Surface-treated hollow silica and method for producing surface-treated hollow silica

Abstract

The present invention relates to surface-treated hollow silica which, in chromatography, has an amine peak area that is 70% or more of a theoretical value and a symmetry factor S of 8 or less. The present invention also relates to a method for producing the surface-treated hollow silica, the method including subjecting untreated hollow silica to a surface treatment, wherein a silane coupling agent to be used for the surface treatment has a value obtained by dividing the molecular weight of the silane coupling agent by the number of Si atoms contained in one molecule of the silane coupling agent of 100-300.

Description

Surface-treated hollow silica and method for producing surface-treated hollow silica

[0001] The present invention relates to a surface-treated hollow silica and a method for producing the surface-treated hollow silica.

[0002] The electrical insulating layer of a printed wiring board requires properties such as a low dielectric constant, a low dielectric loss tangent, and a low linear expansion coefficient. In recent years, resin compositions containing a thermosetting resin and silica particles have been used to manufacture electrical insulating layers for metal clad laminates that can be processed into printed wiring boards (see Patent Documents 1 and 2). Specifically, metal clad laminates are used in which a semi-cured product of the resin composition is laminated on the surface of a metal substrate layer as an electrical insulating layer. Another example is a metal clad laminate in which a glass cloth or the like impregnated with a resin composition is laminated on the surface of a metal substrate layer as an electrical insulating layer. Here, fillers (filling materials) are used as materials for prepregs using thermosetting resins, and the fillers themselves usually tend to increase the relative dielectric constant of the resulting prepreg. Among these, metal clad laminates using hollow fillers have been studied, as described in Patent Documents 1 to 3, because they can reduce the relative dielectric constant compared to those using solid fillers. Furthermore, when used in the resin composition, surface-treated silica is used, as described in Patent Document 4, and this has been studied.

[0003] Japanese Patent Publication No. 2008-31409 Japanese Patent Publication No. 2017-522580 International Publication No. 2019 / 230661 Japanese Patent No. 6347644

[0004] The present inventors have found that conventionally known surface-treated hollow silica does not provide sufficient adhesion between a resin composition, a semi-cured product thereof, a prepreg, etc., and a substrate made of metal, etc. Furthermore, they have found that if the surface treatment conditions are not optimized, silanol groups remain on the silica surface, resulting in a significant decrease in peel strength after a high-temperature, high-humidity test.

[0005] Therefore, an object of the present invention is to provide surface-treated hollow silica that, when mixed with a resin and used in electronic applications, has excellent adhesion to the resin and does not significantly deteriorate even when exposed to a high-temperature, high-humidity environment.

[0006] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by ensuring that the peak area and symmetry factor S of amines in chromatography of surface-treated hollow silica are within specific ranges, and have thus completed the present invention.

[0007] The present invention relates to the following: (1) A surface-treated hollow silica having an amine peak area of ​​70% or more of the theoretical value in chromatography and a symmetry coefficient S of 8 or less. (2) The density of the surface-treated hollow silica is 0.25 to 2.00 g / cm. ３ (3) The surface-treated hollow silica according to (1), wherein the BET specific surface area of ​​the surface-treated hollow silica is 1 to 100 m ２ / g. (4) The surface-treated hollow silica of any one of (1) to (3) above, wherein the median diameter (d50) of the surface-treated hollow silica is 0.1 to 10 μm. (5) A method for producing the surface-treated hollow silica of any one of (1) to (4) above, which comprises subjecting untreated hollow silica to a surface treatment, wherein the molecular weight of the silane coupling agent used in the surface treatment divided by the number of Si atoms contained in one molecule of the silane coupling agent is 100 to 300. (6) The method for producing the surface-treated hollow silica of (5) above, wherein the surface treatment comprises bringing the untreated hollow silica into contact with the silane coupling agent and then heating at a temperature of 50 to 200°C. (7) The method for producing the surface-treated hollow silica according to (6) above, wherein a solvent is used during the contacting, and the product A×B of the density A of the untreated hollow silica and the amount B of the solvent charged per gram of the untreated hollow silica is 0.5 to 2.5. (8) A resin composition comprising the surface-treated hollow silica according to any one of (1) to (4) above, and a resin.

[0008] According to the present invention, there can be provided surface-treated hollow silica which, when mixed with a resin and used in electronic applications, has excellent adhesion to the resin and does not undergo a significant change in adhesion even when exposed to a harsh environment.

