Classifications

• • 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
  • C09C1/36—Compounds of titanium
  • C09C1/3607—Titanium dioxide
  • C09C1/3653—Treatment with inorganic compounds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/69—Water-insoluble compounds, e.g. fillers, pigments modified, e.g. by association with other compositions prior to incorporation in the pulp or paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/675—Oxides, hydroxides or carbonates
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/28—Colorants ; Pigments or opacifying agents
  • D21H21/285—Colorants ; Pigments or opacifying agents insoluble

Definitions

• the subject of the present invention is a composition based on TiO 2 , useful as an opacifying agent in particular in laminated papers and a preparation process making it possible to obtain said composition.
• Laminated paper commonly called decorative paper, is the surface element with an opacifying and decorative function, used for the manufacture of laminated panels, intended for the furniture industry.
• a special feature of decorative paper is that it has an extremely high LO rate of TiO 2 , which can reach up to 40% of the mass of the dry sheet.
• print-write type papers can contain a maximum of 10%.
• Titanium dioxide is conventionally used for this application because it is the only white pigment that can provide the required levels of opacity due to its high refractive index.
• the sheets of paper are prepared from a mixture of cellulose fibers and mineral fillers, mainly TiO 2, dispersed in water. This mixture is contained in
• a "headbox” which feeds a canvas where the sheet is formed by drainage and filtration. During this filtration, the cellulose fibers are retained on the canvas as well as part of the mineral filler, whether or not in interaction with the entangled fibers. This gives the "fibrous mat” which, after drying, gives the sheet of paper.
• TiO 2 is retained in the fibrous mat and furthermore this fraction is generally too agglomerated for the TiO to be able to develop maximum opacity.
• papermakers generally introduce retention agents into their cellulose mixtures. These agents are conventionally cationic polymers which allow the fixation of TiO 2 particles on the fibers by phenomena of homo- and hetero-flocculation.
• the object of the present invention is precisely to propose a new composition based on TiO 2 which meets all of the requirements mentioned above.
• the inventors have thus demonstrated that a solution to the problem of agglomeration of the mineral filler consists in creating mixed mineral flocs by interposing between the TiO 2 particles particles, in the form of aggregates or not, of a agent known as inorganic spacer.
• the mixed mineral flocs obtained according to the invention are advantageous for several reasons:
• the internal cohesion of the mixed mineral flocs resulting from the association with TiO 2 of at least one inorganic spacer agent, is based on the solidity of ionic bonds established between TiO 2 and the spacer agent. This cohesion stems directly from the process used to prepare said mixed mineral flocs.
• these flocs are obtained under operating conditions such as TiO 2 and the inorganic spacer agent considered have opposite and significantly different surface charges.
• the TiO 2 and the inorganic spacer agent considered must have sufficiently different isoelectric points for there to be a pH range in which these two mineral species have opposite charges.
• the two mineral species manifest one towards the other an electrostatic attraction. The resulting attractive forces must be sufficient to lead on the one hand to a structural arrangement of the two compounds and on the other hand to stabilize them in this form.
• the first object of the present invention is a process for preparing a composition based on TiO 2 , useful as an opacifying agent, characterized in that it comprises the steps according to which:
• An aqueous dispersion of at least one inorganic spacer agent is mixed with an aqueous dispersion of TiO 2 , the mixture of the two dispersions being carried out with stirring and at a pH between the respective isoelectric points of said TiO 2 and spacing agent and chosen in such a way that said TiO 2 and spacing agent have opposite surface charges and sufficiently different to conduct, under the effect of electrostatic forces, in their arrangement in mixed mineral flocs in which the TiO 2 particles are globally spaced from one another by particles and / or aggregates of the spacer agent;
• the pH is regulated at the value fixed in step 1,
• the resulting aqueous dispersion of mixed mineral flocs is matured at a temperature sufficient to strengthen the solidity of the bonds established between the TiO 2 particles and the particles and / or aggregates of the spacing agent, - said composition is recovered in the form of an aqueous dispersion of mixed mineral flocs and
• composition is formulated in a dry form.
