Surface modified silica powder, resin composition containing the silica powder, method of producing surface modified silica powder, and method of producing resin composition containing the silica powder

Abstract

To provide surface-modified silica powder in which an amount of silanol groups inside the silica powder is sufficiently reduced and a method of producing the same, and to provide an excellent resin composition with silica powder dispersed therein in a state in which the amount of silanol groups inside the silica powder is reduced and a method of producing the same.SOLUTION: A surface-modified silica powder contains silanol groups in an amount of 200 ppm or less, with a ratio of an amount of modifying group on a silanol group conversion basis is 20% or more, provided that the total value of the amount of silanol groups and modifying groups on a silanol group conversion basis is 100%. The surface-modified silica powder contains silanol groups in an amount of 200 ppm or less and has a methanol wettability value of 60 or more. A method of producing the surface-modified silica powder includes a step of firing the silica powder at a temperature of 1,100°C or more. There are provided a resin composition including the surface-modified silica powder, and a method of producing the same.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a surface-modified silica powder, a resin composition containing the surface-modified silica powder, a method for producing the surface-modified silica powder, and a method for producing a resin composition containing the surface-modified silica powder. [Background technology]

[0002] Silica powder is an industrial material used in a wide range of fields, including as a desiccant, adsorbent, filler for resins and rubber materials, catalyst, paint, adhesive, fireproofing agent, glass material, etc. Among these, micrometer-sized silica powder is mixed with resin and molded to form a resin composition for various applications.

[0003] Well-known silica powders are produced by different manufacturing methods, such as those produced by the thermal decomposition of silicon tetrachloride, those produced by the deionization of alkali silicates such as water glass, and those produced by the hydrolysis and condensation reactions of alkoxysilanes.

[0004] Many studies have been conducted on the production of silica powder and resin compositions containing silica powder. For example, Patent Document 1 discloses silica powder used in semiconductor encapsulants for semiconductor packages, and Patent Document 2 discloses the use of silica powder as a filler for acrylic resin.

[0005] In addition, as described in Patent Documents 3 to 5, a manufacturing method in which silica powder is mixed with resin and molded is common, and its uses include a method of firing or melting the molded body, and a molded body simply mixed with resin as a silica filler in the semiconductor field. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-078105 A [Patent Document 2] JP 2016-156018 A [Patent Document 3] JP 2004-131351 A [Patent Document 4] Japanese Patent Application Publication No. 208230 / 1999 [Patent Document 5] JP 2023-10683 A Summary of the Invention [Problem to be solved by the invention]

[0007] Generally, silica powder is composed of siloxane bonds and has silanol groups at the ends. The silanol groups are present both inside the silica powder and on the surface of the silica powder. The silanol groups present on the surface can be used to change the physical properties of the silica powder itself by bonding various modifying groups to the silica surface through these groups. For example, the silica powder surface is originally hydrophilic due to the presence of silanol groups, but by modifying it with hydrophobic groups, it becomes more hydrophobic and can increase the affinity with highly hydrophobic resins. By such surface modification, it is possible to change the properties of a combination of hydrophilic silica powder and hydrophobic resin, which was originally not able to be uniformly dispersed, to a combination of hydrophobic silica powder and hydrophobic resin, improving the affinity between the silica powder and the resin and making it possible to uniformly disperse silica as a filler throughout the resin composition. As a result, it is known that it has become possible to impart various functions to the resin composition, such as improving heat resistance and improving electrical properties such as insulation.

[0008] While the silanol groups on the surface of silica powder are used to improve functionality through surface modification, there is a demand for methods to reduce the silanol groups inside the silica powder. The silanol groups inside the silica powder are present to break the siloxane bonds inside the silica powder, causing various adverse effects such as a decrease in heat resistance temperature during melting, foaming during melting, a decrease in electrical insulation in semiconductor applications, and optical transmission loss due to light absorption by the silanol groups in optical applications.

[0009] In applications where silica powder is mixed with resin and molded, there is a need to improve heat resistance by reducing the number of silanol groups and to suppress foaming during melting. In molded products for use as overcladding for optical fiber, there is a need to reduce optical transmission loss by reducing the number of silanol groups. In the semiconductor field, when silica filler is mixed with resin, it is desired to reduce the number of silanol groups in order to improve electrical insulation. In applications where baking at high temperatures is not required to change the chemical and / or physical properties, and the product is used in the form of a molded product, for example, when silica filler is mixed with resin in the semiconductor field, it is desired to reduce the number of silanol groups in order to improve electrical insulation.

[0010] The reduction of silanol groups inside the silica powder is generally achieved by calcination at 500°C or higher. The higher the calcination temperature, the lower the silanol content of the resulting silica powder. However, if surface modification is assumed, it is necessary to leave silanol on the silica surface, and due to this constraint, the calcination temperature cannot be raised too much, resulting in a high amount of silanol groups inside the silica powder. For example, the method for producing silica particles and resin compositions disclosed in Patent Document 1 involves generating silanol groups on the surface of silica particles, but the silanol groups inside the silica particles are not optimized and cannot meet the required standards for the applications described above.

