Surface-treated silica powder, method for producing same, and resin composition using same

Abstract

A surface-treated silica powder according to the present invention has an epoxy group on a surface thereof, wherein the amount of trimethylsilyl groups per surface area of the surface-treated silica powder is 0.3-1.5 groups / nm2. The amount of epoxy groups per surface area of a washed powder is 1.0-3.0 groups / nm2, the washed powder being obtained by: repeating, three times, a treatment step that includes dispersing a suspension which has a total volume of 30 mL and which has been obtained by suspending 3 g of the surface-treated silica powder in ethanol for 10 minutes with an ultrasonic disperser having an output of 110 W and then performing solid-liquid separation with a centrifugal separator; and thereafter performing vacuum-drying for 1 hour. The ring-opening rate of the epoxy groups in the washed powder is not more than 25%.

Description

Surface-treated silica powder, method for producing the same, and resin composition using the same

[0001] The present invention relates to a surface-treated silica powder that can be suitably used as a filler for semiconductor encapsulants and the like, a method for producing the same, and a resin composition using the same.

[0002] In recent years, with the increasing performance, miniaturization, and weight reduction of electronic devices, the form of semiconductor packages used in them has also progressed towards higher integration, higher density, and thinner designs. For the practical application of such semiconductor packages, the development of suitable encapsulating materials, along with the design of integrated circuits, is essential.

[0003] For example, epoxy resin is mainly used as the underfill material that fills the space between a semiconductor chip and a wiring board. However, epoxy resin, semiconductor chips, and wiring boards each have different coefficients of thermal expansion. Therefore, if the connection cannot absorb the stress, cracks may occur at the connection. To suppress the occurrence of these cracks, silica powder is widely used as a filler with a relatively small coefficient of thermal expansion in underfill materials. In this case, it is necessary to increase the amount of silica powder used to reduce the coefficient of thermal expansion of the sealing material. Furthermore, underfill materials filled with silica powder are required to have low viscosity immediately after filling and to have stability over time without increasing viscosity after filling.

[0004] Patent Document 1 proposes a silica powder that satisfies the above requirements. Patent Document 1 discloses a surface-treated silica powder in which the viscosity of the resin composition in which the silica powder is filled is highly suppressed by chemically bonding an epoxysilane coupling agent to the surface of the silica particles at a high density, and further by having a large amount of unbonded epoxysilane coupling agent on the surface of the silica particles.

[0005] WO2023 / 189642 publication

[0006] The surface-treated silica powder described in Patent Document 1 can fully exhibit the aforementioned effects when used as is. However, when the surface-treated silica powder is filled into a resin after undergoing physical treatment such as washing to remove foreign matter, a problem arises in which the resin composition becomes thicker. This problem also occurs in conventional surface-treated silica in which the density of epoxy groups chemically bonded to the surface of the silica powder is increased by using a relatively excessive amount of epoxysilane coupling agent during surface treatment.

[0007] Therefore, an object of the present invention is to provide a surface-treated silica powder that has a high density of epoxy groups chemically bonded to the surface of the silica powder, and that can highly suppress the initial viscosity of the resin composition in which it is filled, as well as the subsequent thickening over time, even after the physical treatment for removing foreign matter has been performed.

[0008] The inventors conducted research to achieve the above objective. As a result, they found that in order to increase the density of epoxy groups chemically bonded to the surface of silica powder, it is necessary to use an excess of epoxysilane coupling agent and react at a high temperature. However, in such a reaction, ring-opening of epoxy groups by silanol groups on the silica surface is likely to occur, and these ring-opened epoxy groups cause thickening when filling resin. By adopting a specific reaction temperature and using a specific amount of silane coupling agent having a small molecular weight group such as hexamethyldisilazane (HMDS) in combination for surface treatment, they succeeded in obtaining a surface-treated silica powder in which the density of epoxy groups chemically bonded to the surface of the silica powder is high, and in which ring-opening of the epoxy groups chemically bonded to the surface of the silica powder is suppressed, thus completing the present invention.

[0009] In other words, according to the present invention, a surface-treated silica powder having epoxy groups on its surface, wherein the amount of trimethylsilyl groups per unit surface area of ​​the surface-treated silica powder is 0.3 to 1.5 groups / nm ２and after repeating the treatment process of suspending 3 g of the surface-treated silica powder in ethanol to obtain a total volume of 30 mL of suspension, dispersing it with an ultrasonic disperser at an output of 110 W for 10 minutes, and then performing solid-liquid separation with a centrifuge three times, followed by vacuum drying for 1 hour, the amount of unopened epoxy groups per unit surface area of the washed powder is 1.0 to 3.0 per nm ２ There is provided a surface-treated silica powder characterized in that the ring-opening rate of the epoxy groups in the washed powder is 25% or less.

[0010] The surface-treated silica powder preferably has an amount of unopened epoxy groups per unit surface area of 1.0 to 5.0 per nm ２

[0011] The surface-treated silica powder preferably has an amount of unopened epoxy groups per unit surface area of 1.0 to 4.0 per nm ２ and preferably has 150 or less foreign matters of 20 μm or more per 50 g contained in the surface-treated silica powder.

[0012] The BET specific surface area of the surface-treated silica powder is preferably 1 to 100 m ２ / g.

[0013] The surface-treated silica powder has a cumulative 50 volume% diameter (D ５０ ), a cumulative 90 volume% diameter (D ９０ ), and the amount (V ９０ ) of coarse particles of the surface-treated silica powder obtained by Formula 1 is preferably 10 or more and less than 100.

[0014] V ９０ ={ (D ９０ - D ５０ ) / D ５０} × 100 (1) The present invention also provides a resin composition in which the surface-treated silica powder is dispersed in an epoxy resin.

[0015] According to the present invention, it is a surface-treated silica powder treated with an epoxy silane coupling agent, and even after performing a physical treatment for removing foreign matters, the initial viscosity and the time-dependent thickening (viscosity stability over time) in the resin composition filled with this can be effectively suppressed.​

[0016] The surface-treated silica powder of the present invention has epoxy groups on its surface due to treatment with an epoxysilane coupling agent. A total volume of 30 mL suspension of 3 g of the surface-treated silica powder in ethanol is dispersed for 10 minutes using a 110 W ultrasonic disperser, followed by solid-liquid separation using a centrifuge. This process is repeated three times, and the resulting washed powder is vacuum-dried for 1 hour. The amount of unopened epoxy groups per surface area is 1.0 to 3.0 groups / nm. ２ The ring-opening rate of epoxy groups in the washing powder is 25% or less.

[0017] The amount of non-ring-opened epoxy groups per unit surface area of ​​the washing powder includes only non-ring-opened epoxy groups from all epoxy groups derived from the epoxysilane coupling agent present on the surface of the washing powder, excluding ring-opened epoxy groups. Examples of ring-opened epoxy groups include ring-opened epoxy groups derived from the epoxysilane coupling agent that have opened to form two functional groups (e.g., a combination of two hydroxyl groups, a combination of a hydroxyl group and an alkoxy group, or a combination of a hydroxyl group and a halogenated alkyl group); and linking groups in which an epoxy group has opened and is bonded to an adjacent alkoxysilyl group derived from the epoxysilane coupling agent. The amount of non-ring-opened epoxy groups is measured and calculated according to JIS K 7239.