[0009] The present invention will be described below, but the present invention is not limited to the examples in the following description. In this specification, the term "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] <Surface-treated hollow silica> The surface-treated hollow silica of the present invention is characterized in that the amine peak area in chromatography of the surface-treated hollow silica is 70% or more of the theoretical value, and the symmetry factor S is 8 or less.

[0011] Generally, silanol groups (Si—OH) on silica particles are classified into internal silanol groups present within the Si—O network inside the particles, isolated silanol groups present on the particle surface that are not bonded to water adsorbed on the silica particles, and bonded silanol groups that are bonded to water adsorbed on the silica particles or silanols on the silica surface. When silica particles are surface-treated, these silanol groups react with a surface treatment agent and are replaced with substituents that make the silica surface more compatible with resins. It has been found that if the raw materials and treatment conditions used for surface treatment are not appropriately adjusted, adhesion to resins decreases, and in addition, adhesion to resins decreases significantly after high-temperature, high-humidity testing.

[0012] Therefore, the surface-treated hollow silica of the present invention has an amine peak area of ​​70% or more of the theoretical value in chromatography of the surface-treated hollow silica, and a symmetry coefficient S of 8 or less. When the peak area is 70% or more of the theoretical value and the symmetry coefficient S is 8 or less, it is believed that the silanol groups on the silica particle surface have sufficiently reacted with the silane coupling agent, and the silica surface is sufficiently covered with the silane coupling agent. As a result, excellent peel strength is obtained, and the silanol groups that interact with amines are sufficiently deactivated, and the silanol groups that interact with water molecules when exposed to high-temperature, high-humidity conditions are also deactivated, thereby suppressing a decrease in peel strength after high-temperature, high-humidity testing. Here, deactivation refers to a state in which the silanol groups react with the silane coupling agent and are less likely to interact with amines.

[0013] Since the theoretical value of the peak area is 100%, it is theoretically impossible for it to exceed 100%. The peak area is 70% or more of the theoretical value, preferably 80% or more, more preferably 90% or more, and most preferably 95% or more.

[0014] The theoretical value of the symmetry coefficient S is 1 at the minimum, and therefore, it is theoretically impossible to make it less than 1. The symmetry coefficient S is 8 or less, preferably 3 or less, more preferably 2.5 or less, even more preferably 2 or less, and most preferably 1.5 or less.

[0015] The method for measuring the peak area and symmetry factor of the amine in the above-mentioned chromatography is as follows. The surface-treated hollow silica is wet-packed into a stainless steel column with an inner diameter of 4.6 mm and a length of 100 mm, and this column is loaded into a chromatography apparatus "Prominence (manufactured by Shimadzu Corporation)" and measured under the following conditions: Eluent: MeOH / 20 mM phosphate buffer (pH 7.0) = 82 / 18 Flow rate: 0.5 mL / min Temperature: 25°C Detector: UV at 254 nm Sample: Propranolol hydrochloride The obtained peak is analyzed based on JIS K0124:2011 to obtain the peak area and symmetry factor. Note that the theoretical value of the peak area is the peak area when a similar measurement is performed without packing the surface-treated hollow silica.

[0016] The peak area and symmetry factor S of amines in chromatography of surface-treated hollow silica can be adjusted by the type and amount of surface treatment agent, the amount of solvent during surface treatment, the temperature of surface treatment, etc.

[0017] From the viewpoint of maintaining the strength when dispersed in the resin and further improving the adhesion with the resin by lowering the relative dielectric constant, the density of the surface-treated hollow silica determined by a constant volume expansion method using argon gas and a dry pycnometer is 0.25 to 2.00 g / cm ３ is preferably 0.25 to 1.50 g / cm ３ More preferably, 0.30 to 1.00 g / cm ３ is more preferred.

[0018] The surface-treated hollow silica of the present invention has a BET specific surface area of ​​1 to 100 m ２ / g. ２ It is practically difficult to make the BET specific surface area less than 100 m / g. ２ When the BET specific surface area is 1 to 100 m / g or less, the viscosity increase when the surface-treated hollow silica is dispersed in a resin to form a resin composition can be suppressed, and the dispersibility in the resin composition will not be deteriorated. ２ / g is preferred, and 1 to 50m ２ / g is more preferable, and 1 to 20m ２ / g is more preferable, and 1 to 15m ２ / g is most preferred.

