reaction of a sodium silicate with sulfuric acid.
• sodium sulfate when sodium sulfate is used as the electrolyte in step (i), its concentration in the initial stock is in particular between 8 and 40 g / l, in particular between 10 and 20 g. / L, for example between 13 and 18 g / L.
• the second step (step (ii)) consists of a simultaneous addition of acidifying agent and silicate, in such a way (particularly at such flow rates) that the pH of the reaction medium is maintained between 2.0 and 5.0, preferably between 2.5 and
• a step (iii) the addition of the acidifying agent is stopped while continuing the addition of silicate in the reaction medium so as to obtain a pH value of the reaction medium of between 7.0 and 10, 0, preferably between 7.5 and 9.5.
• this maturing may for example last from 2 to 45 minutes, in particular from 5 to 25 minutes and preferably comprises neither addition of acidifying agent nor addition of silicate.
• step (iii) and the optional ripening a new simultaneous addition of acidifying agent and silicate, in such a way (particularly at such rates) that the pH of the reaction medium is maintained between 7, 0 and 10.0, preferably between 7.5 and 9.5.
• step (iv) is advantageously carried out in such a way that the pH value of the reaction medium is constantly equal (within ⁇ 0.2) to that reached at the end of the previous step.
• step (iii) and step (iv) for example, between, on the one hand, the eventual ripening according to step (iii), and, on the other hand, on the other hand, step (iv), adding to the reaction medium of the acidifying agent, the pH of the reaction medium at the end of this addition of acid is however between 7.0 and 9.5, preferably between 7.5 and 9.5.
• a step (v) the addition of the silicate is stopped while continuing the addition of acidifying agent in the reaction medium so as to obtain a pH value of the reaction medium of less than 6.0, preferably between 3.0 and 5.5, in particular between 3.0 and 5.0, for example between 3.0 and 4.5.
• this curing can for example last from 2 to 45 minutes, in particular from 5 to 20 minutes, and preferably does not include any addition of acid or addition of silicate.
• the reaction chamber in which the entire reaction of the silicate with the acidifying agent is carried out is usually provided with appropriate stirring equipment and heating equipment.
• the overall reaction of the silicate with the acidifying agent is generally carried out between 70 and 95 ° C, in particular between 75 and 95 ° C.
• the entire reaction of the silicate with the acidifying agent is carried out at a constant temperature, usually between 70 and 95 ° C, in particular between 75 and 95 ° C.
• the end of reaction temperature is higher than the reaction start temperature: thus, the temperature is maintained at the beginning of the reaction (for example during steps (i) to (iii) )) preferably between 70 and 85 ° C, then the temperature is increased, preferably to a value between 85 and 95 ° C, value at which it is maintained (for example during steps (iv) and (v)) until the end of the reaction.
• the separation used in the preparation process according to the invention usually comprises a filtration, followed by washing if necessary.
• the filtration is carried out by any suitable method, for example by means of a band filter, a vacuum filter or, preferably, a filter press.
• the filter cake is then subjected to a disintegration operation comprising the addition of an aluminum compound.
• a disintegration operation comprising the addition of an aluminum compound.
• at least one polycarboxylic acid is added during or after the disintegration operation.
• the disintegrated filter cake is then dried.
• This drying can be done by any means known per se.
• the drying is done by atomization.
• any suitable type of atomizer may be used, such as a turbine, nozzle, liquid pressure or two-fluid atomizer.
• a turbine when the filtration is carried out using a filter press, a nozzle atomizer is used, and when the filtration is carried out using a vacuum filter, a turbine atomizer is used. .
• the precipitated silica that can then be obtained is usually in the form of substantially spherical beads.
• it may optionally proceed to a grinding step on the recovered product; the precipitated silica that can then be obtained is generally in the form of a powder.
• the precipitated silica that may then be obtained may be in the form of a powder.
• the dried product in particular by a turbine atomizer or milled as indicated above may optionally be subjected to an agglomeration step, which consists, for example, of a direct compression, a wet-path granulation (that is, with the use of a binder such as water, silica suspension, etc.), extrusion or, preferably, dry compaction.
• an agglomeration step which consists, for example, of a direct compression, a wet-path granulation (that is, with the use of a binder such as water, silica suspension, etc.), extrusion or, preferably, dry compaction.
• deaerate operation also called pre-densification or degassing
• the precipitated silica that can then be obtained by this agglomeration step is generally in the form of granules.
• the invention also relates to precipitated silicas obtained or obtainable by the process according to the invention.
• these precipitated silicas have at their surface molecules of polycarboxylic acid (s) employed and / or carboxylate (s) corresponding to polycarboxylic acid (s). ) employee (s).
• the present invention further relates to a precipitated silica with particular characteristics, in particular usable as an alternative filler for the polymer compositions which advantageously provides a reduction in their viscosity and an improvement in their dynamic properties while retaining their mechanical properties.
