ORGANOSILICA SOL AND PRODUCTION PROCESS THEREOF

Abstract

[Problem] To provide a silica particle dispersion that shows little change over time associated with surface modification and has stable quality. [Solution] A silica particle dispersion in which surface-treated silica particles are dispersed in an organic solvent, wherein the surface-treated silica particles are silica particles surface-treated with a surface-treating agent containing an alkoxysilane containing a radically polymerizable double bond and an ester group, and wherein the rate of change over time in the amount of particle surface treatment with the surface-treating agent is less than 20% and the decomposition rate of the surface-treating agent is 2.0% or less, as well as a method for producing the silica particle dispersion and a composite material comprising the silica particle dispersion.

Description

TECHNICAL FIELD

[0001] The present invention relates to an organosilica sol and a process for its preparation. State of the art

[0002] Composite materials are known that are produced by incorporating inorganic oxide particles, such as silica, into various resins in order to improve mechanical properties, such as strength and elastic modulus, as well as thermal and electrical properties.

[0003] In order to improve the properties of the composite materials, attention has also been focused on the control of the particle interface, such as the compatibility between the silica particles or the like and the resin into which they are to be incorporated, and proposals have been made for surface modifications or the like of the silica particles using various surface treatment agents (also called surface modifiers).

[0004] For example, in order to provide an inorganic oxide sol dispersed in an organic solvent having good dispersibility, low viscosity, excellent transparency, and good compatibility with resin solutions, a method has been disclosed in which hydroxyl groups on the surfaces of inorganic oxide particles such as silica are reacted with an alcohol to introduce alkoxysilyl groups to organicize the surfaces of the inorganic oxide particles, thereby obtaining an inorganic oxide sol dispersed in an organic solvent such as toluene (Patent Document 1).

[0005] In addition, a liquid epoxy resin forming composition containing a colloidal silica sol whose particle surface is coated with an organoalkoxysilane has been disclosed, in which, for example, a silica sol dispersed in methanol is subjected to solvent replacement with acetonitrile to obtain a silica sol dispersed in an acetonitrile-methanol mixed solvent, and then the silica sol is reacted with phenyltrimethoxysilane (Patent Document 2).

[0006] In addition, a silica sol has been disclosed in which the surfaces of the silica particles have been modified with an aluminum compound, the silica sol having excellent dispersion stability in an acidic region, excellent stability and transparency in a coating composition containing the silica sol with a binder component, and improved transparency, film hardness, scratch resistance, adhesion, heat resistance, impact resistance, and the like in a coating film of the coating composition (Patent Document 3). Prior art documentsPatent documents Patent Document 1: JP 2005-200294 A Patent Document 2: WO 2009 / 008509 Patent Document 3: JP 2011-026183 A SUMMARY OF THE INVENTIONProblem to be solved by the invention

[0007] The surface-treated silica particles described above can be used to form a composite with the resin material, for example, in the form of a dispersion of the surface-treated silica particles or a sol of the surface-treated silica. It is desirable that the silica particle dispersion (silica sol), for example, has good compatibility with the resin material, and that the quality of the surface-treated silica particles in the composite formation be constant from production until their use, that is, the surface treatment state of the particles (interfacial state of the particles) is constant and the surface treatment quality is stable.If the surface treatment state of the surface-treated silica particles changes over time, it may affect the stabilization of the quality of the surface-treated silica particles and further affect the stabilization of the quality of the surface-treated silica particles when they are formed into a composite material.

[0008] In view of the above circumstances, it is an object of the present invention to provide a silica particle dispersion which shows little change over time associated with surface treatment and has stable quality. Means of solving the problem

[0009] As a first aspect, an embodiment of the present invention for solving the above-described problem relates to a silica particle dispersion in which surface-treated silica particles are dispersed in an organic solvent, wherein the surface-treated silica particles are silica particles surface-treated with a surface-treating agent comprising an alkoxysilane containing a radically polymerizable double bond and an ester group, and in which in the dispersion the rate of change over time of the amount of particle surface treatment with the surface treatment agent, as defined by the following formula (1), is less than 20%, and the decomposition rate of the surface treatment agent, as defined by the following formula (2), is 2.00% or less: <Veränderungsrate [%] über die Zeit der Menge der Partikel-Oberflächenbehandlung> Rate of change over time of the amount of particle surface treatment = [(B−A) / A] × 100 [%] where in formula (1) A is the amount of particle surface treatment after one week of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion; and B is the amount of particle surface treatment after 14 weeks of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion; <Zersetzungsrate [%] des Oberflächenbehandlungsmittels> Decomposition rate of surface treatment agent=[C×(D / E)÷F]×100[%] where in formula (2) C is the amount (mass %) of a decomposition product originating from the surface treatment agent in the silica particle dispersion after at least two weeks of storage at room temperature (20 to 25°C) to 50°C after preparation of the particle silica dispersion, wherein the decomposition product comprises a radically polymerizable double-bond-containing carboxylic acid and a derivative of the radically polymerizable double-bond-containing carboxylic acid; D is the molecular weight (g / mol) of the surface treatment agent; E is the molecular weight (g / mol) of the decomposition product; and F is the amount (proportion in mass% in the silica particle dispersion) of the surface treatment agent added during surface treatment.

[0010] A second aspect relates to the silica particle dispersion according to the first aspect, wherein the silica particle dispersion has a pH of 6.5 to 8.0.

[0011] A third aspect relates to the silica particle dispersion according to the second aspect, wherein the silica particle dispersion contains a basic substance selected from hydroxide or alkoxide compounds derived from monovalent alkali metals.

[0012] A fourth aspect relates to the silica particle dispersion according to any one of the first to third aspects, wherein the initial reaction rate between the surface treatment agent and the silica particles is 50% or more, wherein the initial reaction rate is defined as a ratio of the amount of particle surface treatment with the surface treatment agent after one week of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion, relative to the amount of the surface treatment agent added during the surface treatment.

[0013] A fifth aspect relates to the silica particle dispersion according to any one of the first to fourth aspects, wherein the silica particles have an average primary particle diameter of 5 nm or greater and less than 100 nm and wherein in the silica particle dispersion, the concentration of the surface-treated silica particles is 20 to 70 mass% and the water concentration is 0.001 to 10 mass%.

[0014] A sixth aspect relates to the silica particle dispersion according to any one of the first to fifth aspects, wherein the surface-treated silica particles are mixed with the surface-treating agent in an amount of 0.5 to 3.0 molecules per nm 2 the surface of the silica particles is surface treated.

[0015] A seventh aspect relates to the silica particle dispersion according to any one of the first to sixth aspects, wherein the surface treating agent is an alkoxysilane of the following formula (a).

[0016] An eighth aspect relates to the silica particle dispersion according to any one of the first to seventh aspects, wherein the organic solvent is at least one organic solvent selected from the group consisting of alcohols, ketones, hydrocarbons, amides, esters, ethers and amines.

[0017] A ninth aspect relates to a composite material comprising the silica particle dispersion according to any one of the first to eighth aspects and an organic resin material.

[0018] A tenth aspect relates to the composite material according to the ninth aspect, wherein the organic resin material is at least one selected from the group consisting of polyethylene resins, polypropylene resins, polystyrene resins, acrylic resins, urethane resins, urethane acrylate resins, polycarbonate resins, ABS resins, diallyl phthalate, and unsaturated polyesters.

[0019] An eleventh aspect relates to a composition comprising the silica particle dispersion according to any one of the first to eighth aspects, a photosensitive resin and a photopolymerization initiator.

[0020] A twelfth aspect relates to the composition according to the eleventh aspect, wherein the photosensitive resin is at least one selected from the group consisting of acrylic resins, methacrylic resins, urethane acrylate resins, urethane methacrylate resins and epoxy resins.

[0021] A thirteenth aspect relates to a process for producing a silica particle dispersion in which surface-treated silica particles are dispersed in an organic solvent, the process comprising the following steps (A), (B) and (C): Step (A): Preparing a silica sol containing silica particles having an average primary particle diameter of 5 nm or more and less than 100 nm as a dispersoid, and a C1-4 -alcohol as a dispersion medium; Step (B): Adding a surface treatment agent comprising an alkoxysilane containing a radically polymerizable double bond and an ester group to the silica sol and stirring the mixture while heating; and Step (C): Perform pH adjustment to achieve a pH value in a system of 6.5 to 8.0 and stir the mixture while heating.

