Classifications

• • 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
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/10—Homopolymers or copolymers of propene
  • C08L23/12—Polypropene
• • 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 the reinforcement of thermoplastic polymer materials, and more specifically relates to the stiffening of thermoplastic polymer materials, and in particular that of materials based on polyolefins, such as polypropylene.
• the rigidity of a thermoplastic polymer composition can in particular be measured by its flexural modulus, which reflects the pressure that it is necessary to apply to the material to deform it.
• flexural modulus is meant more specifically, in the sense of the present description, the Young's modulus of the bending material.
• this flexural modulus may in particular be measured according to the method of ISO 178, which consists in providing a test piece made of the material to be tested, in supporting it on two supports spaced apart by a given distance, and applying a constant rate of deformation to the center of the test piece, continuously measuring the load applied to the test piece, in order to deduce the stress as a function of the displacement.
• impact resistance means the more or less high ability of this polymeric material to resist rupture under the effect of impact, especially under the effect of a high-speed impact.
• the impact resistance of a polymer can in particular be measured by the so-called “impact test” method. This type of test generally involves notching a test piece consisting of the material to be tested (U-notch or, most often, V-shaped notch), then breaking the notched test piece under the impact of a weight (pendulum or hammer). , and to measure the energy absorbed by the fracture of the specimen, which reflects the breaking strength energy (or "resilience") of the material. The higher the energy absorbed, the more the material is shock resistant.
• the impact resistance of a polymer material may in particular be determined by the so-called "Charpy impact test” method, for example according to the specific method of the ISO 179 standard.
• a first solution that has been proposed is to modify the polymer, for example by adding an elastomeric resin, as proposed in US Pat. No. 4,209,504, or else other specific polymers, such as those envisaged, for example in US Patent 5,525,703 or US 5,041,491.
• An object of the present invention is to provide mineral fillers that improve the rigidity of the material, but without adverse effect on its impact resistance.
• the invention aims in particular to provide mineral fillers capable of ensuring such an effect, without having to modify the composition of the polymer by adding specific polymeric fillers of the type. above, or to use mineral fillers treated with fatty acid compounds.
• the subject of the present invention is the use of particular silicas, especially having a BET specific surface area of at least 60 m 2 / g, as mineral filler in a thermoplastic polymer material to increase the rigidity of said material, while maintaining or improving its impact resistance.
• the inventors have now demonstrated that the specific silicas of the type described in application WO 03/016215 provide such an effect in thermoplastic polymer materials, when they have a BET specific surface area of at least 60 m 2 / g.
• BET surface area refers to the specific surface area of the silica as determined according to the method of BRUNAUER-EMMET-TELLER described in The Journal of the American Chemical Society, Volume 60, page 309, February 1938, and corresponding to the international standard ISO 5794/1 (Annex D).
• the incorporation of a silica of the type described in application WO 03/016215 and having a specific surface area of at least 60 m 2 / g in a thermoplastic polymer material leads, in most cases, to an unexpected improvement in other mechanical characteristics of the material.
• the incorporation of such silicas increases, as a rule, the tensile elongation characteristics of the material (in particular the elongation at break in tension of the material, as measured for example according to the ISO 527 standard). may be advantageous especially when the material is intended to be subjected to strong bending, for example when it is used in injected parts of complex shapes, or when it is intended to act as a hinge between two parts .
• the silicas which are used in the context of the present invention are preferably silicas as described in application WO 03/016215, and which specifically have a BET specific surface area of at least 60 m 2 / g.
• they may be analogous silicas having similar properties and having a BET specific surface area of at least 60 m 2 / g. More specifically, the silicas that can be used according to the invention will be described in detail in the description that follows.
• the silica used according to the invention is a silica, called “silica S” below, which has a BET specific surface area of at least 60 m 2 / g and which is obtained (or more generally that is obtainable) according to a process (referred to as “method P" in the following description) which comprises the reaction of a silicate with an acidifying agent whereby a suspension of silica is obtained , then separating and drying this suspension, and wherein the reaction of the silicate with the acidifying agent is carried out according to the following successive steps:
• silicate and acidifying agent are added to said base stock, such that the pH of the reaction medium is maintained between 2 and 5
• silicate and acidifying agent are added simultaneously to the reaction medium, in such a way that the pH of the reaction medium is maintained between 7 and 10, (v) the addition of the silicate is stopped while continuing to addition of the acidifying agent in the reaction medium until a pH value of the reaction medium of less than 6 is obtained.
• the silica S used according to this first embodiment is a silica directly obtained according to process P as defined above.
• the process P gives the silica obtained particular characteristics and properties.
• the silica S may be a silica prepared according to another process but having characteristics similar to those of silicas obtained in the process P.
• the silica S is rather a precipitated silica silica.
• any common form of silicate for example a metasilicate and / or a disilicate, may be used as the silicate.
• the silicate employed is an alkali metal silicate, such as sodium silicate or potassium silicate.
• the silicate is typically used in the form of a solution, generally aqueous, having a concentration (expressed in SiU2) included between 40 and 330 g / l, typically between 60 and 300 g / l, in particular between 60 and 260 g / l (for example of the order of 200 to 250 g / l, in particular of the order of 230 g / l). 1, especially when using sodium silicate).
• the acidifying agent used in process P is generally a strong mineral acid such as sulfuric acid, hydrochloric acid or nitric acid, or, alternatively, an organic acid such as acetic acid, formic acid or carbonic acid, for example.
• the acidifying agent can be used in the diluted or concentrated state. It may for example be used in the form of a solution, generally aqueous, of normality for example between 0.4 and 36 N, in particular between 0.6 and 1.5 N.
• the acidifying agent used in process P is sulfuric acid.
• it is preferably used in the form of a solution, generally aqueous, having a concentration of between 40 and 180 g / l, for example between 60 and 130 g / l (typically of the order of 80 g / l).
• sulfuric acid is used as acidifying agent, and sodium silicate as silicate.
• acidifying agent sulfuric acid
• sodium silicate as silicate.
• the reaction between these compounds is in a very specific manner according to the following steps.
• an aqueous base stock having a pH of between 2 and 5 is formed.
• this base of the tank has a pH of between 2.5 and 5, in particular between 3 and 5. and 4.5.
• This pH is for example between 3.5 and 4.5, and it is typically of the order of 4.
• the initial stock of step (i) can be obtained by adding an acidifying agent to water so as to obtain a pH value of the bottom of the tank between 2 and 5, preferably between 2.5 and 5, especially between 3 and 4.5 and for example between 3.5 and 4.5.