• the BET surface area is determined according to the method of BRUNAUER - EMMET - TELLER described in "The Journal of the American Chemical Society", Vol. 60, page 309, February 1938 and corresponding to standard NF ISO 5794-1 appendix D (June 2010).
• the CTAB specific surface is the external surface, which can be determined according to standard NF ISO 5794-1 appendix G (June 2010).
• the corresponding polycarboxylic acid + carboxylate content (C), expressed as total carbon, can be measured using a sulfur-containing carbon analyzer such as Horiba EMIA 320 V2.
• the principle of the sulfur carbon analyzer is based on the combustion of a solid sample in a flow of oxygen in an induction furnace (set at about 170 mA) and in the presence of combustion accelerators (about 2 grams of tungsten (in particular Lecocel 763-266) and about 1 gram of iron). The analysis lasts about 1 minute.
• the carbon contained in the sample to be analyzed (mass of about 0.2 gram) combines with oxygen to form CO2, CO. These decomposition gases are then analyzed by an infrared detector.
• the moisture of the sample and the water produced during these oxidation reactions is removed by passing on a cartridge containing a desiccant: magnesium perchlorate so as not to interfere with the infrared measurement.
• the result is expressed as a percentage by mass of carbon element.
• the noted aluminum content (Al) can be determined by wavelength dispersive X-ray fluorescence, for example with a Panalytical 2400 spectrometer or, preferably, with a Panalytical MagixPro PW2540 spectrometer.
• the principle of the X-ray fluorescence measurement method is as follows:
• a grinding of the silica is necessary when it is in the form of substantially spherical beads (microbeads) or granules, until obtaining a homogeneous powder.
• the grinding can be carried out with an agate mortar (grinding approximately 15 grams of silica for a period of 2 minutes) or any type of mill containing no aluminum,
• the powder is analyzed as such in a 40 mm diameter vat with a 6 m polypropylene film, under a helium atmosphere, at an irradiation diameter of 37 mm, and the amount of silica analyzed is 9 cm 3 .
• Pre-calibration using another measurement method, such as ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectroscopy), may be used.
• the aluminum content can also be measured by any other suitable method, for example by ICP-AES after solution in water in the presence of hydrofluoric acid.
• polycarboxylic acid (s) in the acid form and / or in the carboxylate form may be established by Surface Infrared or ATR-Diamond (Attenuated Total Reflection).
• Infrared surface analysis (by transmission) is carried out on a Bruker Equinoxe 55 spectrometer on a pellet of pure product.
• the pellet is obtained after grinding the silica as it is in an agate mortar and pelletizing at 2 T / cm 2 for 10 seconds.
• the diameter of the pellet is 17 mm.
• the weight of the pellet is between 10 and 20 mg.
• the pellet thus obtained is placed in the chamber under high vacuum (10 "7 mbar) spectrometer for one hour at room temperature prior to analysis by transmission
• the acquisition takes place under high vacuum (acquisition conditions:. 400 cm -1 to 6000 cm -1 , number of scans 100, resolution 2 cm -1 ).
• the ATR-diamond analysis carried out on a Bruker Tensor 27 spectrometer, consists in depositing on the diamond a tip of silica spatula previously ground in an agate mortar and then exerting a pressure.
• the infrared spectrum is recorded on the spectrometer in 20 scans, from 650 cm -1 to 4000 cm -1 .
• the resolution is 4 cm "1 .
• centrifugal sedimentation XDC granulometric analysis method on the one hand, is used to measure the object size distribution widths of the silica, and on the other hand, the XDC mode, illustrating its size of objects, is described below:
• BRANSON 1500 watts typically used at 60% of maximum power.
• Sample measurement Introduce into the disc 15 ml of the sample to be analyzed, stir the balance and measure the signal.
• the device register record the values of the diameters increasing to 16%, 50% (or median, size for which one has 50% in mass of the aggregates of size smaller than this size) and 84% (% mass) as well as the value of the Mode (the derivative of the cumulative granulometric curve gives a frequency curve whose abscissa of the maximum (abscissa of the main population) is called the Mode).
• XDC after deagglomeration with ultrasound (in water), corresponds to the ratio (d84 - d16) / d50 in which dn is the size for which one% of particles (in mass) of size smaller than this size (the distribution width Ld is therefore calculated on the cumulative grain size curve, taken in its entirety).
• the d of the object size distribution less than 500 nm, measured by XDC granulometry, after ultrasound disagglomeration (in water) corresponds to the ratio (d84 - d16) / d50 in which dn is the size for which one% of particles (in mass), with respect to the particles of size smaller than 500 nm, of size smaller than this size (the width
• the distribution d is thus calculated on the cumulative granulometric curve, truncated above 500 nm).
• the porous volumes and pore diameters are measured by mercury porosimetry (Hg), using a MICROMERITICS Autopore 9520 porosimeter, and are calculated by the WASHBURN relationship with a theta contact angle equal to 140 ° and a voltage superficial gamma equal to 484 Dynes / cm (DIN 66133 standard).