[0022] A fourteenth aspect relates to the process for producing a silica particle dispersion according to the thirteenth aspect, further comprising, after step (C), the following step (D): Step (D): Adding a surface treatment agent comprising an alkoxysilane containing a radically polymerizable double bond and an ester group to the silica sol and stirring the mixture under heating.

[0023] A fifteenth aspect relates to the process for producing a silica particle dispersion according to the thirteenth or fourteenth aspect, wherein step (C) is the step of performing pH adjustment by adding a basic substance selected from hydroxide or alkoxide compounds derived from monovalent alkali metals. Effects of the invention

[0024] According to the present invention, it is possible to provide a silica particle dispersion in which surface-treated silica particles are dispersed in an organic solvent, the silica particle dispersion having little change over time associated with the surface treatment (surface modification) and having stable quality.

[0025] That is, according to the present invention, it is possible to provide a material having little change over time in the surface (interface) state and having uniform quality in a composite material with a resin or the like. MODES FOR CARRYING OUT THE INVENTION [Silica Particle Dispersion]

[0026] The present invention relates to a silica particle dispersion in which the surface-treated silica particles described below are dispersed in an organic solvent.

[0027] The silica particle dispersion relating to the present invention is characterized in that the following change rate over time of the amount of particle surface treatment is less than 20% and the following decomposition rate of the surface treatment agent is 2.00% or less. <Oberflächenbehandelte Silica-Partikel>

[0028] The surface-treated silica particles of the present invention are silica particles surface-treated with the surface-treating agent described below.

[0029] As used herein, the term "surface treatment" encompasses both an embodiment wherein at least a portion of the surfaces of the silica particles is coated with a surface treatment agent, and an embodiment wherein at least a portion of the surface treatment agent is bonded to at least a portion of the surfaces of the silica particles. These embodiments are collectively referred to as the "surface-treated silica particles" described above.

[0030] The term "at least a portion of the surfaces of the silica particles is coated with a surface treatment agent" may refer to any embodiment in which the surface treatment agent described below coats at least a portion of the surfaces of the silica particles. That is, the term encompasses an embodiment in which the surface treatment agent covers a portion of the surfaces of the silica particles; as well as an embodiment in which the surface treatment agent covers the entire surfaces of the silica particles. In the embodiments, the surface treatment agent may or may not be bonded to the surfaces of the silica particles.

[0031] The phrase "at least a portion of the surface treatment agent is bonded to at least a portion of the surfaces of the silica particles" may refer to any embodiment in which the surface treatment agent described below is bonded to at least a portion of the surfaces of the silica particles. That is, the phrase encompasses, for example, an embodiment in which the surface treatment agent is bonded to a portion of the surfaces of the silica particles; an embodiment in which the surface treatment agent is bonded to a portion of the surfaces of the silica particles to cover at least a portion of the surfaces; and an embodiment in which the surface treatment agent is bonded to the entire surfaces of the silica particles to cover the entire surfaces.

[0032] Preferred embodiments of the silica particles related to the surface-treated silica particles and the surface treatment agent will be described below. < <silica-partikel>>

[0033] According to the invention, the silica particles associated with the surface-treated silica particles (ie, untreated silica particles, hereinafter simply referred to as silica particles) may preferably have a primary particle diameter of less than 100 nm, for example, 5 nm or more and less than 100 nm. <Mittlerer Primärpartikeldurchmesser>

[0034] The average primary particle diameter of the silica particles of the present invention may refer to a specific surface area diameter which is determined from the specific surface area (S N2 ), measured by a BET method using nitrogen gas as molecules adsorbed to the particle surface.

[0035] The specific surface diameter (average primary particle diameter: D (nm)) is the primary particle diameter, which is calculated from the specific surface S N2 (m 2 / g), measured by the nitrogen adsorption method (BET method) based on the formula D (Nm) = 2.720 / S, and denotes the particle diameter calculated in terms of spherical silica particles.

[0036] The silica particles according to the invention preferably have an average primary particle diameter of less than 100 nm, and may have an average primary particle diameter in the range of, for example, 5 nm or more and less than 100 nm, 5 nm or more and 80 nm or less, or 5 nm or more and 50 nm or less.

[0037] By using silica particles with an average primary particle diameter of less than 100 nm, the silica particles can be well dispersed in an organic solvent when formed into surface-treated silica particles. Furthermore, when a composite material obtained using a dispersion of the surface-treated silica particles is formed, the formed composite material can exhibit fewer defects and high transparency.

[0038] The method for producing the (untreated) silica particles that constitute the surface-treated silica particles is not particularly limited, but the silica particles are preferably heat-treated in water at 200 to 380°C. The heat treatment can be carried out using a pressure-resistant vessel (autoclave). <<Oberflächenbehandlungsmittel> >

[0039] The surface treatment agent comprises an alkoxysilane containing a radically polymerizable double bond and an ester group.

[0040] Preferably, the surface treatment agent may be an alkoxysilane having one alkoxy group and one group containing a radically polymerizable double bond and an ester group. While the number of groups containing a radically polymerizable double bond and an ester group and the number of alkoxy groups are not particularly limited, the alkoxysilane preferably has 1 to 3 groups containing a radically polymerizable double bond and an ester group and 1 to 3 alkoxy groups (provided that the total number of both groups is 4 or less) per silicon atom.

[0041] Examples of the radically polymerizable double bond include 1-propenyl group, 2-methyl-1-propenyl group, allyl group, methallyl group, vinyl group and (meth)acryloyl group.

[0042] An example of a group containing a radically polymerizable double bond and an ester group is a (meth)acryloyloxy group.

[0043] The alkoxy group is preferably a C 1-3 -alkoxy group, and particularly preferably a methoxy group.

[0044] In a preferred embodiment, the surface treatment agent may be an alkoxysilane-(3-methacryloxypropyltrimethoxysilane) of the following formula (a).

[0045] Specific examples of preferred surface treating agents include, but are not limited to, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 8-methacryloxyoctylmethyldimethoxysilane, and 8-methacryloxyoctyltrimethoxysilane.

[0046] The amount of surface treatment with the surface treatment agent, ie the amount of the surface treatment agent that coats the particle surface and / or is bound to the particle surface, can be in the range of, for example, 0.5 to 3.0 molecules per nm 2 of the surface of the silica particles. As used herein, the number of molecules per nm 2 of the surface (amount of surface treatment) represents the total amount of surface treatment agent required for surface treatment and is not intended to represent the amount of surface treatment with each individual surface treatment agent when surface treatment is carried out with a variety of types of surface treatment agents. «Organic solvent»

[0047] In the silica particle dispersion of the present invention, the organic solvent serving as a dispersion medium is not particularly limited, but may be, for example, an organic solvent selected from alcohols, ketones, hydrocarbons, amides, ethers, esters, and amines.

[0048] Examples of alcohols include C 1-5 -alcohols, and specific examples thereof include methanol, ethanol, isopropyl alcohol and n-butanol.

[0049] Examples of ketones include C 1-5 -Ketones, and specific examples thereof include methyl ethyl ketone, methyl isobutyl ketone, γ-butyrolactone, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone.

[0050] Examples of hydrocarbons include toluene, xylene, n-pentane, n-hexane and cyclohexane.

[0051] Examples of amides include dimethylacetamide, N,N-dimethylformamide, dimethylacrylamide, acryloylmorpholine and diethylacrylamide.

[0052] Examples of ethers include ethylene glycol monomethyl ether and propylene glycol monomethyl ether.

[0053] Examples of esters include ethyl acetate and butyl acetate.

[0054] Examples of amines include triethylamine, tributylamine, N,N-dimethylaniline, pyridine and picoline.

[0055] The content of surface-treated silica particles in the dispersion can be expressed as silica concentration.

[0056] The silica concentration can be calculated by measuring the amount of calcination residue obtained after calcining the silica particle dispersion at 1,000°C. The silica concentration in the silica particle dispersion can be, for example, 20 mass% to 70 mass%, or 20 mass% to 60 mass%, or, for example, 30 mass% to 40 mass%.