• the initial stock of step (i) can be obtained by adding the acidifying agent to a water / silicate mixture so as to obtain this pH value.
• This base of the tank may also be prepared by adding an acidifying agent to a base stock containing silica particles previously formed at a pH of less than 7, so as to obtain a pH value between 2 and 5, preferably between 2 and 5. , 5 and 5, especially between 3 and 4.5 and for example between 3.5 and 4.5 (typically, this pH is of the order of 4).
• the stock formed in step (i) may optionally comprise an electrolyte. Nevertheless, preferably, no electrolyte is added to the stock in step (i). More generally, it is preferable to add no electrolyte to the medium during process P.
• electrolyte is understood in its usual acceptation, that is to say as designating any ionic or molecular substance which, when in solution, decomposes or dissociates to form ions or charged particles.
• electrolyte that may be present in the stockstock, mention may be made especially of a salt of the group of alkali and alkaline earth metal salts, in particular the salt of the metal of the silicate used and of the acidifying agent, for example the sulphate. in the case of the reaction of a sodium silicate with sulfuric acid, or sodium chloride in the case of the reaction of a sodium silicate with hydrochloric acid.
• step (ii) of process P the acidifying agent and the silicate are added simultaneously (ie jointly and generally progressively).
• This simultaneous addition is carried out in such a way that the pH of the reaction medium is maintained between 2 and 5, preferably between 2.5 and 5, in particular between 3 and 4.5, for example between 3.5 and 4.5, at during the addition.
• This maintenance of the pH in the ranges indicated can in particular be ensured by controlling the respective introduction rates of acidifying agent and silicate.
• the silicate is introduced at a constant rate (generally between 150 and 250 l / h, for example of the order of 180 to 200 l / h), and the acidifying agent is introduced together with a variable flow, which is controlled to maintain the pH at the desired value.
• step (ii) is advantageously carried out in such a way that the pH value of the reaction medium is constantly equal (within ⁇ 0.2 units, and preferably to within ⁇ 0.1 pH value between 3 and 4.5, in general the pH value reached at the end of step (i) (typically, the pH is maintained at a value of 4 to ⁇ 0.2 unit, and preferably within ⁇ 0.1 unit).
• the addition of acidifying agent is stopped, while the addition of silicate is continued in the reaction medium. It follows therefore an increase in the pH of the medium, which is used to achieve a pH value of the reaction medium of between 7 and 10, preferably between 7.5 and 9.5, for example between 7.5 and 8.5.
• the pH reached at the end of step (iii) is of the order of 8.
• the reaction medium may optionally be cured.
• this ripening is advantageously carried out by allowing the medium to evolve to the pH obtained at the end of stage (iii), generally with stirring.
• Such ripening is typically conducted for a duration of the order of 2 to 45 minutes, for example between 5 and 25 minutes.
• this maturing does not involve addition of acidifying agent, no addition of silicate. More generally, no compound is usually added to the medium during such ripening.
• acidifying agent may be added to the reaction medium between step (iii) and step (iv), for example between the aforementioned ripening (when it takes place) and the step (iv), or immediately after stopping the silicate addition of step (iii).
• the pH of the reaction medium at the end of this addition of acidifying agent remains between 7 and 9.5, preferably between 7.5 and 9.5.
• step (iv) is followed by a new simultaneous addition of acidifying agent and silicate, so that the pH of the reaction medium is maintained between 7 and 10, preferably between 7.5 and 9.5, for example between 7.5 and 8.5.
• the maintenance of the pH in the ranges indicated is generally ensured by controlling the respective introduction rates of acidifying agent and silicate, typically, by introducing the silicate at a constant flow rate (generally between 150 and 250 l / l). h, for example of the order of 180 to 200 l / h), and by jointly introducing the acidifying agent with a variable flow, controlled to maintain the pH to the desired value.
• step (iii) is advantageously carried out in such a way that the pH value of the reaction medium is constantly equal (at
• ⁇ 0.2 unit and preferably to within ⁇ 0.1 unit) at a pH value between 7 and 10, preferably between 7.5 and 9.5, for example between 7.5 and 8.5 , in general at the pH value reached at the end of the preceding step (typically, in step (iv), the pH is maintained at a value of 8 to ⁇ 0.2 units, and preferably at ⁇ 0,1 unit).
• 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, preferably between 3 and 5.5, in particular between 5 and 5.5, for example of the order of 5.2.
• the ripening is advantageously carried out by allowing the medium to evolve to the pH obtained at the end of stage (v), generally with stirring.
• This ripening is typically conducted for 2 to 45 minutes, for example between 5 and 25 minutes.
• it comprises neither addition of acidifying agent nor addition of silicate. More generally, no compound is usually added to the medium during such ripening.
• 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 entire reaction of the silicate with the acidifying agent is generally carried out between 70 and 95 ° C., in particular between 75 and 90 ° 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 90 ° C., typically between 80 and 90 ° C. 90 0 C.
• the end-of-reaction temperature is higher than the reaction start temperature.
• the temperature is preferably maintained between 70 and 85 ° C. at the beginning of the reaction (for example during steps (i) to (iii) and any subsequent maturing), then the temperature is increased, preferably to a value between 85 and 95 ° C., the value at which it is maintained until the end of the reaction (for example during steps (iv) and (v) and any subsequent maturing ).
• a suspension of silica is obtained.
• This silica suspension is then subjected to separation, generally of the liquid / solid type.
• This separation usually comprises a filtration, which is optionally followed by washing, if necessary, for example with water, which makes it possible in particular to remove unreacted silicates, the acidifying agent, and / or or at least a portion of the salts formed.
• the above-mentioned filtration is carried out according to any suitable method, for example by means of a filter press, a belt filter, or a vacuum filter.
• a silica slurry is recovered, namely an aqueous medium enriched in silica and depleted of water (filter cake, in the case where the separation is a filtration).
• the concentrated silica slurry thus obtained is then dried.
• this 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 concentrated silica slurry filter cake type is not always under conditions allowing its atomization, especially given its generally high viscosity.
• the cake is then subjected to a disintegration operation prior to spray drying.
• This disintegration operation can be performed mechanically, by passing the cake in a colloid mill or ball.
• the disintegration is generally carried out in the presence of an aluminum compound, in particular sodium aluminate and, optionally, in the presence of an acidifying agent as described previously (in the latter case, the aluminum compound and the acidifying agent are generally added simultaneously).
• the disintegration operation makes it possible in particular to lower the viscosity of the suspension to be dried later.
• the silica obtained after drying is usually in the form of substantially spherical beads.
• a grinding step can optionally be carried out on the recovered product to obtain the silica in the form of a powder.