• Hg mercury porosimetry
• MICROMERITICS Autopore 9520 porosimeter a pore diameter of the porous volumes and pore diameters are measured by mercury porosimetry (Hg), using a MICROMERITICS Autopore 9520 porosimeter, and are calculated by the WASHBURN relationship with a theta contact angle equal to 140 ° and a voltage superficial gamma equal to 484 Dynes / cm (DIN 66133 standard).
• the preparation of each sample is as follows: each sample is pre-dried for 2 hours in an oven at 200 ° C.
• V (d5 - dso) represents the pore volume constituted by the pores with diameters between d5 and d50
• V (d 5 - di oo) represents the pore volume constituted by the pores with diameters between d5 and d100
• dn being here the pore diameter for which n% of the total surface of all the pores is provided by the pores with a diameter greater than this diameter (the total surface area of the pores (So) can be determined from the mercury intrusion curve) .
• the porous distribution width Idp is obtained from the porous distribution curve, as shown in FIG.
• N is the average number of carboxylic functions per polycarboxylic acid (for example, if all the polycarboxylic acids are dicarboxylic acids (respectively tricarboxylic acids), N is equal to 2 (respectively 3)),
• CT is the carbon content of the polycarboxylic acids
• MA C is the molecular weight of the polycarboxylic acids.
• the dispersive component of the surface energy Y s d is determined by reverse gas chromatography. Silica grinding is generally necessary when it is in the form of granules, followed by sieving, for example, at 106 m-250 m.
• the technique used to calculate the dispersive component of the surface energy Y s d is Infinite Dilution Reverse Gas Chromatography (CGI-DI), at 10 ° C using a series of (normal) alkanes ranging from 6 to 10 carbon atoms, a technique based on gas chromatography, but where the role of the mobile phase and the stationary phase (filling) are reversed.
• the stationary phase in the column is replaced by the material (solid) to be analyzed, here precipitated silica.
• the mobile phase it consists of the carrier gas (helium) and "probe" molecules chosen according to their interaction capacity. The measurements are carried out successively with each probe molecule.
• each probe molecule is injected into the column, in a very small quantity (infinite dilution), mixed with methane. Methane is used to determine the tO, the dead time of the column. The subtraction of this dead time tO at the retention time of the injected probe leads to the net retention time (f w ) thereof.
• the latter corresponds to the volume of vector gas (brought back to 0 ° C) necessary to elute the probe molecule for 1 gram of stationary phase (solid examined).
• This standard size makes it possible to compare the results regardless of the carrier gas flow rate and the stationary phase mass used.
• the formula [1] uses: Ms, the solid mass in the column, the carrier gas flow rate and T the measurement temperature.
• This quantity AGa is the starting point for the determination of the dispersive component of the surface energy (Y s d ). This is obtained by plotting the straight line representing the adsorption free enthalpy variation (AGa) as a function of the carbon number n c of the n-alkane probes as indicated in the table below.
• the dispersive component of the surface energy Y s d is then connected to the adsorption free enthalpy AGa (CH2) of the methylene group (Dorris and Gray method, J. Colloid Interface Sci., 77 (180) the following relation : wherein N A is Avogadro's number (6,02.10 23 mol "1) has CHi the area occupied by one adsorbed methylene group (0.06 nm 2) and y CHi energy of a solid surface consisting solely of methylene group and determined on polyethylene (35.6 mJ / m 2 at 20 ° C).
• the coordination of aluminum is determined by solid NMR of aluminum.
• the technique used to measure the water uptake generally consists in placing, under given relative humidity conditions and for a predefined duration, the previously dried silica sample; the silica then hydrates, causing the mass of the sample to change from an initial value m (in the dried state) to a final value m + dm.
• water uptake refers to the ratio dm / m (ie the mass of water incorporated in the sample referred to the mass of the sample in the dry state) expressed as a percentage calculated for a silica sample subject to the following conditions in the measurement method:
• the dried silica in a closed container such as a desiccator containing a mixture of water / glycerin, so that the relative humidity of the closed medium is 70%;
• the cohesion of the agglomerates is assessed by a granulometric measurement (by laser diffraction), carried out on a suspension of silica previously deagglomerated by ultra-sonification; the ability to disagglomerate silica (rupture of objects from 0.1 to a few tens of microns) is thus measured.
• Ultrasonic deagglomeration is carried out using a VIBRACELL BIOBLOCK (600 W) sonicator, used at 80% of the maximum power, equipped with a 19 mm diameter probe.
• the particle size measurement is carried out by laser diffraction on a MALVERN particle size analyzer (Mastersizer 2000) using the Fraunhofer theory.
• Deagglomeration is then carried out under ultrasound for 7 minutes.
