Silicia powder and method for producing the same

Abstract: (Object) To provide a silica powder having a good ability to adsorb an ink dye. (Solving Means] A silica powder surface-treated with and epoxy compound having a plurality of epoxy groups, in which at least one epoxy group of the epoxy compound is ring-opened to bind to the surface of the silica powder and the remaining epoxy groups of the epoxy compound are bonded to amine compounds. The silica powder can be produced by the surface treatment of a silica powder with an epoxy compound and an amine compound successively or with both these compounds simultaneously. The surface treatment of the silica powder is performed with 0.1 to 60 parts by weight of an epoxy compound having at least two epoxy groups and 0.1 to 50 parts by weight of an amine compound in an inert gas atmosphere at 90 to 200°C.

Description: [Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a silica powder to be added to a recording material used for an ink jet printer and also relates to a method for producing the silica powder. [Description of the Related Art] In recent years, ink jet printers have been widely used for home and office use, due to such advantages as low price, quietness, low running costs, high printing quality and so on. Factors responsible for the widespread use of ink jet printers are that full-color and very fine images can be formed due to the astonishing advance of ink jet printers, that the price of ink jet printers is lower compared with color laser printers, and so on. In the future, demand for ink jet printers seems to increase more and more as computer penetration increases. In an ink jet printer, an ink dye in an ink tank is ejected from a nozzle as droplets in accordance with an electrical signal from an computer to record a typeface or image on a recording material. A recording material for an ink jet printer can be formed by coating a transparent ink-receiving layer on a base sheet. The base sheet includes a synthetic paper, a polyethylene terephthalate film, and so on. The ink-receiving layer comprises a binder, an inorganic oxide, water and so on as base materials, and can be formed by mixing these components in a slurry. The material for the binder is polyvinyl alcohol, and the inorganic oxide includes silica, alumina and so on. Upon contacting with the ink-receiving layer, the ink dye is absorbed by the binder and the inorganic oxide serves to inhibit the bleeding of the ink. The properties required for the recording material for an ink jet printer are rapid absorption of the ink, no bleeding of the ink, brightness and sharpness of the resulting image, and so on. Document US -A- 4,826,895 deals with a point composition for under coating. The composition consists of two separate components, the first being on epoxy polyol resin, the second being silica particles. The document mentions "silica particles are blended with an appropriately selected resin", the epoxy resin may have reacted before with an amino compound. Document EP -A- 0 870 790 deals with a curable epoxy resin composition. The document describes the presence of an absorbent or adsorbent. The absorbent or adsorbent may absorb or adsorb the polyol resin without a chemical reaction being completed. Document GB -A- 1 071 167 describes a mixture of an epoxy resin and a curing agent. It is the teaching of the document of reacting in a first step the epoxy compound with the amine and adding the reaction product in a second step to the filler. Document US -A- 3,407.165 is understood as providing on a backing two different types of powder, namely a coarse filler and a pulverulent filler. The pulverulent powder is optionally made of silica. Both filler types are embedded in a coating which is generated by the reaction of a curable liquid organic resin. There is no reason to assume a reaction of an epoxyde compound through one of its epoxyde groups with the silica powder, let alone the subsequent reaction of an amine with the initial silica-epoxy product. Document US -A- 4,245,005 deals with porous silica coated with an adsorbate layer which adsorbate layer is stabilized through covalent crosslinking. The document describes polyethyleneimine coatings, these are crosslinked optionally with an epoxy crosslinker. Document US -A- 3,383,347 provides a epoxy resin coating composition, comprising an epoxy component evidently intended to react with the curing agent only. [Problems to be Solved by the Invention] Recently, demand for high definition of images has been increasing. In particular, in the case of printing of photographs, current recording materials for ink jet printers have problems such as bleeding of ink and unsatisfactory gradation in color. Accordingly, the object of the present invention is to provide a silica powder having a good ability to adsorb an ink dye and a method for producing the silica powder. [Means for Solving the Problems] The invention of claim 1 provides a silica powder surface-treated with an epoxy compound having a plurality of epoxy groups, at least one of the epoxy groups of the epoxy compound being ring-opened and bound to the surface of the silica powder, and the remaining epoxy groups of the epoxy compound are reacted with and bound to an amine compound. In the invention of claim I, at least one of the epoxy groups of the epoxy compound having a plurality of epoxy groups is ring-opened and bound to the surface of the silica powder, and the remaining epoxy groups are reacted with and bound to the amine compound, thereby producing a silica