• the silica obtained is most often in the form of a powder.
• the silica obtained in powder form as obtained for example after nozzle spray and grinding, or as obtained after drying by turbine atomizer, may optionally be subjected to a subsequent agglomeration step, for example by direct compression, wet granulation (that is to say with use of a binder such as water, silica suspension, etc.) extrusion or, preferably, dry compaction.
• a subsequent agglomeration step for example by direct compression, wet granulation (that is to say with use of a binder such as water, silica suspension, etc.) extrusion or, preferably, dry compaction.
• the silica obtained by this agglomeration step is generally in the form of granules.
• the silica S used according to the invention is in powder form.
• it is the aforementioned powders, obtained by nozzle atomization drying and grinding, or obtained after drying by turbine atomizer.
• it may also be a powder resulting from the grinding of the compacted silica granules described above.
• the silica S used according to the invention may be in the form of substantially spherical beads, obtainable by the aforementioned nozzle spray drying.
• the process P for preparing the silica S comprises (and for example consists of) the following successive steps:
• step (i) forming an aqueous base stock having a pH of between 3 and 4.5, preferably between 3.5 and 4.5 (typically of the order of 4); (ii) at the same time, silicate and acidifying agent are added to said base stock so that the pH of the reaction medium is maintained at the value reached at the end of step (i) at ⁇ 0 , 2 units, and preferably within ⁇ 0.1 units;
• silicate and acidifying agent are added simultaneously to the reaction medium, so that the pH of the reaction medium is maintained at the value reached at the end of step (iii) at ⁇ 0, 2 units, and preferably within ⁇ 0.1 units;
• the medium is allowed to mature, preferably with stirring, typically for 2 to 20 minutes, for example for 5 minutes;
• step (vii) filtering the silica suspension obtained at the end of step (vi), whereby a filter cake is obtained; (viii) the filter cake is disintegrated mechanically in the presence of sodium aluminate;
• the steps (i) to (vi) are advantageously carried out at a temperature of between 75 and 95 ° C., preferably between 80 and 90 ° C. (at a temperature of the order of 80 0 C or 86 ° C, for example).
• the silicate used according to this specific variant is advantageously a sodium silicate, advantageously having a weight ratio SiO 2 / Na 2 O of between 3.2 and 3.8, typically between 3.5 and 3.6, for example of the order of 3.52.
• This silicate is preferably used in the form of a solution having a concentration (expressed as SiO 2 ) of between 200 and 250 g / l, typically of the order of 230 g / l.
• This solution is generally introduced with a constant flow rate of between 150 and 250 l / h, for example between 180 and 200 l / h, typically of the order of 190 l / h in steps (iii) and (v).
• the acidifying agent is, for its part, preferably sulfuric acid, advantageously in the form of a solution having a concentration of between 60 and 130 g / l, for example between 70 and 100 g / l, typically of the order of 80 g / l.
• the silica used is a silica, called “silica S1", which has the following characteristics:
• CTAB specific surface area of between 40 and 525 m 2 / g
• This silica S1 is advantageously a precipitation silica. According to a particular embodiment, it is a silica obtained according to the method P defined above in the present description.
• CTAB specific surface area refers to the external surface as determined according to standard NF T 45007 (November 1987) (5.12).
• the "XDC granulometric analysis method" referred to in the present description is a method of particle size analysis centrifugal sedimentation, by which one can measure, on the one hand, the widths of object size distribution of a silica, and, on the other hand, the XDC mode illustrating its size of objects. This method is described below:
• the device register record the values of the diameters passing at 16%, 50% (or median) and 84% (% mass) as well as the value of the Mode (the derivative the cumulative granulometric curve gives a frequency curve whose abscissa of the maximum (abscissa of the main population) is called the "Mode").
• this object size distribution width Ld, measured by XDC granulometry, after ultrasonic deagglomeration (in water) is at least 0.91, for example at least 0.94, and it can be at least 1, 04.
• an object size distribution width d less than 500 nm measured by XDC particle size, after ultrasonic deagglomeration (in water).
• a mean (mass) particle size (i.e., secondary particles or aggregates), denoted by w , can be measured using the XDC granulometric analysis method by centrifugal sedimentation. after dispersion, by deagglomeration with ultrasound, silica in water. The method differs from that previously described in that the suspension formed (silica + deionized water) is deagglomerated, on the one hand, for 8 minutes, and on the other hand, using an ultrasonic probe VIBRACELL 1, 9 cm (marketed by Bioblock) of 1500 watts (used at 60% of the maximum power). After analysis (sedimentation for 120 minutes) the mass distribution of the particle sizes is calculated by the granulometer software.
• porous volumes are porous volumes as measured by mercury porosimetry, the preparation of each sample being as follows: each sample is dried beforehand for 2 hours in an oven at 200 0 C, then placed in a test vessel within 5 minutes after leaving the oven and degassed under vacuum, for example using a pump with rotary drawers; the pore diameters (MICROMERITICS Autopore III 9420 porosimeter) are calculated by the WASHBURN relationship with a theta contact angle equal to 140 ° and a gamma surface tension equal to 484 Dynes / cm (or N / m).
• V s-dso pore volume denotes the pore volume constituted by the pores of diameters between d5 and d50
• V (d5 - d 100o ) " porous volume represents the pore volume constituted by the pores of diameters between d5 and d100, where each of the dn denotes 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 pore area (st ot ) can be determined from the mercury intrusion curve).
• the ratio of volumes V ⁇ s. d50 ) A / (ds - dioo) is characteristic of the distribution of the pore volume.
• the ratio V (d5 dso.) A / (d 5 - d ioo) is at least 0.66, for example at least 0.68, and typically at least 0.71 .
• This ratio V (d5 - d50) A / (d5 - dioo) may be at least 0.73, in particular at least 0.74. In some cases, this ratio is at least 0.78, especially at least 0.80, or even at least 0.84.
• porous distribution width Idp from the porous distribution curve representing pore volume (in ml / g) as a function of the pore diameter (in nm). More precisely, as indicated in the application WO 03/016215, this porous distribution width Idp is determined as follows: the coordinates Xs (in nm) and Ys (in ml / g) of the point corresponding to the main population (typically , the maximum of the porous distribution curve).
• the pore size distribution width may optionally also be reflected by the parameter "L / IF" determined by mercury porosimetry.
• the measurement is carried out using the PASCAL 140 and PASCAL 440 porosimeters marketed by ThermoFinnigan, operating as follows: a sample quantity of between 50 and 500 mg (in the present case 140 mg) is introduced into a cell measurement. This measuring cell is installed on the measurement station of the PASCAL 140 device. The sample is then degassed under vacuum, for the time necessary to reach a pressure of 0.01 kPa (typically of the order of 10 minutes). . The measuring cell is then filled with mercury.