[0019] The specific surface area is determined by a multipoint BET method based on a nitrogen adsorption method using a specific surface area / pore distribution measuring device (for example, "BELSORP-mini II" manufactured by Microtrac-Bell, or "Tristar II" manufactured by Micromeritics).

[0020] The surface-treated hollow silica preferably has a median diameter d50 of 0.1 to 10 μm, which is the particle diameter at the point where the cumulative volume from the smallest end in a volume-based particle size distribution curve is 50%. A d50 of 0.1 μm or more can suppress an increase in viscosity of a resin composition in which the surface-treated hollow silica is dispersed in a resin, and a deterioration in the dispersibility of the surface-treated hollow silica in the resin. The d50 is more preferably 0.2 μm or more, even more preferably 0.25 μm or more, and particularly preferably 0.3 μm or more. Furthermore, if the d50 is too large, it can cause granulation when the resin composition is molded into a film. Therefore, the d50 is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, particularly preferably 5 μm or less, and most preferably 3 μm or less.

[0021] d50 is the volume-based cumulative 50% diameter determined using a laser diffraction particle size distribution analyzer (for example, "MT3300EXII" manufactured by Microtrac-Bell Co., Ltd.). That is, particle size distribution is measured by a laser diffraction / scattering method, and a cumulative curve is calculated from the smaller volume, assuming the total volume of the surface-treated hollow silica to be 100%, and d50 is the particle diameter at the point on the cumulative curve where the cumulative volume reaches 50%.

[0022] The surface-treated hollow silica of the present invention is surface-treated with a silane coupling agent. Surface treatment with the silane coupling agent forms a strong bond between the functional group of the silane coupling agent and the silanol group, preventing the bond from being broken when the surface-treated hollow silica is mixed with a resin. Furthermore, the bond is less susceptible to moisture severance, even in high-temperature, high-humidity environments. Furthermore, bonding of organic functional groups to the silica surface by the silane coupling agent reduces the amount of residual silanol groups on the surface, hydrophobizing the surface and improving affinity with the resin in the resin composition. This improves the dispersibility of the surface-treated hollow silica in the resin and the strength of the resin film after formation, while also suppressing moisture adsorption and reducing the decrease in peel strength after high-temperature, high-humidity testing. Examples of silane coupling agents include aminosilane coupling agents, allylsilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, alkylsilane coupling agents, fluorine-containing silane coupling agents, and organosilazane compounds. Silane coupling agents may be used alone or in combination of two or more.Specific examples of the silane coupling agent include aminosilane-based coupling agents such as aminopropyl methoxysilane, aminopropyl triethoxysilane, ureidopropyl triethoxysilane, N-phenylaminopropyl trimethoxysilane, and N-(2-aminoethyl)aminopropyl trimethoxysilane; allylsilane-based coupling agents such as methyltrimethoxysilane, vinyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, metachloroxypropyl trimethoxysilane, imidazole silane, and triazine silane; and glycidoxypropyl trimethoxysilane and glycidoxypropyl trimethoxysilane. Epoxysilane-based coupling agents such as ethoxysilane, glycidoxypropylmethyldiethoxysilane, glycidylbutyltrimethoxysilane, and (3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercaptosilane-based coupling agents such as mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane; alkylsilane-based coupling agents such as methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, octadecyltrimethoxysilane, dimethyldimethoxysilane, and octyltriethoxysilane; CF. ３ (CF ２ ) ７ CH ２ CH ２ Si(OCH ３ ) ３ , C.F. ３ (CF ２ ) ７ CH ２ CH ２ SiCl ３ , C.F. ３ (CF ２ ) ７ CH ２ CH ２ Si(CH ３ ) (OCH ３ ) ２ , C.F. ３ (CF ２ ) ７ CH ２ CH ２ Si(CH ３ ) Cl ２ , C.F.３ (CF ２ ) ５ CH ２ CH ２ SiCS ３ 、CF ３ (CF ２ ) ５ CH ２ CH ２ Si (OCH ３ ) ３ 、CF ３ CH ２ CH ２ SiCS ３ 、CF ３ CH ２ CH ２ Si (OCH ３ ) ３ 、C ８ F １７ SO ２ N (C ３ H ７ )CH ２ CH ２ CH ２ Si (OCH ３ ) ３ 、C ７ F １５ [NNHCH ２ CH ２ CH ２ Si (OCH ３ ) ３ 、C ８ F １７ CO ２ CH ２ CH ２ CH ２ Si (OCH ３ ) ３ 、C ８ F １７ -O-CF(CF ３ )CF ２ -O-C ３ H ６ SiCS ３ 、C ３ F ７ -O-(CF(CF ３ )CF ２ -O) ２ -CF(CF ３ )CONNH-(CH ２ ) ３ Si (OCH ３ )３ fluorine-containing silane coupling agents such as hexamethyldisilazane, hexaphenyldisilazane, trisilazane, cyclotrisilazane, 1,1,3,3,5,5-hexamethylcyclotrisilazane, and other organosilazane compounds.

