FR2831179A1 - Production of a pigment composition, useful as a coloring filler, comprises contacting silica particles with a coupling agent in an aqueous medium and reacting a dye with the coupling agent - Google Patents

Abstract

Production of a pigment composition, comprises: (1) contacting silica particles with a water-soluble coupling agent in an aqueous medium; and (2) reacting a water-soluble dye with the coupling agent. An Independent claim is also included for a pigment composition.

Description

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 The present invention relates to a process for the preparation of pigment compositions comprising silica-based particles on the surface of which coloring agents are immobilized. It also relates to the pigment compositions obtained according to this process, as well as their use as coloring fillers in various media, such as cements, cosmetic or pharmaceutical compositions, or even polymer matrices.

composition comprenant au moins une espèce chimique (je plus souvent un agent de type colorant) immobilisée sur un support (notamment de type oxyde métallique) se présentant généralement sous forme de particules de dimensions réduites. Generally, the term "pigment composition" means a

composition comprising at least one chemical species (I more often a coloring agent) immobilized on a support (in particular of metal oxide type) generally being in the form of particles of reduced dimensions.

 Such compositions are known from the state of the art and are widely used, in particular in the field of paints and inks. The advantages presented by the use of a pigment preparation compared to a coloring agent used in the raw state are multiple. Thus, it allows in particular an improvement in the coloring force, generally associated with a stabilization of the coloring agent, in particular with regard to light, heat and / or oxidation. The passage from a coloring agent to a pigmentary preparation is also often used to make certain water-soluble dyes insoluble, which in particular makes it possible to improve their dispersibility within aqueous compositions, in particular in inks.

 However, in addition to these advantages, one of the main problems with which we are confronted with pigmentary compositions is that of disgorging, that is to say the at least partial release over time of the coloring compound immobilized on the support.

 To avoid this type of problem, attempts have been made to improve the connection of the dye compound immobilized with respect to the support. In the context of the use of silica-based supports, it has in particular been proposed to use coupling agents, such as amino-silanes by

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 example, so as to ensure effective cohesion between the silica support and the coloring agent, by creating covalent bonds. For more information on this subject, reference may in particular be made to US patents 5,378, 574, US 5,576, 888 or even US 4,204, 871.

 The use of such coupling agents proves to be advantageous in terms of improving the stability of the fixing of coloring agents on the surface of silica-based particles. However, the methods currently known using this type of coupling agents involve the use of organic solvents, which are found in trace amounts in the pigment compositions produced according to these methods.

 Pigment compositions having such traces of solvent are generally used in inks, where the presence of residual solvent is generally of no consequence. However, this presence of solvent poses more problems when it is sought to introduce these pigmentary compositions into other types of formulations, such as cosmetic or pharmaceutical compositions or polymer or elastomeric matrices, where, even when present in trace amounts, an organic solvent can prove to be an unacceptable pollution.

 However, unexpectedly in view of the teaching of the state of the art, the inventors have now discovered that, in the context of the use of coupling agents such as amino-silanes, it is possible to carry out pigment compositions having very good stability, without having to use an organic solvent, that is to say by using an exclusively aqueous medium during the preparation process, subject to using water-soluble coloring agents in the preparation process.

 Even more surprisingly, the inventors have demonstrated that by adapting the reaction conditions of coupling agents of the amino-silane type on silica-based particles, the preparation of pigment compositions can be carried out with increased efficiency. compared to the processes of the prior art carried out in the presence of organic solvents. This improvement in reaction yield, associated

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 the use of water as a solvent, is reflected in particular in terms of lower production costs. The inventors have obtained, by these processes carried out in an aqueous medium, pigmentary compositions which are extremely advantageous in terms of the stability of the fixed agent, and which are not polluted by organic solvents. The work carried out by the inventors with regard to these pigment compositions has also made it possible to demonstrate that these compositions make it possible to color many media, both hydrophilic in nature and hydrophobic in nature.

 On the basis of these discoveries, the present invention aims to provide a new process for the preparation of pigment compositions which is both simple to use and economical.