• the porosimeters are used in "PASCAL" mode, so as to continuously adjust the rate of intrusion of the mercury as a function of variations in the volume of intrusion.
• the velocity parameter in "PASCAL" mode is set to 5.
• the pore radii Rp are calculated from the pressure values P using the WASHBURN relation, with a hypothesis of cylindrical pores, by choosing an angle of theta contact equal to 140 ° and a gamma surface tension equal to 480 Dynes / cm (or N / m).
• the porous volumes Vp are related to the mass of silica introduced and expressed in cm 3 / g.
• the pore size distribution is obtained by calculating the dVp / dRp derivative of the smoothed intrusion curve.
• the fineness index IF is the value of pore radius (expressed in angstroms) corresponding to the maximum of the pore size distribution dVp / dRp.
• L the width at half height of the pore size distribution dVp / dRp.
• a silica S1 useful according to the invention may for example have the following characteristics:
• V (d5 dso / Vys -. D ioo) is at least 0.71, for example at least 0.73, in particular of at least 0.74, and in some cases at least 0.78, especially at least 0.80, or even at least 0.84.
• the silica used is a silica, called "silica S2", which has the following characteristics: a BET specific surface area of between 60 and 550 m 2 / g;
• CTAB specific surface area of between 40 and 525 m 2 / g
• This silica S 2 is advantageously a precipitation silica.
• it is a silica obtained according to the method P defined above in the present description.
• the silica S2 may in particular have a porous distribution width Idp greater than 0.80, for example greater than 0.85. In some cases, this porous distribution width Idp is greater than 1.05, for example greater than 1.25, or even greater than 1.40. Moreover, the silica S2 preferably has a width Ld ((d84-d16) / d50) of object size distribution measured by XDC granulometry after deagglomeration with ultrasound (in water) of at least 0.91, for example at least 0.94, especially at least 1, typically at least 1.04.
• the silica used according to the present invention is a silica, called “silica S3", which has the following characteristics:
• This silica S3 is advantageously a precipitation silica.
• it is a silica obtained according to the method P defined above in the present description.
• the silica S3 may in particular have a ratio V (d5 - d50) / V (d5 - d100) 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 silica used according to the present invention is a silica, called "silica S4", which has the following characteristics:
• This silica S4 is advantageously a precipitation silica.
• it is a silica obtained according to the method P defined above in the present description.
• This silica S4 may for example have a ratio V ( d 5 - d 5 O) A / ( d 5 - dioo) of at least 0.78, especially at least 0.80, or even at least 0.84.
• the above-mentioned silicas S, S1, S2, S3 and S4 have the following characteristics: a BET specific surface area of between 70 and 350 m 2 / g, in particular between 90 and 320 m 2 / g; and
• CTAB specific surface area of between 60 and 330 m 2 / g, for example between 80 and 290 m 2 / g.
• their BET specific surface area may be between 110 and 270 m 2 / g, especially between 115 and 250 m 2 / g, for example between 135 and 235 m 2 / g.
• their CTAB specific surface area may be between 90 and 230 m 2 / g, in particular between 95 and 200 m 2 / g, for example between 120 and 190 m 2 / g.
• the silicas S, S1, S2, S3 and S4 have the following characteristics: a BET specific surface area of between 60 and 400 m 2 / g, in particular between 60 and 300 m 2 / g; and
• CTAB specific surface area of between 40 and 380 m 2 / g, in particular between 45 and 280 m 2 / g.
• their BET specific surface area may be between 120 and 280 m 2 / g, in particular between 150 and 280 m 2 / g.
• their CTAB specific surface area may be between 115 and 260 m 2 / g, in particular between 145 and 260 m 2 / g.
• the silicas S, S1, S2, S3 and S4 may have a certain microporosity.
• the difference between their BET surface area and their CTAB specific surface area is greater or equal to 5 m 2 / g, typically greater than or equal to 15 m 2 / g, for example greater than or equal to 25 m 2 / g, this difference remaining, however, most often less than 50 m 2 / g, preferably less than 40 m 2 / g.
• the pore volume provided by the larger pores is usually the largest part of the structure.
• These silicas S1, S2, S3 and S4 may have a pore volume consisting of pores with diameters of between 3.7 and 80 nm of at least 1.35 cm3 / g, in particular at least 1.40 cm3 / cm3. g, or even at least 1.50 cm3 / g.
• the silicas S, S1, S2, S3 and S4 can have both an object size distribution width Ld of at least 1, 04 and a width distribution width D d of objects less than 500 nm of not less than 0.95.
• the object size distribution width Ld of the silicas S, S1, S2, S3 and S4 may, in some 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 S, S1, S2, S3 and S4 may be, for example, at least 1.0, in particular at least 1, 10, especially at least 1, 20.
• the silicas S, S1, S2, S3 and S4 generally have a high object size, which is atypical.
• the mode of their particle size distribution as measured by XDC granulometry after deagglomeration with ultrasound (in water) can for example satisfy the following condition: Mode XDC (nm)> (5320 / CTAB surface (m2 / g)) +8 or even the following condition:
• the silicas S, S1, S2, S3 and S4 which are useful according to the invention can moreover possess a particular surface chemistry, such that they have a ratio (Sears number x 1000) / (BET surface area) less than 60, preferably less than 55, e.g. less than 50. '
• the "Sears number" referred to herein corresponds to the volume of 0.1 M sodium hydroxide solution that is required to raise the pH of 4 to 9 of a suspension of the silica tested to 10 g / l. in 200 g / l sodium chloride medium, as determined by the method described by GW SEARS in Analytical Chemistry, vol. 28, No. 12, December 1956.
• this number of Sears is determined under the following conditions.
• a solution of sodium chloride at 200 g / l acidified to pH 3 with a 1M hydrochloric acid solution is prepared from 400 g of sodium chloride.
• the weighings are carried out using a weighing scale. Precision METTLER.
• 150 ml of this sodium chloride solution are added gently into a 250 ml beaker into which a mass M (in g) of the sample to be analyzed corresponding to 1.5 grams of dry silica has been introduced beforehand.
• Ultrasound was applied to the dispersion for 8 minutes (1500 W BRANSON ultrasound probe, 60% amplitude, 13 mm diameter), the beaker being in a crystallizer filled with ice.
• the solution obtained is homogenized by magnetic stirring, using a magnetic bar of dimensions 25 mm ⁇ 5 mm. It is checked that the pH of the suspension is less than 4, adjusting it if necessary with a 1M hydrochloric acid solution.