• the particle size measurement is then carried out by introducing into the granulometer tank all of the homogenized suspension.
• the median diameter 050 M (or Malvern median diameter), after deagglomeration with ultrasound, is such that 50% of the particles by volume have a size less than 050 M and 50% have a size greater than 050 M- the value of the median diameter 0 50 M obtained is even lower than the silica has a high ability to deagglomerate.
• Deagglomeration is then carried out under ultrasound for 7 minutes.
• the particle size measurement is then carried out by introducing into the granulometer tank all of the homogenized suspension.
• This deagglomeration factor is determined by the ratio (10 x darkness value of the blue laser / obscuration value of the red laser), this optical density corresponding to the actual value detected by the granulometer during the introduction of the silica.
• This ratio (Malvern F D M disaggregation factor) is indicative of the rate of particles smaller than 0.1 m which are not detected by the granulometer. This ratio is higher when the silica has a high deagglomeration ability.
• the pH is measured according to the following method derived from ISO 787/9
• the precipitated silica according to the invention is characterized in that it possesses:
• a BET specific surface area between 45 and 550 m 2 / g, in particular between 70 and 370 m 2 / g, in particular between 80 and 350 m 2 / g,
• CTAB specific surface area of between 40 and 525 m 2 / g, in particular between 70 and 350 m 2 / g, in particular between 80 and 310 m 2 / g,
• V (d 5 -dso) V (d 5 -dioo) is at least 0.65, in particular at least 0.66, in particular at least 0.68
• the silica according to this variant of the invention has for example:
• This silica may have a ratio V (d 5 d n.) A / (d5 - ioo d) of at least 0.73, in particular at least 0.74. This ratio may be at least 0.78, especially at least 0.80, or even at least 0.84.
• the precipitated silica according to the invention is characterized in that it possesses:
• a BET specific surface area between 45 and 550 m 2 / g, in particular between 70 and 370 m 2 / g, in particular between 80 and 350 m 2 / g,
• CTAB specific surface area of between 40 and 525 m 2 / g, in particular between 70 and 350 m 2 / g, in particular between 80 and 310 m 2 / g,
• Al aluminum content of at least 0.20% by weight, in particular at least 0.25% by weight
• a porous distribution width Idp greater than 0.65, in particular greater than 0.70, in particular greater than 0.80.
• This silica may have a porous distribution width Idp of greater than 1.05, for example 1, 25, or even 1, 40.
• the silica according to this variant of the invention preferably has a width Ld ((d84 - d16) / d50) of size distribution of size of objects measured by XDC granulometry after disintegration with ultrasound of at least 0 , 91, in particular of at least 0.94, for example of at least 1.0.
• the precipitated silicas according to the invention may in particular have a BET specific surface area of between 100 and 320 m 2 / g, in particular between 120 and 300 m 2 / g, for example between 130 and 280 m 2 / g.
• the precipitated silicas according to the invention may in particular have a CTAB specific surface area of between 100 and 300 m 2 / g, in particular between 120 and 280 m 2 / g, for example between 130 and 260 m 2 / g.
• the precipitated silicas according to the invention have a BET specific surface area / CTAB surface area ratio of between 0.9 and 1.2, that is to say that it has a low microporosity.
• the precipitated silicas according to the invention may in particular have a content (C) of polycarboxylic acid + corresponding carboxylate, expressed as total carbon, of at least 0.24% by weight, in particular of at least 0.30% by weight. for example at least 0.35% by weight, or even at least 0.45% by weight.
• They generally have a content of polycarboxylic acid + carboxylate (C) of at most 10 00% by weight, in particular at most 5.00% by weight.
• the precipitated silicas in accordance with the invention may in particular have an aluminum (Al) content of at least 0.30% by weight, in particular at least 0.33% by weight. They generally have an aluminum (Al) content of less than 1% by weight, in particular of at most 0.50% by weight, for example at most 0.45% by weight.
• the precipitated silica according to the invention has on its surface molecules of the above-mentioned polycarboxylic acid (s), in particular polycarboxylic acids of the abovementioned mixtures, and / or carboxylate (s). (s) corresponding to ⁇ (the) acid (s) polycarboxylic (s) above, in particular corresponding to the polycarboxylic acids of the aforementioned mixtures.
• adipic acid molecules in acid form and / or in carboxylate form
• adipic acid molecules in acid form and / or in carboxylate form.
• the precipitated silicas according to the invention have a ratio (R) of between 0.4 and 3.5, in particular between 0.4 and 2.5.
• This ratio (R) may also be between 0.5 and 3.5, especially between 0.5 and 2.5, in particular between 0.5 and 2, for example between 0.7 and 2, or even between 0. , 7 and 1, 8, or between 0.7 and 1.6.