• FIG. 1 gives a schematic representation of the structure of mixed mineral flocs obtained according to the invention. It is confirmed by the transmission electron microscopy image presented in Figure 2.
• floc is intended to denote mixed agglomerates of two mineral species of the TiO 2 type and inorganic spacer agent such as SiO 2 for example. These agglomerates result from the association between aggregates of said spacer agent and TiO 2 particles.
• a spacer is made up of particles or aggregates of particles which are interposed between the TiO 2 particles.
• the isoelectric point corresponds to the pH for which the particle of the mineral species considered has a generally zero surface charge. For a pH higher than this value, the charge is generally negative and for a lower pH, the charge is generally positive.
• the TiO 2 used according to the invention is preferably a rutile TiO 2 . More preferably, it is a rutile TiO 2 of pigmentary size.
• this surface treatment comprises at least one compound chosen from alumina, silica, zirconia, phosphate, cerium oxide, zinc oxide, titanium oxide and their mixtures.
• the amount of oxide (s) can be of the order of 1 to 20% by weight or less or preferably of the order of 3 to 10% by weight or less, relative to the total weight of the pigment.
• titanium dioxides By way of illustration of these titanium dioxides, mention may be made in particular of the two rutile pigments Rhoditan RL18 and RL62 *, sold by Rhône-Poulenc. These two pigments are differentiated by the composition of their surface treatment and the resulting Zeta potentials.
• RL 18 has a silica-alumina surface treatment (SiO 2 / AI 2 O 3 ) and a negative Zeta potential at pH 6, it is called “anionic TiO 2 ".
• RL62 has a phosphate-alumina (P 2 Os AI 2 O 3 ) surface treatment with a positive Zeta potential at pH 6, it is called “cationic TiO 2 ".
• the choice of pH 6 is close to the industrial implementation pH.
• the choice of TiO 2 , anionic or cationic conditions the choice of the inorganic spacer agent associated with it.
• an inorganic spacing agent is chosen having an isoelectric point sufficiently different from that of the TiO 2 considered so that the electrostatic attractions between the two compounds which are necessary for their arrangement can manifest themselves.
• the aqueous dispersion of TiO 2) used according to the invention comprises approximately 5 to 80% by weight of TiO 2 and preferably approximately 5 to 40%.
• the limiting point is the viscosity of the suspension which must remain at a reasonable value to be easily manipulated.
• the TiO 2 selected is a cationic pigmented rutile TiO 2 and in particular Rhoditan RL62.
• the inorganic spacing agents considered according to the invention they must not interfere with the other reagents conventionally used in the paper industry.
• they do not significantly absorb visible light.
• the size of their particles is smaller than that of the TiO 2 particles .
• these particles are preferably arranged in the form of aggregates whose size is then greater than those of the TiO 2 particles.
• Preferably these aggregates have a size of between approximately 0.5 and 2 ⁇ m.
• inorganic spacing agents which can be used according to the invention, mention may in particular be made of oxides of silicon, titanium, zirconium, zinc, magnesium, aluminum, yttrium, antimony, cerium and tin; barium and calcium sulfates; zinc sulfide; zinc, calcium, magnesium, lead and mixed metal carbonates; aluminum, calcium, magnesium, zinc, cerium and mixed metal phosphates; titanates of magnesium, calcium, aluminum and mixed metals; magnesium and calcium fluorides; silicates of zinc, zirconium, calcium, barium, magnesium, mixed alkaline earth and silicate minerals; alkali and alkaline earth aluminosilicates; calcium, zinc, magnesium, aluminum and mixed metal oxalates; zinc, calcium, magnesium and alkaline earth aluminates; aluminum hydroxide and their mixtures.
• this spacing agent is made so that it has a sufficient isoelectric point difference with the TiO 2 form used.
• inorganic spacing agents which are particularly suitable for the present invention, mention may be made of inorganic oxides which are preferably chosen from oxides of silicon, zirconium, aluminum, antimony, cerium and tin and their mixtures.