 Another objective of the invention is to produce pigmentary compositions having the lowest possible bleeding tendency, by using coupling agents of the amino-silane type, but without using organic solvents.

 The invention also aims to provide pigment compositions which can play the role of coloring filler in many formulations, and in particular within cement compositions, within cosmetic or pharmaceutical compositions, or even within polymer matrix or elastomers.

 Thus, according to a first aspect, the subject of the present invention is a process for the preparation of a pigmentary composition, consisting in immobilizing water-soluble coloring compounds and having at least one reactive chemical function R, on silica-based particles, by means water-soluble coupling agents having: (i) at least one chemical function Rs capable of inducing a strong chemical bond between said coupling agents and the surface of the silica-based particles; and (ii) at least one chemical function Rc capable of reacting with the reactive chemical functions R present on the coloring agents for

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 lead to the formation of strong bonds, generally of covalent, complexing or electrostatic nature, and advantageously of covalent nature, between the coupling agents and the coloring agents, said process specifically comprising the steps consisting in: (A) bringing into contact, in said coupling agents and said silica-based particles, an aqueous medium and generally free from any organic solvent, whereby an aqueous medium is obtained comprising silica-based particles on the surface of which coupling agents are immobilized by the 'through their Rs function; and (B) adding said coloring agents to the aqueous medium, whereby strong, advantageously covalent bonds are formed between the coupling agents and the coloring agents, which leads to immobilization of at least part of the coloring agents on silica-based particles, through the coupling agent; and (C) recovering the silica-based particles grafted with the coloring agents thus obtained.

 Generally, step (B) of the method of the invention is implemented after completion of step (A). A process using the addition of all or part of the coloring agents of step (B) together with the immobilization of the coupling agents of step (A) is not however excluded from the scope of the present invention. .

 Within the meaning of the present description, the term “silica-based particle” is intended to denote any solid particle, generally of isotropic or anisotropic morphology (for example of substantially spherical shape, or in the form of rods or platelets), comprising an oxide of silicon Si02, this oxide, which may or may not be the majority constituent of the particle, generally being at least partially

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 accessible on the surface of the particle. The silica particles used according to the present invention are preferably precipitation silica particles.

 Thus, the silica particles used in the process of the invention can be particles comprising at least one other mineral oxide, for example titanium oxide, alumina, covered by a layer of silica.

 According to a specific variant, the silica particles used in the process of the invention can be so-called “doped” silica particles, comprising, in particular at the surface, metal cations, advantageously chosen, if appropriate, from the cations divalent metals (such as beryllium, magnesium, calcium, strontium, barium, radium, zinc, cadmium and / or platinum, for example), trivalent metal cations (in particular boron, aluminum cations (very preferred cation), gallium, indium, thallium, nickel, cobalt and / or rhodium), tetravalent metal cations (titanium, zirconium and / or cerium cations, for example), or among mixtures of these different cations. Such particles can in particular be obtained according to the methods described for example in EP 345 116, EP 762 991, EP 762 992, EP 762 993, EP 767 758, EP 1 046 690, or US 4,360,388.

 The term "coloring agent" designates, within the meaning of the invention, a chemical compound having absorption or emission properties in the field of visible light. By extension, it is also possible to denote by "coloring agent" a compound exhibiting absorption, emission or re-emission properties in a wider range, ranging from near ultra-violet to near infrared, ie in a wavelength range generally from 280 to 3000 nm.

dissolution à chaud) au moins égale à 25 g/l, et de préférence supérieure à 50 g/i. Typically, the coloring agents used according to the process of the invention are water-soluble agents. Thus, they generally have a solubility in water at 25 C (after a possible

hot dissolution) at least equal to 25 g / l, and preferably greater than 50 g / i.

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 Another characteristic of the coloring agents of the invention is the presence of a reactive function R capable of reacting with the function Rc of the coupling agent. In the following description, the functions R and Rc will generally be designated by the term "complementary functions".