• the silicas according to the invention have a dispersive component of the surface energy Y s d less than 52 mJ / m 2 , in particular less than 50 mJ / m 2 , in particular at most 45 mJ / m 2 for example less than 40 mJ / m 2 , or even less than 35 mJ / m 2
• the silicas according to the invention have a width d ((d84-d16) / d50) of an object size distribution of less than 500 nm, measured by XDC granulometry after ultrasound deagglomeration, from less 0.95.
• the pore volume provided by the larger pores usually represents most of the structure.
• They may have both an object size distribution width Ld of at least 1.04 and an object size distribution width d (less than 500 nm) of at least 0.95.
• the width Ld of the object size distribution of the silicas according to the invention may in certain cases be at least 1, 10, in particular at least 1, 20; it may be at least 1, 30, for example at least 1, 50 or even at least 1.60.
• the width D of the object size distribution (less than 500 nm) of the silicas according to the invention can be, for example, at least 1.0, in particular at least 1.10, in particular at least 1, 20.
• the precipitated silicas according to the invention may have a distribution of the coordination of specific aluminum, determined by solid NMR of aluminum.
• not more than 85% in number, in particular not more than 80% by number, in particular between 70 and 85% by number, for example between 70 and 80% by number, of the aluminum atoms of the silicas according to the invention can present a tetrahedral coordination, that is to say can be in a tetrahedral site.
• aluminum atoms of the silicas according to the invention may exhibit a pentahedral and octahedral coordination, that is to say they may be pentahedral or octahedral site.
• the precipitated silica according to the invention may have a water uptake of greater than 6%, in particular greater than 7%, especially greater than 7.5%, for example greater than 8%, or even greater than 8.5%.
• the precipitated silicas according to the invention have dispersibility (especially in elastomers) and high deagglomeration.
• the precipitated silicas according to the invention may have a median diameter ⁇ 50 M after deagglomeration with ultrasound of at most 10.0 m, preferably at most 9.0 m, in particular between 3.5 and 8, 5 m.
• the precipitated silicas according to the invention may have an ultrasound deagglomeration factor F D M greater than 5.5 ml, in particular greater than 7.5 ml, for example greater than 12.0 ml.
• the precipitated silicas according to the invention preferably have a pH of between 3.5 and 7.5, more preferably between 4 and 7, in particular between 4.5 and 6.5.
• the physical state in which the precipitated silicas according to the invention occurs may be arbitrary, that is to say that they may be in the form of substantially spherical beads (microbeads), powder or granules.
• They may thus be in the form of substantially spherical beads of average size of at least 80 ⁇ m, preferably at least 150 ⁇ m, in particular between 150 and 270 ⁇ m; this average size is determined according to standard NF X 1 1507 (December 1970) by dry sieving and determination of the diameter corresponding to a cumulative refusal of 50%.
• They may also be in the form of a powder of average size of at least 15 ⁇ m, in particular at least 20 ⁇ m, preferably at least 30 ⁇ m.
• They may be in the form of granules (generally of substantially parallelepiped shape) of size of at least 1 mm, for example between 1 and 10 mm, especially along the axis of their largest dimension.
• the silicas according to the invention are preferably obtained by the process described above.
• the silicas precipitated according to the present invention or (capable of being obtained) by the method according to the invention described above confer on the polymer compositions (elastomer (s)) in which they are introduced, a compromise properties very satisfactory, including a reduction in their viscosity and preferably an improvement in their dynamic properties while retaining their mechanical properties. They thus advantageously make it possible to improve the compromise implementation / reinforcement / hysteretic properties.
• they exhibit good dispersibility and disagglomeration in the polymer (s) compositions (elastomer (s)).
• the silicas precipitated according to the present invention or (capable of being obtained) by the process according to the invention described above can be used in many applications.
• They can be used, for example, as a catalyst support, as absorbent for active substances (in particular a liquid carrier, especially used in foodstuffs, such as vitamins (vitamin E), choline chloride), in polymer compositions.
• active substances in particular a liquid carrier, especially used in foodstuffs, such as vitamins (vitamin E), choline chloride
• S polymer compositions.
• S including elastomer (s), silicone (s), as viscosifying agent, texturizing or anti-caking agent, as an element for battery separators, as an additive for toothpaste, for concrete, for paper.
• the polymer compositions in which they may be used, especially as reinforcing filler, are generally based on one or more polymers or copolymers (especially bipolymers or terpolymers), in particular of one or more elastomers, preferably having at least a glass transition temperature of between -150 and +300 ° C, for example between -150 and + 20 ° C.
• Possible polymers that may be mentioned include diene polymers, in particular diene elastomers.
• polymers or copolymers in particular bipolymers or terpolymers
• aliphatic or aromatic monomers comprising at least one unsaturation (such as, in particular, ethylene, propylene, butadiene, isoprene or styrene).
• unsaturation such as, in particular, ethylene, propylene, butadiene, isoprene or styrene.
• silicone elastomers functionalized elastomers, for example by chemical groups arranged all along the macromolecular chain and / or at one or more of its ends (for example by functions capable of reacting with the surface of the silica) and halogenated polymers.