[0011] The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface-modified silica powder in which the amount of silanol groups inside the silica powder is sufficiently reduced, and a method for producing the same. Another object of the present invention is to provide an excellent resin composition in which silica powder with a reduced amount of silanol groups inside is dispersed in the resin composition. [Means for solving the problem]

[0012] When surface modification was assumed for conventional silica powders, the calcination temperature had to be adjusted to control the amount of silanol groups on the surface, and the problem of not being able to completely reduce the silanol groups inside the silica powder had not been fully resolved. However, after extensive research, the inventors discovered a method for producing surface-modified silica powder by reducing the amount of silanol groups in the entire silica powder and generating silanol groups only on the surface of the silica powder, thereby completing the present invention.

[0013] That is, the gist of the present invention is as follows. [1] A surface-modified silica powder having a silanol group amount of 200 ppm or less, and a proportion of the amount of modifying groups calculated as silanol groups of 20% or more when the total amount of silanol groups and the amount of modifying groups calculated as silanol groups is taken as 100%. [2] The surface-modified silica powder according to [1], having a methanol wettability value of 60 or more. [3] The surface-modified silica powder according to [1] or [2], wherein the ratio of the amount of modifying groups calculated as silanol groups to the amount of silanol groups (amount of modifying groups / amount of silanol groups) is 40% or more. [4] The surface-modified silica powder according to any one of [1] to [3], wherein the amount of silanol groups is 100 ppm or less. [5] A surface-modified silica powder having a silanol group content of 200 ppm or less and a methanol wettability value of 60 or more. [6] The surface-modified silica powder according to [5], wherein the amount of silanol groups is 100 ppm or less. [7] The surface-modified silica powder according to any one of [1] to [6], which has an average particle size of 0.1 to 500 μm. [8] The surface-modified silica powder according to any one of [1] to [6], which has an average particle size of 100 to 500 μm. [9] The surface-modified silica powder according to any one of [1] to [6], which has an average particle size of 0.1 to 100 μm.

[10] The surface-modified silica powder according to any one of [1] to [6], which has an average particle size of 1 to 20 μm.

[11] The surface-modified silica powder according to any one of [1] to

[10] , which is surface-modified with an alkylsilyl group.

[12] The surface-modified silica powder according to

[11] , wherein the alkylsilyl group is at least one functional group selected from a trimethylsilyl group, a triethylsilyl group, and a tert-butyldimethylsilyl group.

[13] The surface-modified silica powder according to any one of [1] to

[12] , which is surface-modified with at least one functional group selected from a phenylsilyl group, a diphenylsilyl group, and a triphenylsilyl group.

[14] The surface-modified silica powder according to any one of [1] to

[13] , which is amorphous.

[15] A method for producing a surface-modified silica powder according to any one of [1] to

[14] , comprising a step of calcining the silica powder at 1100° C. or higher.

[16] The method for producing a surface-modified silica powder according to

[15] , further comprising a step of roughening the surface of the calcined silica powder to generate silanol groups.

[17] The method for producing a surface-modified silica powder according to

[15] or

[16] , wherein the silica powder having a silanol group content of 200 ppm or less is subjected to a surface roughening treatment to produce a surface-modified silica powder.

[18] The method for producing a surface-modified silica powder according to any one of

[15] to

[17] , wherein the silica powder is subjected to a surface-roughening treatment in the presence of a surface modifier.

[19] A resin composition comprising the surface-modified silica powder according to any one of [1] to

[14] .

[20] The resin composition according to

[19] , wherein the content of the surface-modified silica powder is 10 to 85 mass %. [twenty one] The resin composition according to

[19] or

[20] , having a viscosity of 42 Pa s or less. [twenty two] A method for producing a resin composition according to any one of

[19] to

[21] , comprising a step of mixing a resin with the surface-modified silica powder under conditions in which the dissolution temperature of the resin is equal to or higher than the boiling point of water under production conditions. Effect of the Invention

[0014] The surface-modified silica powder of the present invention can sufficiently reduce the amount of silanol groups inside the silica powder. By reducing the amount of silanol groups, it can be preferably used as a raw material for silica materials that have low optical transmission loss and improve electrical insulation. Furthermore, according to the manufacturing method of the modified silica powder of the present invention, it is possible to obtain a surface-modified silica powder that can sufficiently reduce the amount of silanol groups inside the silica powder. [Brief description of the drawings]

[0015] [Figure 1] 1 is a graph showing the relationship between the methanol wettability value of the silica powders obtained in Examples 1 and 2 and Comparative Examples 2 and 3 and the viscosity of the resin composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified and practiced in various ways within the scope of the invention. In this specification, "x and / or y (x and y are optional configurations)" means at least one of x and y, and means three possibilities: x only, y only, and x and y. In this specification, when expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably larger than X" or "preferably smaller than Y". In this specification, when it is expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y". In the present specification, the upper limit or lower limit of a numerical range described in stages can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage. In addition, in the numerical range described in this specification, the upper limit or lower limit of the numerical range can be replaced with a value shown in the examples.

[0017] (Surface-modified silica powder) The surface-modified silica powder according to one embodiment of the present invention (hereinafter, sometimes referred to as "the present surface-modified silica powder") has a silanol group amount of 200 ppm or less. When the surface-modified silica powder has a silanol group amount of 200 ppm or less, the function of the resin composition itself is improved when the surface-modified silica powder is used as a filler for the resin composition, and the surface-modified silica powder can be used preferably. The silanol group amount refers to the mass ratio of silanol groups per mass of the silica powder.