• a Metrohm titration meter pH meter (titroprocessor 672, dosimat 655), previously calibrated with buffer solutions pH 7 and pH 4, 0.1 M sodium hydroxide solution at a flow rate of 2 ml / min.
• the titration pH meter has been programmed as follows: 1) Call the program "Get pH", 2) Enter the following parameters: pause (waiting time before start of titration): 3 s, reagent flow: 2 ml / min, anticipation (adaptation of the titration rate to the slope of the pH curve): 30, pH stop: 9.40, critical EP (detection sensitivity of the equivalence point): 3, report (parameters of printing of the titration report): 2,3,5 (ie creation of a detailed report, list of measuring points, titration curve)).
• the exact volumes V 1 and V 2 of the added sodium hydroxide solution are determined by interpolation to obtain a pH of 4, respectively. and a pH of 9.
• the number of Sears for 1, 5 grams of dry silica is equal to the ratio:
• silicas S, S1, S2, S3 and S4 that are useful according to the invention generally have at least one, and preferably all, of the following three characteristics:
• SCTAB refers to the CTAB surface area expressed in m2 / g.
• the number of silanols per nm 2 of surface is determined by grafting methanol on the surface of the silica, preferably under the conditions set out below:
• N S i0H / nm2 [(% C g -% C b) ⁇ 6.023 ⁇ 10 23] / [SBET x 10 18 x 12 x 100] with following meanings:
• an important characteristic of this silica is its specific surface, which is greater than or equal to 60 m 2 / g, which makes it possible to obtain the increase in rigidity of the desired material according to the invention.
• silicas having a BET surface area of at least 80m 2 / g, - or even at least 90 m 2 / g, more preferably at least 100 m 2 / g.
• a silica used according to the invention be present in the form of objects (particles, aggregates and / or agglomerates) which are as finely divided and dispersed as possible, which proves to be particularly advantageous in regarding the impact resistance of the material.
• objects particles, aggregates and / or agglomerates
• the work of the inventors allows to establish that we observe an increase in the impact resistance even more pronounced that the silica is finely dispersed in the material.
• silicas S, S1, S2, S3, and S4 which have been described above in the present description are silicas which have BET specific high surface areas, typically greater than or equal to 60 m 2 / g.
• these specific silicas are generally dispersed in the form of very small objects in thermoplastic polymer materials where they are introduced as mineral filler (typically they are found essentially in the form of objects smaller than 5 microns in size, and most often less than 1 micron, or even lower). These silicas are therefore of particular interest for the implementation of the present invention.
• the silicas S, S1, S2, S3, and S4 often have a very good dispersibility, especially in thermoplastic polymers. This dispersibility (and disagglomeration) ability can be quantified in particular by means of the following specific disagglomeration tests:
• a first deagglomeration test is carried out by appreciating the cohesion of the agglomerates by a granulometric measurement (by laser diffraction) carried out on a suspension of silica previously deagglomerated by ultra-sonification. The ability of the silica to deagglomerate (rupture of the objects from 0.1 to a few tens of microns) is thus measured.
• the deagglomeration under ultrasound is performed using a VIBRACELL BIOBLOCK sonicator (600 W), equipped with a 19 mm diameter probe.
• the particle size measurement is carried out by laser diffraction on a SYMPATEC granulometer. 2 grams of silica are weighed into a pillbox (height: 6 cm and diameter: 4 cm) and the mixture is made up to 50 grams by addition of deionized water: a 4% aqueous suspension of silica is thus obtained which is homogenized during 2 minutes by magnetic stirring.
• Deagglomeration under ultrasound is then carried out as follows: the probe being immersed over a length of 4 cm, the output power is adjusted so as to obtain a power dial needle deflection indicating 20%.
• the disagglomeration is carried out for 420 seconds.
• the granulometric measurement is then carried out after introducing into the vat of the granulometer a known volume (expressed in ml) of the homogenized suspension.
• the value of the median diameter 0 5 bone (or “medial diameter Sympatec") that is obtained is even lower than the silica has a high ability to deagglomerate.
• Another deagglomeration test is carried out by appreciating the cohesion of the agglomerates by a granulometric measurement (by laser diffraction), carried out on a suspension of silica previously deagglomerated by ultra-sonification. The ability of the silica to deagglomerate (rupture of the objects from 0.1 to a few tens of microns) is thus measured.
• the deagglomeration under ultrasound is carried out using a VIBRACELL BIOBLOCK (600 W) sonifier, used at 80% of the maximum power, equipped with a 19 mm diameter probe.
• the granulometric measurement is carried out by laser diffraction on a MALVERN granulometer (Mastersizer 2000).
• a gram of silica is weighed into a pillbox (height: 6 cm and diameter: 4 cm) and the mixture is made up to 50 g by addition of deionized water: an aqueous suspension of 2% silica, which is homogenized during 2 minutes by magnetic stirring.
• Deagglomeration is then carried out under ultrasound for 420 seconds.
• the granulometric measurement is then carried out after the whole of the homogenized suspension has been introduced into the vat of the particle size analyzer.
• the median diameter value 0 5 OM (OR “Malvern median diameter") that is obtained is much lower than the silica has an aptitude for deagglomeration.
• a deagglomeration rate can be measured by means of another ultrasonic deagglomeration test, at 100% power of a 600 watt probe, operating in pulsed mode (ie: 1 second ON, 1 second OFF) to prevent excessive heating of the ultrasonic probe during measurement.
• This known test in particular the subject of the application WO99 / 28376 (see also the applications WO99 / 28380, WO00 / 73372, WO00 / 73373), makes it possible to measure continuously the evolution of the average size (in volume) of the agglomerates of particles during sonication, as indicated below.
• the assembly used consists of a laser granulometer (type "MASTER RS I ZE RS", marketed by Malvern Instruments - He-Ne laser source emitting in the red, wavelength 632.8 nm) and its preparer (" Malvern Small Sample Unit MSX1 "), between which was interposed a continuous flow treatment unit (BIOBLOCK M72410) equipped with an ultrasonic probe (12.7 mm type VIBRACELL type 600-watt sonifier marketed by Bioblock). A small amount (150 mg) of silica to be analyzed is introduced into the preparator with 160 ml of water, the circulation speed being set at its maximum.
• a laser granulometer type "MASTER RS I ZE RS”
• MSX1 Malvern Small Sample Unit MSX1
• At least three consecutive measurements are carried out to determine, according to the known Fraunhofer calculation method (Malvern 3 $$ D calculation matrix), the average initial diameter (in volume) of the agglomerates, denoted d v [0].