[0057] The water content (water concentration) in the silica particle dispersion can be 20 mass% or less, for example, 0.001 to 10 mass% or 0.1 to 5 mass%. Adjusting the water content within this range results in good dispersion stability and facilitates the formation of a composite material with an organic resin material. <Veränderungsrate über die Zeit>

[0058] In the dispersion of surface-treated silica particles, if the surface treatment agent used for surface treatment remains in the system, the surface treatment agent may react with the surfaces of the silica particles over time, and the amount of surface treatment of the silica particles may change between immediately after the dispersion is prepared and after the passage of time. This amount of change is referred to herein as the rate of change over time of the amount of particle surface treatment, and the rate of change over time is defined by the following formula (1): <Veränderungsrate [%] über die Zeit der Menge der Partikel-Oberflächenbehandlung> Rate of change over time of the amount of particle surface treatment = [(B−A) / A] × 100 [%] wherein in formula (1), A is the amount of particle surface treatment after one week of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion; and

[0059] B is the amount of particle surface treatment after 14 weeks of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion.

[0060] In the present invention, the change rate over time is less than 20%, that is, the silica particle dispersion shows little variation in the amount of surface treatment after preparation, and thus, when forming a composite between the silica particle dispersion and a resin material, the silica particle dispersion can show excellent compatibility with the resin, and after composite formation, the resulting composite material (product) is expected to have little variation in mechanical properties such as elastic modulus, strength, and hardness.

[0061] The amount of particle surface treatment can be quantified as the content (%) of the surface treatment agent bound to the particle surface from the carbon content (%) quantified by elemental analysis of the surface-treated silica particles. <zersetzungsrate>

[0062] After preparing a dispersion of the surface-treated silica particles, the surface treatment agent used for the surface treatment may decompose over time in the dispersion due to the structure of the surface treatment agent.

[0063] According to the invention, the decomposition rate of the surface treatment agent is defined by the following formula (2): <Zersetzungsrate [%] des Oberflächenbehandlungsmittels> Decomposition rate of surface treatment agent=[C×(D / E)÷F]×100[%] wherein in formula (2), C is the amount (mass %) of a decomposition product originating from the surface treatment agent in the silica particle dispersion after at least two weeks of storage at room temperature (20 to 25°C) to 50°C after preparation of the silica particle dispersion; D is the molecular weight (g / mol) of the surface treatment agent; E is the molecular weight (g / mol) of the decomposition product; and F is the amount (proportion in mass % in the silica particle dispersion) of the surface treatment agent added during the surface treatment.

[0064] According to the invention, the decomposition rate is 2.00% or less, that is, after preparation, the resulting silica particle dispersion has a small amount of decomposition of the surface treatment agent bonded to / coated on the silica particle surface, and thus, when a composite is formed between the silica particle dispersion and a resin material, the resulting composite material (product) is expected to have little variation in physical properties such as adhesion.

[0065] The decomposition product derived from the surface treatment agent includes acid compounds formed by hydrolysis of an ester moiety of the alkoxysilane containing a radically polymerizable double bond and an ester group serving as a surface treatment agent, i.e., it includes carboxylic acids containing a radically polymerizable double bond and derivatives thereof. Examples of the decomposition product include (meth)acrylic acid and compounds derived from methacrylic acid and acrylic acid (such as methyl methacrylate). <reaktionsrate>

[0066] In a preferred embodiment, the dispersion of surface-treated silica particles may have an initial reaction rate between the surface treatment agent and the silica particles of 5% or more, 10% or more, 30% or more, or 50% or more, and more preferably 60% or more or 70% or more. Additionally, the initial reaction rate between the surface treatment agent and the silica particles may be 100% or less, 95% or less, 90% or less, or 85% or less.

[0067] As used herein, the initial reaction rate between the surface treatment agent and the silica particles can be defined as a ratio of the amount of particle surface treatment with the surface treatment agent after one week of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion, relative to the amount of the surface treatment agent added during the surface treatment.

[0068] That is, the initial reaction rate between the surface treatment agent and the silica particles can be defined as the value obtained by dividing F [amount (proportion in mass% in the silica particle dispersion) of the surface treatment agent added during the surface treatment] in the formula (2) by A [amount (%) of the particle surface treatment after one week of storage at room temperature (20 to 25°C) after the preparation of the silica particle dispersion] in the formula (1).

[0069] A higher reaction rate means that a smaller amount of the surface treatment agent remains unreacted in the system (in the dispersion). <pH-Wert der Silica-Partikeldispersion>

[0070] The silica particle dispersion of the present invention preferably has a pH of 6.5 to 8.0, for example, a pH of 6.5 to 7.5 or a pH of 7.0 to 7.5. When the silica particle dispersion has a pH of 6.5 to 8.0, the hydrolysis or dehydration condensation of the surface treatment agent containing an alkoxysilane does not proceed excessively, and the reaction over time between the surface treatment agent and the silica particles contained in the silica particle dispersion can be inhibited, so that the rate of change over time of the amount of particle surface treatment can be reduced to less than 20%.

[0071] The pH value of the silica particle dispersion can be determined by measuring the pH value of a liquid obtained by mixing the silica particle dispersion, the dispersion medium (e.g., methanol) of the dispersion, and pure water in a mass ratio of 1:1:1 with a pH meter.

[0072] The silica particle dispersion according to the invention can be used after preparation by adjusting the pH in the basic range, for example, to 9.0 to 10.0. The present invention also relates to a basic silica particle dispersion thus adjusted to a basic pH.

[0073] The silica particle dispersion according to the invention preferably contains an inorganic base, and preferably contains a basic substance selected from, for example, hydroxides or alkoxide compounds derived from monovalent alkali metals.

[0074] Examples of hydroxides derived from monovalent alkali metals include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and preferred examples include sodium hydroxide and potassium hydroxide. Examples of alkoxide compounds derived from monovalent alkali metals include sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, and potassium t-butoxide. [Method for preparing the silica particle dispersion]

[0075] The present invention is also directed to a process for producing a silica particle dispersion wherein surface-treated silica particles are dispersed in an organic solvent.

[0076] The method for producing the dispersion also includes an embodiment of a method for producing the surface-treated silica particles, that is, a method for treating the surfaces of the silica particles with the surface-treating agent (alkoxysilane containing a radically polymerizable double bond and an ester group). The method is not particularly limited, but for example, the surface-treating agent may be added and mixed into a dispersion of the (untreated) silica particles in an organic solvent, causing hydrolysis and condensation of the alkoxy groups in the surface-treating agent, so that the silica particles are surface-treated.

[0077] The amount of surface treatment agent added may be such that the surface is coated with, for example, about 0.5 to 3.0 molecules of surface treatment agent per nm 2 the surface of the silica particles is treated. For example, the surface treatment agent can be used in an amount of 0.5 to 2.5 molecules or 0.7 to 2.5 molecules per nm 2 added to the surface of the silica particles. As used herein, the amount of surface treatment agent refers to the total amount (number of molecules) of the added surface treatment agent. For example, when two types of surface treatment agents are added, the amount of surface treatment agent added refers to the total amount (number of molecules) of the two types of surface treatment agents added. An excess of the surface treatment agent that does not contribute to the surface treatment may remain in the system after the surface treatment reaction.

[0078] The hydrolysis of the alkoxy group in the alkoxysilane containing a radically polymerizable double bond and an ester group, which serves as a surface treatment agent, can be complete or partial hydrolysis; however, water is required, and it is preferable to add about 1 mol or more of water per mol of the alkoxy group. Alternatively, water contained in the organic solvent can be used.

[0079] A catalyst can be used for the hydrolysis and condensation. A chelate compound, an organic acid, an inorganic acid, an organic base, or an inorganic base can be used as the hydrolysis catalyst, alone or in combination. More specifically, for example, an aqueous solution of hydrochloric acid, acetic acid, an aqueous ammonia solution, or the like can be used.

[0080] For example, the surface-treated silica particles can be produced by a process comprising the step of mixing silica particles and the surface-treating agent in an organic solvent. The surface-treating agent can then be the surface-treating agent described above. The silica particles to be surface-treated are preferably silica particles that have been heat-treated in water at 200 to 380°C using a pressure-resistant vessel (autoclave) or the like, as described above.