powder having amino group(s) on its surface. By using the silica powder thus produced as an additive for a recording material of an ink jet printer, the property of adsorbing an ink is increased and the smearing or bleeding of the ink can be prevented. The invention of claim 2 is an invention according to claim 1, and provides the silica powder, wherein the epoxy compound is one which contains no metal and has a molecular weight ranging from 200 to 1000. In the invention of claim 2, the epoxy compound contains no metal. If the epoxy compound contains any metal, then the percent surface occupation of the metal on the surface of the silica powder is high, and therefore it becomes impossible to provide many epoxy groups on the surface of the silica powder. The molecular weight of the epoxy compound falls within the range from 200 to 1000, preferably from 200 to 700. Since an epoxy compound having a molecular weight greater than 1000 is highly viscous, dilution of the epoxy compound with a large amount of a solvent is needed, and hence it becomes also impossible to provide many epoxy groups on the surface of the silica powder. The invention of claim 3 is an invention according to claim 1, and provides the silica powder, wherein the silica powder has a primary mean particle size ranging from 5 to 50 nm. In the invention of claim 3, the primary mean particle size of the silica powder falls within the range from 5 to 50 nm, preferably from 5 to 7 nm. If the primary mean particle size is larger than 50 nm, when used as the base material of an recording material for an ink jet printer, the ability to adsorb an ink is decreased, which may cause a problem of smear by bleeding of the ink. The invention of claim 4 is an invention according to claim 1, and provides the silica powder, wherein the amine compound is an amine which is aliphatic and contains at least one nitrogen atom. In the invention of claim 4, the amine compound is preferably an amine containing at least two nitrogen atoms in a molecule. The silica powder prepared using such an amine compound has many non-covalent electron pairs on its surface and, therefore, can have an improved ability to adsorb an ink. The invention of claim 5 is an invention according to claim 1, and provides the silica powder, wherein the silica powder has a specific surface area ranging from 50 to 380 m 2 /g. In the invention of claim 5, the specific surface area falls within the range from 50 to 380 m 2 /g, preferably from 300 to 380 m 2 /g. If a silica powder having a specific surface area smaller than 50 m 2 /g is used as the base material of the recording material, the amount of an ink adsorbed by the silica powder is decreased, and therefore a trouble of smear by bleeding of the ink may be caused, leading to unclearness of the resulting image. If the specific surface area exceeds 380 m 2 /g, a trouble of poor dispersilibity of the silica powder may occur. The invention of claim 6 is an invention according to claim 1, and provides the silica powder, wherein the silica powder has an amine group equivalent ranging from 6.0 x 10 -6 to 1.2 x 10 -2 mol/g. In the invention of claim 6, the amino group equivalent falls within the range from 6.0 x 10 -6 to 1.2 x 10 -2 mol/g, preferably from 4.0 x 10 -4 to 1.2 x 10 -2 mol/g. If a silica powder having an amino group equivalent lower than 6.0 x 10 -6 mol/g is used as a base material of the recording material, the amount of an ink adsorbed by the silica powder is decreased, and therefore a trouble of smear by bleeding of the ink may be caused, leading to unclearness of the resulting image. If the amino group equivalent exceeds 1.2 x 10 -2 mol/g, a trouble of poor dispersilibity of the silica powder may occur. The invention of claim 7 provides a method for producing a silica powder, comprising surface-treating a silica powder with an epoxy compound and an amine compound. According to the invention of claim 7, use of the method enables to produce a silica powder having a good ink-adsorptive ability. The invention of claim 7 provides the method for producing a silica powder, wherein the method comprise the following steps, as shown in FIGs. 1(a) and 1(b): adding dropwise or spraying a liquid of the epoxy compound (11) having a plurality of epoxy groups to or onto the silica powder (10) which is kept in a fluidized state; heating the silica powder (10), which has been added dropwise or sprayed with the epoxy compound (11), in a fluidized state to a temperature from 90 to 200°C to produce a primary product (12); adding dropwise or spraying a liquid of the amine compound (13) to or onto the primary product (12) which is kept in a fluidized state; and heating the primary product (12), which has been added dropwise or sprayed with the amine compound (13), in a fluidized state to a temperature from 90 to 200°C. In the invention of claim 7, the epoxy compound can be ring-opened by reacting with hydroxyl group(s) present on the surface of the silica powder to bind to the surface of the silica powder, due to the high reactivity of the epoxy compound. Then, the surface of the primary product having the epoxy groups thereon reacts with the amine compound. In this manner, a silica powder having amino group(s) thereon can be produced. The temperature required for the surface-treatment is 90 to 200°C. If the temperature is lower than 90°C, the reaction of the epoxy compound with the surface of the silica powder cannot proceed sufficiently. In addition, in this case, when the first and second solvents are used, the solvents may not