[0018] The washed powder is silica powder obtained by performing three washing treatments and one drying treatment in the order of the surface-treated silica powder of the present invention. The washing treatment consists of the following steps (1) to (3), and the drying is the following step (4). (1) A step of suspending 3 g of surface-treated silica powder in ethanol to obtain a suspension with a total volume of 30 mL. (2) A step of dispersing the suspension in an ultrasonic disperser at an output of 110 W for 10 minutes to obtain a dispersed slurry. (3) A step of separating the dispersed slurry into solid and liquid using a centrifuge to obtain a cake (i.e., 3 g of surface-treated silica powder). (4) A step of drying the cake under vacuum for 1 hour.

[0019] Conventionally, in surface-treated silica using epoxysilane coupling agents, excessive use of the silane coupling agent is necessary to chemically bond epoxy groups to the surface of the silica powder at a high density. As a result, the silica particle surface contains both epoxy groups derived from the groups bonded to the silica surface and physically adsorbed epoxysilane coupling agent. Therefore, when mixed with epoxy resin, affinity is determined to some extent by the amount of physically adsorbed silane coupling agent, and thickening of the resin composition filled with this was not a major problem. However, when the aforementioned foreign matter is physically removed, much of the physically adsorbed silane coupling agent is removed, and the properties of the surface-treated silica powder become dependent on the epoxy groups derived from the groups bonded to the silica surface. In this case, if the amount of epoxy groups, i.e., the amount of epoxy groups in the washing powder, is less than the aforementioned range, the amount of epoxy groups after physical removal of foreign matter becomes insufficient, reducing the affinity with the epoxy resin and causing the resulting resin composition to thicken. Furthermore, the inventors have confirmed that some of the epoxy groups derived from the groups bonded to the silica surface are ring-opened, which reduces the affinity with the epoxy resin and makes the resin composition more prone to thickening.

[0020] The surface-treated silica of the present invention has a high density of epoxy groups derived from groups bonded to the silica surface. Furthermore, the ring-opening rate of epoxy groups in the washing powder is kept low. This means that even when physical loads such as foreign matter removal are applied, ring-opening of epoxy groups is less likely to occur. As a result, since ring-opening of epoxy groups is less likely to occur even after physical removal of foreign matter, it has good affinity with epoxy resins and can highly prevent the initial viscosity and thickening over time of the resin composition. In addition, in the surface-treated silica powder after physical removal of foreign matter, the low epoxy ring-opening rate of the washing powder is a result of the absence of ring-opening of epoxy groups during foreign matter removal, and it can be said that if this characteristic is present, thickening of the resin composition can be highly suppressed. In surface-treated silica obtained by methods specifically implemented in conventional patent documents, etc., there have been no cases in which ring-opening of epoxy groups has been observed after the removal of physically adsorbed silane coupling agents, and it has been confirmed that the ring-opening rate of the epoxy groups in the surface-treated silica obtained by these manufacturing methods is high and exceeds the range.

[0021] A key feature of the present invention is that the amount of unopened epoxy groups per unit surface area of ​​the washing powder is 1.0 to 3.0 groups / nm. ２ Preferably, 1.2 to 1.8 particles / nm ２ That is the case.

[0022] A key feature of the present invention is that the ring-opening rate of epoxy groups in the washing powder (epoxy ring-opening rate) is 25% or less. The epoxy ring-opening rate refers to the ratio of ring-opened epoxy groups to epoxy groups originating from groups bonded to silica particles in the surface-treated silica powder.

[0023] The epoxy ring-opening rate was determined by first determining the total amount of epoxy groups (A) from the amount of carbon in the groups present on the surface of the washed powder, and by determining the amount of un-ring-opened epoxy groups according to the test method of JIS K 7239, and then using these values ​​to calculate the rate using the following formulas (1) and (2).

[0024] Ring-opened epoxy group amount (B) = Total epoxy group amount (A) - Non-ring-opened epoxy group amount (1) Epoxy ring-opening rate (%) = B / A × 100 (2) The total epoxy group amount (A), ring-opened epoxy group amount (B), and non-ring-opened epoxy group amount of the washing powder all represent the number of each epoxy group (total epoxy group, ring-opened epoxy group, or non-ring-opened epoxy group) present per unit surface area of ​​the washing powder, and these units are groups / nm ２ The total amount of epoxy groups (A) can be calculated by using the number of carbon atoms of the silane coupling agent used if the type of silane coupling agent used is known in advance, or by identifying the number of carbon atoms of the group by chemical analysis if it is unknown, or by determining the proportion of the groups by known analytical methods if multiple groups are present, and using these values.

[0025] For example, in the manufacturing method described later, when surface treatment is performed using an epoxysilane coupling agent and HMDS, the surface of the cleaned powder contains hydrocarbon groups having epoxy groups derived from the epoxysilane coupling agent and trimethylsilyl groups derived from the HMDS. The total amount of epoxy groups (A) can be calculated as follows from the amount of carbon in these groups and the amount of trimethylsilyl groups obtained by analysis.

[0026] "Total epoxy groups per unit surface area of ​​the washing powder (A)" = {("Amount of carbon per unit surface area of ​​the washing powder" - "Amount of trimethylsilyl group-containing carbon per unit surface area of ​​the washing powder") / "Number of carbon atoms derived from the epoxysilane coupling agent"} × "Number of epoxy groups in the epoxysilane coupling agent"

[0027] The "amount of carbon per unit surface area of ​​the washing powder" is the total number of carbon atoms present per unit surface area of ​​the washing powder. This can be calculated, for example, using a total nitrogen-to-total carbon analyzer. Specifically, the "mass percentage of carbon in the washing powder (mass%)" is measured using a total nitrogen-to-total carbon analyzer, converted to the "number of carbon atoms per unit mass of the washing powder (atoms / g)," and then the "specific surface area of ​​the washing powder" is used to calculate the "amount of carbon per unit surface area of ​​the washing powder (atoms / nm)." ２ The calculation should be as follows: "Carbon content per unit surface area of ​​washing powder (carbons / nm)". ２) = "mass percentage of carbon in the washing powder (mass%)" / 100 / "atomic weight of carbon (g / mol)" × "Avogadro's number (atomic atoms / mol)" / "specific surface area of ​​the washing powder (nm) ２ It is calculated using the formula ( / g). The specific surface area of ​​the washing powder is the BET specific surface area, and for example, the washing powder can be measured by the nitrogen adsorption BET single-point method. Note that the washing powder, surface-treated silica, and untreated silica (raw material silica) have substantially the same specific surface area, so any of their specific surface areas can be substituted for each other. The amount of carbon per unit surface area of ​​the washing powder is, for example, 10 to 25 atoms / nm ２ Preferably, 12 to 18 particles / nm ２ That is the case.