 A "coupling agent", within the meaning of the present description, is itself a chemical, molecular or ionic compound, having the chemical functions Rs and Rc as defined above. Apart from this characteristic, the nature of the coupling agents of the invention can vary to a fairly large extent, it being understood, however, that the coupling agents of the invention must not have chemical functions such as to attack chemically the particles based on of silica, or of a nature to affect the coloring character of the coloring agents. Thus, it is in particular preferable that the reaction of the chemical function Rc of the coupling agent with the function R of the coloring agent does not modify the coloring character of the coloring agent.

 The "strong chemical bond" existing between the coupling agents and the silica-based particles is generally a covalent, complexing, or electrostatic bond. Whatever its exact nature, this bond is generally such that, if the particles from step (A) are subjected to washing with water at the rate of 30 ml of water per gram of grafted particles, less than 5% of the grafted species, advantageously less than 2% of the grafted species, and preferably less than 1% of the grafted species are found in the free state in the washing waters obtained.

 According to an advantageous embodiment of the process of the invention, the chemical function Rs present in the coupling agents used, is a silane function, and advantageously a function - SiR1R2R3, where R \ R2 and R3 each represent a group capable of being hydrolyzed in the form of an —OH group. Thus, each of the groups R1, R2 and R3 can, for example, denote a halogen atom (in particular CI, Br, 1 or F), or a group -Or, where r denotes an alkyl group or an aryl group. Such a function is capable of reacting with silica so as to form covalent Si-O bonds between the

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 silica-based particles and coupling agents. Generally, according to this embodiment, the pH of the aqueous medium of step (A) is between 5 and 14, and preferably between 7 and 10, and the implementation temperature of step (A) is generally between 20 and 98 C.

 In the context of this particular embodiment, the coupling agents having the silane function can, during step (A), be brought into contact initially with the silica-based particles at a temperature T1 below 50 ° C. , generally between 15 and 40 C, and advantageously of the order of 20 C, following which the temperature of the medium is raised to a temperature T2 generally greater than or equal to 70 C, and advantageously greater than or equal to 80 C According to another possibility, generally implemented, step (A) is carried out throughout its duration at a temperature greater than or equal to 50 ° C., and preferably greater than or equal to 75 ° C.

 According to another conceivable mode of implementation, the silica particles used specifically have metal cations on the surface, in particular of the type of the aforementioned preferred divalent, trivalent and / or tetravalent metal cations, and the chemical function Rs of the coupling agents. generally used is an anionic group, this group preferably being a carboxylate group or a sulfonate group.

2+ 21 ou tétravalents, tels que Ca2+, Zn2+, ou A ! , et la quantité de cations métalliques présents à la surface des particules à base de silice est alors avantageusement comprise entre let 30 cations par nm2, typiquement entre let 10 cations par nm2, et cette quantité est de préférence supérieure à 2 cations par nm2, et avantageusement supérieure à 3 cations par nm2 Les particules de silice mises en oeuvre dans ce cadre peuvent notamment être This embodiment leads to a binding of the binding agents by electrostatic bonding or complexing on the surface of the silica-based particles. In particular so that this connection is as high as possible, the metal cations present on the surface of the silica-based particles are generally chosen from divalent, trivalent cations

2+ 21 or tetravalents, such as Ca2 +, Zn2 +, or A! , and the quantity of metallic cations present on the surface of the silica-based particles is then advantageously between 30 cations per nm2, typically between let 10 cations per nm2, and this quantity is preferably greater than 2 cations per nm2, and advantageously greater than 3 cations per nm2 The silica particles used in this context can in particular be

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 particles as described in EP 345 116, EP 762 991, EP 762 992, EP 762 993, EP 767 758, EP 1 046 690, or US 4,360,388.