[0081] In the mixing step, the added amount of the surface treatment agent may be such that the surface is treated in a ratio of, for example, 0.5 to 3.0 molecules per nm 2 the surface of the silica particles is surface-treated with the surface-treating agent. Specifically, the surface-treating agent may be used in a ratio of 0.5 to 2.5 molecules, 0.7 to 2.5 molecules, or the like, per nm 2 added to the surface of the silica particles. The added amount of surface treatment agent refers to the total amount of the added surface treatment agent. For example, if two types of surface treatment agents are added, the added amount of surface treatment agent is considered the total amount of the two types of surface treatment agents. The surface treatment agent can be added in divided portions. Excess surface treatment agent that does not contribute to the surface treatment may be present in the reaction system.

[0082] The organic solvent used in the mixing step may be an organic solvent containing an alcohol and / or a ketone-based solvent. Examples of the alcohol include C 1-5 -alcohols, and specific examples thereof include methanol, ethanol, isopropyl alcohol, and n-butanol. Examples of the ketone-based solvent include C 1-5 -Ketone-based solvents, and specific examples thereof include methyl ethyl ketone, methyl isobutyl ketone, and γ-butyrolactone.

[0083] The mixing step is not particularly limited as long as the temperature is such that the hydrolysis and condensation reaction of the surface treatment agent proceeds. For example, the mixing step can be carried out at a temperature of 20°C or higher and lower than 120°C. In view of reaction efficiency, the mixing step is preferably carried out at about the boiling point of the organic solvent. For example, when the mixing step is carried out using an organic solvent containing methanol, the mixing step is preferably carried out at about 60 to 65°C. In order to minimize changes in the silica concentration and the surface treatment agent concentration during the mixing step, the reaction can be carried out using an apparatus equipped with a reflux device or the like, if necessary.The mixing step can be performed several times at the same temperature, or can be performed several times at different temperatures.

[0084] The mixing step can be carried out for 30 minutes to 24 hours, and is preferably carried out for 24 hours or less in view of industrial requirements.

[0085] The mixing step may also include the step of adjusting the pH with an inorganic base. The pH adjustment step may be performed once or multiple times at any time before, during, or after the mixing step, but is preferably performed after or during the mixing step.

[0086] Examples of inorganic bases include hydroxides derived from monovalent alkali metals, such as sodium hydroxide and potassium hydroxide, as well as alkoxide compounds derived from monovalent alkali metals, such as sodium methoxide, sodium ethoxide, and potassium t-butoxide. These inorganic bases can be used alone or in combinations of two or more.

[0087] The added amount of the inorganic base can be, for example, 0.001 to 5 mass% or 0.01 to 1 wt%, based on the mass of the silica particles. By adding the inorganic base, the pH of the mixed solution can be adjusted to, for example, 6.0 to 8.5, for example, 6.5 to 7.5 or 7.0 to 7.5.

[0088] A specific example of the process for producing the silica particle dispersion of the present invention may be a process comprising the following steps (A), (B) and (C), but is not limited to these processes (steps): Step (A): Preparing a silica sol containing silica particles having an average primary particle diameter of 5 nm or greater and less than 100 nm as a dispersoid, and a C 1-4 -alcohol as a dispersion medium; Step (B): Adding a surface treatment agent comprising an alkoxysilane containing a radically polymerizable double bond and an ester group to the silica sol and stirring the mixture while heating; and Step (C): Perform pH adjustment to achieve a pH value in the system of 6.5 to 8.0 and stir the mixture while heating.

[0089] In step (A), examples of the C 1-4 -Alcohols methanol, ethanol, isopropyl alcohol and n-butanol.

[0090] The silica sol prepared in step (A) may have a water content of, for example, about 0.1 to 2 mass%.

[0091] The silica sol prepared in step (A) may be a silica sol prepared by subjecting an aqueous silica sol hydrothermally synthesized at 200 to 380°C and 2 MPa to 22 MPa to a solvent replacement with the C 1-4 -Alcohol.

[0092] Step (B) is not particularly limited, as long as the temperature is such that the hydrolysis and condensation reaction of the surface treatment agent comprising an alkoxysilane containing a radically polymerizable double bond and an ester group proceeds. In view of reaction efficiency, step (B) is preferably carried out at approximately the boiling point of the silica sol dispersion medium. For example, when step (B) is carried out using a methanol sol of silica particles, step (B) is preferably carried out at approximately 60 to 65°C.

[0093] This step can be performed for 30 minutes to 24 hours, and from an industrial point of view is preferably performed for 24 hours or less.

[0094] This step can also be performed at reduced pressure.

[0095] In terms of reaction efficiency, step (B) is preferably carried out under acidic conditions. For example, if the silica sol in step (A) is acidic, the silica sol can be directly subjected to step (B) without adjusting the pH of the silica sol.

[0096] Step (C) may be the step of performing pH adjustment by adding a basic substance selected from hydroxide or alkoxide compounds derived from monovalent alkali metals.

[0097] Examples of the hydroxides derived from monovalent alkali metals include sodium hydroxide and potassium hydroxide, and examples of the alkoxide compounds derived from monovalent alkali metals include sodium methoxide, sodium ethoxide and potassium t-butoxide.

[0098] In a preferred embodiment, the process may further comprise, after step (C), the following step (D): adding a surface treatment agent containing an alkoxysilane containing a radically polymerizable double bond and an ester group to the silica sol, and stirring the mixture while heating.

[0099] The heating stirring and pressure conditions in this step are similar to those in step (B); however, there is no need to adjust the pH to an acidic level.

[0100] The silica particle dispersion in which surface-treated silica particles are dispersed in an organic solvent can be used as a component of the composite material described below.

[0101] From the viewpoint of ease of preparation of the composite material, at least a part of the organic solvent contained in the silica particle dispersion can be replaced with another organic solvent. The other organic solvent may be at least one or two or more selected from the group consisting of alcohols, ketones, hydrocarbons, amides, esters, ethers, and amines. The type of solvent used for replacement is not particularly limited as long as the solvent is different from the organic solvent in the silica particle dispersion, and the solvent can be selected in consideration of the solubility of the organic resin material used for composite formation.

[0102] Examples of the other organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, and n-butanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, γ-butyrolactone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone; hydrocarbons such as toluene, xylene, n-pentane, n-hexane, and cyclohexane; esters such as ethyl acetate and butyl acetate; ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether; amides such as dimethylacetamide, N,N-dimethylformamide, N,N-dimethylformamide, dimethylacrylamide, acryloylmorpholine, and diethylacrylamide; and amines such as triethylamine, tributylamine, N,N-dimethylaniline, pyridine, and picoline.

[0103] A known method can be used for the replacement. For example, the replacement with the other organic solvent can be carried out by an evaporation method using a rotary evaporator or the like, or an ultrafiltration method using an ultrafiltration membrane. [Composite material]

[0104] The composite material of the present invention is a composite material containing the silica particle dispersion of the present invention and an organic resin material.

[0105] The organic resin material may be selected from at least one selected from the group consisting of polyethylene resins, polypropylene resins, polystyrene resins, acrylic resins, methacrylic resins, urethane resins, urethane-acrylate resins, urethane-methacrylate resins, polycarbonate resins, ABS resins, diallyl phthalate, and unsaturated polyesters.

[0106] Although the method for producing the composite material is not particularly limited, the composite material can be produced, for example, by mixing the silica particle dispersion and a monomer or polymer solution of the organic resin material to prepare a polymerizable composition, and then removing excess solvent, followed by photo- or thermal curing. The composite material can also be obtained by removing the dispersion medium from the silica particle dispersion to obtain a powder of the surface-treated silica particles, adding the powder to a monomer or polymer solution of the organic resin material to prepare a polymerizable composition, removing excess solvent, and then photo- or thermal curing the composition.

[0107] The mixing ratio of the silica particle dispersion to the monomer or polymer solution of the organic resin material in the polymerizable composition may be such that the mass ratio of the surface-treated silica particles in the silica particle dispersion to the monomer or polymer of the organic resin material, ie, surface-treated silica particles: monomer or polymer of the organic resin material, is 1:100 to 0.1, for example 1:20 to 0.1.