[0028] The "amount of trimethylsilyl groups per unit surface area of ​​the washing powder" is the number of carbon atoms that constitute trimethylsilyl groups among the carbon atoms present per unit surface area of ​​the washing powder. For example, it can be determined by measuring the number of trimethylsilyl groups (trimethylsilyl group amount) present per unit surface area of ​​the washing powder and multiplying that number by three. The trimethylsilyl group amount (TMS group amount) can be calculated by measuring the peak area of ​​trimethylsilyl groups in the washing powder using pyrolysis GC / MS and comparing it with the peak area of ​​a standard sample with a known number of trimethylsilyl groups. The amount of trimethylsilyl groups per unit surface area of ​​the washing powder is, for example, 0.3 to 1.5 groups / nm. ２ Preferably, 0.5 to 0.9 particles / nm ２ The amount of carbon atoms containing the trimethylsilyl group is three times the amount of trimethylsilyl group, for example, 0.9 to 4.5 atoms / nm. ２ Preferably, 1.5 to 2.8 particles / nm ２ That is the case.

[0029] The "number of carbon atoms derived from the epoxysilane coupling agent" is the number of carbon atoms present in each epoxysilane coupling agent when bonded to the surface of the washed powder. This can be estimated, for example, from the number of epoxysilane coupling agents used in the surface treatment. However, when the epoxysilane coupling agent bonds to the silica powder, hydrolyzable groups (such as alkoxy groups) present in the epoxysilane coupling agent are removed, so the number of carbon atoms decreases after surface treatment compared to the original number of carbon atoms in the epoxysilane coupling agent. Therefore, the "number of carbon atoms derived from the epoxysilane coupling agent" should be the value obtained by subtracting a "predetermined number (defined as N)" from the "original number of carbon atoms in the epoxysilane coupling agent". That is, "number of carbon atoms derived from the epoxysilane coupling agent" = "original number of carbon atoms in the epoxysilane coupling agent" - N.

[0030] N is the number of carbon atoms in the hydrolyzable groups that are hydrolyzed during surface treatment in a single epoxysilane coupling agent. N is determined according to the surface treatment method and the type of epoxysilane coupling agent. For example, in the case of wet surface treatment, substantially all hydrolyzable groups (such as alkoxy groups) are hydrolyzed and eliminated. Therefore, the total number of carbon atoms contained in all hydrolyzable groups becomes N. For example, if 3-glycidoxypropyltrimethoxysilane (which originally has 9 carbon atoms) is used as the epoxysilane coupling agent, three methoxy groups, and therefore three carbon atoms, are eliminated, so N becomes 3. If 3-glycidoxypropyltriethoxysilane is used, N becomes 6. On the other hand, for example, in the case of dry surface treatment, only some of the multiple hydrolyzable groups are hydrolyzed and eliminated. Therefore, the number of carbon atoms contained in some of the hydrolyzable groups that are eliminated becomes N. Generally, two-thirds of the hydrolyzable groups are eliminated. For example, when 3-glycidoxypropyltrimethoxysilane is used as the epoxysilane coupling agent, 2 / 3 of the 3 methoxy groups, i.e., 2 methoxy groups, are eliminated, resulting in 2 nitrogen atoms (N). When 3-glycidoxypropyltriethoxysilane is used, there are 4 nitrogen atoms. In other words, in the dry process, N can be determined by assuming that 2 / 3 of all hydrolyzable groups in one epoxysilane coupling agent are eliminated. N is usually 1 to 6 atoms, preferably 2 to 4 atoms.

[0031] The "number of epoxy groups in the epoxysilane coupling agent" refers to the number of epoxy groups present in each epoxysilane coupling agent used for surface treatment. This number of epoxy groups represents the original epoxy groups of the silane coupling agent before use in surface treatment, and is counted assuming that ring opening has not occurred. Therefore, when 3-glycidoxypropyltrimethoxysilane is used, the number of epoxy groups in the epoxysilane coupling agent is one.

[0032] The total amount of epoxy groups (A) per unit surface area of ​​the washing powder is, for example, 1.0 to 5.0 groups / nm. ２Preferably, 1.5 to 2.5 particles / nm ２ The number of ring-opening epoxy groups (B) per unit surface area of ​​the washing powder is, for example, 0.8 groups / nm. ２ Preferably, 0.3 to 0.5 particles / nm ２ That is the case.

[0033] In the surface-treated silica powder of the present invention, the epoxy ring-opening rate has a significant effect on the properties when the surface-treated silica, after physical removal of foreign matter, is mixed with a resin. Specifically, if the ring-opening rate of the epoxy groups exceeds 25%, the affinity of the surface-treated silica, after physical removal of foreign matter (described later), with the epoxy resin decreases, and the resin composition is more likely to thicken. The ring-opening rate of the epoxy groups is 25% or less, and particularly preferably 20% or less. The lower limit of the ring-opening rate is not particularly limited, and a lower rate is preferable from the viewpoint of affinity with the resin, but it can be adjusted as appropriate considering that lowering the ring-opening rate increases manufacturing costs, for example, it can be 0% or more, preferably 10% or more, and more preferably 15% or more.

[0034] The surface-treated silica powder of the present invention is manufactured by requiring the use of a large amount of epoxysilane coupling agent in the surface treatment in order to achieve the above properties. Therefore, a large amount of physically adsorbed epoxysilane coupling agent is often present on the surface of the surface-treated silica powder. The amount of unopened epoxy groups per unit surface area of ​​the surface-treated silica powder (silica powder before the above washing and drying treatments) is, for example, 1.0 to 5.0 groups / nm. ２ Preferably, 1.0 to 4.0 particles / nm ２ More preferably, 1.5 to 3.0 particles / nm ２ That is the case.

[0035] Furthermore, in the surface-treated silica powder of the present invention, the amount of each epoxy present in the surface-treated silica powder and the washing powder is adjusted to facilitate achieving the aforementioned properties, so that the amount of trimethylsilyl groups per unit surface area of ​​the surface-treated silica powder is 0.3 to 1.5 groups / nm. ２ It is characterized by the following: Preferably, 0.5 to 1.5 particles / nm ２ More preferably, 0.5 to 0.9 particles / nm ２The carbon content per unit surface area of ​​surface-treated silica powder is, for example, 10 to 30 atoms / nm. ２ Preferably, 15 to 26 particles / nm ２ More preferably, 17 to 26 particles / nm ２ Yes. The ratio of the amount of non-ring-opened epoxy groups (b) to the amount of carbon per unit area (a) (b / a) is, for example, 0.10 or more, more preferably 0.10 to 0.20, and more preferably 0.10 to 0.15.

[0036] Furthermore, the method for measuring the composition of surface-treated silica powder (amount of each epoxy group, amount of trimethylsilyl group, amount of carbon, etc.) can be applied to the method for measuring the composition of each component of washed powder, except that the target of measurement is changed from washed powder to surface-treated silica powder.

[0037] In the present invention, the product obtained by the manufacturing method described later can be used as is, but the above-mentioned remarkable effect is particularly evident in surface-treated silica powder after physical removal of foreign matter.

[0038] Here, examples of foreign matter include resin fragments introduced during the process, condensed products formed by the condensation of a portion of the silane coupling agent, and magnetic foreign matter. The foreign matter of this invention is limited to foreign matter with a maximum particle length of 20 μm or more. Such foreign matter can be sieved off using a 20 μm mesh filter. One method of removing foreign matter is to physically remove at least one of these foreign matter. Such a treatment reduces the amount of epoxysilane coupling agent physically adsorbed on the silica surface, thus reducing the amount of physically adsorbed epoxysilane coupling agent.