• Polyamides and fluorinated polymers such as polyvinylidene fluoride
• Thermoplastic polymers such as polyethylene can also be mentioned.
• the polymer may be a bulk polymer (copolymer), a polymer latex (copolymer) or a polymer solution (copolymer) in water or in any other suitable dispersing liquid.
• diene elastomers mention may be made, for example, of polybutadienes (BR), polyisoprenes (IR), butadiene copolymers, isoprene copolymers, or mixtures thereof, and in particular styrene-butadiene copolymers (SBR).
• BR polybutadienes
• IR polyisoprenes
• SBR styrene-butadiene copolymers
• ESBR emulsion
• SSBR solution
• isoprene-butadiene copolymers BIR
• isoprene-styrene copolymers SIR
• isoprene-butadiene-styrene copolymers SBIR
• terpolymers ethylene-propylene-diene EPDM
• NR natural rubber
• EMR epoxidized natural rubber
• the polymer compositions may be vulcanized with sulfur (vulcanizates are obtained) or crosslinked, in particular with peroxides or other crosslinking systems (for example diamines or phenolic resins).
• the polymer compositions (s) further comprise at least one coupling agent (silica / polymer) and / or at least one covering agent; they may also include, inter alia, an antioxidant.
• Coupling agents that may be used as non-limiting examples include polysulphide silanes, called “symmetrical” or “asymmetrical”silanes; there may be mentioned more particularly polysulphides (especially disulphides, trisulphides or tetrasulphides) bis (alkoxyl (Ci-C 4) alkyl (Ci-C 4) alkyl-silyl (Ci-C 4)) such as polysulphides bis (3- (trimethoxysilyl) propyl) or polysulfides of bis (3- (triethoxysilyl) propyl), such as triethoxysilylpropyl tetrasulfide. Mention may also be made of monoethoxydimethylsilylpropyl tetrasulfide. Mention may also be made of silanes with thiol function, masked or otherwise, with amino function.
• the coupling agent may be grafted onto the polymer beforehand. It can also be used in the free state (that is to say, not previously grafted) or grafted to the surface of the silica. The same is true of the possible collector.
• the coupling agent may optionally be combined with a suitable "coupling activator", that is to say a compound which, when mixed with this coupling agent, increases the effectiveness of the coupling agent.
• the proportion by weight of silica in the polymer composition (s) can vary within a fairly wide range. It usually represents 0.1 to 3.0 times by weight, in particular 0.1 to 2.0 times by weight, especially 0.2 to 1.5 times by weight, for example 0.2 to 1.2 times by weight. weight, or even 0.3 to 0.8 times by weight, of the amount of the polymer (s).
• the silica according to the invention may advantageously constitute all of the reinforcing inorganic filler, and even the whole of the reinforcing filler, of the polymer composition (s).
• silica according to the invention may be optionally associated with at least one other reinforcing filler, such as in particular a commercial highly dispersible silica such as for example Z1 165MP, Z1 1 15MP, a treated precipitated silica (for example "doped With a cation such as aluminum or treated with a coupling agent such as silane); another reinforcing inorganic filler such as, for example, alumina, or even a reinforcing organic filler, especially carbon black (optionally covered with an inorganic layer, for example silica).
• the silica according to the invention then preferably constitutes at least 50% or even at least 80% by weight of the totality of the reinforcing filler.
• finished articles comprising at least one (in particular based on) said polymer compositions (s) described above (in particular based on the vulcanisais mentioned above), the soles of shoes (preferably in the presence of a coupling agent (silica / polymer), for example triethoxysilylpropyl tetrasulfide), floor coverings, gas barriers, fire-retardant materials and also technical parts such as ropeway rollers, appliances, liquid or gas line joints, brake system joints, hoses, ducts (including cable ducts), cables, motor mounts, battery separators, conveyor belts, transmission belts, or, preferably, tires, in particular tire treads (especially for light vehicles or pedestrians). our heavy goods vehicles (trucks for example)).
• a coupling agent for example triethoxysilylpropyl tetrasulfide
• a solution of sodium silicate (SiO 2 / Na 2 O weight ratio equal to 3.52) having a concentration of 230 g / l at a flow rate of 190 l / h and 100 g / l was introduced simultaneously into the reactor for 35 minutes.
• sulfuric acid of concentration equal to 80 g / l, at a controlled rate so as to maintain the pH of the reaction medium at a value of 4.
• reaction medium is brought to a pH of 5.2 with sulfuric acid of concentration equal to 80 g / l.
• the medium is cured for 5 minutes at pH 5.2.
• the slurry is filtered and washed under a filter press and a precipitated silica cake having a solids content of 22% is obtained.