[0108] The polymerizable composition can be cured with light or heat using a polymerization initiator. Examples of the photopolymerization initiator include photoradical polymerization initiators or photocationic polymerization initiators, and examples of thermal polymerization initiators include thermal radical polymerization initiators or thermal cationic polymerization initiators. The polymerization initiator can be used in an amount of 0.01 parts by mass to 50 parts by mass, relative to 100 parts by mass of the polymerizable compound. In addition, as optional components, conventional additives used in polymerizable compositions (composite materials) of the prior art, such asvarious additives used in the relative technical field, such as pigments and catalysts for curing acceleration, radical scavengers (quenchers), leveling agents, viscosity modifiers, antioxidants, UV absorbers, stabilizers, plasticizers and surfactants are mixed and used.

[0109] By selecting a suitable organic resin material depending on the application, the composite material of the present invention can be used as a semiconductor device material, a copper-clad laminate, a flexible wiring material, a flexible display material, an antenna material, an optical wiring material, or a sensor material. [Composition]

[0110] The present invention also relates to a composition containing the silica particle dispersion, a photosensitive resin, and a photopolymerization initiator. As used herein, the photosensitive resin refers to a resin material that can be photocured among organic resin materials, that is, a UV-curable resin.

[0111] Examples of the UV-curable resin include acrylic resins, methacrylic resins, urethane-acrylate resins, and urethane-methacrylate resins. More specifically, examples include a polymer of a monofunctional (meth)acrylate having a group (hereinafter referred to as a (meth)acryloyloxy group) selected from the group consisting of an acryloyloxy group (CH2=CH-COO-) and a methacryloyloxy group (CH2=C(CH3)-COO-) in the molecule; a polymer of a polyfunctional (meth)acrylate having two or more (e.g., two or more and six or less) (meth)acryloyloxy groups in the molecule; and a polymer of a monofunctional or polyfunctional urethane (meth)acrylate additionally having a urethane bond in the (meth)acryloyloxy group(s); or a polymer of a mixture thereof.

[0112] Examples of UV-curable resin also include epoxy resins.

[0113] In one embodiment, the present invention relates to a composition comprising the silica particle dispersion and, for example, one or more resins selected from acrylic resins, methacrylic resins, urethane acrylate resins and urethane methacrylate resins as photosensitive resins, and a photo-radical polymerization initiator.

[0114] In another embodiment, the present invention relates to a composition comprising the silica particle dispersion and, for example, an epoxy resin as a photosensitive resin as well as a photo-cationic polymerization initiator.

[0115] In the composition, the mixing ratio of the silica particle dispersion to the photosensitive resin and the proportion of the photopolymerization initiator incorporated, as well as the optional components and the like, may be, for example, the conditions, the components and the like mentioned above in [Composite Material].

[0116] As described above, in the formation of a composite between the surface-treated silica particles and another resin material, any change in the treatment state of the surface of the silica particles (the amount of the bonded surface treatment agent or the type of the surface treatment group), that is, any change in the state of the particle interface, may cause a change over time in the compatibility with the resin material and further cause poor uniformity of the composite material.

[0117] For example, it is theoretically desirable that all of the surface treatment agent used in the surface treatment enters the surface treatment; however, in reality, some of the surface treatment agent may remain in the dispersion of the surface-treated silica particles, and the remaining surface treatment agent may, for example, bind to the silica particles over time, resulting in a change in the amount of surface treatment to that immediately after treatment.

[0118] This can lead to variations in the physical properties of the cured product (product), such as hardness, when formed into a composite material.

[0119] Furthermore, if, for example, the surface treatment agent comprises double bond groups, this may lead to variations in performance properties, such as adhesion, if the proportion of double bond groups at the particle interface changes due to a loss of double bond groups or variations in the amount of treatment with the surface treatment agent itself.

[0120] The present inventors have focused on the potential effects of this quality stability of the surface-treated silica particles on variations in the properties of the composite material, and have completed the present invention to provide surface-treated silica particles that show little change over time from an initial amount of surface treatment. Examples

[0121] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited by the following examples.

[0122] The silica sols, surface treating agents and basic compounds used in the examples and comparative examples are as follows. [Silica sol]

[0123] Methanol-dispersed silica sol A (manufactured by Nissan Chemical Corporation, product name: MT-ST, average primary particle diameter (nitrogen adsorption method): 12 nm, silica concentration 30 mass%). Methanol-dispersed silica sol B (manufactured by Nissan Chemical Corporation, product name: MA-ST-S, average primary particle diameter (nitrogen adsorption method): 9 nm, silica concentration 20 mass%). Methanol-dispersed silica sol C (manufactured by Nissan Chemical Corporation, product name: MA-ST-M, silica concentration (nitrogen adsorption method): 22 nm, silica concentration 40 mass%). Methanol-dispersed silica sol D (manufactured by Nissan Chemical Corporation, product name: MA-ST-L, silica concentration (nitrogen adsorption method): 45 nm, silica concentration 40 mass%).

[0001] [Surface treatment agent]

[0124] MPS: 3-Methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM-503)

[0002] [Basic compound]

[0125] Basic compound a: Sodium hydroxide (Kanto Chemical Co., Inc., Product name: 4 mol / l sodium hydroxide solution, Product number: 37845-08)

[0126] Basic compound b: Sodium methoxide (Junsei Chemical Co., Ltd., Product name: Sodium methoxide 28% solution in methanol, Product number: 51055-1601)

[0127] The physical properties of the methanol-dispersed silica sols A to D, the dispersions of the surface-treated silica particles prepared in the Examples and Comparative Examples, and the silica sols and dispersions during the dispersion preparation process were measured and investigated by the following methods. [Measurement of silica concentration]

[0128] The silica concentration in each silica sol or dispersion of surface-treated silica particles was calculated by placing the silica sol or dispersion in a crucible, removing the solvent by heating, calcining at 1,000°C, and measuring the amount of calcination residue. [Method for measuring the pH of silica sol dispersed in organic solvent]

[0129] The pH value during the manufacturing process of each surface-treated silica particle dispersion was measured for a liquid mixture of methanol-dispersed silica sol, methanol, and pure water in a mass ratio of 1:1:1 using a pH meter (MM-43X, manufactured by DKK-Toa Corporation). The pH value measured by this method was referred to as pH (1 + 1 + 1). The measurement results of pH (1 + 1 + 1) measured in the Examples and Comparative Examples were expressed as follows: • pH (1 + 1 + 1) < 3.0: acidic • 3.0 ≤ pH (1 + 1 + 1) < 6.0: slightly acidic • 6.0 ≤ pH (1 + 1 + 1) ≤ 8.0: neutral • 8.0 < pH (1 + 1 + 1) ≤ 11.0: slightly alkaline • 11.0 < pH (1 + 1 + 1): alkaline [Viscosity measurement]

[0130] The viscosity of each surface-treated silica particle dispersion was measured using an Ostwald viscometer (manufactured by Sibata Scientific Technology Ltd.). [Amount of decomposition product of the surface treatment agent]

[0131] After preparing the surface-treated silica particles (methanol dispersion), the surface-treated silica particles were stored at 50°C for two weeks or at room temperature (20 to 25°C) for 12 weeks, and then the amount of a decomposition product derived from the surface treatment agent in the dispersion was quantified by gas chromatography (GC-2014s; Shimadzu Corporation). [Gas chromatographic conditions] Column: 3 mm × 1 m glass column Packing material: Porapack Q (GL Sciences Inc.) Column temperature: 130 to 230°C (heating rate: 8°C / min) Carrier: N2 40 ml / min Detector: FID Injection volume: 1 µl Internal standard: Acetonitrile [Decomposition rate of the surface treatment agent]

[0132] The decomposition rate of the surface treatment agent in each silica particle dispersion was calculated from the amount of the decomposition product derived from the surface treatment agent in the silica particle dispersion (C, unit: mass%), quantified in [amount of decomposition product of the surface treatment agent], the molecular weight of the surface treatment agent (D, unit: g / mol), the molecular weight of the decomposition product (E, unit: g / mol), and the amount of the added surface treatment agent (proportion in the silica particle dispersion: F, unit: mass%) according to the following formula (2). In the examples, the decomposition rate was determined assuming that the decomposition product (MPS) derived from the surface treatment agent was methacrylic acid. Decomposition rate of surface treatment agent=[C×(D / E)÷F]×100[%] [Measurement of the amount of particle surface treatment]

[0133] The amount of surface treatment of the silica particles with the surface treatment agent was calculated using the following procedure: (1) A 30 cc centrifugal tube was charged with 3 ml of the organic solvent silica sol, and a poor solvent was added to it. (2) After centrifugation, the supernatant in which unbound surfactant was dissolved was removed. (3) A good solvent was added to redissolve the gel, and then a poor solvent was added, and (2) was repeated. (4) (2) to (3) were carried out again. (5) The resulting gel was vacuum dried, and the resulting powder was then ground in a mortar and dried at 150°C for 2 hours. The carbon content in this dry powder was measured using an elemental analyzer.