be evaporated completely and remain on the surface of the silica powder, inhibiting the properties of the resulting silica powder. If the temperature is higher than 200°C, the epoxy compound and the amine compound may be thermally decomposed. The invention of claim 8 is an invention according to claim 7 and the invention of claim 11 is an invention according to claim 10, and individually provide the method for producing a silica powder, wherein the liquid of the epoxy compound is prepared by dissolving the epoxy compound in a first solvent and the liquid of the amine compound is prepared by dissolving the amine compound in a second solvent. In both the inventions of claims 8 and 11, the epoxy compound and the amine compound are dissolved in the first and second solvent, respectively, to form liquids. Each of the liquids is added dropwise to or sprayed onto the silica powder so that both the compounds can be deposited on the surface of the silica powder uniformly. The invention of claim 9 is an invention according to claim 8 and the invention of claim 12 is an invention according to claim 11, and individually provide the method for producing a silica powder, wherein each of the first and second solvents is acetone, hexane, toluene, chloroform, diisopropyl ether or tetrahydrofuran. In both the inventions of claims 9 and 12, the first solvent is preferably acetone that has no reactivity with the epoxy compound, is less toxic and inexpensive. The second solvent is preferably tetrahydrofuran (hereinafter, simply referred to as "THF") that is less toxic and inexpensive, or acetone. The invention of claim 10 is an alternative embodiment to the invention according to claim 7 and provides the method for producing a silica powder, wherein the method comprises the following steps: adding dropwise or spraying both a liquid of the epoxy compound having a plurality of epoxy groups and a liquid of the amine compound to or onto a silica powder which is kept in a fluidized state simultaneously; and heating the silica powder, which has been added dropwise or sprayed with the epoxy compound and the amine compound, in a fluidized state to a temperature from 90 to 200°C. In the invention of claim 10, the surface of the silica powder is treated with both the epoxy compound and the amine compound simultaneously. In the method, the epoxy group that is higher reactive compared with the amine compound can preferentially bind to the surface of the silica powder. Accordingly, the same silica powder as that produced in the invention of claim 7 can be obtained. The invention of claim 13 is an invention according to claim 7 or 10, and provides the method for producing a silica powder, wherein the surface treatment of the silica powder is performed with the epoxy compound in an amount of 0.1 to 60 parts by weight and the amine compound in an amount of 0.1 to 50 parts by weight, both based on 100 parts by weight of the silica powder. In the invention of claim 13, the blending ratio of the epoxy compound is 0.1 to 60 parts by weight, preferably 20 to 60 parts by weight, based on 100 parts by weight of the silica powder. If the blending ratio is smaller than 0.1 part by weight, unreacted hydroxyl groups may remain on the surface of the silica powder. If the blending ratio is higher than 60 parts by weight, the silica powder may cause coagulation. The blending ratio of the amine compound is 0.1 to 50 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the silica powder. If the blending ratio is smaller than 0.1 part by weight, sufficient number of amino groups may not be provided on the surface of the silica powder. If the blending ratio is larger than 50 parts by weight, the silica powder may cause coagulation. The invention of claim 14 is an invention according to claim 8 or 11, and provide the method for producing a silica powder, wherein the epoxy compound has at least two epoxy groups, contains no metal and has a molecular weight ranging from 200 to 1000. In the invention of claim 14, if the epoxy group has only one epoxy group, the epoxy group may be ring-opened upon the binding to the surface of the silica powder, and therefore the amine compound cannot be modified onto the surface of the silica powder. The invention of claim 15 is an invention according to claim 7 or 10, and provides the method for producing a silica powder, wherein the surface treatment of the silica powder or the primary product is carried out in an inert gas atmosphere. In the invention of claim 15, it is preferable to carry out the surface treatment in an inert gas atmosphere. If performed in an atmosphere which is not an inert gas atmosphere, the epoxy group may be ring-opened due to its high reactivity. [Description of the Embodiments] The silica powder surface-treated according to the present invention can be produced by a wet or dry method. Exemplary epoxy compound to be used in the production method of the present invention includes glycidyl ethers each having at least two epoxy groups, such as glycerol triglycidyl ether [FIG. 2 (a)], glycerol diglycidyl ether [FIG. 2 (b)], diglycerol polyglycidyl ether, polypropylene glycol diglycidyl ether [FIG. 2 (c)], ethylene glycol diglycidyl ether [FIG. 2 (d)], trimethylolpropane polyglycidyl ether [FIG. 2 (e)], neopentyl glycol diglycidyl ether [FIG. 2 (f)] and polyethylene glycol diglycidyl ether [FIG. 2 (g)]. Exemplary amine compound includes diethylamine [(C 2 H 5 ) 2 NH], diethanolamine [(C 2 H 4 OH) 2 NH]), N-methylethanolamine (CH 3 NHCH 2 CH 2 OH), ethylenediamine (H 2 NCH 2 CH 2 NH 2 ), diethlenetriamine [(H 2 NCH 2 CH 2 ) 2 NH] and tetraethylenepentamine. The production method of the present invention will be described with reference to FIG. 1. As shown in FIG. 1(a), a silica powder 10 having a primary mean particle size of 5 to 50 nm is surface-treated with an epoxy compound 11. When the silica powder is produced by a dry method, the surface treatment with the epoxy compound is preferably also performed by a dry method so that the advantageous properties of the silica powder produced by a dry method, particularly no coagulating property and good dispersing property, are not be impaired. In addition to this advantage, the surface treatment by a dry method also has other advantages such that small amounts of the epoxy compound and the amine compound are needed for the surface treatment, that the amounts of these compounds adhered onto the silica powder can be controlled readily, and that separation of the silica powder after the surface treatment, which is needed in a wet method, can be eliminated. The surface treatment of the silica powder with the epoxy compound may also be performed by a wet method, in which the silica powder is dispersed in a solution of the epoxy compound dissolved in an appropriate solvent. Hereinbelow, the method for surface treatment of the silica powder with the epoxy compound by a dry method is described. First, the silica powder 10 is maintained in a fluidized state in a vessel using, for example, a high speed mixer. When the epoxy compound 11 is a liquid having a low viscosity, the liquid epoxy compound is then added dropwise to or sprayed onto the silica powder that is maintained in a fluidized state. When the epoxy compound is a solid or a liquid having a high viscosity, the epoxy compound is diluted with a first solvent and the resulting dilution is added dropwise to or sprayed onto the silica powder that is maintained in a fluidized state. In this manner, the epoxy compound can be adhered onto the surface of the silica powder uniformly. Next, the resulting silica powder is heated to 90 to 200°C to fully proceed the reaction, whereby a primary product 12 can be produced. Even when the epoxy compound is a liquid having a low viscosity, it may be preferable to prepare a dilution of the epoxy compound by dissolving it in the first solvent and then add dropwise to or spray onto the silica powder. In this manner, the epoxy compound can be adhered onto the surface of the silica powder uniformly. The first solvent is not particularly limited so long as it can dissolve the epoxy compound used. Specifically, the first solvent may be acetone, hexane, toluene, chloroform, diisopropyl ether, THF or the like. By the surface treatment, at least one of a plurality of epoxy groups of the epoxy compound can react with the hydroxyl group present on the surface of the silica powder to be ring-opened, and the remaining epoxy groups are left to be unreacted. Thus, the epoxy compound can chemically bind to the silica powder by the ring-opening reaction of the epoxy groups in such a state that at least one unreacted epoxy group remains, thereby providing the epoxy groups on the surface of the silica powder effectively. That is, the silica powder can be coated with an organic material containing epoxy groups chemically bound to the surface of the silica powder, and therefore it becomes possible to provide many epoxy groups on the surface of the silica powder. The epoxy compound to be used for the surface treatment may be an organic compound having at least two epoxy groups. The binding sites of the epoxy groups in the epoxy compound molecule are not particularly limited. However, a compound is preferable in which two epoxy groups are present at both ends of the epoxy compound molecule. As shown in FIG. 1(b), the primary product 12 is further surface-treated with the amine compound 13. By this surface treatment, the unreacted epoxy groups remaining on the surface of the silica powder can react with the amine compound to give a silica powder having amino groups on its surface. That is, the epoxy groups remaining on the surface of the primary product can cause ring-opening reaction with the amine compound, whereby a secondary product 14 which has amino groups on its surface can be produced. When the silica powder is produced by a dry method, the surface treatment with the amine compound is preferably performed by a dry method so that the advantageous properties of the silica powder produced by the dry method, such as no coagulating properties and good dispersing property, are not impaired, as in the case of the surface treatment of the silica powder with the epoxy compound mentioned above. The surface treatment of the primary product with the amine compound may be performed in a wet method. Hereinbelow, the method for surface treatment of the primary product with the amine compound by a dry method is described. First, the primary product 12 is maintained in a fluidized state in a vessel using, for example, a high speed mixer. When the amine compound 13 is a liquid having a low viscosity, the liquid amine compound is then added dropwise to or sprayed onto the primary product that is maintained in a fluidized state. When the amine compound is a solid or a liquid having a high viscosity, the amine compound is diluted with a second solvent and the resulting dilution is added dropwise to or sprayed onto the primary product that is maintained in a fluidized state. In this manner, the amine compound can be adhered onto the surface of the primary product