[0023] The amount of the silane coupling agent to be used is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and even more preferably 0.10 parts by mass or more, relative to 100 parts by mass of the hollow silica, and is preferably 5 parts by mass or less, more preferably 2 parts by mass or less. When two or more types of silane coupling agents are used in combination, the above-mentioned amount to be used means the total amount to be used of the multiple types of silane coupling agents.

[0024] Examples of methods for treating with a silane coupling agent include a dry method in which a silane coupling agent is sprayed onto untreated hollow silica 1 before surface treatment, and a wet method in which hollow silica 1 is dispersed in a solvent and then a silane coupling agent is added to cause a reaction. (Here, "hollow silica 1" refers to untreated hollow silica before surface treatment.)

[0025] The fact that the surface of the surface-treated hollow silica has been treated with a silane coupling agent can be confirmed by detecting a peak due to a substituent of the silane coupling agent by IR. The amount of the silane coupling agent attached can be measured by the carbon content. The carbon content can be measured by a combustion method using a SUMIGRAPH NC-80 (manufactured by Sumika Chemical Analysis Center, Ltd.).

[0026] The surface treatment is preferably carried out under wet treatment conditions in order to achieve uniform treatment, and examples of the solvent used include hydrocarbon organic solvents.

[0027] Furthermore, the value obtained by dividing the molecular weight of the silane coupling agent by the number of Si atoms contained in one molecule of the silane coupling agent is preferably 100 or more and 300 or less. This value corresponds to the molecular weight of the group to which the silane coupling agent is bonded when it is bonded to the surface of the silica particles. If this value is 100 or more, the volatility of the silane coupling agent can be suppressed, preventing it from evaporating during the reaction. If this value is 300 or less, steric hindrance can be prevented, preventing the phenomenon of silanol groups remaining. This value is preferably 100 or more, more preferably 150 or more, and most preferably 180 or more. Furthermore, it is preferably 300 or less, more preferably 270 or less, and most preferably 260 or less. When two or more silane coupling agents are used in combination, it is preferable that the above value for each silane coupling agent be 100 or more and 300 or less.

[0028] Furthermore, in the surface treatment, the heating temperature after contacting the hollow silica 1 with the silane coupling agent is preferably 50 to 200°C. A high heating temperature increases the remaining proportion of the silane coupling agent, but if the heating temperature is too high, partial decomposition begins, and silanol groups are regenerated. A low heating temperature also reduces the reaction rate, making it easier for silanol groups to remain, which in turn deteriorates the peel strength of the resin, particularly after high-temperature, high-humidity testing. The heating temperature is more preferably 60°C or higher, even more preferably 70°C or higher, and most preferably 80°C or higher. The heating temperature is more preferably 170°C or lower.

[0029] Furthermore, in the surface treatment, the product A×B of the density A of the hollow silica 1 and the amount B of the solvent charged per gram of hollow silica 1 is preferably 0.5 to 2.5. This product corresponds to the amount of solvent charged per volume of hollow silica 1, and when this product is 0.5 or more, an amount of solvent sufficient to sufficiently cover the surface of the hollow silica 1 is ensured, making it difficult for silanol groups to remain, and preventing a decrease in peel strength, particularly after a high-temperature, high-humidity test. Furthermore, when this product is 2.5 or less, the amount of solvent distilled off is reduced, resulting in excellent productivity. The product is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1.0 or more. Furthermore, it is preferably 2.5 or less, more preferably 2.0 or less, and most preferably 1.5 or less.