[0134] From the obtained carbon content, the amount of treatment with the surface treatment agent bound to the particle surface was quantified. [Calculation of the rate of change of the amount of particle surface treatment over time]

[0135] The surface-treated silica particles were stored at room temperature (20 to 25°C) for x weeks after synthesis. Then, the initial (after one week) amount of particle surface treatment (A) and the amount of particle surface treatment after x weeks after synthesis (B) were measured. The rate of change over time of the amount of particle surface treatment was calculated according to the following formula (1): Rate of change over time of the amount of particle surface treatment = [(B−A) / A] × 100 [%] [Example 1-1]

[0136] Step (i): A 3-liter receiving flask was charged with 2,700 g of methanol-dispersed silica sol A, and MPS was added thereto in such an amount while stirring with a magnetic stirrer that the number of molecules per nm 2 of the surface area of ​​the silica particles, determined by nitrogen adsorption, was 1.3, and the mixture was heated to 60°C and kept at this temperature for 1 hour.

[0137] Step (ii): Next, a basic compound a diluted with methanol was added to adjust the pH (1 + 1 + 1) to neutral (6 to 8), and the mixture was heated to 60°C and kept at this temperature for 1 hour.

[0138] Step (iii): MPS was then added in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles was 0.5, and the mixture was heated to 60°C and kept at that temperature for 1 hour to prepare a methanol dispersion of surface-treated silica particles.

[0139] The total amount of MPS added in steps (i) to (iii) was 1.8 molecules per nm 2 the surface of the silica particles in the sol. The resulting methanol dispersion of the surface-treated silica particles had a silica concentration of 30.0 mass%, a water content of 1.6 mass%, and a viscosity of 2.1 mPa s. [Example 1-2]

[0140] A methanol dispersion of surface-treated silica particles was prepared by the same steps as in steps (i) to (iii) of Example 1-1, except that the amount of MPS added in step (i) of Example 1-1 was 1.7 molecules per nm 2 the surface of the silica particles and the amount of MPS added in step (iii) was 0.6 molecules per nm 2 of the surfaces of the silica particles. [Example 1-3]

[0141] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that a basic substance b diluted with methanol was added to adjust the pH (1 + 1 + 1) to neutral (6 to 8) instead of the basic substance a in step (ii) of Example 1-1. [Example 1-4]

[0142] Step (iv): A 3-liter receiving flask was charged with 2,700 g of the methanol-dispersed silica sol A, and while stirring with a magnetic stirrer, MPS was added in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles, determined by the nitrogen adsorption method, was 1.8, and the mixture was heated to 60°C and kept at this temperature for 3 hours.

[0143] Step (v): Next, a basic compound a diluted with methanol was added to adjust the pH (1 + 1 + 1) to neutral (6 to 8), and the mixture was heated to 60°C and kept at this temperature for 1 hour.

[0144] The resulting methanol dispersion of the surface-treated silica particles had a silica concentration of 30.5 mass% and a water content of 1.5 mass%. [Example 1-5]

[0145] Step (vi): A 3-liter receiving flask was charged with 2,700 g of the methanol-dispersed silica sol A, and while stirring with a magnetic stirrer, MPS was added thereto in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles, determined by the nitrogen adsorption method, was 1.8, and the mixture was heated to 60°C and kept at this temperature for 6 hours.

[0146] Step (vii): Thereafter, a basic compound a diluted with methanol was added to adjust the pH (1 + 1 + 1) to neutral (6 to 8), and the mixture was heated to 60°C and kept at this temperature for 1 hour.

[0147] The resulting methanol dispersion of surface-treated silica particles had a silica concentration of 30.5 mass% and a water content of 1.5 mass%. [Example 1-6]

[0148] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that the methanol-dispersed silica sol B was used instead of the methanol-dispersed silica sol A in step (i) of Example 1-1. [Example 1-7]

[0149] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that the methanol-dispersed silica sol C was used instead of the methanol-dispersed silica sol A in step (i) of Example 1-1. [Example 1-8]

[0150] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that the methanol-dispersed silica sol D was used instead of the methanol-dispersed silica sol A in step (i) of Example 1-1. [Example 1-9]

[0151] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that in step (i) of Example 1-1, MPS was added in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles was 0.7 molecules instead of 1.3 molecules, and that in step (iii) MPS was added in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles was 0.2 molecules instead of 0.5 molecules. [Example 1-10]

[0152] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that in step (i) of Example 1-1, MPS was added in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles was 1.0 molecule instead of 1.3 molecules, and that in step (iii) MPS was added in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles was 0.4 molecules instead of 0.5 molecules. [Example 1-11]

[0153] A 3-liter receiving flask was charged with 2,700 g of the methanol-dispersed silica sol A, and the methanol-dispersed silica sol A was concentrated using an evaporator to a silica concentration of 35 mass% with stirring and heating at 170°C.

[0154] Thereafter, the same operations as in steps (i) to (iii) of Example 1-1 were performed to prepare a methanol dispersion of surface-treated silica particles.

[0155] Thereafter, the methanol dispersion of surface-treated silica particles was further concentrated with stirring and heating at 70°C using an evaporator until the silica concentration reached 40 mass% or more.

[0156] The resulting methanol dispersion of surface-treated silica particles had a silica concentration of 40.3 mass%, a water content of 1.7 mass% and a viscosity of 3.8 mPa s. [Example 1-12]

[0157] A methanol dispersion of surface-treated silica particles was prepared as in Example 1-1.

[0158] Thereafter, the receiving flask containing the methanol dispersion of surface-treated silica particles was placed in a rotary evaporator, and distillation was carried out while supplying methyl ethyl ketone at a bath temperature of 80°C and a reduced pressure of 600 to 400 Torr until the water content in the dispersion was reduced to 1.0 mass% or less, so that replacement of the dispersion medium from methanol to methyl ethyl ketone was achieved, thereby obtaining a methyl ethyl ketone dispersion of surface-treated silica particles.

[0159] The resulting methyl ethyl ketone dispersion of surface-treated silica particles had a silica concentration of 30.4 mass%, a water content of 0.1 mass% and a viscosity of 1.1 mPa s. [Comparison example 1-1]

[0160] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that in step (ii) of Example 1-1, the basic substance was added to adjust the pH (1 + 1 + 1) to weakly alkaline (8 to 11) instead of neutral (6 to 8).

[0161] The resulting methanol dispersion of surface-treated silica particles had a silica concentration of 29.9 mass%, a water content of 1.7 mass% and a viscosity of 2.1 mPa s. [Comparison example 1-2]

[0162] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in steps (i) to (iii) of Example 1-1, except that the amount of MPS added in step (i) of Example 1-1 was 1.7 molecules per nm 2 of the surfaces of the silica particles; the basic substance a was added in step (ii) to adjust the pH (1 + 1 + 1) to weakly alkaline (8 to 11) instead of neutral (6 to 8); and the amount of MPS added in step (iii) was 0.6 molecules per nm 2 the surface of the silica particles.