 According to yet another possible implementation mode, the silica-based particles used specifically have metal cations on the surface, and the chemical function Rs present in the coupling agents used, is a phosphonic group - PO (OH ) 2, a phosphine group = PO (OH) or a phosphoric group-O-PO (OH) 2. This mode of implementation ultimately leads to a binding of the binding agents by covalent bond to the surface of the particles based silica, generally of type (particle) -Si-O- (metal) -OP- (coupling agent). In this case, the metal cations present on the surface of the silica-based particles are generally chosen from divalent, trivalent or tetravalent cations, such as Ca2 +, Zn2 +, or A13 + and the quantity of metal cations present on the surface of the particles to be silica base is then advantageously between 1 and 10 cations per nm2, and preferably greater than 5 cations per nm2. The silica particles used in this context can in particular be particles as described in EP 345 116, EP 762 991, EP 762 992, EP 762 993, EP 767 758, EP 1 046 690, or US 4,360,388.

 In general, step (A) of the process of the invention is advantageously carried out by using a quantity of coupling agent calculated as a function of the surface of silica developed by the particles present. It should in fact be noted that, unlike the methods of the state of the art, the method of the invention leads to an excellent yield during the grafting step, and there is therefore no need to use a excess coupling agent, as is generally the case in other methods, which, again, is reflected in terms of reduced cost of implementation.

 The nature of the complementary chemical functions R and Rc present respectively on the coloring agents and the coupling agents can vary to a fairly large extent. However, we generally prefer

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que la fonction chimique réactive R présente sur les agents colorants et la fonction chimique Rc des agents de couplage soient des fonctions choisies parmi les couples (Rs/R) suivants : (amine 1 fonction halogénée), (fonction halogénée/amine), (alcool/isocyanate), (isocyanate/alcool), (thiol halogène), (halogène/thiol), (amine/aldéhyde), ou (aldéhyde 1 amine).

that the reactive chemical function R present on the coloring agents and the chemical function Rc of the coupling agents are functions chosen from the following pairs (Rs / R): (amine 1 halogenated function), (halogenated / amine function), (alcohol / isocyanate), (isocyanate / alcohol), (halogen thiol), (halogen / thiol), (amine / aldehyde), or (aldehyde 1 amine).

 A specific embodiment of the process of the invention, which proves to be particularly advantageous, consists in using coupling agents of the amino-silane type (where Rs = silane and Rc = primary or secondary amine), and coloring agents having a reactive chemical function R of halogenated function type, preferably a radicål-Cl or-Br. Preferably, the reactive chemical function R present on the coloring agents is a halogen radical carried by an aromatic nucleus, such as a halogen present on a cycle or heterocycle of the benzene, naphthalene, anthraquinone type, and preferably on a triazine.

 In the context of this specific embodiment, it is particularly advantageous to use coupling agents corresponding to the following formula (1): (r10) (r20) (r30) Si-Ra-NH-r4 in which: - the radicals r1, r2, r3 and r4, identical or different, each represent a hydrogen atom or an alkyl or aryl group having from 1 to 8 carbon atoms; and the radical Ra represents an alkylene group comprising from 1 to 18 carbon atoms.

 According to this specific embodiment, the amount of amino-silane coupling agents introduced during step (A) is generally between 1.10-5 and 2.10-5 moles per m2 of silica surface. available, this available silica surface is calculated from the BET specific surface of the silica used, as measured according to the method

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 BRUNAUER-EMMET-TELLER described in the Journal of the American Chemical Society, vol. 60, page 309 (February 1938).

 Generally by implementing this specific embodiment, it can be seen, in particular by an analysis of the carbon dosage type that, at the end of step (A), more than 80% (advantageously more than 95% and again more preferably more than 97%) of the amino silane introduced is covalently bonded to the surface of the silica. In particular in this context, the quantity of coloring agents added during step (B) is advantageously such that, in the reaction medium, the molar ratio of the quantity of R functions provided by the coloring agents compared to the quantity of Rc functions provided by the coupling agents is of the order of 1: 1 in moles.

Generally this ratio is between 1: 2 and 2: 1 in moles.

 As already pointed out, the process of the present invention makes it possible to obtain pigmentary compositions having a very low tendency to disgorging, and they are most often free of any trace of organic solvent. These particular pigment compositions constitute another object of the present invention.