[0018] The amount of silanol groups in the surface-modified silica powder is 200 ppm or less, preferably 150 ppm or less, and more preferably 100 ppm or less. When the amount of silanol groups in the surface-modified silica powder is equal to or less than the upper limit, the powder is excellent in heat resistance during melting, foaming, electrical insulation, and optical transmission loss, and a resin composition containing the powder uniformly and a fired product thereof can have excellent properties. In addition, there is no particular lower limit for the amount of silanol groups in the surface-modified silica powder, but from the viewpoint of ease of production, it is preferably 10 ppm or more.

[0019] The amount of silanol groups in the surface-modified silica powder can be measured, for example, using an infrared spectrometer (FTIR) at a wave number of 3670 cm -1 The concentration can be calculated from the height of the nearby absorption peak by comparison with a standard specimen.

[0020] The amount of silanol groups in the surface-modified silica powder can be set within the desired range by adjusting the production conditions of the surface-modified silica powder, particularly the calcination temperature for the amount of internal silanol groups in the silica powder, and the vibration frequency and time of the vibration mill, which greatly affect the roughening of the silica surface, for the amount of silanol groups on the silica powder surface.

[0021] When the total value of the silanol group amount and the modified group amount calculated as silanol group of the surface-modified silica powder is taken as 100%, the proportion of the modified group amount calculated as silanol group is preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, and particularly preferably 60% or more. When the ratio of the silanol group amount and the modified group reacted in the surface-modified silica powder is equal to or more than the lower limit, the surface-modified silica powder can be easily dispersed in the resin. In addition, there is no particular upper limit for the silanol group amount of the surface-modified silica powder, but from the viewpoint of ease of production, it is preferably 70% or less.

[0022] The ratio of the modifying group reacted with the silanol group of the surface-modified silica powder may be calculated from the amount of silanol group after the surface roughening treatment and the amount of silanol group after the subsequent surface modification, or may be calculated by converting the amount of modifying group after the surface modification into the amount of silanol group after quantitative analysis. A specific calculation method will be described later in the Examples.

[0023] In the surface-modified silica powder, the ratio of the amount of modifying groups calculated as silanol groups to the amount of silanol groups (amount of modifying groups / amount of silanol groups) is preferably 20% or more, more preferably 40% or more, with the upper limit being 100%.

[0024] In the surface-modified silica powder, when the total value of the silanol group amount and the amount of modification group converted into silanol group is taken as 100%, the ratio of the amount of modification group converted into silanol group can be set to a desired range by controlling the production conditions of the surface-modified silica powder, particularly the amount of silanol generated during the surface roughening process. For example, when a vibration mill is used during the surface roughening process, a large amount of silanol groups can be generated on the silica surface by increasing the vibration frequency and lengthening the vibration time. A large amount of modification group can be imparted by administering a large amount of surface modifier thereto. Since the amount of internal silanol groups in the silica powder does not change, the ratio of the surface modification group can be increased as a ratio of the entire surface-modified silica powder.

[0025] The methanol wettability value of the surface-modified silica powder is preferably 60 or more, more preferably 65 or more, and even more preferably 70 or more, from the viewpoint of compatibility with hydrophobic resins. The upper limit is 100%, but is usually 90% or less.

[0026] The methanol wettability value of the surface-modified silica powder can be measured, for example, by the following method. (i) Place 0.5 g of sample in a 500 mL Erlenmeyer flask. (ii) Add 50 mL of ion-exchanged water to (i) and stir with a stirrer. (iii) While stirring, drip methanol from the burette and read the amount of methanol dripped when the entire amount of the sample is suspended in the ion-exchanged water. (iv) The hydrophobicity is calculated according to the following formula (1). Methanol wettability value = amount of methanol dropped (mL) × 100 / (amount of methanol dropped (mL) + amount of ion-exchanged water (mL)) (1)

[0027] The methanol wettability value of the surface-modified silica powder can be controlled by the production conditions of the surface-modified silica powder, and can be set within a desired range, for example, by adjusting the amount of surface modifier added during the surface roughening step.

[0028] The average particle size of the surface-modified silica powder is usually 0.1 to 100 μm, preferably 0.5 to 50 μm, and more preferably 1 to 20 μm, from the viewpoint of suitable use as a filler for a resin composition. On the other hand, when a silica sintered body is desired at high temperatures, the average particle size is preferably about 100 to 500 μm, since fine powder can cause fumes.

[0029] The particle size distribution can be measured, for example, using a Microtrac MT3300EX manufactured by Microtrac Bell, Inc., using a laser diffraction / scattering method.

[0030] The average particle size of the surface-modified silica powder can be controlled by the production conditions of the surface-modified silica powder, and can be set within a desired range, for example, by adjusting the operating conditions of a jet mill pulverizer.

[0031] The surface of the surface-modified silica powder can be modified with various functional groups, but from the viewpoint of compatibility with the resin, it is preferable to include a functional group that the resin has. For example, for a rubber material having a butadiene skeleton, a surface modifier having a butadiene skeleton is preferable, and for an amide resin, a surface modifier having a ureido group is preferable. In addition, one or more functional groups may be selected from acrylic groups, methacrylic groups, styryl groups, epoxy groups, vinyl groups, amino groups, isocyanate groups, mercapto groups, alkylsilyl groups, arylsilyl groups, etc. to modify the resin. Among these, alkylsilyl groups are preferred from the viewpoint of ease of introduction into silica and compatibility, and trimethylsilyl groups, triethylsilyl groups, and tert-butyldimethylsilyl groups are particularly preferred. On the other hand, from the viewpoint of compatibility with resins containing a benzene ring, arylsilyl groups that also contain a benzene ring are preferred, and phenylsilyl groups, diphenylsilyl groups, and triphenylsilyl groups are particularly preferred.