[0163] The resulting methanol dispersion of surface-treated silica particles had a silica concentration of 29.8 mass%, a water content of 1.6 mass% and a viscosity of 2.1 mPa s. [Comparison example 1-3]

[0164] A methanol dispersion of surface-treated silica particles was prepared by performing the same operations as in Examples 1-1 and 1-3, except that in step (i) of Example 1-1, 181 g of the methanol-dispersed silica sol A and 2,592 g of the methanol-dispersed silica sol D were charged instead of 2,700 g of the methanol-dispersed silica sol A; in step (ii) of Example 1-3, the basic substance b diluted with methanol was added to adjust the pH (1 + 1 + 1) to weakly acidic (2 to 6) instead of the basic substance b diluted with methanol was added to adjust the pH (1 + 1 + 1) to neutral (6 to 8); and the amount of MPS added in step (iii) of Example 1-1 is 1.2 molecules instead of 1.3 molecules per nm 2 the surface of the silica particles. [Comparison examples 1-4]

[0165] Step (viii): A 3-liter receiving flask was charged with 2,700 g of the methanol-dispersed silica sol A, and the basic compound a diluted with methanol was added while stirring with a magnetic stirrer to adjust the pH (1 + 1 + 1) to neutral (6 to 8), and the mixture was heated to 60°C and kept at this temperature for 1 hour.

[0166] Step (ix): MPS was then added in such an amount that the number of molecules per nm 2 the surface area of ​​the silica particles, determined by the nitrogen adsorption method, was 1.8, and the mixture was heated to 60°C and kept at that temperature for 3 hours to prepare a methanol dispersion of surface-treated silica particles.

[0167] The resulting methanol dispersion of surface-treated silica particles had a silica concentration of 29.8 mass%, a water content of 1.8 mass% and a viscosity of 2.7 mPa s. [Example 2-1]

[0168] The methanol dispersion of surface-treated silica particles obtained in Example 1-1 was stored at 50°C for two weeks after preparation, and the amount of a decomposition product of the surface treatment agent was then measured by gas chromatography. Methyl methacrylate (detected as a reaction product between methacrylic acid and methanol as the dispersion medium) was detected as the decomposition product of MPS.

[0169] The decomposition rate of the surface treatment agent was calculated according to the following formula (2). In formula (2), the amount of the decomposition product derived from the surface treatment agent in the silica particle dispersion is defined as (C, unit: mass%), the molecular weight of the surface treatment agent is defined as (D, unit: g / mol), the molecular weight of the decomposition product is defined as (E, unit: g / mol), and the added amount of the surface treatment agent (proportion of the surface treatment agent in the system) is defined as (F, unit: mass%). Decomposition rate of surface treatment agent=[C×(D / E)÷F]×100[%]

[0170] Table 1 shows the decomposition rate of the surface treatment agent in the methanol dispersion of surface-treated silica particles obtained in Example 1-1. In Table 1, a decomposition rate of 2% or less is evaluated as "OK," and a decomposition rate of 2% or higher is evaluated as "NG." [Examples 2-2 and 2-3, and Comparative Examples 2-1 and 2-2]

[0171] Regarding the decomposition rate of the surface treatment agent in each of the methanol dispersions of surface-treated silica particles obtained in Examples 1-2 and 1-3 and Comparative Examples 1-1 and 1-2, the methanol dispersions of surface-treated silica particles were stored at 50°C for two weeks after preparation, and the amount of the decomposition product of the surface treatment agent was then measured as in Example 2-1, thus calculating the decomposition rate of the surface treatment agent. Table 1 shows the decomposition rates of the surface treatment agent in the methanol dispersions of surface-treated silica particles obtained in Examples 1-2 and 1-3 and Comparative Examples 1-1 and 1-2. [Comparison example 2-3]

[0172] The methanol dispersion of surface-treated silica particles obtained in Example 1-1 was stored at room temperature (20 to 25°C) for 12 weeks after preparation. Then, the amount of the decomposition product of the surface-treating agent was measured as in Example 2-1, and the decomposition rate of the surface-treating agent was calculated. Table 1 shows the decomposition rate of the surface-treating agent in the methanol dispersion of surface-treated silica particles obtained in Comparative Example 2-3. [Example 3-1]

[0173] The methanol dispersion of surface-treated silica particles obtained in Example 1-1 was stored at room temperature (20 to 25°C), and the amounts (mass %) of particle surface treatment from the first week (initial, x = 1) to the 14th week (x = 14) were calculated from the carbon content values ​​quantified using an elemental analyzer. In addition, the initial MPS reaction rate was calculated from the initial (after one week) amount of surface treatment and the amount of MPS added (mass % of MPS in the system). Furthermore, the rate of change in the amount of particle surface treatment over time was calculated from the initial (after one week) amount of particle surface treatment (A) and the amount of particle surface treatment after x weeks after synthesis (B) according to the following formula (1): Rate of change of the amount of particle surface treatment over time = [(B−A) / A] × 100 [%]

[0174] The rate of change in the amount of particle surface treatment over time in Example 1-1 was at most 13.6% (x = 14). Table 2 shows the initial (after one week) amount of surface treatment, the MPS reaction rate, and the state of change over time after x weeks. The threshold for the state of change over time in the surface was set at 20%, with less than 20% being rated as "○" and 20% or more being rated as "×." [Examples 3-2 and 3-3 and Comparative Example 3-1]

[0175] The methanol dispersions of surface-treated silica particles obtained in Examples 3-2 and 3-3 and Comparative Example 3-1 were stored at room temperature (20 to 25°C), and the amount of particle surface treatment from the first week (initial, x = 1) to the 14th week (x = 14) was measured as in Example 3-1, and the MPS reaction rate and the rate of change over time were calculated. Table 2 shows the initial (after one week) amount of surface treatment, the MPS reaction rate, and the state of change over time after x weeks for each of the methanol dispersions of surface-treated silica particles obtained in Examples 3-2 and 3-3 and Comparative Example 3-1. [Table 1] [Table 1] Decomposition rate study Classification Basic compound pH value (1 + 1 + 1) Storage conditions before measurement (temperature × time period) Decomposition rate (%) of the surface treatment agent Evaluation Example 2-1 Example 1-1 a Neutral 50°C × 2 weeks 0, 8 OK Example 2-2 Examples 1-2 a Neutral 50°C × 2 weeks 1,6 OK Examples 2-3 Examples 1-3 b Neutral 50°C × 2 weeks 1,9 OK Compare Example 2-1 Compare Example 1-1 a Weakly alkaline 50°C × 2 weeks 5, 8 NG Compare Example 2-2 Compare examples 1-2 a Weakly alkaline 50°C × 2 weeks 7,2 NG Compare examples 2-3 Compare examples 1-3 b Sour 25°C × 12 weeks 2,6 NG

[0079] [Table 2] Study of the rate of change over time Classification Initial particle surface Change state over time at the particle surface after x weeks Evaluation Amount (mass%) of treatment MPS response rate (%) x=2 x=3 x=4 x=8 x=14 Example 3-1 Example 1-1 3,7 63 ◯ ◯ ◯ ◯ ◯ OK Example 3-2 Example 1-4 3,7 64 ◯ ◯ ◯ ◯ ◯ OK Example 3-3 Example 1-5 3,6 61 ◯ ◯ ◯ ◯ ◯ OK Compare - Example 3-1 Compare - Examples 1-3 3,1 53 ◯ × × × × NG

[0176] The results in the examples and comparative examples described above are summarized in Table 3.

[0177] Regarding the method of adding the surface treatment agent shown in Table 3, the addition method in steps (i) to (iii) of Example 1-1 was designated as A, the addition method B of the surface treatment agent: the addition method in steps (iv) to (v) of Example 1-4 is designated as B, the addition method in steps (vi) to (vii) of Example 1-5 is designated as C, and the addition method in steps (vi) to (vii) of Comparative Example 1-3 is designated as D.