uniformly. Next, the resulting primary product is heated to 90 to 200°C to fully proceed the reaction, whereby a secondary product 14 can be produced on which the amine compound is fixed. Even when the amine compound is a liquid having a low viscosity, it may be preferable to prepare a dilution of the amine compound 13 by dissolving it in the second solvent and then add it dropwise to or spray it onto the primary product. In this manner, the amine compound can be adhered onto the surface of the primary product uniformly. The second solvent is not particularly limited so long as it can dissolve the amine compound used and has no reactivity with the epoxy compound. Exemplary second solvent includes acetone, hexane, toluene, chloroform, diisopropyl ether and THF. The silica powder is heated for the purpose of proceeding the reaction of the hydroxyl group present on the surface of the silica powder with at least one epoxy group of the epoxy compound and the reaction of the remaining epoxy groups with the amine compound, respectively. This heat treatment is preferably carried out in an inert gas atmosphere so that the oxidation of the epoxy compound can be prevented. The inert gas includes nitrogen, argon and helium. The time period required for the heat treatment may vary depending on the temperature of the heat treatment and the types of the epoxy compound and amine compound used, but preferably from 1 to 6 hours, more preferably from 1 to 3 hours. Too short heat treatment may cause disadvantages such that the reaction of the epoxy compound with the surface of the silica powder cannot proceed sufficiently and that the solvent cannot be fully evaporated and, consequently, the advantageous properties of the silica powder are likely to be impaired, as in the case where the temperature of the heat treatment is too low. When the silica powder prepared by the method described above is used as the base material for forming an ink-receptive layer of a recording material for an ink jet printer, protonization of the non-covalent electron pair of the amino group occurs, whereby the surface of the silica powder is rendered electrically positive. On the other hand, the chromophore (which develops a color) of an anionic compound which forms an ink dye component (i.e., primary colors of cyan, magenta and yellow, and black) has an electrically negatively charged ion with an electrically negative ion, which is attracted by the positive ion of the amino group and captured on the surface of the silica powder. As a result, the dispersion of the ink dye component in a binder can be prevented, leading to the formation of a bright and clear color. The amount of the amino groups provided on the surface of the silica powder produced according to the present invention is determined in terms of an amino group equivalent. As used herein, the term "amino group equivalent" refers to the number of moles of the amino groups adhered onto 1 g of the silica powder. The determination of the amino group equivalent is performed as follows. First, 40 ml of a mixed solution comprising chloroform : acetic acid = 1:2 and 0.1 mol/l of a perchloric acid-acetic acid solution are provided. Next, 1 g of a silica powder which had been surface-treated is charged in a beaker together with 40 ml of the chloroform-acetic acid mixed solution and a stirring bar, and the resultant is then titrated with the perchloric acid-acetic acid solution using a potentiometric titration apparatus while stirring with a stirrer. The inflection point of the resulting titration curve is defined as the end point, and the amino group equivalent is determined according to the following equation (1) based on the titration amount (ml). Amino group equivalent = [(concentration of perchloric acid) x (factor of perchloric acid) x (titration amount)] / 1000 [Examples] The examples and comparative examples of the present invention will be described hereinbelow. <Example 1> A silica powder having a specific surface area of 130 m 2 /g ("Aerosil #130", a product from Nippon Aerozyl) (100 g) was provided. Glycerol triglycidyl ether ("EX-314", a product from Nagase Chemicals Ltd.) (31 g) was provided as an epoxy compound and acetone was provided as a first solvent. The epoxy compound was dissolved in acetone to prepare an epoxy dilution. Diethylamine (22 g) was provided as an amine compound and acetone was provided as a second solvent. The amine compound was dissolved in acetone to prepare an amine dilution. The silica powder was charged and stirred in a mixer so that the silica powder was maintained in a fluidized state. The epoxy dilution was added to the silica powder maintained in a fluidized state to adhere the epoxy compound to the silica powder uniformly. The silica powder thus adhered with the epoxy compound was then heated at 180°C in inert gas stream and left to stand for 1 hour, thereby producing a primary product. The primary product was added with the amine dilution while maintaining a fluidized state, so that the amine compound was adhered onto the primary product uniformly. The primary product thus adhered with the amine compound was heated at 180°C in inert gas stream, and then left to stand for 2 hours, thereby producing a surface-treated silica powder as a secondary product. <Example 2> The same silica powder and epoxy compound as those in Example 1 were provided and the reaction was performed under the same conditions as in Example 1, except that diethanolamine (8 g) was used as the amine compound, thereby producing a surface-treated silica powder as a secondary