• this inorganic spacer agent is preferably a silica, an alumina, a silicoaluminate or one of their mixtures.
• the ratio between TiO 2 and the spacing agent it is of course variable depending on the nature of the spacing agent retained.
• the lower limit of this ratio is constituted by the minimum quantity of inorganic spacer agent which is necessary to observe a positive effect at the level of the opacifying yield and its upper limit by the maximum quantity of spacer agent beyond which effects undesirable would appear on the paper incorporating the composition obtained according to the claimed process.
• These undesirable effects can in particular result in a fragility of the paper, in particular in terms of resistance, whether in the dry state or in the wet state.
• This spacing agent can generally be used in an amount of approximately 1 to 40% relative to the weight of TiO 2 , preferably in an amount of approximately 5 to 15% by weight and more preferably in an amount of approximately 10% by weight. weight.
• these two compounds are brought into contact in the form of corresponding aqueous dispersions, under operating conditions such as are produced by heterocoagulation of TiO 2 with the particles and / or aggregates of particles of the inorganic spacer agent, mixed mineral flocs.
• the spacer can also be precipitated in situ. In this case, the pH adjustment conducive to heterocoagulation will be made after the precipitation agent precipitation step.
• the isoelectric points of the spacer agent and of the TiO 2 be spaced by at least one pH unit.
• the mixed mineral flocs making up the expected composition therefore form with stirring of said dispersions, generally at room temperature and at a pH as defined above. If necessary, it may be necessary to adjust the pH during the reaction in order to maintain it at a value suitable for the formation of said flocs.
• TiO 2 is used in a cationic pigmented rutile form and preferably is RL62, and the associated spacer agent is silica.
• the silica used is a silica with a large specific surface, in particular between around 20 and 300 m 2 / g. It can be in the form of aggregates of sizes between approximately 0.5 and 10 ⁇ m.
• silica as a spacer agent in accordance with the present invention is advantageous for several reasons.
• silica has the advantage of not significantly adsorbing visible light, which is favorable in terms of the whiteness of the sheet.
• the pH for bringing the two corresponding dispersions into contact is between the isoelectric points of the spacer agent and of TiO 2 .
• the upper limit is imposed by the isoelectric point of the TiO 2 considered and the lower limit should be imposed by the isoelectric point of the spacing agent concerned.
• this pH should be between 2 and 6.5.
• the pH range will be limited between 4.5 and 6.5. More preferably, the process according to the invention is carried out at a pH of the order of 5.5.
• the silica is used in an amount of at least 1% by weight relative to the weight of TiO 2 .
• silica is preferably used at a rate of approximately 5 to 15% by weight of the weight of TiO 2 and more preferably at a rate of 10% by weight.
• the silica can be introduced either in the form of an aqueous dispersion of silica particles of the slurry type or can be generated in situ by acidification of a solution of silicates.
• the pH of the reaction medium is adjusted after the precipitation stage to a value conducive to the manifestation of electrostatic forces between TiO 2 and the silica thus generated. These forces are therefore necessary for their heterocoagulation.
• the second step required according to the claimed process in fact corresponds to an operation of ripening the mixed mineral flocs formed in the previous step.
• the mixed mineral flocs obtained according to the claimed process are in particular intended to be used as an opacifying agent in the paper industry. This implies a whole series of manipulations of said flocs.
• the TiO 2 particles present in the composition obtained according to the invention are not only sufficiently dispersed to improve their opacity yield, but also better retained during the formation of the sheet. Consequently, the ripening operation carried out according to the claimed process proves to be particularly advantageous for reinforcing the chemical or even steric interactions established within the mixed mineral flocs. It is moreover likely that some of the ionic bonds are converted into covalent bonds at the end of this ripening step.
• this ripening step is performed at a temperature above 40 ° C.
• the temperature is between about 60 ° C and 100 ° C.
• the duration of the heating it is at least 30 minutes and if necessary can be extended up to three hours.