[0039] The foreign matter removal process should ideally be one that can reduce the amount of foreign matter contained in the surface-treated silica powder by 50% or more.

[0040] A typical method for physically removing foreign matter is a wet removal method, in which a dispersion of surface-treated silica powder in a liquid solvent is filtered. The solvent used to disperse the surface-treated silica powder is not particularly limited as long as it is a solvent that disperses the surface-treated silica powder easily. Common solvents include alcohols such as methanol, ethanol, and 2-propyl alcohol, and organic solvents such as ethers and ketones can also be used. A mixed solvent of water and one or more of the aforementioned organic solvents may also be used. In addition, various additives such as dispersants such as surfactants and defoamers may be added to improve the stability and dispersibility of the surface-treated silica powder. On the other hand, in addition to the wet removal method, dry removal methods such as wind classification can also be used. The wet removal method is preferred because it has good foreign matter removal efficiency.

[0041] Regarding the surface-treated silica powder after physical removal of foreign matter, for example, if physical removal is carried out by the filtration means described above, it is possible to obtain surface-treated silica in which the amount of foreign matter 20 μm or larger is 150 or less per 50 g, preferably 100 or less per 50 g, and more preferably 50 or less, while maintaining the characteristic properties (i.e., high density of chemically bonded epoxy groups and low epoxy ring-opening rate). If the amount of foreign matter contained in 50 g of silica powder is within the above range, short circuits between wiring such as semiconductor wires can be effectively suppressed when the surface-treated silica powder is filled into epoxy resin as a filler. Note that the surface-treated silica powder before foreign matter removal generally contains 200 or more foreign matter 20 μm or larger per 50 g, and particularly 300 or more per 50 g. The upper limit is, for example, 1000 or less per 50 g, and particularly 800 or less per 50 g.

[0042] Furthermore, if physical removal is performed on magnetic foreign matter, it is possible to obtain surface-treated silica that has the characteristic properties described above while having the magnetic foreign matter removed.

[0043] The surface-treated silica powder after the physical removal of the aforementioned foreign matter (surface-treated silica powder after foreign matter removal) has a reduced amount of unopened epoxy groups derived from the physically adsorbed epoxysilane coupling agent. The amount of unopened epoxy groups per unit surface area of ​​the surface-treated silica powder is, for example, 1.0 to 4.0 groups / nm. ２ Preferably, 1.2 to 2.5 particles / nm ２ The carbon content is, for example, 10 to 30 atoms / nm. ２ Preferably, 12 to 20 particles / nm ２ Therefore, the amount of trimethylsilyl groups is the same as that of the surface-treated silica powder before foreign matter removal, and the same numerical range can be applied.

[0044] The cleaning powder (cleaning powder after foreign matter removal) in the surface-treated silica powder after the physical removal of the aforementioned foreign matter has the same structure and properties as the cleaning powder before foreign matter removal. The cleaning powder after foreign matter removal is silica powder after the above cleaning treatment and drying are performed on the surface-treated silica powder after foreign matter removal. In the cleaning powder after foreign matter removal, the amount of non-ring-opening epoxy groups, the total amount of epoxy groups, the amount of ring-opening epoxy groups, the epoxy ring-opening ratio, the amount of carbon, and the amount of trimethylsilyl groups are the same as those of the cleaning powder before foreign matter removal, and the numerical range of the cleaning powder before foreign matter removal can be applied.

[0045] In this invention, the amount of trimethylsilyl groups in the surface-treated silica powder is 0.3 to 1.5 groups / nm, both before and after foreign matter removal. ２ The washing powder contains 1.0 to 3.0 non-ring-opened epoxy groups / nm. ２ The epoxy ring-opening rate of the washing powder is 25% or less.

[0046] In the surface-treated silica powder of the present invention, other properties are not particularly limited, but those having the following properties are preferred.

[0047] In the present invention, the BET specific surface area of ​​the surface-treated silica powder is 1 to 100 m². ２ It is preferable that the BET specific surface area is 1 m². ２If the amount is less than / g, although the viscosity of the resin composition using surface-treated silica powder after surface treatment is low, when used as an underfill material, for example, the silica particle size is large relative to the gap, which may result in voids being generated during gap penetration and cause molding defects. In other words, sufficient narrow gap penetration may not be obtained. BET specific surface area is 100 m² ２ If the value exceeds / g, the viscosity of the resin composition will be high, and there is a risk that a sufficient amount of filler may not be obtained.

[0048] In the present invention, the V of the surface-treated silica powder ９０ It is preferable that it is 10 or more and less than 100. ９０ If the value is 100 or higher, there are many coarse particles, which may cause voids to form when the material penetrates gaps during use as an underfill material, potentially leading to molding defects. If the value is less than 10, industrial manufacturing may be difficult.

[0049] <Resin Composition> The present invention also provides a resin composition in which the surface-treated silica powder is dispersed in a resin. The type of resin is not particularly limited, but from the viewpoint of affinity, it is preferable to use an epoxy resin.

[0050] The aforementioned resin composition can be manufactured using known proportions and mixing methods. The resin composition may also contain known additives as needed.

[0051] <Applications> The applications of the surface-treated silica of the present invention are not particularly limited, but it can be suitably used as a filler for epoxy resins. In particular, since it does not increase viscosity when mixed with epoxy resin even after physical removal of foreign matter, it is useful as a filler in epoxy resin compositions for underfill materials where there are strict restrictions on the inclusion of foreign matter.

[0052] [Method for Producing Surface-Treated Silica Powder] The method for producing the surface-treated silica powder of the present invention is not particularly limited, but a typical method is exemplified below. An epoxysilane coupling agent is added to the silica powder to be treated, such that the total amount of epoxy groups per unit surface area of ​​the silica powder to be treated is 2.0 to 10 groups / nm. ２The amount used is such that the amount of trimethylsilyl groups per unit surface area of ​​the silica powder treated with hexamethyldisilazane (HMDS) is 0.3 to 1.5 groups / nm. ２ One possible method involves using the amount described above, and mixing the silica powder to be treated in such a ratio that the ratio of the amount of epoxy groups (E) to the amount of trimethylsilyl groups (T) per unit surface area (T / E) is 0.10 to 0.30, followed by stirring at a temperature of 120 to 180°C for 60 to 300 minutes.

[0053] In the above manufacturing method, the silica powder to be treated (silica powder before surface treatment, i.e., raw material silica) can be any known hydrophilic silica powder without particular limitation. Specifically, this includes dry silica powder obtained by dry methods such as flame combustion and melting, and wet silica powder obtained by wet methods such as sol-gel methods.

[0054] The silica powder to be treated above has a BET specific surface area of ​​1 to 100 m². ２ It is preferable that it be / g. Also, the above V ９０ It is preferable that the value is 10 or more and less than 100.

[0055] The epoxysilane coupling agent used in the above-mentioned manufacturing method can be any known agent without particular limitation. Examples include 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltrimethoxysilane. Of these, 3-glycidoxypropyltrimethoxysilane is preferably used.