product. <Example 3> The same silica powder and epoxy compound as those in Example 1 were provided and the reaction was performed under the same conditions as in Example 1, except that diethanolamine (23 g) and THF were provided as the amine compound and the second solvent, respectively, and the amine compound was dissolved in THF to prepare an amine dilution, thereby producing a surface-treated silica powder as a secondary product. <Example 4> The same silica powder and epoxy compound as those in Example 1 were provided and the reaction was performed under the same conditions as in Example 1, except that N-methylethanolamine (6 g) and THF were provided as the amine compound and the second solvent, respectively, the amine compound was dissolved in TBF to prepare an amine dilution and the primary product was heated at 150°C, thereby producing a surface-treated silica powder as a secondary product. <Example 5> A silica powder having a specific surface area of 380 m 2 /g ("Aerosil #380S", a product from Nippon Aerosil) (100 g) was provided. Glycerol triglycidyl ether ("EX-314", a product from Nagase Chemicals Ltd.) (45 g) was provided as an epoxy compound and acetone was provided as a first solvent. The epoxy compound was dissolved in acetone to prepare an epoxy dilution. Diethanolamine (24 g) was provided as an amine compound and acetone was provided as a second solvent. The amine compound was dissolved in acetone to prepare an amine dilution. The silica powder was charged in a mixer and stirred so that the silica powder was maintained in a fluidized state. The epoxy dilution was added to the silica powder maintained in a fluidized state to adhere the epoxy compound onto the silica powder uniformly. The silica powder thus adhered with the epoxy compound was then heated at 180°C in inert gas stream and left to stand for 1 hour, thereby producing a primary product. The primary product was added with the amine dilution while maintaining in a fluidized state, so that the amine compound was adhered onto the primary product uniformly. The primary product thus adhered with the amine compound was heated at 180°C in inert gas stream, and then left to stand for 2 hours, thereby producing a surface-treated silica powder as a secondary product. <Example 6> The same silica powder and epoxy compound as those in Example 5 were provided and the reaction was performed under the same conditions as in Example 5, except that diethylamine (22 g) and THF were provided as the amine compound and the second solvent, respectively, and the amine compound was dissolved in THF to prepare an amine dilution, thereby producing a surface-treated silica powder as a secondary product. <Example 7> The same silica powder and epoxy compound as those in Example 5 were provided and the reaction was performed under the same conditions as in Example 5, except that ethylenediamine (13 g) and toluene were provided as the amine compound and the second solvent, respectively, and the amine compound was dissolved in toluene to prepare an amine dilution, thereby producing a surface-treated silica powder as a secondary product. <Example 8> The same silica powder and epoxy compound as those in Example 7 were provided and the reaction was performed under the same conditions as in Example 7, except that ethylenediamine (5 g) was provided and the primary product was heated at 110°C, thereby producing a surface-treated silica powder as a secondary product. <Example 9> The same silica powder and epoxy compound as those in Example 7 were provided and the reaction was performed under the same conditions as in Example 7, except that ethylenediamine (16 g) was provided and the primary product was heated at 150°C, thereby producing a surface-treated silica powder as a secondary product. <Example 10> The same silica powder and epoxy compound as those in Example 7 were provided and the reaction was performed under the same conditions as in Example 7, except that ethylenediamine (16 g) was provided and the primary product was heated at 150°C and then left to stand for 1 hour, thereby producing a surface-treated silica powder as a secondary product. <Example 11> The same silica powder, epoxy compound and amine compound as those in Example 9 were provided and the reaction was performed under the same conditions as in Example 9, except that the primary product was heated at 90°C, thereby producing a surface-treated silica powder as a secondary product. <Example 12> The same silica powder, epoxy compound and amine compound as those in Example 10 were provided and the reaction was performed under the same conditions as in Example 10, except that the primary product was heated at 90°C, thereby producing a surface-treated silica powder as a secondary product. <Example 13> The same silica powder and epoxy compound as those in Example 5 were provided and the reaction was performed under the same conditions as in Example 5, except that diethylenetriamine (16 g) was provided as the amine compound and the primary product was heated at 130°C, thereby producing a surface-treated silica powder as a secondary product. <Example 14> The same silica powder and epoxy compound as those in Example 5 were provided and the reaction was performed under the same conditions as in Example 5, except that tetraethylenepentamine (20 g) and THF were provided as the amine compound and the second solvent, respectively, the amine compound was dissolved in THF to prepare an amine dilution and the primary product was heated at 130°C, thereby producing a surface-treated silica