[0032] The surface-modified silica powder is preferably amorphous silica. On the other hand, natural or artificial crystalline silica is not preferable because it contains a lot of impurities. In addition, the thermal expansion coefficient is high, which may be problematic depending on the application. Furthermore, crystalline silica powder is a harmful substance that can cause silicosis and the like in the human body, so it is preferable that it is amorphous.

[0033] The amorphous surface-modified silica powder can be obtained by a known method, but it is preferable to use silica powder obtained by, for example, drying and baking a gel obtained by hydrolyzing an alkoxysilane as the raw material. Whether the silica powder is amorphous or crystalline can be confirmed by X-ray diffraction.

[0034] There is no limitation on the shape of the present surface-modified silica powder, but a spherical or crushed shape is preferred, and a crushed shape is preferred from the viewpoint of ease of production.

[0035] The specific surface area of ​​the surface-modified silica powder is 0.5 to 10 m from the viewpoint of dispersion. 2 / g is preferable, and 1 to 5m 2 / g is more preferred.

[0036] The specific surface area of ​​the surface-modified silica powder is measured by a gas adsorption method such as a nitrogen gas adsorption method.

[0037] The impurity content of the surface-modified silica powder is preferably 1 mass ppb or less in terms of radioactive element content. In the case of K, the content is preferably 1 mass ppm or less, more preferably 500 mass ppb or less, and even more preferably 100 mass ppb or less. In the case of Na, the content is preferably 1 mass ppm or less, more preferably 500 mass ppb or less, and even more preferably 100 mass ppb or less. In addition, the total content of metal elements excluding Al and Zr is preferably 1 mass ppm or less. The impurity content is measured, for example, by ICP-MS (inductively coupled plasma mass spectrometry). Alkali metals such as K and Na are factors that reduce the viscosity of silica glass when melted and also cause deterioration in electrical insulation, so low concentrations are preferable. The preferred Al and Zr contents in the particles vary depending on the application. For example, if the application requires heat resistance, it is preferable that the content is about several ppm by mass to several hundred ppm by mass, but if the particle is used for semiconductor jigs and the like that require high purity as the final product, it is preferable that the content is less than 1 ppm by mass.

[0038] (Method of manufacturing surface-modified silica powder) The surface-modified silica powder can be obtained by a manufacturing method including a step of calcining the silica powder at 1100°C or higher. In the calcination step of the silica powder, calcination is preferably performed at 1200°C or higher, and more preferably at 1300°C or higher. The upper limit is usually 1600°C or lower, and more preferably 1400°C or lower. By calcining the silica powder at a temperature equal to or higher than the lower limit, the amount of silanol groups on the surface and inside of the silica powder can be sufficiently reduced. If the temperature is too low, the removal of silanol groups OH will be insufficient, and if the temperature is too high, the particles will solidify.

[0039] The method for producing the surface-modified silica powder preferably includes a step of roughening the surface of the silica powder after the calcination step, which can selectively generate silanol groups on the silica surface by breaking siloxane bonds on the silica surface and reacting the broken bonds with moisture around the silica.

[0040] The surface roughening step of the silica powder can be carried out by various methods, for example, only silica powder and ceramic balls may be placed in a cylinder and subjected to a vibration mill, a solvent and balls may be placed in a cylinder and subjected to a vibration mill, or silica powder and resin may be kneaded in a kneader. The surface roughening step may be carried out in a gas atmosphere or a liquid atmosphere.

[0041] Since the resin composition can have improved functions such as heat resistance and insulation, and can be used as a raw material for a silica material with low optical transmission loss, the surface roughening step of the silica powder is preferably performed on silica powder with a silanol group content of 200 ppm or less, more preferably on silica powder with a silanol group content of 150 ppm or less, and even more preferably on silica powder with a silanol group content of 100 ppm or less. There is no particular lower limit, but from the viewpoint of ease of production, it is preferable to perform the surface roughening step on silica powder with a silanol group content of 10 ppm or more.

[0042] There is no particular limitation on the timing of surface modification of the silica powder, but since silanol groups are generated by surface roughening and the silanol groups can be modified with functional groups immediately after the generation, it is preferable to add a surface modifier at the same time as the surface roughening step of the silica powder. In other words, it is preferable to perform the surface roughening treatment of the silica powder in the presence of the surface modifier. By including this step, silanol groups are generated only on the silica powder surface, and a sufficient amount of functional groups can be modified on the silica powder surface in the reaction between the silica powder and the surface modifier.

[0043] There are no particular limitations on the surface modifier as long as it has the effect of improving compatibility with the resin to be combined, but it is preferable to use a surface modifier capable of modifying an alkylsilyl group, which has a low bulkiness of the modifying group due to its high reactivity with the silanol group present on the silica powder surface, and in particular, it is preferable to use a surface modifier capable of modifying at least one functional group selected from a trimethylsilyl group, a triethylsilyl group, a tert-butyldimethylsilyl group, etc. In the case of a resin containing a benzene ring, it is preferable to use a surface modifier capable of modifying at least one functional group selected from a phenylsilyl group, a diphenylsilyl group, a triphenylsilyl group, etc., which also contain a benzene ring. One type of surface modifier may be used, or multiple types may be used.