[0030] The surface-treated hollow silica of the present invention preferably contains titanium (Ti) in the range of 30 to 1500 ppm by mass. The Ti content is more preferably 80 ppm by mass or more, even more preferably 100 ppm by mass or more, and more preferably 1000 ppm by mass or less, even more preferably 500 ppm by mass or less. The Ti content can be measured by inductively coupled plasma (ICP) emission spectrometry after adding perchloric acid and hydrofluoric acid to the silica, igniting the mixture to remove the main component silicon.

[0031] Ti is an optional component that can be included in the production of surface-treated hollow silica. If fine powder is generated due to cracking of silica particles during the production of surface-treated hollow silica, the fine powder will adhere to the surface of the base particles, increasing the specific surface area of ​​the particles. By including Ti during the production of surface-treated hollow silica, densification during firing is facilitated. This makes the silica less likely to crack during post-treatment after firing, thereby suppressing the generation of fine powder and reducing the number of particles adhering to the surface of the silica base particles, thereby suppressing an increase in the specific surface area. By including 30 ppm by mass or more of Ti, densification during firing is facilitated, thereby suppressing the generation of fine powder due to cracking. When the Ti content is 1500 ppm by mass or less, the above effects can be achieved, and an increase in the amount of silanol groups can be suppressed, thereby suppressing a deterioration in the dielectric loss tangent.

[0032] The surface-treated hollow silica of the present invention may contain impurity elements other than titanium (Ti) as long as the effects of the present invention are not impaired. Examples of impurity elements include, in addition to Ti, Na, K, Mg, Ca, Al, and Fe. The total content of alkali metals and alkaline earth metals among the impurity elements is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less, and even more preferably 200 mass ppm or less. The total is preferably 1 mass ppm or more, more preferably 2 mass ppm or more, and even more preferably 5 mass ppm or more.

[0033] <Hollow Silica 1> Hollow silica 1, i.e., untreated hollow silica before surface treatment, can be obtained by a conventionally known production method. Examples of the production method include a template method in which a hollow structure is formed using a mold. Alternatively, commercially available hollow silica 1 may be used. Hollow silica 1 may be appropriately selected depending on the properties required for the surface-treated hollow silica.

[0034] The density, BET specific surface area, and median diameter d50 of hollow silica 1 generally coincide with those of the surface-treated hollow silica. Therefore, these characteristics of hollow silica 1 may be appropriately selected based on the characteristics desired for the surface-treated hollow silica.

[0035] <Resin Composition> The surface-treated hollow silica of the present invention has excellent adhesion to resins, and therefore excellent mixability with resin compositions. The resin composition according to this embodiment contains the surface-treated hollow silica of the present invention and a resin. The content of the surface-treated hollow silica in the resin composition is preferably 5 to 70% by volume, more preferably 10 to 60% by volume, even more preferably 15 to 60% by volume, and most preferably 20 to 60% by volume. When the content of the surface-treated hollow silica is 5% by volume or more, a sufficient reduction in the dielectric constant is obtained, and when it is 70% by volume or less, adhesion between the resin composition and the metal substrate is maintained.

[0036] Examples of the resin include epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester resin, fluororesin, polyamide resin such as polyimide resin, polyamideimide resin, and polyetherimide; polyester resin such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene ether resin, polyphenylene sulfide resin, orthodivinylbenzene resin, aromatic polyester resin, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS (acrylonitrile butadiene styrene) resin, AAS (acrylonitrile-acrylic rubber styrene) resin, AES (acrylonitrile ethylene propylene diene rubber styrene) resin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). One or more of these may be used. The dielectric loss tangent of a resin composition also depends on the properties of the resin, so the resin to be used should be selected taking these into consideration.

[0037] The resin preferably contains a thermosetting resin. One type of thermosetting resin may be used, or two or more types may be used. Examples of the thermosetting resin include epoxy resin, polyphenylene ether resin, polyimide resin, phenol resin, and orthodivinylbenzene resin. From the viewpoints of adhesion, heat resistance, and the like, the thermosetting resin is preferably an epoxy resin, polyphenylene ether resin, or orthodivinylbenzene resin.

[0038] From the viewpoint of adhesion, dielectric properties, etc., the weight average molecular weight of the thermosetting resin is preferably 1000 to 7000, more preferably 1000 to 5000, and even more preferably 1000 to 3000. The weight average molecular weight is determined using gel permeation chromatography (GPC) in terms of polystyrene.