• the sonification (pulsed mode: 1 s ON, 1 s OFF) is then established at a power of 100% (ie 100% of the maximum position of the "tip amplitude") and the evolution of the average diameter is followed for about 8 minutes.
• (in volume) d v [t] as a function of time "t" at the rate of one measurement every 10 seconds approximately.
• the deagglomeration rate ⁇ is calculated by linear regression of the evolution curve of 1 / d v [t] as a function of time "t", in the zone of stable deagglomeration regime (in general, between 4 and 8 minutes approximately ); it is expressed in ⁇ m "1 .mn " 1 .
• the application WO99 / 28376 describes in detail a measuring device that can be used for carrying out this ultrasound disagglomeration test.
• This device consists of a closed circuit in which a flow of agglomerates of particles suspended in a liquid can flow.
• This device essentially comprises a sample preparer, a laser granulometer and a treatment cell. Atmospheric pressure, at the level of the sample preparer and the treatment cell itself, allows the continuous removal of air bubbles that form during sonication (action of the ultrasound probe).
• the Sample Dispenser (“Malvern Small Sample Unit MSX1”) is intended to receive the test silica sample (in suspension in the liquid) and to circulate it through the circuit at the preset speed (potentiometer - maximum speed). about 3 l / min), in the form of a liquid suspension stream.
• This preparer is simply a receiving tank which contains, and through which circulates, the suspension to be analyzed. It is equipped with a stirring motor, at variable speed, in order to avoid sedimentation of the particle agglomerates of the suspension; a centrifugal mini-pump is intended to ensure the circulation of the suspension in the circuit; the inlet of the preparator is connected to the open air via an opening intended to receive the test sample to be tested and / or the liquid used for the suspension.
• a laser granulometer (“Mastersizer S”) whose function is to continuously measure, at regular intervals of time, the average volume size "d v " of the agglomerates, at the passage of the flow, thanks to a cell of measurement to which are coupled the means for recording and automatic calculation of the granulometer.
• the laser granulometers use, in a known manner, the principle of diffraction of light by solid objects suspended in a medium whose refractive index is different from that of the solid. According to Fraunhofer's theory, there is a relation between the size of the object and the diffraction angle of light (the smaller the object, the higher the angle of diffraction).
• a treatment cell equipped with an ultrasonic probe, which can operate in continuous or pulsed mode, intended to continuously break the particle agglomerates at the passage of the flow.
• This flow is thermostatically controlled by means of a cooling circuit arranged at the level of the cell in a double envelope surrounding the probe, the temperature being controlled for example by a temperature probe immersed in the liquid at the level of the preparer.
• the median diameter ⁇ 50 of the silicas S, S1, S2, S3 and S4, after deagglomeration with ultrasound, is generally less than 8.5 ⁇ m; it may be less than 6.0 ⁇ m, for example less than 5.5 ⁇ m.
• the median diameter 0 5 OM silicas S, S1, S2, S3 and S4, after ultrasonic disintegration, is in general less than 8.5 microns; it may be less than 6.0 ⁇ m, for example less than 5.5 ⁇ m.
• the silicas S, S1, S2, S3 and S4 may moreover have a deagglomeration rate ⁇ , measured according to the ultrasonic deagglomeration test in the pulsed mode described above, at 100% power of a 600 ultrasound probe. watts, at least 0.0035 ⁇ m '1 .mn "1 , in particular at least
• the silicas S, S1, S2, S3 and S4 may moreover have an ultrasonic deagglomeration factor (SDS) greater than 3 ml, in particular greater than 3.5 ml, especially greater than 4.5 ml.
• SDS ultrasonic deagglomeration factor
• F D M ultrasonic deagglomeration factor
• the silicas according to the present invention may have an average size (in mass) of particles, measured by XDC granulometry after deagglomeration with ultrasound, d w , between 20 and 300 nm, in particular between 30 and 300 nm, by example between 40 and 160 nm.
• the subject of the present invention is the use of any silica (hereinafter referred to as "silica S 0 ”) having a BET specific surface area of at least 60 m 2 / g, and presents in the polymer essentially in the form of dispersed objects having a size of less than 5 microns (and preferably less than 1 micron), as a mineral filler in a thermoplastic polymer material, to increase the rigidity of said material, while maintaining or improving its impact resistance.
• silica hereinafter referred to as "silica S 0 ”
• BET specific surface area of at least 60 m 2 / g
• silica So of the aforementioned type, the specific silicas S, S1, S2, S3, and S4 described above in the present description.
• Other silicas which have the required surface area, coupled with sufficient dispersibility within the polymeric material, are also suitable for the practice of the present invention.
• the silica So is preferably a precipitation silica.
• silicas having very high specific surface areas have relatively limited dispersibility properties, and as a result it is generally difficult to disperse them in a polymeric material in the form of very small objects.
• a silica that is used as silica S has, as a rule, a BET specific surface area of between 60 and 300 m 2 / g, for example between 100 and 250 m 2 / g, and especially between 150 and 200 m 2 / g.
• the use of silicas having higher specific surface areas is not excluded, provided that they can be dispersed in the material essentially in the form of dispersed objects having a size of less than 5 microns, and preferably less than 1 micron.
• an important characteristic of the So type silicas is their state of dispersion in the material in which they are incorporated.
• the impact resistance properties of the material obtained by using an S 0 type silica depend to a large extent on this state of dispersion, especially as the specific surface area of the silica used is high.
• the silica So it is generally preferable for the silica So to be present in the material in the form of aggregates, agglomerates and / or particles of which at least 90% by number, preferably at least 95% by number, and advantageously at least 98% by weight. % in number, have dimensions less than 5 microns, preferably 1 micron, the rest of the particles generally having dimensions less than 10 microns.
• the silica So is dispersed in the form of objects (aggregates, agglomerates and / or particles) of which at least 80% by number, preferably at least 90% by number, and advantageously at least 95% by number, have dimensions between 30 nm and 1000 nm, for example between 50 and 900 nm, in particular between 100 nm and 800 nm.
• objects aggregates, agglomerates and / or particles
• the silica So is dispersed in the form of objects (aggregates, agglomerates and / or particles) of which at least 80% by number, preferably at least 90% by number, and advantageously at least 95% by number, have dimensions between 30 nm and 1000 nm, for example between 50 and 900 nm, in particular between 100 nm and 800 nm.
• the state of dispersion of the silica in a thermoplastic polymer material of the type of that of the invention can moreover be quantified by analysis of several scanning electron microscopy (typically with a magnification ⁇ 1000) micrographs taken on several flat sections of the material obtained by ultracryotomy (typically cuts of dimensions 110 ⁇ m ⁇ 70 ⁇ m).