powder as a secondary product. <Example 15> The same silica powder as that in Example 5 was provided and the reaction was performed under the same conditions as in Example 5, except that pentaerythritol polyglycidyl ether ("EX-411", a product from Nagase Chemicals Ltd.) (60 g) and ethylenediamine (13 g) were provided as the epoxy compound and the amine compound, respectively, and the primary product was heated at 110°C and then left to stand for 1 hour, thereby producing a surface-treated silica powder as a secondary product. <Example 16> The same silica powder as that in Example 5 was provided and the reaction was performed under the same conditions as in Example 5, except that trimethylolpropane polyglycidyl ether ("SR-TMP", a product from Sakamoto Yakuhin Kogyo Co., Ltd.) (44 g) and ethylenediamine (13 g) were provided as the epoxy compound and the amine compound, respectively, and the primary product was heated at 110°C and then left to stand for 1 hour, thereby producing a surface-treated silica powder as a secondary product. <Example 17> The same silica powder as that in Example 5 was provided and the reaction was performed under the same conditions as in Example 5, except that polyglycerol polyglycidyl ether ("SR-4GL", a product from Sakamoto Yakuhin Kogyo Co., Ltd.) (45 g), ethylenediamine (13 g) and THF were provided as the epoxy compound, the amine compound and the secondary solvent, respectively, the amine compound was dissolved in THF to prepare an amine dilution, and the primary product was heated at 110°C and then left to stand for 1 hour, thereby producing a surface-treated silica powder as a secondary product. <Example 18> The same silica powder as that in Example 5 (100 g) was provided. Glycerol triglycidyl ether ("EX-314", a product from Nagase Chemicals Ltd.) (45 g) was provided as an epoxy compound. Ethylenediamine (5 g) was provided as an amine compound. The epoxy compound was dissolved in acetone to prepare an epoxy dilution, and the amine compound was dissolved in the epoxy dilation to prepare a mixed solution. The silica powder was charged in a mixer and stirred so that the silica powder was maintained in a fluidized state. The mixed solution was added to the silica powder maintained in a fluidized state to adhere the epoxy compound and the amine compound onto the silica powder uniformly. The silica powder thus prepared was then heated at 150°C in inert gas stream and left to stand for 2 hour, thereby producing a surface-treated silica powder as a secondary product. <Example 19> The same silica powder, epoxy compound and amine compound as those in Example 18 were provided and the reaction was performed under the same conditions as in Example 18, except that silica powder is heated at 180°C, thereby producing a surface-treated silica powder as a secondary product. <Example 20> The same silica powder as that in Example 5 was provided and the reaction was performed under the same conditions as in Example 5, except that glycerol triglycidyl ether ("EX-314", a product by Nagase Chemicals Ltd.) (60 g) and N-methylethanolamine (0.2 g) were provided as the epoxy compound and the amine compound, respectively, and the primary product was heated at 160°C, thereby producing a surface-treated silica powder as a secondary product. <Example 21> The same silica powder as that in Example 5 was provided and the reaction was performed under the same conditions as in Example 5, except that glycerol triglycidyl ether ("EX-314", a product by Nagase Chemicals Ltd.) (0.1 g), ethylenediamine (45 g) and THF were provided as the epoxy compound, the amine compound and the secondary solvent, respectively, the amine compound was dissolved in THF to prepare an amine dilution, and primary product was heated at 150°C, thereby producing a surface-treated silica powder as a secondary product. <Comparative Example 1> The same silica powder as that in Example 5 (100 g) was provided and evaluated for an ability to adsorb an anion without any surface treatment. <Comparative Example 2> The surface-treated silica powders obtained in Examples 1 to 21 as the secondary products and the silica powder of Comparative Example 1 were evaluated for an ability to adsorb an anion according to the following method. A silica powder (2 g) to be tested was added with 10 mmol/l of an aqueous sodium 2-naphthalene sulfonate solution (100 ml) to prepare a mixed solution. The mixed solution was stirred for 5 min. to adsorb the anion species on the silica powder. The resulting mixed solution in which the anion species was adsorbed on the powder was filtered. A portion (1 ml) of the filtrate was transferred in a mess-flask and then diluted with water (100 ml). The absorbance of the resulting dilution was determined using a UV spectrophotometer to evaluate the ability of the surface-treated silica powder to adsorb the anion. Each of the surface-treated silica powders was also determined for its amino group equivalent by the method as described above. The results for the silica powders produced in Examples 1 to 12 are shown in Table 1 and the results for the silica powders produced in Examples 13 to 21 and Comparative Example 1 are shown in Table 2. As shown in Tables 1 and 2, it is found that the silica powders of Examples 1 to 21 showed higher ability to adsorb an anion compared with the silica powder of Comparative Example 1 in which no surface treatment, was performed. [Advantages] As stated above, according to the present invention, there is provided a silica powder in which at least one epoxy group of an epoxy compound