[0039] The particle size distribution of the surface-treated hollow silica contained in the resin composition is preferably unimodal, which can be confirmed by the presence of a single peak in the particle size distribution measured by a laser diffraction / scattering method.

[0040] The resin composition may contain any component other than the resin and medium (e.g., toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.) Examples of the optional component include a dispersing aid, a surfactant, and a filler other than silica particles.

[0041] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In the following description, the same components are used.

[0042] <Hollow Silica A1> Hollow silica A1 was prepared as follows.

[0043] (Preparation of Emulsion) 4 g of EO-PO-EO block copolymer (Pluronic (registered trademark) F68, manufactured by ADEKA Corporation) was added to 1,250 g of pure water and stirred until dissolved, yielding an aqueous solution. 42 g of n-decane in which 4 g of sorbitan acid monooleate (IONET (registered trademark) S-80, manufactured by Sanyo Chemical Industries, Ltd.) had been dissolved was added to this aqueous solution, and the mixture was stirred using an IKA homogenizer until the entire liquid became uniform, yielding a crude emulsion. This crude emulsion was emulsified using a high-pressure emulsifier (LAB1000, manufactured by SMT Corporation) at a pressure of 50 bar, yielding an emulsion with an emulsion diameter of 1 μm.

[0044] (Aging) The resulting emulsion was allowed to stand at 40° C. for 12 hours.

[0045] (Formation of the first shell layer) After standing, 1300 g of the emulsion was diluted with an aqueous sodium silicate solution (SiO ２ Concentration 10.4% by volume, Na ２23 g of 2M hydrochloric acid (O concentration 3.6 vol%) was added and stirred while maintaining the temperature at 30°C to obtain a mixed solution. Next, while stirring the mixed solution, 1M aqueous sodium hydroxide solution was slowly added dropwise so that the pH became 6, to obtain an oil core-silica shell particle dispersion. The obtained oil core-silica shell particle dispersion was maintained and aged.

[0046] (Second-stage shell layer formation) The oil core-silica shell particle dispersion was heated to 70°C, and 1M aqueous sodium hydroxide solution was slowly added while stirring to adjust the pH to 9. Next, a diluted aqueous sodium silicate solution (SiO ２ Concentration 10.4% by volume, Na ２ 330 g of HCl (3.6% by volume) was gradually added together with 0.5 M hydrochloric acid to adjust the pH to 9. The suspension was kept at 80° C. for 1 day and then cooled to room temperature to obtain a hollow silica precursor dispersion.

[0047] (Filtration, washing, drying, calcination) The entire hollow silica precursor dispersion was neutralized to pH 2 with 2M hydrochloric acid and then filtered using quantitative filter paper 5C. 350 ml of 80°C ion-exchanged water was then added and pressure filtered again to wash the hollow silica precursor cake. The filtered cake was dried in a nitrogen atmosphere at 100°C for 1 hour and then at 400°C for 2 hours (heating rate 10°C / min) to remove organic matter, thereby obtaining a hollow silica precursor. The obtained hollow silica precursor was calcined at 1050°C for 1 hour (heating rate 10°C / min) to sinter the shell, thereby obtaining hollow silica A1.

[0048] <Hollow Silica A2> Hollow Silica A2 was obtained in the same manner as Hollow Silica A1, except that the amount of the EO-PO-EO block copolymer used was changed to 2 g and the amount of sorbitan acid monooleate used was changed to 2 g.

[0049] <Hollow Silica A3> Hollow Silica A3 was obtained in the same manner as Hollow Silica A1, except that the amount of EO-PO-EO block copolymer used was changed to 10 g, sorbitan acid monooleate was not used, and the pressure in emulsification was changed to 100 bar.

[0050] <Hollow Silica A4> Hollow Silica A4 was obtained in the same manner as Hollow Silica A1, except that the calcination conditions for the hollow silica precursor were changed to 1,100°C for 1 hour (heating rate: 10°C / min).

[0051] <Hollow Silica A5> Hollow Silica A5 was obtained in the same manner as Hollow Silica A1, except that the calcination conditions for the hollow silica precursor were changed to 800°C for 1 hour (heating rate 10°C / min).