[0056] In the above manufacturing method, the amount of epoxysilane coupling agent used is calculated to be 2.0 to 10 epoxy groups / nm per surface area of ​​the silica powder to be treated. ２ It is preferable to have an amount such that [a certain amount]. More preferably, 4.0 to 6.0 particles / nm. ２If the amount used is less than the range described above, the resulting surface-treated silica powder will have difficulty satisfying the lower limit of the amount of epoxy groups per unit surface area of ​​the washing powder in the surface-treated silica powder of the present invention, leading to an increase in viscosity when mixed with epoxy resin. Furthermore, if the amount used is more than the range described above, the resulting surface-treated silica powder will have an excessive amount relative to the silica powder surface, and will tend to form aggregates of silica particles.

[0057] Furthermore, in the above manufacturing method, HMDS, when used in combination with an epoxysilane coupling agent in an appropriate amount, has the effect of suppressing ring opening without reducing the density of epoxy groups chemically bonded to the particle surface of silica powder.

[0058] The amount of HMDS used, in relation to the amount of epoxysilane coupling agent used, is calculated to be 0.3 to 1.5 trimethylsilyl groups per unit surface area of ​​the silica powder to be treated. ２ It is preferable to use an amount such that the following is the result. More preferably, 0.5 to 1.0 particles / nm. ２ If the amount used is less than the range described above, it becomes difficult to keep the ring-opening rate of epoxy groups low in the surface treatment, depending on the combination of the mixing conditions with the silica powder to be treated and the amount of epoxysilane coupling agent used, as described later. Also, if the amount used is more than the range described above, the resulting surface-treated silica powder will have an insufficient amount of epoxy groups derived from groups bonded to the silica particle surface, leading to an increase in viscosity when mixed with epoxy resin.

[0059] Furthermore, the ratio (T / E) of the amount of epoxy silane coupling agent used (E), which is indicated by the amount of epoxy groups and trimethylsilyl groups per unit surface area of ​​the silica powder to be treated, to the amount of HMDS used (T) is also important for reducing the ring-opening rate of epoxy groups in the surface-treated silica of the present invention. That is, if T / E is smaller than the above range, it becomes difficult to keep the ring-opening rate of epoxy groups low in the surface treatment, depending on the combination with the mixing conditions with the silica powder to be treated, which will be described later. Also, if it is larger than the above range, the amount of epoxy groups derived from groups bonded to the surface of the silica particles in the resulting surface-treated silica powder will be insufficient, leading to an increase in viscosity when mixed with epoxy resin. T / E is preferably in the range of 0.10 to 0.30, and more preferably in the range of 0.10 to 0.25.

[0060] In the above manufacturing method, the surface treatment of the silica powder to be treated is preferably carried out dry. Specifically, a suitable method is to place the silica powder to be treated in a mixing container, fluidize the silica powder by shaking or stirring, and then add a predetermined amount of epoxysilane coupling agent and HMDS by dropwise addition or spraying. In the above addition, there are no particular restrictions on the order in which the epoxysilane coupling agent and HMDS are added, but it is preferable to add them simultaneously or after the addition of HMDS. In addition to dry mixing, a wet mixing method can be used. In the wet mixing method, an organic solvent such as ethanol or toluene is added to the above components and the mixture is carried out in the liquid phase.

[0061] After adding the epoxysilane coupling agent and HMDS, it is preferable to continue stirring at a temperature of 100°C or lower, preferably 40°C or lower, for 5 minutes or more, preferably 10 minutes or more. There is no particular upper limit to the above stirring time, but economically it is preferable to keep it within 60 minutes.

[0062] Examples of the mixing vessels include Henschel type mixing devices and Reidige mixers equipped with stirring blades and mixing blades, air blenders that mix by airflow using air, V-blenders that mix by the rotation or oscillation of the container body, double-cone type mixing devices, and rocking mixers.

[0063] In the above manufacturing method, the heat treatment of the mixture is a process in which the epoxysilane coupling agent and HMDS react with the particle surface of the silica powder. Here, the temperature in the heat treatment is preferably 120 to 180°C, more preferably 120 to 150°C. If the heating temperature is lower than the above range, it becomes difficult to secure a sufficient amount of epoxy groups derived from the groups bonded to the particle surface of the silica powder. If the heating temperature is higher, decomposition of the silane coupling agent and aggregation due to polymerization reactions occur, making it difficult to secure a sufficient amount of epoxy groups derived from the groups bonded to the particle surface of the silica powder.

[0064] The aforementioned heat treatment time can be appropriately determined depending on the reactivity of the surface treatment agent used. Typically, a sufficient reaction rate can be obtained within 60 to 300 minutes.

[0065] In the above manufacturing method, it is preferable to replace the gas inside the container with an inert gas such as nitrogen or argon after stirring in order to remove by-products generated when the epoxysilane coupling agent and HMDS react with the silica particle surface.

[0066] Examples and comparative examples are shown below to further illustrate the present invention, but the present invention is not limited to these examples and comparative examples.

[0067] In the examples, the measurement and evaluation of various physical properties were performed by the following methods.

[0068] (1) Method for preparing the washing powder As the first washing, the following washing process was carried out. Specifically, 3 g of surface-treated silica powder was suspended in ethanol to obtain a suspension with a total volume of 30 mL. This suspension was placed in a centrifuge tube (AS ONE Bioremo Centrifuge Tube II 50 mL) and dispersed for 10 minutes using a benchtop ultrasonic cleaner (Branson M2800-J, output 110 W, oscillation frequency 40 kHz) to obtain dispersion slurry A. The centrifuge tube containing dispersion slurry A was subjected to a centrifuge (AS ONE CN-1050) at 5000 rpm for 30 minutes, and the supernatant liquid separated to the upper layer was removed to obtain a precipitated cake (3 g of surface-treated silica powder) in the centrifuge tube. As the second washing, the precipitated cake obtained in the first washing was washed under the same conditions as the first washing. Specifically, the suspension preparation, dispersion slurry A preparation, and cake preparation described above were carried out in order to obtain the precipitated cake for the second washing. As a third wash, the settled cake obtained in the second wash was washed under the same conditions as the first wash to obtain the settled cake for the third wash. That is, the suspension preparation, dispersion slurry A preparation, and cake preparation described above were carried out in order to obtain the settled cake for the third wash.

[0069] The settled cake obtained in the third wash was vacuum-dried at room temperature for 1 hour using a desiccator (AS ONE molded vacuum desiccator MVD-100, AS ONE dry vacuum pump) to obtain the washed powder.

[0070] (2) Ring-opening rate of epoxy groups The total amount of epoxy groups (A) was determined from the amount of carbon in the groups present on the surface of the washed powder, and the amount of non-ring-opened epoxy groups was determined by the test method of JIS K 7239, and these values ​​were used to calculate the following equations (1) and (2).

[0071] (1) Ring-opening epoxy group amount (B) = Total epoxy group amount (A) - Non-ring-opening epoxy group amount (2) Epoxy ring-opening rate (%) = B / A × 100

[0072] (2-1) Total amount of epoxy groups The total amount of epoxy groups (A) was calculated from the amount of trimethylsilyl groups obtained by analysis and the number of carbon atoms derived from the epoxysilane coupling agent using the following formula.