• the resulting composition is left to cool to room temperature and can be recovered as it is.
• composition can be used directly in this form as an opacifying agent.
• the flocs agglomerate on drying it is preferable to deagglomerate the product by an air jet grinding step.
• the mixed mineral flocs obtained at the end of the first or of the second step of the process can undergo a mineral surface treatment.
• This comprises at least one hydrated oxide as defined above. The latter can be precipitated from the reaction medium after bringing into contact the dispersions of TiO 2 and the spacer agent.
• the mineral surface treatment represents approximately 16% by weight or less or preferably of the order of 10% by weight or less, relative to the total weight of the mixed mineral flocs thus treated.
• the present invention extends to compositions based on TiO 2 which can be obtained according to the claimed process.
• SiO 2 characterized in that the particles of TiO 2 and SiO 2 are arranged therein in the form of mixed mineral flocs in which the particles of TiO 2 are generally spaced from one another by aggregates of said silica.
• These mixed mineral flocs of TiO and SiO 2 are stabilized thanks to electrostatic forces established between the particles of TiO 2 and the aggregates of SiO 2 .
• this stability of the mineral flocs is reinforced by the fact that they undergo a ripening as described above. This ripening operation in particular contributes to creating covalent bonds between TiO 2 and SiO 2 within the flocs.
• the TiO 2 is preferably a rutile TiO 2 of pigment size.
• This surface treatment can be chosen from phosphate, alumina, silica, zirconia, cerium oxide, zinc oxide, titanium oxide and their mixtures.
• the amount of oxide (s) can be of the order of 1 to 20% by weight or less or preferably of the order of 3 to 10% by weight or less, relative to the total weight of the pigment.
• the TiO 2 is preferably a rutile TiO 2 cationic pigment.
• the TiO 2 is RL62.
• the silica used is a silica with a large specific surface, in particular between around 20 and 300 m 2 / g. It is in the form of aggregates of sizes between approximately 0.5 and 10 ⁇ m.
• the silica is preferably a precipitation silica. It can also be a silica generated in situ by acidification of a silicate solution.
• the silica is preferably present in an amount of about 1 to 20% by weight of the weight of TiO 2 and more preferably in an amount of about 5 to 15% by weight and more preferably 10%.
• these mineral flocs based on TiO 2 and SiO 2 can be coated with at least one mineral surface treatment as defined above.
• the amount of mineral surface treatment can be of the order of 16% by weight or less or preferably of the order of 10% by weight or less, relative to the total weight of the mixed mineral flocs.
• compositions as defined above or obtained according to the invention prove to be advantageous for the preparation of paper including laminated paper and very particularly advantageous in terms of retention at the level of the cellulose fibers and of opacity yield of TiO 2 used.
• the conventional processes for preparing laminated paper or decor paper generally use, in addition to cellulose fibers of anionic nature, and the opacifying agent, a polymeric agent of cationic nature playing the role of reinforcing agent in the state moist and retention agent.
• compositions based on mixed mineral flocs claimed and obtained according to the invention are particularly advantageous as an opacifying agent and in particular in the paper industry.
• the gain in opacity measured on the sheets prepared using a composition based on mixed mineral flocs according to the invention clearly results from the combination of two phenomena: the increase in the quantity of TiO 2 retained on the sheet. , resulting from better retention at the time of the formation of the fibrous mat, and the improvement of the opacity yield resulting from the better dispersion of the titanium particles contained in said flocs.
• these compositions favor the whiteness of the paper incorporating them.
• the compositions claimed and obtained according to the invention are also advantageous as an opacifying agent in the paints and plastics industries.
• Figure 1 schematic representation of TiO 2 pigments spaced apart by SiO 2 aggregates.
• Figure 2 electron microscopy image in transmission of mixed mineral flocs based on TiO 2 and SiO 2 .
• Figure 3 evolution of charge retention for different mixed minerals as a function of the stirring speed imposed on the "cellulose / PAE / charge" mixture before formation of the fibrous mat.