[0044] The silica powder, which is the raw material of the surface-modified silica powder, can be produced by a known method, and it is preferable to use a high-purity silica powder produced by a sol-gel method using a high-purity alkoxysilane as the raw material. If the silica powder is high-purity, it is possible to precisely control the composition by adding the required amounts of various necessary elements later.

[0045] Because of its high purity, silica powder produced by the sol-gel method using a high purity starting material can be suitably used for the present surface-modified silica powder. Silica powder obtained by the sol-gel method may be calcined, but it is possible to obtain a desired particle size distribution by pulverizing it in the state of a soft wet gel before calcination and its dried product, a dry gel. For example, when a particle size of about several hundred μm is desired, it is possible to obtain a pulverized product while suppressing contamination from the pulverizer by pulverizing it in the state of a wet gel. When a particle size of about several μm is desired, it is possible to obtain a pulverized product while suppressing contamination by pulverizing the dry gel, which is a dried product, with a jet mill pulverizer.

[0046] (Resin composition) A resin composition according to one embodiment of the present invention (hereinafter, may be referred to as "the present resin composition") contains the present surface-modified silica powder.

[0047] In the present resin composition, the content of the surface-modified silica powder is preferably 10 to 85% by mass, more preferably 25 to 80% by mass, and even more preferably 30 to 70% by mass, when the mass of the entire resin composition is taken as 100% by mass. When the content of the surface-modified silica powder is equal to or more than the lower limit, the effect of improving the functions of the resin composition, such as heat resistance and insulating properties, is easily obtained, and when the content of the surface-modified silica powder is equal to or less than the upper limit, the mixability with the resin is improved, and the production stability is improved.

[0048] In the present resin composition, the present surface-modified silica powder may be used as it is, or the present surface-modified silica powder may be subjected to a known pretreatment before use.

[0049] The resin material contained in the resin composition is not particularly limited, and for example, a thermoplastic resin or a thermosetting resin can be used. Examples of the thermoplastic resin include silicone resin, cellulose derivative, polyphenyl ether resin, polysulfone resin, thermoplastic polyurethane resin, halogen-containing resin, organic acid vinyl ester resin, organic acid vinyl ester resin derivative, (meth)acrylic resin, styrene resin, olefin resin, polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, polyvinyl chloride resin, and the like. Examples of the thermosetting resin include epoxy resin, phenol resin, polycarbonate resin, unsaturated polyester resin, melamine resin, urea resin, silicone resin, cyanate resin, polyimide resin, polyamide resin, maleimide resin, and the like. These resins may be used alone or in combination of two or more.

[0050] The resin composition may contain other components in addition to the resin and surface-modified silica powder. Examples of other components include phosphorus-based, phenol-based and other various antioxidants, phenol acrylate-based and other process stabilizers, heat stabilizers, hindered amine radical scavengers (HAAS), impact modifiers, processing aids, metal deactivators, copper inhibitors, antistatic agents, flame retardants, silane coupling agents and other additives, extenders, etc. These can be used alone or in combination of two or more. When these additives are used, the amount of addition may be within the range of the amount usually used for these purposes.

[0051] From the viewpoint of ease of handling when forming a molded article, the viscosity of the present resin composition at room temperature (23°C) is preferably 42 Pa·s or less, more preferably 40 Pa·s or less, and even more preferably 39 Pa·s or less. There is no particular lower limit, but the viscosity is preferably 5 mPa·s or more, more preferably 10 mPa·s or more, and even more preferably 20 mPa·s or more.

[0052] The viscosity of the present resin composition can be measured, for example, by using a rheometer.

[0053] (Method of producing resin composition) An example of a method for producing the present resin composition according to one embodiment of the present invention will be described below, however, the method for producing the present resin composition is not limited to the following method.

[0054] The method for producing the resin composition includes a step of mixing raw materials such as a resin and surface-modified silica powder. For mixing, a general mixing / stirring device such as a mixer, blender, three-roll kneader, ball mill, kneader, single-screw or twin-screw kneader can be used, and heating may be applied during mixing as necessary. The order of mixing each compounding component is also arbitrary as long as there is no particular problem such as the occurrence of reaction or precipitation. It is preferable to include a step of mixing the resin with the surface-modified silica powder under conditions in which the dissolution temperature of the resin is equal to or higher than the boiling point of water under the manufacturing conditions. This is because, during mixing, the moisture in the resin may cause the formation of silanol groups on the surface of the silica powder, so that during mixing with the silica powder, it is preferable to maintain the temperature at or higher than the boiling point of water (100°C at normal pressure).

[0055] The method for producing the resin composition includes a step of molding a mixture of raw materials. A known method can be used as the molding method. For example, the doctor blade method, the solvent casting method, the extrusion molding method, etc. can be used. These can be used alone or in combination of two or more kinds.

[0056] The method for producing the resin composition may include a step of drying the molded raw material mixture. In the drying step, the solvent and low molecular weight components can be removed. The drying temperature can be adjusted to a temperature at which the molded raw material does not harden rapidly and a uniform resin composition can be obtained.