[0178] In Table 3, the rating is OK if either the decomposition rate (Table 1) or the rate of change over time (Table 2) is rated as OK. [Table 3] [Table 3] Classification Surface-treated silica particle dispersion Addition method of the surface treatment agent Structural analysis Evaluation Particle diameter (nm) Added amount (molecules / nm 2 ) of surface treatment agents Basic compound pH value (1 + 1 + 1) Solids content (%) Dispersion medium Decomposition rate of the surface treatment agent (Table 1) Rate of change over time in the particle surface (Table 2) Example 3-1 Example 2-1 Example 1-1 12 1, 8 a Neutral 30 Methanol A OK OK OK - Example 2-2 Examples 1-2 12 2,3 a Neutral 30 Methanol A OK - OK - Examples 2-3 Examples 1-3 12 1, 8 b Neutral 30 Methanol A OK - OK Example 3-2 - Examples 1-4 12 1, 8 a Neutral 30 Methanol B - OK OK Example 3-3 - Examples 1-5 12 1, 8 a Neutral 30 Methanol C - OK OK - - Examples 1-6 9 1, 8 a Neutral 20 Methanol A - - OK* - - Examples 1-7 22 1, 8 a Neutral 40 Methanol A - - OK* - - Examples 1-8 45 1, 8 a Neutral 40 Methanol A - - OK* - - Examples 1-9 12 0,9 a Neutral 30 Methanol A - - OK* - - Examples 1-10 12 1,4 a Neutral 30 Methanol A - - OK* - - Examples 1-11 12 1, 8 a Neutral 40 Methanol A - - OK* - - Examples 1-12 12 1, 8 a Neutral 30 MEK A - - OK* - See - Example 2-1 See - Example 1-1 12 1, 8 a Weakly alkaline 30 Methanol A NG - NG - See - Example 2-2 See examples 1-2 12 2,3 a Weakly alkaline 30 Methanol A NG - NG - See examples 2-3 See examples 1-3 40 2,5 b Sour 35 Methanol A NG - NG See Example 3-1 - See examples 1-3 12 1, 8 a Neutral 30 Methanol D - NG NG * Based on the manufacturing conditions, both the decomposition rate and the Rate of change over time rated as OK.

[0179] As shown in Table 3, it was confirmed that the dispersions of neutral surface-treated silica containing MPS and an alkali metal and the dispersions of surface-treated silica obtained by the methods A, B and C for adding the surface-treating agent are each stable with respect to the structure of the surface-treating agent or the structure of the silica particle surface, and each have excellent quality or excellent feeding stability.

[0180] In contrast, it was confirmed that the dispersions of the weakly acidic or weakly alkaline surface-treated silica containing MPS and an alkali metal and the dispersion of surface-treated silica obtained by the method D for adding the surface-treating agent are each unstable with respect to the structure of the surface-treating agent or the structure of the silica particle surface, and each poses concerns about the feeding stability in terms of quality.

[0181] As used herein, the term "feed stability" refers to the ability to feed a dispersion of surface-treated silica of stable quality, wherein the surface-treated silica particles undergo little change in the interfacial state of the silica particles, such as a change in the amount of bonded surface-treating agent (amount of treatment) or a change in the structure of the surface-treating group. This is one of the important properties that can further lead to the provision of a material that is homogeneous in terms of compatibility with a resin material upon formation of a composite therewith, in physical properties such as hardness of the material obtained after composite formation, and in properties such as adhesion. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2005-200294 A

[0006] WO 2009 / 008509

[0006] JP 2011-026183 A

[0006] Cited non-patent literature

[0000] Shin-Etsu Chemical Co., Ltd., product name: KBM-503

[0124] < / reaktionsrate> < / zersetzungsrate>

Claims

[1] Silica particle dispersion in which surface-treated silica particles are dispersed in an organic solvent, wherein the surface-treated silica particles are silica particles surface-treated with a surface-treating agent comprising an alkoxysilane containing a radically polymerizable double bond and an ester group, and wherein in the dispersion, the rate of change of the amount of particle surface treatment with the surface treatment agent over time, as defined by the following formula (1), is less than 20%, and the decomposition rate of the surface treatment agent, as defined by the following formula (2), is 2.0% or less: <Veränderungsrate [%] der Menge der Partikel-Oberflächenbehandlung über die Zeit > Rate of change of the amount of particle surface treatment over time = [(B−A) / A] × 100 [%] where in formula (1) A is the amount of particle surface treatment after one week of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion; and B is the amount of particle surface treatment after 14 weeks of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion; <Zersetzungsrate [%] des Oberflächenbehandlungsmittels> Decomposition rate of surface treatment agent=[C×(D / E)÷F]×100[%] where in formula (2) C is the amount (mass %) of a decomposition product originating from the surface treatment agent in the silica particle dispersion after at least two weeks of storage at room temperature (20 to 25°C) to 50°C after preparation of the silica particle dispersion, wherein the decomposition product comprises a carboxylic acid containing a radically polymerizable double bond and a derivative of the carboxylic acid containing a radically polymerizable double bond; D is the molecular weight (g / mol) of the surface treatment agent; E is the molecular weight (g / mol) of the decomposition product; and F is the amount (proportion in mass% in the silica particle dispersion) of the surface treatment agent added during surface treatment. [2] The silica particle dispersion according to claim 1, wherein the silica particle dispersion has a pH of 6.5 to 8.

0. [3] Silica particle dispersion according to claim 2, wherein the silica particle dispersion contains a basic substance selected from hydroxide or Alkoxide compounds derived from monovalent alkali metals. [4] Silica particle dispersion according to any one of claims 1 to 3, wherein an initial reaction rate between the surface treatment agent and the silica particles is 50% or more, wherein the initial reaction rate is defined as a ratio of the amount of particle surface treatment with the surface treatment agent after one week of storage at room temperature (20 to 25°C) after preparation of the silica particle dispersion, relative to the amount of the surface treatment agent added during the surface treatment. [5] Silica particle dispersion according to any one of claims 1 to 4, wherein the silica particles have an average primary particle diameter of 5 nm or larger and smaller than 100 nm, and wherein in the silica particle dispersion, the concentration of surface-treated silica particles is 20 to 70 mass% and the water content is 0.001 to 10 mass%. [6] Silica particle dispersion according to any one of claims 1 to 5, wherein the surface-treated silica particles are present in an amount of 0.5 to 3.0 molecules per nm 2 the surface of the silica particles is surface treated with the surface treatment agent. [7] Silica particle dispersion according to any one of claims 1 to 6, wherein the surface treatment agent is an alkoxysilane of the following formula (a): [8] The silica particle dispersion according to any one of claims 1 to 7, wherein the organic solvent is at least one organic solvent selected from the group consisting of alcohols, ketones, hydrocarbons, amides, esters, ethers and amines. [9] A composite material comprising the silica particle dispersion according to any one of claims 1 to 8 and an organic resin material. [10] The composite material according to claim 9, wherein the organic resin material is at least one selected from the group consisting of polyethylene resins, polypropylene resins, polystyrene resins, acrylic resins, methacrylic resins, urethane resins, urethane acrylate resins, urethane methacrylate resins, polycarbonate resins, ABS resins, diallyl phthalate, and unsaturated polyesters. [11] A composition comprising the silica particle dispersion according to any one of claims 1 to 8, a photosensitive resin and a photopolymerization initiator. [12] The composition according to claim 11, wherein the photosensitive resin is at least one selected from the group consisting of acrylic resins, methacrylic resins, urethane acrylate resins, urethane methacrylate resins and epoxy resins. [13] A process for producing a silica particle dispersion in which surface-treated silica particles are dispersed in an organic solvent, the process comprising the following steps (A), (B) and (C): Step (A): Preparing a silica sol containing silica particles having an average primary particle diameter of 5 nm or larger and less than 100 nm as a dispersoid, and a C 1-4 -alcohol as a dispersion medium; Step (B): Adding a surface treatment agent containing an alkoxysilane containing a radically polymerizable double bond and an ester group to the silica sol, and stirring the mixture while heating; and Step (C): Perform pH adjustment to achieve a pH value in a system of 6.5 to 8.0 and stir the mixture while heating. [14] A process for producing a silica particle dispersion according to claim 13, further comprising, after step (C), the following step (D): Step (D): Adding a surface treatment agent containing an alkoxysilane containing a radically polymerizable double bond and an ester group to the silica sol, and stirring the mixture while heating. [15] A process for producing a silica particle dispersion according to claim 13 or 14, wherein step (C) is the step of performing pH adjustment by adding a basic substance selected from hydroxide or alkoxide compounds derived from monovalent alkali metals.