[0073] Although the carbon number derived from the epoxysilane coupling agent can be measured by NMR, in this example, since the structure of the epoxysilane coupling agent used is known, its original carbon number was used for calculation. Specifically, it was KBM-403 (3-glycidoxypropyltrimethoxysilane; molecular formula C) manufactured by Shin-Etsu Silicone. ９ H ２０ O ５ Since Si was used, the original carbon number of the epoxysilane coupling agent is 9, and the calculation was performed based on the following N.

[0074] Total epoxy group content (number / nm) ２ )(A) = {("mass percentage of carbon in the washing powder (mass%)" / 100 / "atomic weight of carbon (g / mol)" × "Avogadro's number (atoms / mol)" / "BET specific surface area (m²) ２ / g) / 10 １８ ) - ("Trimethylsilyl group amount (number / nm) ２ ) × 3)} / ("Original number of carbon atoms in the epoxysilane coupling agent" - N) × "Number of epoxy groups in the epoxysilane coupling agent" (In this example, since the surface-treated silica powder is manufactured by a dry process, N is set to the total number of carbon atoms in all hydrolyzable groups of the epoxysilane coupling agent × 2 / 3, in other words, the number of carbon atoms in one hydrolyzable group of the epoxysilane coupling agent × 2. Specifically, since 3-glycidoxypropyltrimethoxysilane was used, N was set to 2 (units). The number of epoxy groups in the epoxysilane coupling agent was set to 1 (unit). The atomic weight of carbon is 12 (g / mol), and Avogadro's number is 6.02 × 10 ２３ (It is (individuals / mol).)

[0075] (2-1-1) The mass percentage of carbon in the washing powder (i.e., the mass percentage of carbon originating from groups present on the surface of the washing powder) was measured using a total nitrogen and total carbon analyzer (Sumigraph NC-22F, manufactured by Sumika Analysis Center). The sample size was 50-100 mg. Next, the amount of carbon per unit surface area of ​​the washing powder (carbon atoms / nm) was measured. ２) is calculated as: "mass percentage of carbon in the washing powder (mass%)" / 100 / "atomic weight of carbon (g / mol)" × "Avogadro's number (atoms / mol)" / "BET specific surface area (m²)" ２ / g) / 10 １８ It was calculated using the following formula.

[0076] (2-1-2) 14-15 mg of trimethylsilyl group-containing washing powder was wrapped in foil for Curie Point pyrolizer and thermally decomposed using a Curie Point pyrolizer (portable pyrolizer JCI-22, manufactured by Nippon Analytical Industries). The peak area of ​​the trimethylsilyl group was measured using a GC / MS instrument (HP5890 / HP5973, manufactured by Agilent). The thermal decomposition temperature at this time was 445°C, and the program TSUGM 210825.M was used. The amount of trimethylsilyl group was calculated from the peak area of ​​the trimethylsilyl group of a standard sample with a known amount of trimethylsilyl group using the following formula. The standard sample was HMDS-treated Silfil NSS-40D, manufactured by Tokuyama Corporation (trimethylsilyl group amount: 2.1 groups / nm). ２ ) was used. Trimethylsilyl group amount (groups / nm) ２ ) = (Peak area of ​​trimethylsilyl groups per unit mass / Peak area of ​​trimethylsilyl groups per unit mass of standard sample) × Amount of trimethylsilyl groups in standard sample (groups / nm) ２ )

[0077] (2-2) For the non-ring-opened epoxy group washing powder, measure the molar amount of non-ring-opened epoxy groups (μmol / g) using the test method of JIS K 7239, and calculate the amount of non-ring-opened epoxy groups per surface area (particles / nm) from the following formula. ２ Avogadro's number was calculated as follows: 6.02 × 10⁻¹⁴ ２３ (Number of particles / mol). Number of non-ring-opening epoxy groups (Number of particles / nm) ２ ) = Molar amount of non-ring-opened epoxy group (μmol / g) × 10 －６ × Avogadro's number (particles / mol) / BET specific surface area (m²) ２ / g) / 10 １８

[0078] Furthermore, the (2-1-1) carbon content, (2-1-2) trimethylsilyl group content, and (2-2) non-ring-opened epoxy group content were determined for the surface-treated silica powder using the same method as described above for the washed powder.

[0079] (3) BET specific surface area BET specific surface area (m ２ The specific surface area ( / g) was measured using a specific surface area analyzer (SA-1000, manufactured by Shibata Rika) by the nitrogen adsorption BET single-point method.

[0080] (4) Amount of coarse particles (V ９０ Approximately 0.1 g of surface-treated silica powder was weighed into a 50 mL glass bottle using an electronic balance, approximately 40 mL of ethanol was added, and the mixture was dispersed using an ultrasonic homogenizer (Branson Sonifier 250) at 40 W for 10 minutes. The average particle size (nm) and coefficient of variation of the surface-treated silica powder were then measured using a laser diffraction scattering particle size distribution analyzer (Beckman Coulter LS 13 320). Here, the average particle size (nm) refers to the volume-based cumulative 50% diameter. From the obtained volume-based particle size distribution, the cumulative 50% volume diameter (D ５０ ) and cumulative 90% volume diameter (D ９０ The result D was calculated. ５０ and D ９０ From this, the amount of coarse particles in the surface-treated silica powder, which can be determined by Equation 1, is (V ９０ ) was sought. V ９０ = {(D ９０ -D ５０ ) / D ５０} × 100 (1)

[0081] (5) Evaluation of viscosity properties 30 g of surface-treated silica powder was added to 26 g of bisphenol F type epoxy resin (YDF-8170C manufactured by Nippon Steel Chemical & Material Co., Ltd.) and kneaded by hand. The hand-kneaded resin composition was pre-kneaded using a rotation-and-revolution type mixer (Awatori Rentaro AR-500 manufactured by THINKY) (kneading: 1000 rpm, 8 minutes, degassing: 2000 rpm, 2 minutes). After pre-kneading, the resin composition was stored in a 25°C constant temperature water bath and then kneaded using a three-roll mixer (BR-150HCV manufactured by AIMEX, roll diameter φ63.5). The kneading conditions were a kneading temperature of 25°C, a roll distance of 20 μm, and 8 kneading cycles. An amine curing agent (KAYAHARD A-A, manufactured by Nippon Kayaku Co., Ltd.) was added to the kneaded resin composition so that the silica content was 45% by mass, and the mixture was kneaded using a rotary-orbit mixer (Awatori Rentaro AR-500, manufactured by THINKY) (kneading: 1000 rpm, 8 minutes; degassing: 2000 rpm, 2 minutes). The resulting resin composition was degassed under reduced pressure for 30 minutes using a vacuum pump (TSW-150, manufactured by Sato Vacuum) to obtain a kneaded resin composition.

[0082] The initial viscosity (η1) and viscosity after one day (η2) of the aforementioned mixed resin composition were measured using a rheometer (HAAKE MARS40, manufactured by Thermo Fisher Scientific) at a shear rate of 20 s⁻¹. The measurement temperature was 25°C, and the sensor used was a C35 / 1 (cone plate type, 35 mm diameter, 1° angle, titanium material). The resin composition was stored at 25°C.