[0057] The method for producing the resin composition may include a curing step. In the curing step, the resin composition may be cured while being pressurized in order to eliminate large voids in the resin composition and to smooth the surface of the resin composition. EXAMPLES

[0058] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0059] The methods for measuring and calculating various physical properties in the following Examples and Comparative Examples are as follows.

[0060] <Silanol group amount (OH concentration)> The amount of silanol groups in the surface-modified silica powder was measured using an infrared spectrometer (FTIR) at a wave number of 3670 cm -1 The OH concentration was calculated from the height of the absorption peak in the vicinity, and the amount of silanol groups was determined by comparing with a standard.

[0061] <Proportion of modified group amount calculated as silanol group> The ratio of the amount of modified groups converted into silanol groups to the total amount of silanol groups and the amount of modified groups converted into silanol groups, which is taken as 100%, can also be said to be the surface modification rate relative to the total silanol groups, including the silanol groups increased by the surface roughening treatment. The amount of modified groups can be calculated using silica powder that has not been surface-modified in the same manner as above as a standard. in particular, Surface modification rate relative to total silanol groups = (amount of modified groups converted into silanol groups) / (amount of modified groups converted into silanol groups + amount of silanol groups in surface-modified silica powder) Or, Surface modification rate relative to total silanol groups=(amount of silanol groups reacted with surface modifier) / (amount of silanol groups in silica powder after surface roughening treatment) In this case, the numerators and denominators of each equation are interchangeable.

[0062] <Average particle size> The particle size distribution was measured using a Microtrac MT3300EX2 manufactured by Microtrac Bell, using the laser diffraction and scattering method, and the average particle size D 50 asked for.

[0063] <Methanol wettability value> The methanol wettability value of the surface-modified silica powder was measured, for example, by the following method. (i) Place 0.5 g of sample in a 500 mL Erlenmeyer flask. (ii) Add 50 mL of ion-exchanged water to (i) and stir with a stirrer. (iii) While stirring, drip methanol from the burette and read the amount of methanol dripped when the entire amount of the sample is suspended in the ion-exchanged water. (iv) The hydrophobicity is calculated according to the following formula (1). Methanol wettability value = amount of methanol dropped (mL) × 100 / (amount of methanol dropped (mL) + amount of ion-exchanged water (mL)) (1)

[0064] <Viscosity measurement of resin composition> The viscosity of the resin composition was measured by first mixing the silica and resin using a Thinky Mixer (model ARV-200), and then measuring the viscosity using an Anton Paar rheometer (model MCR102) with a cone plate model CP25.

[0065] <Manufacturing of silica powder> 300 g of tetramethoxysilane was placed in a 1 L glass jacketed separable flask equipped with a stirrer, and after heating to an internal temperature of 45°C, 210 g of ultrapure water (6 times molar ratio) was added to carry out a hydrolysis reaction of tetramethoxysilane. The resulting agar-like wet gel was taken out and crushed by pressing the gel through a sieve with 0.8 mm openings. The crushed gel was then placed in a vacuum dryer and heated to 200° C. under reduced pressure to evaporate the water and methanol from the gel, yielding 130 g of silica dry gel powder. The obtained dry gel was pulverized using a single track jet mill FS-4 manufactured by Seishin Enterprise Co., Ltd. This powder was placed in a quartz glass crucible and heated (fired) to 1150 to 1300°C in an electric furnace with dry air circulating. The dew point of the dry air was set to -80°C. At this time, the heating time was changed between 1 and 100 hours to produce silica powders with different amounts of silanol groups.

[0066] [Comparative Example 1] In Comparative Example 1, the heating temperature was 1220°C and the heating time was 5 hours. 50 A silica powder having a particle size of 3 μm was obtained. The amount of silanol groups was 50 ppm. The methanol wettability value was 0. In addition, the X-ray diffraction spectrum was obtained using a powder X-ray diffractometer X'Pert Pro (manufactured by Spectris Corporation), and it was confirmed that the powder was amorphous.

[0067] [Comparative Example 2] 0.71 g of hexamethyldisilazane (HMDS) manufactured by Tokyo Chemical Industry Co., Ltd. was sprayed onto 5 g of the silica powder obtained in Comparative Example 1 as a silane coupling agent, and then vacuum dried at 120°C for 6 hours to obtain a surface-modified product. The methanol wettability value was 58, and the hydrophobicity was insufficient. Furthermore, the obtained silica powder was mixed with 1,2-polybutadiene (B-1000 manufactured by Nippon Soda Co., Ltd.) to obtain a resin composition. The viscosity of the resin composition was 42.1 Pa s, which was also high.

[0068] [Comparative Example 3] The same procedure as in Comparative Example 2 was carried out, except that 1.76 g of phenyltrimethoxysilane (KBM-103) manufactured by Shin-Etsu Chemical Co., Ltd. was used as the silane coupling agent. The methanol wettability value was 50, and the hydrophobicity was insufficient. Furthermore, a resin composition was obtained by mixing the obtained silica powder with 1,2-polybutadiene (B-1000 manufactured by Nippon Soda Co., Ltd.) The viscosity of the resin composition was 49.6 Pa s, which was also high.

[0069] [Comparative Example 4] The same procedure as in Comparative Example 1 was carried out, except that the firing temperature was 1050°C and the dew point of the circulating air was 50°C or higher. As a result, the amount of silanol groups was 600 ppm. 50 The silica powder obtained had a methanol wettability value of 0.