• the products used are commercial products:
• the titanium dioxide used in the examples is rutile titanium dioxide sold under the name of Rhoditan RL62 by the company RHONE-POULENC.
• This pigment consists of rutile TiO 2 coated by a phosphate alumina surface treatment (P 2 Os AI 2 O 3 ). At pH 6, its zeta potential is positive. Its isoelectric point is located around 6.5-7.
• Cellulose fibers dry leaves of a 70/30 mixture of short fibers / long fibers previously refined at 35 ° SR, supplied by the company ARJO WIGGINS.
• Silica is a precipitation silica with a large specific surface area between 20 and 300 m 2 . g "1 and having agglomerates of sizes between 0.5 and 10 ⁇ m. Its isoelectric point is around 2.
• test portion of the well homogenized mixture is drawn off in a test tube.
• the test tube is inverted 2 times to mix well. This test portion is then introduced into the retention form to obtain a sheet.
• the formation of the sheet is triggered after a stirring time of 30 s at a speed of 1300 rpm followed by a rest time of 1 s.
• the sheet obtained is recovered on the canvas in the form of a "paton”, dried in an oven and then calcined at 800 ° C. The ash obtained is then weighed to the nearest 10 g.
• the retention rate is given by: P2 / P1.
• P1 weight of fillers (TiO 2 + SiO 2 ) in an initial sample of 500 ml
• P2 weight of ash after calcination of the prepared sheet.
• the opacity yield tests were carried out using manufactured formulas in order to know the spatial distribution of titanium dioxide in the dry sheet.
• optical properties of the impregnated and pressed form were also measured according to the method described below.
• Opacifying composition 100 parts (expressed as TiO 2 ) or 15 g
• PAE 0.8% dry compared to cellulose
• Cellulose is torn by hand into small squares after moistening it with water.
• the small cellulose squares are gradually added to 500 ml of water with stirring in the Dispermat bowl at 1000 rpm. After adding the cellulose, the speed is increased to 3000 rpm and left to stir
• the defibrated cellulose is diluted to 1 liter. Then, it is stirred in a mixer with paddle.
• the opacifying composition is added in the form of a powder or a suspension and then the mixture is stirred for 5 min.
• test tube 500 ml of well homogenized suspension are taken in a test tube. PAE is added (commercial solution diluted 10 times to have an acceptable intake volume), ie 1 ml. The test tube is turned over several times to mix well.
• test tube The contents of the test tube are poured into the bowl of the form filler filled with 6 liters of distilled water. It is mixed by bubbling for 10 s, it is left to stand for 10 s, then the form is made by drawing under vacuum. The form is then collected on a cardboard support, then placed in a vacuum dryer for 7 min.
• a sheet has the desired grammage and has no manufacturing defect, it is selected for the subsequent operations, that is to say, chemical and optical characterizations.
• the amount of TiO 2 present in the sheet of 80 g / m 2 is measured by calcining a third of the form at 800 ° C for one hour.
• the percentage of TiO 2 present in the sheet is thus calculated:
• the ash rate measures the quantity of mineral fillers present in the sheet. This determination is made according to the method NF 03- 047 (Collection of French Standards Paper, cardboard and paste: test method, volume A, 4 th "16th edition, 1985).
• Strips of paper 7 cm by 10 cm are cut. The strips are then impregnated by capillary action by placing them for 1 minute on the resin. It is expressed between two glass rods and dried for 2 minutes in an oven at 120 ° C.
• the strips are impregnated a second time by immersion in the resin for 1 min.
• These sheets are fixed on a support made up from the bottom of 2 white barriers and 3 kraft barriers, the form being in direct contact with the kraft barriers.
• the laminates obtained are pressed for 8 min at 150 ° C. under a pressure of 100 bars.
• the opacity measurements on the laminates are made by evaluating the contrast ratio, for each of the papers to be tested, between the area on a kraft background and the area on a white background, using the "opacity of the Elrepho 2000 spectrocolorimeter company DATACOLOR.