• the image analysis of this type of image allows, by image analysis, to determine the fraction of the surface of the image occupied by objects larger than 5 ⁇ m.
• a surface fraction "FS 5 ⁇ m " (equal to the area occupied by the objects of size greater than 5 ⁇ m relative to the total surface area of the image) is determined, the ratio of this surface fraction FS 5 ⁇ m being brought back to the volume fraction.
• Silica FV in the material (ratio of the volume occupied by the silica in the material to the total volume of the material) is characteristic of the dispersion of silica in the material.
• a suitable dispersion according to the invention generally corresponds to a ratio FS 5 ⁇ m / FV less than or equal to 4, preferably less than or equal to 3, advantageously less than or equal to 2, and more preferably less than or equal to 1.
• the surface fraction FS ⁇ m to which reference is made above can be measured under the following conditions:
• the surface block obtained is then observed by scanning microscopy for the evaluation of the macrodispersion.
• the microscope used is a SEM / FEG
• the digital images obtained are then processed by image analysis using the VISILOG software, according to the following steps:
• thresholding makes it possible to extract from the image all the pixels having a value in a given interval, it thus makes it possible to discriminate the particles within the matrix; binarization consists in assigning to each pixel of the image a numerical value (0 or 1) according to its membership in the matrix or the load (0 for the matrix, 1 for the load).
• Erosion / dilation An erosion of the image obtained by a structuring element of size 2.5 microns makes it possible to subtract from the image all the objects having a size smaller than 5 microns. A Expansion of the resulting image then makes it possible to reconstruct the image.
• the silicas S, S1, S2, S3, S4 and So that are useful according to the invention preferably have a BET specific surface area of between 60 and 300 m 2 / g, for example between 100 and 250 m 2 / g. , and especially between 150 and 200m 2 / g.
• the silicas S 1 S 1 , S 2 , S 3, S 4 and S 0 useful according to the invention preferably have a pH of between 6.3 and 7.8, especially between 6.6 and 7.5. This pH is that measured according to the ISO 787/9 standard (pH of a suspension of the silica tested at 5% in water).
• the silicas S, S1, S2, S3, S4 and So also have an intake of DOP oil that varies, for the most part, between 220 and 330 ml / 100 g, for example between
• the DOP oil uptake to which reference is made in the present description is determined according to standard NF T 30-022 (March 1953) using dioctyl phthalate.
• the silicas S, S1, S2, S3, S4 and S0 useful according to the invention are advantageously in the form of powders, preferably powders having an average size of at least 15 .mu.m, for example of between 15 and 60 ⁇ m (in particular between 20 and 45 ⁇ m) or between 30 and 150 ⁇ m (especially between
• the silicas S, S1, S2, S3, S4 and S 0 used according to the invention may also be in the form of substantially spherical beads of average size of at least 80 .mu.m.
• This average size of the beads may be at least 100 ⁇ m, for example at least 150 ⁇ m; it is generally at most 300 ⁇ m and is preferably between 100 and 270 ⁇ m.
• This average size is determined according to standard NF X 11507 (December 1970) by dry sieving and determination of the diameter corresponding to a cumulative refusal of 50%.
• the S silicas, S1, S2, S3, S4 and S0 above are particularly suitable as inorganic fillers to improve the stiffness material thermoplastic polymer, without decreasing the impact resistance, even by improving this impact resistance in some cases, and at the same time improving, at the same time, other characteristics, such as the tensile elongation of the material and the scratch resistance.
• thermoplastic polymer material is understood to mean a material comprising as majority constituent a thermoplastic polymer or a mixture of thermoplastic polymers, and generally behaving like a thermoplastic polymer.
• thermoplastic polymer material in the sense of the present description generally comprises at least 50% by weight of a thermoplastic polymer or a mixture of thermoplastic polymers, most often at least 75% by weight, for example at least 80% by weight. in bulk, and typically at least 90%, or even at least 95% by weight.
• thermoplastic polymer (s) and the silica used as a filler the thermoplastic polymer material may comprise other ingredients such as additives allowing the conservation or the proper use of the polymer, or additives to further improve the impact properties of the material (for example polymeric fillers or surface fillers treated with fatty acids).
• the silica of the invention may also be used in combination with other mineral fillers, such as other silicas, talc, wollastonite, kaolin, mica, calcium carbonate, glass fibers, and the like. or silicates.
• other mineral fillers such as other silicas, talc, wollastonite, kaolin, mica, calcium carbonate, glass fibers, and the like. or silicates.
• the presence of these additional agents may make it possible to further improve the effect of improving the rigidity desired according to the invention, and / or to improve other characteristics of the material, in particular the impact resistance.
• the use of the silica of the invention together with other mineral fillers may be advantageous for improving the scratch resistance of the material. Nevertheless, the presence of such additional components is not required to achieve the effect of improving the rigidity sought according to the invention.
• the silica of the invention is used as sole mineral filler in the thermoplastic polymer material.
• the silica used according to the invention does not generally require any surface treatment, in particular with organic molecules such as fatty acids, to ensure the effect of improving the rigidity of the invention.
• the polymeric material may comprise an additive chosen from silanes, fatty acids, phosphonic acids, titanates, polypropylene waxes, polyethylene waxes and / or maleic anhydride grafted polypropylenes, which makes it possible in particular to ensure better compatibility between silica (and any other mineral fillers present) and thermoplastic polymers.
• the silicas of the invention are particularly advantageous as mineral fillers in thermoplastic polymer materials based on one or more polymers chosen from polyolefins, polyamides (in particular polyamides 6, polyamides 66, polyamides 11, polyamides 12, polymetaxylylenediamines, mixtures and copolymers based on these polyamides), polyesters, poly (arylene) oxides, polyvinyl chlorides, polyvinylidene chloride, polyvinyl acetate, mixtures of these polymers and copolymers based on these polymers.
• polymers chosen from polyolefins, polyamides (in particular polyamides 6, polyamides 66, polyamides 11, polyamides 12, polymetaxylylenediamines, mixtures and copolymers based on these polyamides), polyesters, poly (arylene) oxides, polyvinyl chlorides, polyvinylidene chloride, polyvinyl acetate, mixtures of these polymers and copolymers based on these poly
• the silicas of the invention are particularly suitable for improving the impact resistance of thermoplastic polymer materials based on one or more polyolefins, and in particular on polymeric materials which comprise:
• a homopolyolefin selected from polyethylene, polypropylene, polybutylene, or poly (methylpentene); a copolymeric polyolefin based on at least two types of units chosen from ethylene, propylene, butylene and methylpentene units; or a mixture of two or more of said homopolyolefins and / or said copolymeric polyolefins.