[0052] (Surface Treatment) 200 g of hollow silica was placed in a 3.5 L planetary mixer (Hibismix 3L-5, manufactured by PRIMIX Corporation). 1.4 g of the silane coupling agent listed in Table 1 was added to hexane adjusted so that the density A of untreated hollow silica 1 x the amount of solvent charged B per gram of untreated hollow silica 1 was the value in Table 1, and the mixture was stirred with a magnetic stirrer for 5 minutes to prepare a solution. The prepared solution was added to the planetary mixer containing the hollow silica, and nitrogen was passed through for 10 minutes while stirring at 60 rpm. The mixture was then heated to 80°C at a rate of 2°C / min while passing nitrogen through, and held at 80°C for 1 hour. After being cooled to 50°C and taken out into the atmosphere, surface-treated hollow silica was obtained. Surface-treated hollow silica of Examples 2 to 10 and 16 to 23 was obtained in this manner. In Example 1, hollow silica A1 was used as is without surface treatment. In Examples 11 to 15, the heating temperature was changed from 80°C to the temperature shown in Table 1, and surface-treated hollow silica was prepared in the same manner as in Example 1. In Example 24, the amount of silane coupling agent shown in Table 1 was changed to 0.1 g, in Example 25, to 0.4 g, in Example 26, to 5.0 g, and in Example 27, to 14.0 g of the silane coupling agent shown in Table 1, and surface-treated hollow silica was prepared in the same manner as in Example 1. Hereinafter, the hollow silica of Example 1 and the surface-treated hollow silica of Examples 2 to 27 may be collectively referred to as "hollow silica."

[0053] The hollow silica particles obtained in Examples 1 to 27 were subjected to the following measurements. The results are shown in Table 1.

[0054] (Measurement by chromatography) For each hollow silica example, the peak area and symmetry factor of the amine in chromatography were measured by the following measurement method, and the results are shown in Table 1. The hollow silica was wet-packed into a stainless steel column with an inner diameter of 4.6 mm and a length of 100 mm, and this column was loaded into a chromatography apparatus "Prominence (manufactured by Shimadzu Corporation)" and measured under the following conditions. Eluent: MeOH / 20 mM phosphate buffer (pH 7.0) = 82 / 18 Flow rate: 0.5 mL / min Temperature: 25 ° C. Detector: UV at 254 nm Sample: Propranolol hydrochloride The obtained peak was analyzed based on JIS K0124:2011 to obtain the peak area and symmetry factor. Note that the theoretical value of the peak area was the peak area when a similar measurement was performed without packing the hollow silica. In Table 1, the symmetry coefficient S is "-" indicates that the amine was adsorbed to the hollow silica and could not be detected.

[0055] (Method for measuring density of hollow silica) The hollow silica used in each example was dried under reduced pressure at 230°C to completely remove moisture and prepare a sample. The density of this sample was measured using a dry pycnometer (AccuPycII 1340 manufactured by Micromeritics). The measurement conditions were as follows. The results are shown in Table 1 as "Ar density". (Measurement conditions) Sample cell: 10 cm ３ Cell Sample weight: 1.0 g Measurement gas: argon gas Number of purges: 10 times Purge treatment filling pressure: 135 kPaG Number of cycles: 10 times Cycle filling pressure: 135 kPaG Rate for completing pressure equilibration: 0.05 kPaG / min

[0056] (Method for measuring BET specific surface area of ​​hollow silica) The hollow silica used in each example was dried under reduced pressure at 230°C to completely remove moisture, and used as a sample. The specific surface area of ​​this sample was determined by the multi-point BET method using nitrogen gas with an automatic specific surface area and pore distribution measuring device "Tristar II" manufactured by Micromeritics. The results are shown in Table 1.

[0057] (Method for measuring d50 of hollow silica) The d50 of the hollow silica used in each example was measured by a laser diffraction / scattering method using a particle size distribution analyzer (MT3300EXII, manufactured by Microtrac Bell). Specifically, measurement was performed after dispersing the secondary particles of hollow silica by irradiating with ultrasonic waves for 120 seconds, and the value at which the cumulative distribution of the particle size obtained reached 50% was taken as d50. The results are shown in Table 1.

[0058] (Method for measuring bulk density of hollow silica) The bulk density of hollow silica is measured at 100 cm ３ The hollow silica was placed in a measuring cylinder and tapped until the volume no longer changed, and the volume and mass at that time were measured.