• RL 62 is used in the form of an aqueous suspension grading 40 g / l.
• the mineral flocs are produced by heterocoagulation of the TiO 2 particles with the silica aggregates.
• the heterocoagulation process consists in adding the silica slurry to a regulated pH in a stirred base stock containing the suspension of TiO 2 .
• the pH is regulated by simultaneously adding an HCl solution to the silica slurry. This operation takes place at room temperature.
• the final suspension contains 10% by mass of silica relative to the content of pigment TiO 2 and the overall dry extract (TiO 2 + SiO 2 ) is approximately 11%.
• the suspension After contact for 15 minutes at a regulated pH of 5.5, the suspension, still stirred, is brought to a temperature between 60 ° C. and the boiling temperature for 1 to 3 h and then cooled to room temperature. All the samples prepared according to this protocol, were tested by preparing formulas (round sheet). For all the tests, the volume of "fiber + filler + PAE" mixture taken from the mixing tank was adjusted so as to obtain sheets of the same grammage: 80 g / m 2 .
• the other part of the form is impregnated with resin and pressed so as to obtain a laminated paper whose opacity and whiteness are then measured.
• the impregnation and opacity measurement protocols are also described above.
• Table 2 below also reports the results obtained with a control composition 1 (T1). This is prepared by simply mixing the silica and the TiO 2 .
• ⁇ cen gain in ash rate resulting from better retention of
• compositions according to the invention can use less TiO 2 while retaining the same level of opacity as a conventional formulation without silica since the mixed minerals improve the ash rate and the opacity yield.
• the potential gain in TiO 2 can be estimated by evaluating the gain in ash rate corresponding to an opacity gain equal to the opacity yield. This value compared to the rate of ash from the silica-free tests corresponds to the percentage of TiO 2 which can be saved while remaining at the same level of opacity as the control test. Under these conditions, the use of a mineral mixture containing 10% of silica should make it possible to save at least 7 to 10% of TiO 2 while retaining the same level of opacity as a conventional formulation without silica.
• Product C TiO 2 Rhoditan RL18 15
• Product D TiO 2 Rhoditan RL62.
• FIG. 3 shows the evolution of the charge retention for different compositions as a function of the stirring speed imposed on the "cellulose / PAE / filler" mixture before formation of the fibrous mat.
• the ripening stage is therefore a stage necessary for the formation of effective mixed mineral flocs.
• the whiteness of the laminated sheets was measured for each test. The results are collated in Table 4 below.
• the whiteness measurements were carried out according to the CIE I * a * b * scale, on an ELREPHO 2000 * spectrocolorimeter from the company DATACOLOR.
• compositions according to the invention improves the whiteness of the laminated sheet and this all the more so as the silica content increases.
• silica we measure a gain of around 0.2 point in L * and especially a reduction in b * from 0.4 to 0.6 point.
• Such a decrease in b * gives a pronounced blue undertone to the laminated sheet and reinforces the impression of whiteness.
• the heterocoagulation is carried out according to the method described in Example 1.
• the product is dried in a thin layer (15 h in an oven at 150 ° C ).
• the product obtained is divided into two parts: one is used as it is while the other is subjected to air jet grinding (micronization).
• RHODITAN RL62 put in slurry at 40%.
• the formulation used is as follows:
• Cellulose fiber 100 parts (15 g) Opacifying pigment: 100 parts (15 g) PAE resin: 0.8% dry / fibers

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Organic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Paper (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Silicon Compounds (AREA)
• Colloid Chemistry (AREA)
• Medicines Containing Material From Animals Or Micro-Organisms (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)
• Paints Or Removers (AREA)

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• 1997
  • 1997-12-30 FR FR9716709A patent/FR2773167A1/fr not_active Withdrawn
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  • 1998-12-24 WO PCT/FR1998/002877 patent/WO1999035193A1/fr not_active Application Discontinuation
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  • 1998-12-24 CN CN98813310.5A patent/CN1284103A/zh active Pending
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• 2000
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