 In particular, taking into account their disgorging resistance, the pigment compositions obtained according to the process of the invention can advantageously be used as coloring fillers in numerous media, and in particular in cement compositions, in cosmetic or pharmaceutical formulations, or even within polymer or elastomeric matrices. This use constitutes yet another object of the invention.

 The various characteristics and advantages of the present invention will appear even more clearly in the light of the various examples of implementation set out below.

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Example 1: Preparation of a Red Pigment Composition Based on Silica - Preparation of a Silica Cake (G)
In a stainless steel reactor equipped with a propeller stirring system and a jacket heating, were introduced with stirring: - 660 liters of water - 11.8 kg of Na2SO4 (electrolyte) - 323 liters of aqueous sodium silicate, having a Si02 / Na20 weight ratio of 3.45 and a density of 1.230 at 20 C, whereby it was achieved forming a base stock characterized by an SiO2 concentration of 77g per liter. The mixture was then brought to a temperature of 82 C, while keeping it under stirring.

 395 liters of dilute sulfuric acid were then introduced with a density equal to 1.050 at 20 ° C., until a pH equal to 7.5 was obtained for the reaction medium. During the first 15 minutes of the reaction, the temperature was maintained at 82 ° C., then it was gradually raised from 820 ° C. to 950 ° C. over about 15 minutes, then maintained at 95 ° C. until the pH of 7.5 was obtained. .

 To the medium thus produced, 77 liters of aqueous sodium silicate of the type defined above were then added together, and 106 liters of sulfuric acid, also as defined above, this joint addition being carried out so that the pH of the medium of reaction is constantly maintained at a value equal to 7.5 (to within +/- 0.1 unit of pH) throughout the period of introduction of the silicate. After all the silicate had been introduced, the addition of the acid was continued, at a rate of 306 liters per hour (for 5 minutes), until the 106 liters of sulfuric acid were added. At the end of the addition, the pH of the medium obtained was measured equal to 5.

(total reaction time: 85 minutes)
A precipitated silica slurry was then obtained which is washed and filtered on a filter press. There was thus obtained a silica cake (G).

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1 - Preparation of the pigment composition
In a 2 liter reactor, 102 g of the silica cake (G) were dispersed in 2 liters of water. The pH of the suspension obtained was brought to 9 by addition of an aqueous NaOH solution at 1 mole / l, whereby a suspension (Sg1) was obtained.

 In parallel, a basic solution of aminopropyltriethoxysilane (APS) was prepared by adding 8g of APS in 20g of water, and then raising the pH to a value of 12 by adding an aqueous solution of NaOH at 1 mole / 1.

 The basic solution of aminopropyltriethoxysilane was then added to the suspension (Sg1) in 28 minutes, maintaining the pH at a constant value of 9 by simultaneous addition of an aqueous solution of H2SO4 at 0.5 mol / L. Once the addition was complete the suspension was heated to 87 C.

 8 g of Procion Red MX5B (red dye sold by the company Aldrich) were then added. The suspension was kept at 870C for 1 hour following the addition of the dye.

The suspension was then filtered under vacuum, then washed with demineralized water until the washings are clear. The product obtained was then dried in an oven at 700C for 12 hours, whereby a powder was obtained whose dry extract is 98% and red in color.

Example 2: Preparation of a blue pigment composition based on silica In a reactor, 102 g of the silica cake (G) as obtained in Example 1 were dispersed in 2 liters of water. The pH of the suspension obtained was brought to 9 by addition of an aqueous solution of NaOH at 1 mole / l, whereby a suspension (Sg2) was obtained.

In parallel, a basic solution of aminopropyltriethoxysilane (APS) was prepared by adding 8g of APS in 20g of water, and then raising the pH to a value of 12 by adding an aqueous solution of NaOH at 1 mole / ).

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 The basic solution of aminopropyltrietoxysilane was then added to the suspension (Sg2) in 28 minutes, maintaining the pH at a constant value of 9 by simultaneous addition of an aqueous solution of H2SO4 at 0.5 mol / L.