[0083] The viscosity change rate over time was calculated using the following formula, based on the viscosity (η1) at the time of resin composition preparation (initial) and the viscosity (η2) after one day: Thickening index [times] = η2 / η1

[0084] (6) Evaluation of gap permeability The kneaded resin composition (at the time of production) prepared by the same method as the viscosity property evaluation was injected between two pieces of glass overlapped with a 30-μm gap and heated to 110°C, and a high-temperature intrusion test was conducted. The portion where the resin was injected was visually inspected through the glass to check for the presence or absence of flow marks. If no flow marks were observed, it was determined that the gap permeability was good; if flow marks were observed, it was determined that the gap permeability was poor. If the gap permeability is good, it can be said that the surface-treated silica powder is excellent in filling property and viscosity property.

[0085] (7) Amount of foreign matter 110 mL of a glass bottle for clean room (SCC screw tube bottle white N manufactured by AS ONE) Ｏ． (8) Five sets of a mixture containing 45 g of Solmix, 45 g of ultrapure water, and 10 g of surface-treated silica powder were prepared, and after dispersing them in an ultrasonic cleaner (USK-3R manufactured by AS ONE) for 120 minutes, the dispersed slurry was filtered under reduced pressure through a 20-μm mesh filter (NY2004700 manufactured by Merck). The filter after filtration under reduced pressure was collected in a petri dish, and the total amount of resin pieces, condensates of silane coupling agents, and magnetic foreign substances on the filter was counted using a digital microscope (VHX-800 manufactured by KEYENCE, magnification 100 times).

[0086] Example 1 Spherical dry silica powder with an average particle diameter of 385 nm (Silfil NSS-40D manufactured by Tokuyama Corporation, specific surface area 9.2 m ２ / g) was put into a mixing container, and while stirring, hexamethyldisilazane (SZ-31 manufactured by Shin-Etsu Silicone Co., Ltd.) was added in an amount such that the amount of trimethylsilyl groups (T) per unit surface area of the silica powder was 1.0 piece / nm ２ Also, an epoxy silane coupling agent (KBM-403 manufactured by Shin-Etsu Silicone Co., Ltd.) was added in an amount such that the amount of all epoxy groups (E) per unit surface area of the silica powder was 4.2 pieces / nm ２The mixture was supplied in the specified amount using a peristaltic pump (ATTA SJ-1211 II-H). Stirring was continued after supply, and the mixture was mixed for 15 minutes (dry mixing). After that, the mixture in the container was heated to 125°C in 60 minutes, and then maintained at 125°C for 180 minutes to complete the reaction process. After the reaction process was completed, the container was cooled, and nitrogen was circulated through the container to remove unreacted material, obtaining surface-treated silica powder. The amount of foreign matter in the surface-treated silica before removal was 340 particles / 50g.

[0087] The obtained surface-treated silica powder was subjected to a wet process to remove foreign matter. Specifically, 2000 g of surface-treated silica powder was supplied to 4800 g of methanol and 1200 g of water, and stirred with a stirring blade for 4 hours and dispersed for 2 hours using an ultrasonic disperser (GSD600AT, manufactured by Sonic Technology Co., Ltd.) to obtain a silica powder dispersion. The silica powder dispersion was wet-filtered using a polypropylene filter (TCPD-1-S1FE, manufactured by Advantec Co., Ltd.), and the filtrate was separated into solid and liquid using a centrifuge (WU-15x8, manufactured by Chikara Engineering Co., Ltd.). After solid and liquid separation, nitrogen was circulated through the machine overnight to dry the mixture and obtain a cake. Further reduced-pressure drying was performed at 80°C for 20 hours to obtain surface-treated silica powder from which foreign matter had been removed. The amount of foreign matter in this surface-treated silica powder after foreign matter removal was 59 particles / 50 g.

[0088] Furthermore, the surface-treated silica powder obtained has a specific surface area of ​​9.2 m². ２ The values ​​were as follows: D90 was 527 nm, D50 was 385 nm, and V90 was 37%. Other examples and comparative examples using the same silica powder as the raw material also showed similar values. Furthermore, these physical properties such as specific surface area remained the same before and after the removal of foreign matter.

[0089] Example 2 Surface-treated silica powder was obtained in the same manner as in Example 1. The obtained surface-treated silica powder was subjected to a dry process to remove foreign matter. Specifically, the surface-treated silica powder was classified using an air classifier (AC-30 manufactured by Nisshin Engineering Co., Ltd.). The classified surface-treated silica powder was supplied to an iron remover (CG-150MINI manufactured by Nippon Magnetics Co., Ltd.) to remove magnetic foreign matter. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 143 particles / 50g.

[0090] Example 3 In Example 1, the amount of hexamethyldisilazane (SZ-31, manufactured by Shin-Etsu Silicone) used for the surface-treated silica powder was 0.5 groups / nm, expressed as the amount of trimethylsilyl groups (T) per unit surface area of ​​the silica powder. ２ Surface-treated silica powder was manufactured under the same conditions as in Example 1, except for the quantity used. The amount of foreign matter in the surface-treated silica before foreign matter removal was 365 particles / 50 g. Wet foreign matter removal was performed on the obtained surface-treated silica powder in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 62 particles / 50 g.

[0091] Example 4 Surface-treated silica powder was produced under the same conditions as in Example 1, except that the mixture in the container was heated to 150°C and maintained at that temperature for 180 minutes. The amount of foreign matter in the surface-treated silica before foreign matter removal was 360 particles / 50 g. Wet foreign matter removal was performed on the obtained surface-treated silica powder in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 71 particles / 50 g.

[0092] Example 5 Surface-treated silica powder was produced under the same conditions as in Example 1, except that the mixture in the container was heated to 175°C and maintained at that temperature for 180 minutes. The amount of foreign matter in the surface-treated silica before foreign matter removal was 405 particles / 50g. Wet foreign matter removal was performed on the obtained surface-treated silica powder in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 78 particles / 50g.

[0093] Comparative Example 1 In Example 1, hexamethyldisilazane (SZ-31, manufactured by Shin-Etsu Silicone Co., Ltd.) was used in an amount of 1.0 group / nm, where T is the amount of trimethylsilyl groups per unit surface area of ​​silica powder. ２ In addition, the amount of epoxy silane coupling agent (KBM-403, manufactured by Shin-Etsu Silicone Co., Ltd.) used is such that the amount of epoxy groups (E) per unit surface area of ​​silica powder is 1.0 groups / nm. ２Using the amount that results in, after raising the temperature of the mixture in the container to 150°C and maintaining it for 180 minutes, surface-treated silica powder was produced under the same conditions except for this. The amount of foreign matter in the surface-treated silica before foreign matter removal was 225 pieces / 50 g. For the obtained surface-treated silica powder, foreign matter removal by wet method was carried out in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 66 pieces / 50 g.

[0094] Comparative Example 2 In Example 1, an epoxy silane coupling agent (KBM-403 manufactured by Shin-Etsu Silicone Co., Ltd.) was used in an amount such that the amount of epoxy groups (E) per unit surface area of the silica powder was 3.0 pieces / nm ２ Using the amount that results in, surface-treated silica powder was produced under the same conditions except for this. The amount of foreign matter in the surface-treated silica before foreign matter removal was 304 pieces / 50 g. For the obtained surface-treated silica powder, foreign matter removal by wet method was carried out in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 70 pieces / 50 g.