• thermoplastic polymer material in which the silica filler according to the invention is incorporated is a material based on polypropylene or a copolymer of propylene and ethylene.
• the silica used as a filler according to the invention is generally in a content between
• thermoplastic polymer material including silica
• the incorporation of the silica into the material can be done by any means known per se for the incorporation of mineral fillers in a thermoplastic polymer matrix, provided that it leads to a dispersion of the silica as required according to the invention .
• this incorporation is preferably carried out by mixing under stress and the silica or polymeric material beyond their glass transition temperature, optionally in the presence of additives, for example thermal stabilizers of the type of I'IRGANOX ® B225 sold by the company Ciba, advantageously using devices of the internal mixer or extruder types.
• the invention also relates to thermoplastic polymer materials comprising a silica S, S1, S2, S3, S4, or SO, of the aforementioned type, as mineral filler improving their rigidity.
• the invention also relates to thermoplastic polymer materials of this type which comprise one or more polyolefins as a major constituent (namely constituting more than 50% by weight, generally at least 75% by weight, for example at least 90% or even 95% by weight of the material), and more specifically materials of this type comprising polypropylene as a major constituent.
• polyolefins as a major constituent
• the introduction of the silica of the invention as a mineral filler usually leads to obtaining polymeric materials having similar optical properties to the unfilled material, contrary to what is observed with most mineral fillers that lead to a change in the shade of the material, its transparency or its light scattering properties.
• the preservation of optical properties of the starting material is often such that the introduction of silica into the material does not lead to a change in the appearance of the material visually.
• the modification of the properties of the material can moreover be more accurately quantified, for example by spectro-colorimetry, from which it appears most often that the introduction of a silica according to the invention into a polymer material based on A polyolefin such as polyethylene leads at most to very slight changes in the properties of transparency, light transmission and coloring of the material.
• silica which is a silica with a BET specific surface area of greater than 5%, is used as the silica according to the invention.
• 100 m 2 / g which is obtained according to the method P as defined above in the present description.
• silica S to improve the impact resistance of a thermoplastic polypropylene material (incorporation of silica into the material by means of an internal mixer)
• Silica S has been used as a mineral filler for the improvement of the impact resistance of a polymeric material having the following Formulation (1) (the percentages given are percentages by weight relative to the total mass of the formulation ):
• the polypropylene used in this example is the polypropylene sold under the name PPH 4060 by the company Atofina (polypropylene homopolymer having a melt index (230 ° C. under 2.16 kg) of 3 g / 10 min).
• the thermal stabilizer is meanwhile I'1RGANOX ® B225 marketed by Ciba (mixed-based antioxidant phenolic compounds).
• the polymeric material incorporating the silica was prepared by introducing 35 g of polypropylene, 0.07 g of thermal stabilizer and 1.1 g of silica S into a Brabenber internal mixer initially heated to a temperature of 150 ° C., with a filling 0.7, where the tank of the internal mixer is provided with two rotors of type W50 for thermoplastic, rotating at a speed of 125 revolutions per minute.
• Part of the formulation thus obtained was molded by pressing into a parallelepiped mold of dimensions 100 mm ⁇ 100 mm ⁇ 10 mm, between two compression plates heated to 200 ° C., under a pressure of 200 bar (2.10 "3 Pa) for 2 minutes The mold was then cooled between the two plates brought to 18 0 C under a pressure of 200 bar for 4 minutes.
• the surface fraction FS 5 ⁇ m (the proportion of area occupied by the objects larger than 5 ⁇ m in the images obtained) was determined. by image analysis under the specific conditions defined above in the description.
• the surface fraction FS 5 ⁇ m thus measured is 4%.
• the volume fraction FV of silica in the material (ratio of the volume occupied by the silica in the material reduced to the total volume of the material) is 1.4% (mass fraction of 3%).
• the FS 5 ⁇ m / FV ratio of the material is therefore 2.93 in this example.
• the flexural modulus was measured under the conditions of ISO 178 at 23 ° C.
• silica S to improve the impact resistance of a polypropylene thermoplastic material (incorporation of silica into the material by means of an extruder)
• Silica S was used as a mineral filler for the improvement of the impact resistance of a polymer material having generally the same formulation as that of Example 2, but differing by the silica incorporation mode. More specifically, in this example, the polymeric material has the following Formulation (2):
• the incorporation of the silica in the material was carried out by introducing 2420 g of polypropylene, 5 g of thermal stabilizer and 75 g of silica S into a cube mixer and mixing for 10 minutes at 150 ° C., and then introducing the mixture. in a WERNER twin screw extruder ZSK30 (die), with a temperature profile in the extruder of 168 ° C / 168 O C / 182 O C / 188o C / 182 ° C, a speed of rotation of the screws co-rotating 230 rpm, and a feed rate of the constituents at the inlet adjusted to obtain a torque of 45% of the maximum torque of the extruder.
• the rod obtained on exiting the die was cooled and then cut into granules, then the obtained pellets were introduced into an injection mold ARBLJRG with a temperature profile of 180 ° C / 180o C / 180o C / 180o C / 40 ° C, and an injection pressure set at 55% of the maximum pressure of the machine, so as to form a polymer plate.
• the surface fraction FS 5 ⁇ m was determined by image analysis under the specific conditions defined above in FIG. the description.
• the surface fraction FS 5 .mu.m thus measured is, in this example, 5.5%.
• the volume fraction FV of silica in the material is 1.4% (mass fraction of 3%).
• the FS 5 ⁇ m / FV ratio of the material is therefore 4.
• the fracture energy was measured according to the Charpy impact test at 23 ° C. on a notched specimen, under the conditions of the ISO 179. Furthermore, a dumbbell test specimen was also cut out. to determine elongation at break in tension according to ISO 527.
• the dynamic scratch resistance properties of the material were also measured and a diamond stylet having an internal angle of 90 ° and a tip radius of 90 microns was moved on the surface of a sample of the material at the speed of 1 mm / s, applying a normal controlled force on the surface. This operation was carried out several times to make several scratches on the material with increasing applied forces (0.25N, 0.5N, 1N, 5N) until a scratch of at least 200 microns wide was obtained. being then analyzed using an ALTI SURF 500 profilometer to measure the topological characteristics of the stripes (depth, width, profile).
• L * luminance on a black background
• a * colorimetric index (red-green axis)
• b * colorimetric index (yellow-blue axis)
• contrast contrast black background / white background; reflects the light transmission properties

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