[0070] [Comparative Example 5] 0.71 g of hexamethyldisilazane (HMDS) manufactured by Tokyo Chemical Industry Co., Ltd. was sprayed as a silane coupling agent onto 5 g of the silica powder obtained in Comparative Example 4, and then vacuum dried at 120° C. for 6 hours to obtain a surface-modified product. As a result, a silica powder with sufficient hydrophobicity was obtained with a methanol wettability value of 73. However, the amount of silanol groups was 595 ppm, which is insufficient for applications requiring low silanol content. When the amount of silanol groups on the surface of silica is large, there are many reaction sites with silane coupling agent, and surface modification can be performed sufficiently.In this way, in order to generally surface-modify silica, it is necessary to ensure a sufficient amount of silanol groups, and the amount of silanol groups of the silica powder that has been surface-modified is inevitably large.Therefore, in such conventional technology, it is not possible to obtain a surface-modified silica powder with a small amount of silanol groups.

[0071] [Comparative Example 6] 1.76 g of phenyltrimethoxysilane (KBM-103) manufactured by Shin-Etsu Chemical Co., Ltd. was sprayed onto 5 g of the silica powder obtained in Comparative Example 4 as a silane coupling agent, and then vacuum dried at 120°C for 6 hours to obtain a surface-modified product. The methanol wettability value was 71, and the hydrophobicity was sufficient. However, the amount of silanol groups was 535 ppm, which was insufficient for applications requiring low silanol.

[0072] [Comparative Example 7] The silica powder obtained in Comparative Example 1 was subjected to surface roughening using a Retsch mixer mill MM 400 (vibration mill). A 30 mL grinding jar was charged with one zirconia ball having a diameter of 20 mm and 5 g of silica powder, and a particle surface roughening treatment was performed under conditions of a vibration frequency of 10 Hz and a vibration time of 5 minutes. As a result, the amount of silanol groups in the obtained silica increased to 112 ppm, and the increase in the amount of silanol due to surface roughening was 62 ppm. The methanol wettability value was 0. The particle size after surface roughening was measured, and D 50 It was confirmed that the particle size remained at 3 μm, and there was no change in the particle size.

[0073] [Example 1] The same procedure as in Comparative Example 7 was carried out, except that 0.71 g of hexamethyldisilazane (HMDS) manufactured by Tokyo Chemical Industry Co., Ltd. was added to the 30 mL grinding jar. As a result, the amount of silanol groups in the obtained silica remained at a sufficiently low value of 67 ppm, and the methanol wettability value was 74, which showed sufficient hydrophobicity. From this, it is believed that the silica powder originally had a silanol group amount of 50 ppm, but after the surface roughening treatment, the amount increased by 62 ppm to 112 ppm, and then reacted with HMDS, decreasing the amount by 45 ppm to 67 ppm. Therefore, it is believed that the silica surface is modified with trimethylsilyl groups derived from HMDS, which is equivalent to 79 ppm of silanol groups. From the above results, it is believed that 62 ppm of silanol was generated on the silica surface by the roughening treatment, of which 45 ppm reacted with HMDS. The reactivity of HMDS with respect to the generated surface silanol was (45 ppm of reacted silanol groups) / (62 ppm of silanol groups generated on the surface) = 72.6%, and the proportion of the amount of modified groups calculated as silanol groups with respect to the total silanol groups, including the silanol groups increased by the roughening treatment, was (45 ppm of reacted silanol groups) / (112 ppm of silanol groups after roughening treatment) = 40.2%. The ratio of the amount of silanol groups lost by surface modification to the amount of silanol groups generated on the surface by the surface roughening treatment is 70% or more, so it is believed that the modifying groups are selectively bonded to the surface. In addition, the ratio of the amount of modifying groups calculated as silanol groups to the total silanol groups, including the silanol groups increased by the surface roughening treatment, is 40% or more, so it is believed that a sufficient amount of modifying groups is bonded to the silica, even including the amount of silanol groups present inside the silica particles. Ultimately, it is determined that the hydrophilicity of the silica powder was significantly reduced as more than 40% of the total silanol groups were modified. Furthermore, a resin composition was obtained by mixing the obtained silica powder with 1,2-polybutadiene (B-1000 manufactured by Nippon Soda Co., Ltd.) The viscosity of the resin composition was 37.3 Pa s, which is a sufficiently low viscosity.