• the cake obtained in the filtration stage is subjected to a disintegration operation in a continuously stirred reactor with simultaneous addition to the cake of 33.62 grams of a sodium aluminate solution (weight ratio
• the characteristics of the silica S1 obtained are then as follows:
• the cake obtained in the filtration stage is subjected to a disintegration operation in a continuously stirred reactor with simultaneous addition to the cake of 27.8 grams of a sodium aluminate solution (Al / SiO 2 O 2 weight ratio). , 3%) and 29.8 grams of a 7.7% by weight sulfuric acid solution.
• This disintegrated cake (having a solids content of 22% by weight) is then dried by means of a bi-fluid nozzle atomizer by spraying the disintegrated cake through a nozzle SU5 (Spraying System) of 2. 54 mm with a pressure of 1 bar under the following medium flow and temperature conditions:
• composition 1 Composition 1
• N-cyclohexyl-2-benzothiazyl-sulfenamide (Rhenogran CBS-80 from RheinChemie) Process for the preparation of elastomeric compositions:
• a first phase consists in a thermomechanical work phase at high temperature. It is followed by a second phase of mechanical work at temperatures below 1 10 ° C. This phase allows the introduction of the vulcanization system.
• the first phase is carried out by means of a mixing apparatus, internal mixer type Brabender brand (capacity of 380 ml).
• the filling factor is 0.6.
• the initial temperature and the speed of the rotors are set each time so as to reach mixing temperatures of the temperature close to 1-15-170 ° C.
• the first phase allows to incorporate in a first pass, the elastomers and then the reinforcing filler (fractional introduction) with the coupling agent and stearic acid.
• the duration is between 4 and 10 minutes.
• a second pass makes it possible to incorporate the zinc oxide and the protective / antioxidant agents (6-PPD in particular). The duration of this pass is between 2 and 5 minutes.
• the second phase allows the introduction of the vulcanization system (sulfur and accelerators, such as CBS). It is carried out on a roll mill, preheated to 50 ° C. The duration of this phase is between 2 and 6 minutes.
• sulfur and accelerators such as CBS
• the Mooney consistency is measured on the compositions in the uncured state at 100 ° C. by means of a MV 2000 rheometer as well as the determination of the Mooney stress relaxation rate according to the NF ISO 289 standard.
• composition 1 silica S1 of the present invention
• Control 1 the silica S1 of the present invention
• silica S1 of the present invention (Composition 1) makes it possible to maintain the advantage in raw reduced viscosity, with respect to the value of the mixture with the reference (Control 1), after 3 weeks of storage.
• the composition to be tested is placed in the controlled test chamber at a temperature of 160 ° C. for 30 minutes, and the resistive torque opposite the composition is measured at a low amplitude oscillation (3 °).
• a biconical rotor included in the test chamber the composition completely filling the chamber in question.
• the toasting time TS2 corresponding to the time required to have a rise of 2 points above the minimum torque at the considered temperature (160 ° C) and which reflects the time during which it is possible to implement the raw mixtures at this temperature without initiation of vulcanization (the mixture cures from TS2).
• composition 1 The use of the silica S1 of the present invention (Composition 1) makes it possible to reduce the minimum viscosity (sign of an improvement in the green viscosity) with respect to the control mixture (Control 1) without penalizing the vulcanization behavior.
• composition 1 silica S1 of the present invention
• the measurements are carried out on the optimally vulcanized compositions (T98) for a temperature of 160 ° C.
• the uni-axial tensile tests are carried out in accordance with the NF ISO 37 standard with specimens of type H2 at a speed of 500 mm / min on an INSTRON 5564.
• the modules x%, corresponding to the stress measured at x % tensile strain, and tensile strength are expressed in MPa; the elongation at break is expressed in%. It is possible to determine a reinforcement index (I.R.) which is equal to the ratio between the 300% deformation modulus and the 100% deformation modulus.
• the Shore A hardness measurement of the vulcanisais is carried out according to the indications of ASTM D 2240. The value given is measured at 15 seconds.
• compositions Witness 1 Composition 1
• composition 1 a silica S1 of the present invention
• composition 1 silica S1 of the present invention
• composition 1 makes it possible to maintain the dynamic properties at the level of that of the control mixture (Control 1).
• Tables II to V shows that the composition according to the invention (Composition 1) makes it possible to obtain a good compromise implementation / reinforcement / hysteretic properties compared to the control composition (Control 1) and in particular a consequent gain in raw viscosity which remains stable storage over time.
• reaction medium is brought to a pH of 5.6 by the introduction of sulfuric acid (having a mass concentration of 7.7% and a density of 1050 g / l. gets 2090 liters of slurry at the end of this reaction.
• the slurry is filtered and washed under a filter press and a precipitated silica cake having a solids content of 20% is obtained.
• a first portion of the silica cake obtained in Example 5 is then subjected to a disintegration step to obtain a silica S2.
• a solution of a 34% by weight MGA mixture is used (mixture of polycarboxylic acids: 94.8% by weight of methylglutaric acid, 4.9% by weight of ethylsuccinic anhydride, 2% by weight of adipic acid, 0.1% other).