[0095] Comparative Example 3 In Example 1, surface-treated silica powder was produced under the same conditions except that hexamethyldisilazane (SZ-31 manufactured by Shin-Etsu Silicone Co., Ltd.) was not used. The amount of foreign matter in the surface-treated silica before foreign matter removal was 360 pieces / 50 g. For the obtained surface-treated silica powder, foreign matter removal by wet method was carried out in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 75 pieces / 50 g.

[0096] Comparative Example 4 In Example 1, hexamethyldisilazane (SZ-31 manufactured by Shin-Etsu Silicone Co., Ltd.) was used in an amount such that the amount of trimethylsilyl groups (T) per unit surface area of the silica powder was 2.0 pieces / nm ２ Using the amount that results in, surface-treated silica powder was produced under the same conditions except for this. The amount of foreign matter in the surface-treated silica before foreign matter removal was 336 pieces / 50 g. For the obtained surface-treated silica powder, foreign matter removal by wet method was carried out in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 78 pieces / 50 g.

[0097] Comparative Example 5: In Example 1, the epoxysilane coupling agent (KBM-403, manufactured by Shin-Etsu Silicone Co., Ltd.) was used in an amount of 15.0 epoxy groups / nm per unit surface area of ​​silica powder (E). ２ Except for using a specific amount, surface-treated silica powder was manufactured under the same conditions. The amount of foreign matter in the surface-treated silica before foreign matter removal was 370 particles / 50 g. The obtained surface-treated silica powder was subjected to wet foreign matter removal in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 88 particles / 50 g.

[0098] Comparative Example 6 Surface-treated silica powder was produced under the same conditions as in Example 1, except that the mixture in the container was heated to 100°C and maintained at that temperature for 180 minutes. The amount of foreign matter in the surface-treated silica before foreign matter removal was 335 particles / 50g. Wet foreign matter removal was performed on the obtained surface-treated silica powder in the same manner as in Example 1. The amount of foreign matter in the surface-treated silica powder after foreign matter removal was 71 particles / 50g.

[0099] Tables 1 to 5 show the preparation conditions, physical properties (carbon content, trimethylsilyl group content, epoxy group content, etc.), and evaluation results (viscosity specification, gap penetration, foreign matter content) of the surface-treated silica powders of Examples 1 to 5 and Comparative Examples 1 to 6. Specifically, Table 1 shows the preparation conditions for the surface-treated silica, Table 2 shows the physical properties and foreign matter content of the surface-treated silica powder before foreign matter removal, Table 3 shows the physical properties and foreign matter content of the washing powder in the surface-treated silica powder before foreign matter removal, Table 4 shows the physical properties and evaluation results of the surface-treated silica powder after foreign matter removal, and Table 5 shows the physical properties of the washing powder in the surface-treated silica powder after foreign matter removal. Note that the physical properties and foreign matter content of the washing powder before foreign matter removal are the physical properties and evaluation results obtained according to the physical property measurement and evaluation methods in (2) to (7) above for silica powder obtained by applying the above "(1) Method for preparing washing powder of surface-treated silica powder" to the surface-treated silica powder before foreign matter removal. The physical properties of the washed powder after foreign matter removal are those obtained by applying the preparation method described in (1) above to the surface-treated silica powder after foreign matter removal, according to the measurement methods described in (2) to (7) above.

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] As is clear from Tables 1 to 5, the surface-treated silica powders of Examples 1 to 5 have a trimethylsilyl group content of 0.3 to 1.5 groups / nm per unit surface area of ​​the surface-treated silica powder. ２ (See Table 2), and the number of unopened epoxy groups per unit surface area of ​​the washing powder is 1.0 to 3.0 groups / nm. ２ As shown in Table 3, the epoxy ring-opening rate of the cleaning powder is 25% or less (see Table 3). Therefore, after foreign matter removal, the initial viscosity of the resin composition is less than 10.0 Pa·s, resulting in excellent low viscosity. Furthermore, after foreign matter removal, the thickening index of the resin composition is 1.5 times or less (see Table 4), so thickening can be suppressed to a high degree, resulting in excellent viscosity stability over time. The resin composition also has excellent gap penetration (see Table 4). Moreover, the gap penetration of the resin composition is also good. On the other hand, in Comparative Examples 1 to 6, the epoxy ring-opening rate of the cleaning powder exceeds 25%, so the initial viscosity of the resin composition is 10.0 Pa·s or higher, resulting in poor initial viscosity or a thickening index of the resin composition exceeding 1.5 times, resulting in poor viscosity stability over time. Furthermore, the gap penetration of the resin composition is poor.

Claims

1. Surface-treated silica powder having epoxy groups on its surface, wherein the amount of trimethylsilyl groups per unit surface area of ​​the surface-treated silica powder is 0.3 to 1.5 groups / nm ２ The process involves suspending 3 g of the surface-treated silica powder in ethanol to form a 30 mL suspension, which is dispersed in an ultrasonic disperser with an output of 110 W for 10 minutes. This suspension is then separated into solid and liquid components using a centrifuge, and this process is repeated three times. Finally, the washing powder is vacuum-dried for 1 hour. The resulting washing powder has a non-ring-opening epoxy group count per surface area of ​​1.0 to 3.0 groups / nm. ２ The surface-treated silica powder is characterized in that the ring-opening rate of epoxy groups in the washing powder is 25% or less.

2. The amount of unopened epoxy groups per unit surface area of ​​the surface-treated silica powder is 1.0 to 5.0 groups / nm. ２ The surface-treated silica powder according to claim 1.

3. The amount of unopened epoxy groups per unit surface area of ​​the surface-treated silica powder is 1.0 to 4.0 groups / nm. ２ The surface-treated silica powder according to claim 1, wherein the amount of foreign matter 20 μm or larger contained in the surface-treated silica powder is 150 pieces / 50 g or less.

4. BET specific surface area is 1 to 100 m² ２ The surface-treated silica powder according to claim 1, wherein the amount is / g.

5. The amount (V ５０ ) of coarse particles of the surface-treated silica powder obtained by the formula (1) from the cumulative 50 volume% diameter (D ９０ ) and the cumulative 90 volume% diameter (D ９０ ) of the volume-based particle size distribution obtained by the laser diffraction scattering method is 10 or more and less than 100. The surface-treated silica powder according to claim 1. V ９０ = { ( D ９０ - D ５０ ) / D ５０ } × 100 (1) 6. A resin composition comprising the surface-treated silica powder described in claim 1 dispersed in a resin.

7. To the silica powder, the epoxysilane coupling agent is added when the total epoxy group content per unit surface area of ​​the silica powder is 2.0 to 10 groups / nm. ２ With this usage amount, the amount of hexamethyldisilazane per unit surface area of ​​the silica powder is 0.3 to 1.5 trimethylsilyl groups / nm. ２ A method for producing surface-treated silica powder, characterized by mixing the silica powder in the amount specified above, such that the ratio (T / E) of the amount of epoxy groups (E) to the amount of trimethylsilyl groups (T) per unit surface area of ​​the silica powder is 0.10 to 0.30, and then stirring at a temperature of 120 to 180°C for 60 to 300 minutes.

8. The manufacturing method according to claim 7, wherein after stirring, a physical removal treatment of foreign matter is performed.

Images