[0074] [Example 2] The same procedure as in Example 1 was carried out, except that 1.76 g of phenyltrimethoxysilane (KBM-103) manufactured by Shin-Etsu Chemical Co., Ltd. was used as the silane coupling agent. As a result, the amount of silanol groups in the obtained silica remained at a sufficiently low value of 56 ppm, and the methanol wettability value was 69, which was sufficient hydrophobicity. From this, it is believed that the silica powder originally had a silanol group amount of 50 ppm, but after the surface roughening treatment, the amount increased by 62 ppm to 112 ppm, and then reacted with phenyltrimethoxysilane, decreasing the amount by 56 ppm to 56 ppm. Therefore, it is believed that the silica surface is modified with phenylsilyl groups derived from phenyltrimethoxysilane, equivalent to 56 ppm of silanol groups. From the above results, it is believed that 62 ppm of silanol was generated on the silica surface by the roughening treatment, of which 56 ppm reacted with phenyltrimethoxysilane. The reactivity rate of phenyltrimethoxysilane with the generated surface silanol groups was (56 ppm of reacted silanol groups) / (62 ppm of silanol groups generated on the surface)=90.3%, and the surface modification rate with respect to all silanol groups, including the silanol groups increased by the roughening treatment, was (56 ppm of reacted silanol groups) / (112 ppm of silanol groups after roughening treatment)=50.0%. The ratio of the amount of silanol groups lost by surface modification to the amount of silanol groups generated on the surface by the surface roughening treatment is 70% or more, so it is believed that the modifying groups are selectively bonded to the surface. In addition, the ratio of the amount of modifying groups calculated as silanol groups to the total silanol groups, including the silanol groups increased by the surface roughening treatment, is 40% or more, so it is believed that a sufficient amount of modifying groups is bonded to the silica, even including the amount of silanol groups present inside the silica particles. Ultimately, it is determined that the hydrophilicity of the silica powder was significantly reduced as more than 40% of the total silanols were modified. Furthermore, a resin composition was obtained by mixing the obtained silica powder with 1,2-polybutadiene (B-1000 manufactured by Nippon Soda Co., Ltd.) The viscosity of the resin composition was 38.2 Pa s, which is a sufficiently low viscosity.

[0075] The evaluation results of each of the obtained silica powders and resin compositions are shown in Table 1. Moreover, the relationship between the methanol wettability value of the silica powders obtained in Examples 1 and 2 and Comparative Examples 2 and 3 and the viscosity of the resin compositions is shown in FIG.

[0076] [Table 1]

[0077] As can be seen from Table 1 and FIG. 1, by carrying out the surface roughening treatment and surface modification treatment, it became possible to modify the surface while suppressing the increase in the amount of silanol groups in the silica powder. This makes it possible to surface modify the low silanol silica powder, and by carrying out the surface modification, it is possible to increase the methanol wettability value even in the case of low silanol silica, and to reduce the viscosity of the resin composition. Since a low-viscosity resin composition has high fluidity, it is easy to mold and process, and products with complex shapes can be made. Furthermore, it is easy to fill a mold, and the occurrence of air bubbles and voids can be suppressed, so that improvement in product quality can be expected. [Industrial Applicability]

[0078] Since the present surface-modified silica powder has a low silanol group content and its surface is modified, it can be suitably used as a filler for resin compositions or a raw material for sintered bodies.

Claims

1. A surface-modified silica powder having a silanol group amount of 200 ppm or less, and a proportion of a modifying group amount calculated as a silanol group of 20% or more when the total amount of silanol groups and the modifying group amount calculated as a silanol group is taken as 100%.

2. 2. The surface-modified silica powder according to claim 1, which has a methanol wettability value of 60 or more.

3. 2. The surface-modified silica powder according to claim 1, wherein the ratio of the amount of modifying groups calculated as silanol groups to the amount of silanol groups (amount of modifying groups / amount of silanol groups) is 40% or more.

4. 2. The surface-modified silica powder according to claim 1, wherein the amount of silanol groups is 100 ppm or less.

5. A surface-modified silica powder having a silanol group content of 200 ppm or less and a methanol wettability value of 60 or more.

6. 6. The surface-modified silica powder according to claim 5, wherein the amount of silanol groups is 100 ppm or less.

7. 2. The surface-modified silica powder according to claim 1, having an average particle size of 0.1 to 500 μm.

8. 2. The surface-modified silica powder according to claim 1, having an average particle size of 100 to 500 μm.

9. 2. The surface-modified silica powder according to claim 1, having an average particle size of 0.1 to 100 μm.

10. 2. The surface-modified silica powder according to claim 1, having an average particle size of 1 to 20 μm.

11. 2. The surface-modified silica powder according to claim 1, which is surface-modified with an alkylsilyl group.

12. 12. The surface-modified silica powder according to claim 11, wherein the alkylsilyl group is at least one functional group selected from the group consisting of a trimethylsilyl group, a triethylsilyl group, and a tert-butyldimethylsilyl group.

13. 2. The surface-modified silica powder according to claim 1, which is surface-modified with at least one functional group selected from the group consisting of a phenylsilyl group, a diphenylsilyl group, and a triphenylsilyl group.

14. The surface-modified silica powder according to claim 1 , which is amorphous.

15. The method for producing the surface-modified silica powder according to any one of claims 1 to 14, comprising a step of calcining the silica powder at 1100°C or higher.

16. The method for producing a surface-modified silica powder according to claim 15, further comprising a step of roughening the surface of the fired silica powder to generate silanol groups.

17. The method for producing a surface-modified silica powder according to claim 15, wherein the silica powder having a silanol group content of 200 ppm or less is subjected to a surface roughening treatment to produce a surface-modified silica powder.

18. The method for producing a surface-modified silica powder according to claim 16, wherein the silica powder is subjected to a surface roughening treatment in the presence of a surface modifier.

19. A resin composition comprising the surface-modified silica powder according to any one of claims 1 to 14.

20. The resin composition according to claim 19, wherein the content of the surface-modified silica powder is 10 to 85 mass%.

21. The resin composition according to claim 19, having a viscosity of 42 Pa·s or less.

22. The method for producing a resin composition according to claim 19, comprising the step of mixing a resin and the surface-modified silica powder under conditions in which the dissolution temperature of the resin is equal to or higher than the boiling point of water under production conditions.

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