• the cake obtained in the filtration stage is subjected to a disintegration operation in a continuously stirred reactor with simultaneous addition to the cake of 15.32 grams of a sodium aluminate solution (Al / SiO 2 weight ratio of , 3%) and 16.00 grams of the MGA solution (MGA / SiO 2 mixture weight ratio of 1.0%).
• This disintegrated cake (having a solids content of 20% by weight) is then dried by means of a bi-fluid nozzle atomizer by spraying the disintegrated cake through a 2.54 mm SU5 (Spraying System) nozzle with a pressure of 1 bar under the following medium flow and temperature conditions:
• a second portion of the silica cake obtained in Example 5 is then subjected to a disintegration step, to obtain a silica S3, using a solution of a mixture of MGA at 34% by mass (mixture of polycarboxylic acids: 94, 8% by weight of methylglutaric acid, 4.9% by weight of ethylsuccinic anhydride, 0.2% by weight of adipic acid, 0.1% other).
• the cake obtained in the filtration stage is subjected to a disintegration operation in a continuously stirred reactor with the addition to the cake of 15.32 grams of a sodium aluminate solution (weight ratio Al / SiO 2 of 0.3%). Once the disintegration has been carried out, 16.00 grams of the MGA solution are added to the disintegrated cake (MGA / SiO 2 mixture weight ratio of 1.0%).
• This disintegrated cake (having a solids content of 20% by weight) is then dried as described above for the first portion of the cake with an average flow rate of 11.1 l / h.
• the cake obtained in the filtration stage is subjected to a disintegration operation in a continuously stirred reactor with simultaneous addition to the cake of 15.32 grams of a sodium aluminate solution (Al / S 10 O 2 weight ratio). , 3%) and 37.9 grams of a 7.7% by weight sulfuric acid solution.
• This disintegrated cake (having a solids content of 20% by weight) is then dried by means of a bi-fluid nozzle atomizer by spraying the disintegrated cake through a nozzle SU5 (Spraying System) of 2. 54 mm with a pressure of 1 bar under the following medium flow and temperature conditions:
• the Mooney consistency is measured on the compositions in the uncured state at 100 ° C. by means of a MV 2000 rheometer as well as the determination of the Mooney stress relaxation rate according to the NF ISO 289 standard.
• compositions 2 and 3 allow a consequent reduction of the initial green viscosity, with respect to the value of the mixture with the reference (control 2).
• compositions 2 and 3 allow to preserve the advantage in reduced raw viscosity, compared to the value of the mixture with the reference (control 2), after 28 days of storage.
• compositions 2 and 3 make it possible to reduce the minimum viscosity (sign of an improvement in the raw viscosity) with respect to the control mixture (control 2) without penalizing the behavior in vulcanization.
• compositions 2 and 3 make it possible to improve the toasting time TS2 with respect to the control mixture (control 2) without penalizing the time T98.
• the measurements are performed on the optimally vulcanized compositions (T98) for a temperature of 160 ° C.
• the uni-axial tensile tests are carried out in accordance with the NF ISO 37 standard with specimens of type H2 at a speed of 500 mm / min on an INSTRON 5564.
• the modules x%, corresponding to the stress measured at x % tensile strain, and tensile strength are expressed in MPa; the elongation at break is expressed in%. It is possible to determine a reinforcement index (I.R.) which is equal to the ratio between the 300% deformation modulus and the 100% deformation modulus.
• the Shore A hardness measurement of the vulcanisais is carried out according to the indications of ASTM D 2240. The value given is measured at 15 seconds.
• compositions 2 and 3 make it possible to obtain a satisfactory level of reinforcement with respect to the control mixture (Control 2) and in particular to maintain a high level of the 300% deformation module. .
• Compositions 2 and 3 thus have relatively low 10% and 100% moduli and a relatively high 300% modulus, hence a good reinforcement index.
• Dynamic properties are measured on a viscoanalyzer (Metravib VA3000) according to ASTM D5992.
• the values of loss factor (tan ⁇ ) and elastic modulus in dynamic shear (G * 12%) are recorded on vulcanized samples (parallelepipedal specimen of section 8 mm 2 and height 7 mm).
• the sample is subjected to an alternating double shear sinusoidal deformation at a temperature of 40 ° C. and at a frequency of 10 Hz.
• the amplitude-deformation sweep processes are carried out in a round-trip cycle, ranging from 0.degree. 1% to 50% then return 50% to 0, 1%.
• compositions 2 and 3 make it possible to maintain the dynamic properties at the level of that of the control mixture (control 2).
• compositions in accordance with the invention make it possible to improve the compromise implementation / reinforcement / hysteretic properties at 40 ° C. with respect to the control composition (Control 2) and in particular a significant gain in raw viscosity which remains stable on storage over time.

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