Once the addition was complete the suspension was heated to 87 C.

 8 g of Procion PX-3R (brilliant blue dye sold by the company Aldrich) were then added. The suspension was kept at 87 ° C. for 1 hour following the addition of the dye.

The suspension was then filtered under vacuum, then washed with demineralized water until the washings are clear. The product obtained was then dried in an oven at 70 C for 12 hours, whereby a powder was obtained whose dry extract is 98% and blue in color.

 As a control, the same experiment was carried out without grafting the amino-silane. By carrying out only the dye addition step, the total discoloration of the silica was observed by entraining the dye in the washing waters.

Claims (12)

1. Process for the preparation of a pigment composition, consisting in immobilizing water-soluble coloring compounds and having at least one reactive chemical function R, on silica-based particles, by means of water-soluble coupling agents having: (i) at less a chemical function Rs capable of inducing a strong chemical bond between said coupling agents and the surface of the silica-based particles; and (ii) at least one chemical function Rc capable of reacting with the reactive chemical functions R present on the coloring agents to lead to the formation of strong bonds between the coupling agents and the coloring agents, said method comprising specifically the steps consisting in : (A) bringing into contact, in an aqueous medium, said coupling agents and said silica-based particles, whereby an aqueous medium is obtained comprising silica-based particles on the surface of which coupling agents are immobilized by through their Rs function; and (B) adding said coloring agents to the aqueous medium, whereby strong bonds are formed between the coupling agents and the coloring agents, which leads to immobilization of at least part of the coloring agents on particles based on silica, through the coupling agent; and (C) recovering the silica-based particles grafted with the coloring agents thus obtained.  2. Method according to claim 1, characterized in that the silica-based particles used comprise metal cations on the surface. <Desc / CRUD Page number 15>  3. Method according to claim 1 or according to claim 2, characterized in that, in the coupling agents used, the chemical function Rs is a silane function.  4. Method according to claim 2, characterized in that in the coupling agents used, the chemical function Rs is a carboxylate or sulfonate group.  5. Method according to claim 2, characterized in that in the coupling agents used, the chemical function Rs is a phosphonic group-PO (OH) 2, a phosphinic group = PO (OH) or a phosphoric group-0 -PO (OH) 2.  6. Method according to any one of claims 1 to 5, characterized in that the reactive chemical function R present on the coloring agents and the chemical function Rc of the coupling agents are functions chosen from the following pairs (Rs / R) : (amine! halogenated function), (halogenated / amine function), (alcohol / isocyanate), (isocyanate / alcohol), (halogen thiol), (halogen / thiol), (amine / aldehyde), or (aldehyde / amine) .  7. Method according to claim 1, characterized in that the coupling agent used is an amino-silane, and in that the reactive chemical function R present on the coloring agents is a halogenated function.  8. Method according to claim 7, characterized in that the coupling agent used is an amino-silane corresponding to the following formula (1):

 in which: - the radicals r1, r2, r3 and r4, identical or different, each represent a hydrogen atom or an alkyl or aryl group having from 1 to 8 carbon atoms; and - the radical Ra represents an alkylene group comprising from 1 to 18 atoms <Desc / Clms Page number 16>  of carbon.  9. Method according to claim 7 or according to claim 8, characterized in that, in step (A), the amount of aminosilane coupling agents introduced is between 1. 10-5 and 2. 10-5 moles per m2 of available silica surface.  10. Method according to any one of claims 1 to 9, characterized in that the amount of coloring agents added during step (B) is such that, in the reaction medium, the molar ratio of the amount of functions R provided by the coloring agents relative to the amount of Rc functions provided by the coupling agents is between 1: 2 and 2: 1 in moles.  11. Pigment composition capable of being obtained by the process of any one of claims 1 to 10.  12. Use of a pigment composition according to claim 11, as a coloring filler in a concrete, in a cosmetic or pharmaceutical composition, or in a polymer or elastomer matrix.