[0059] (Measurement of peel strength, dielectric loss tangent, and relative dielectric constant of resin composition using hollow silica) [Example 1] 25 parts by mass of polyphenylene ether resin, 50 parts by mass of butadiene-styrene random copolymer, 0.75 parts by mass of α,α'-di(t-butylperoxy)diisopropylbenzene, 40 parts by volume of hollow silica A1, and 50 parts by mass of toluene were placed in a planetary centrifugal mixer (Thinky Mixer ARE-310) and mixed at 2000 rpm for 30 minutes to obtain a resin composition. The obtained resin composition was vacuum dried at 120°C for 1 hour, and then 5 g of the composition was sampled and placed in a square mold measuring 0.3 mmt x 80 mm squares. Low-profile copper foil (thickness: 18 μm, Rz: 3.5 μm, Mitsui Kinzoku Co., Ltd., 3EC-M3-V-18) was laminated on top and bottom. The resulting laminate was heated to 200°C at a heating rate of 5°C / min and held at a pressure of 10 MPa for 120 minutes for heat molding to obtain a resin-coated metal substrate. The peel strength between the cured prepreg and the copper foil was measured for the resulting resin-coated metal substrate in accordance with IPC-TM650-2.4.8. In Table 1, this peel strength is referred to as "Peel (PPE)." Furthermore, the peel strength after a high-temperature, high-humidity test was similarly measured after the resulting resin-coated metal substrate was left in a constant-temperature, constant-humidity chamber set at 85°C and 85% RH for 24 hours. In Table 1, the peel strength after the high-temperature, high-humidity test is referred to as "High-Temperature, High-Humidity Peel." The obtained resin-coated metal substrate was etched with an etching solution (H-1000A, manufactured by Sanhayato Corporation) and dried in an oven at 100°C for 1 hour, after which the relative permittivity and dielectric loss tangent were measured using a split post dielectric resonator (SPDR) (manufactured by Agilent Technologies). The measurement results are summarized in Table 1.

[0060] [Examples 2 to 27] Resin compositions, prepregs, and resin-coated metal substrates were produced in the same manner as in Example 1, except that hollow silica A1 was changed to the surface-treated hollow silica shown in Table 1, and measurements similar to those in Example 1 were carried out.

[0061]

[0062] It was found that the surface-treated hollow silica of Examples 3 to 27 all had higher peel strength and peel strength after high-temperature, high-humidity testing than the comparative examples (Examples 1 and 2), and were excellent in both adhesion to resin and its reliability. On the other hand, the surface-treated hollow silica of Comparative Example 1 and Example 2 had low peel strength and a significant decrease in peel strength after the high-temperature, high-humidity testing, indicating that they were inferior in adhesion to resin and its reliability.

[0063] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-099441) filed on June 16, 2023, the entire contents of which are incorporated by reference.

Claims

1. A surface-treated hollow silica having an amine peak area in chromatography of 70% or more of the theoretical value and a symmetry factor S of 8 or less.

2. The density of the surface-treated hollow silica is 0.25 to 2.00 g / cm ３ The surface-treated hollow silica according to claim 1 , 3. The BET specific surface area of ​​the surface-treated hollow silica is 1 to 100 m ２ The surface-treated hollow silica according to claim 1, wherein the molecular weight of the surface-treated hollow silica is 1 / g.

4. The surface-treated hollow silica according to claim 1, wherein the median diameter (d50) of the surface-treated hollow silica is 0.1 to 10 μm.

5. A method for producing surface-treated hollow silica according to any one of claims 1 to 4, comprising subjecting untreated hollow silica to a surface treatment, wherein the molecular weight of a silane coupling agent used in the surface treatment is 100 to 300 when divided by the number of Si atoms contained in one molecule of the silane coupling agent.

6. The method for producing surface-treated hollow silica according to claim 5, wherein the surface treatment comprises contacting the untreated hollow silica with the silane coupling agent and then heating the resultant at a temperature of 50 to 200°C.

7. The method for producing surface-treated hollow silica according to claim 6, wherein a solvent is used during the contacting, and the product A×B of the density A of the untreated hollow silica and the amount B of the solvent charged per gram of the untreated hollow silica is 0.5 to 2.

5.

8. A resin composition comprising the surface-treated hollow silica according to any one of claims 1 to 4 and a resin.

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