is ring-opened to bind to the surface of the silica powder and the remaining epoxy groups of the epoxy compound are bonded to amine compounds, thereby providing amino groups on its surface. When the silica powder is used as a base material of a recording material for an ink jet printer, the amino group provided on the surface of the silica powder (which has an electrically positive charge) can capture an ink dye (which has an electrically negative charge) on the surface of the silica powder. The ink dye component is not dispersed in a binder, a bright and clear color can be formed. Accordingly, the surface-treated silica powder of the present invention has a good ability to adsorb an ink dye. [Brief Description of the Drawings] [Fig. 1] Fig. 1 illustrates the steps for producing a silica powder having an amino group on its surface according to the present invention. [Fig. 2] Fig. 2 shows chemical formulae of epoxy compounds usable in the production method of the present invention. [Reference Numerals] 10: silica powder 11: epoxy compound 12: primary product 13: amine compound 14: secondary product

Claims: A silica powder (10) surface-treated with an epoxy compound (11) having a plurality of epoxy groups, at least one of the epoxy groups of the epoxy compound (11) being ring-opened and bound to the surface of the silica powder (10), and the remaining epoxy groups of the epoxy compound (11) are reacted and bound to an amine compound (13). The silica powder according to claim 1, wherein the epoxy compound (11) is one which contains no metal and has a molecular weight ranging from 200 to 1000. The silica powder according to claim 1, wherein the silica powder (10) has a primary mean particle size ranging from 5 to 50 nm. The silica powder according to claim 1, wherein the amine compound (13) is an amine which is aliphatic and contains at least one nitrogen atom. The silica powder according to claim 1, wherein the silica powder has a specific surface area ranging from 50 to 380 m 2 /g. The silica powder according to claim 1, wherein the silica powder has an amine group equivalent ranging from 6.0 x 10 -6 to 1.2 x 10 -2 mol/g. A method for producing a silica powder, comprising surface-treating a silica powder (10) with an epoxy compound (11) and an amine compound (13), wherein the method comprises the following steps: adding dropwise or spraying a liquid of the epoxy compound (11) having a plurality of epoxy groups to or onto the silica powder (10) which is kept in a fluidized state; heating the silica powder (10), which has been added dropwise or sprayed with the epoxy compound (11), in a fluidized state to a temperature from 90 to 200°C to produce a primary product (12); adding dropwise or spraying a liquid of the amine compound (13) to or onto the primary product (12) which is kept in a fluidized state; and heating the primary product (12), which has been added dropwise or sprayed with the amine compound (13), in a fluidized state to a temperature from 90 to 200°C. The method for producing a silica powder according to claim 7, wherein the liquid of the epoxy compound is prepared by dissolving the epoxy compound in a first solvent and the liquid of the amine compound is prepared by dissolving the amine compound in a second solvent. The method for producing a silica powder according to claim 8, wherein each of the first and second solvents is acetone, hexane, toluene, chloroform, diisopropyl ether or tetrahydrofuran. The method for producing a silica powder according to claim 7, wherein the method instead comprises the following steps: adding dropwise or spraying both a liquid of the epoxy compound (11) having a plurality of epoxy groups and a liquid of the amine compound (13) to or onto a silica powder (10) which is kept in a fluidized state simultaneously; and heating the silica powder (10), which has been added dropwise or sprayed with both the epoxy compound (11) and the amine compound (13), in a fluidized state to a temperature from 90 to 200°C. The method for producing a silica powder according to claim 10, wherein the liquid of the epoxy compound is prepared by dissolving the epoxy compound in a first solvent and the liquid of the amine compound is prepared by dissolving the amine compound in a second solvent. The method for producing a silica powder according to claim 11, wherein each of the first and second solvents is acetone, hexane, toluene, chloroform, diisopropyl ether or tetrahydrofuran. The method for producing a silica powder according to claim 7 or 10, wherein the surface treatment of the silica powder is performed with the epoxy compound in an amount of 0.1 to 60 parts by weight and the amine compound in an amount of 0.1 to 50 parts by weight, both based on 100 parts by weight of the silica powder. The method for producing a silica powder according to claim 7 or 10, wherein the epoxy compound (11) has at least two epoxy groups, contains no metal and has a molecular weight ranging from 200 to 1000. The method for producing a silica powder according to claim 7 or 10, wherein the surface treatment of the silica powder (10) or the primary product (12) is carried out in an inert gas atmosphere.

Inventors: HIRATA HIROKI, OGI KATSUMI, SUGINO MAKI, HIRATA, HIROKI, OGI, KATSUMI, SUGINO, MAKI, Hirata, Hiroki, Mitsubishi Materials Corp., OGI, KATSUMI, MITSUBISHI MATERIALS CORP., Sugino, Maki, Mitsubishi Materials Corp.
Applicants: MITSUBISHI MATERIALS CORP, MITSUBISHI MATERIALS CORPORATION
Application year: 2001
Main classification: C09C1
IPC codes: C09C3, B41J2, C09C1, C01B33