JP7369862B2 - Hydrophobic silica gel for energy beam curable paint matting - Google Patents

Description

The present invention relates to a hydrophobic silica gel for matting energy ray-curable paints. More specifically, the present invention relates to a hydrophobic silica gel surface-treated with silicone oil that is used as a matting agent for paints that are cured by energy rays such as ultraviolet (UV) or electron beam (EB).
Cross-reference to related applications This application claims priority to Japanese Patent Application No. 2020-079708 filed on April 28, 2020, the entire disclosure of which is specifically incorporated herein by reference.

Energy ray-curable paints have advantages such as superior film strength and fast curing properties, and can use less solvent, so their usage has increased in recent years as a replacement for conventional paints that use solvents. There is.

Silica matting agents used in conventional paints that use solvents create a matting effect by creating unevenness on the surface by taking advantage of the large difference in film thickness between painting and film formation after the solvent evaporates. . However, in the case of energy ray-curable paints, the film thickness decreases little during coating and film formation. Therefore, the silica matting agent conventionally used could not exhibit a sufficient matting effect.

WAX treated silica has been proposed as a solution to this problem. The WAX-treated silica described in Patent Document 1 is silica having a pore volume of at least 1.5 cm ³ /g and surface-treated with 5.6 to 15% by weight of WAX having a melting point of less than 85° C. The WAX-treated silica described in Patent Document 2 is silica having a median particle size of 2 to 12 μm and surface-treated with 15 to 30% by weight of WAX. Both exhibit high matting performance and excellent sedimentation stability in energy beam-curable paints.

Patent Document 1: Japanese Patent Publication No. 11-512124 (WO97/08250)
Patent Document 2: Special Publication No. 2003-522219 (WO01/004217)
The entire descriptions of Patent Documents 1 and 2, respectively, are specifically incorporated herein by reference.

With the recent rapid spread of energy ray-curable paints, demands for performance other than matte performance are also increasing. In particular, for electronic devices, home appliances, and flooring top coats, matte coatings containing silica are often used to hide molding unevenness and scratches on the base, protect the surface, and create a luxurious appearance. It is used. In addition to matte performance, this application requires improved chemical resistance and scratch resistance.

However, the wax-treated silicas of Patent Documents 1 and 2 had insufficient chemical resistance and scratch resistance. When the wax-treated silica is blended into a paint, when the paint temperature rises, the wax dissolves and deteriorates the appearance. Alternatively, if the paint is stored for a long period of time, WAX will be eluted, leading to concerns about deterioration of the physical properties and appearance of the paint film.

Therefore, the present inventors conducted extensive research on hydrophobic silica gel, which is a matting agent suitable for energy beam-curable paints and has excellent chemical resistance and scratch resistance in addition to matting performance.

As a result, it was found that the problem of scratch resistance of the coating film could be solved by using silica gel having a strong secondary particle aggregation structure. On the other hand, such silica gel had a drawback in chemical resistance, and attempts were made to solve this problem by treating the surface of the silica gel to make it hydrophobic with silicone oil. The thickness of a coating film formed using an energy beam curable paint is usually about 5 to 40 μm, and in order to achieve matte performance with a coating film of this thickness, the particle size of the silica gel is adjusted, for example, to 5 μm. Adjust to ~20μm.

However, hydrophobic silica gel surface-treated with silicone oil has fewer silanol groups on its surface than untreated silica gel. As a result, they do not form flocculates in solvents, and have poor sedimentation stability and turn into hard cakes, which is another problem that is essential for paint applications. It has also been found that this point can be improved by controlling the hydrophobization treatment conditions within a predetermined range, and that a balance between chemical resistance and sedimentation stability can be achieved.

Based on these findings, the present inventors discovered that it is possible to provide a hydrophobic silica gel for energy beam-curable paint matting that has excellent chemical resistance, scratch resistance, and sedimentation stability in addition to matting performance, and has developed the present invention. The invention was completed.

The present invention is as follows.
[1] Hydrophobic silica gel surface-treated with silicone oil,
The pore volume measured by nitrogen adsorption/desorption method is in the range of 0.6 to 2 ml/g,
The M value is in the range of 5 to 40 vol%, and the ratio of the pore volume with a pore radius of 109 nm or less after compression to the pore volume with a pore radius of 109 nm or less before compression at a pressure of 260 MPa (pore volume after compression) A hydrophobic silica gel for energy beam-curable paint matting, which has a ratio (volume/pore volume before compression) of from 0.8 to 1.5.
[2] The hydrophobic silica gel according to [1], wherein the hydrophobic silica gel has a volume average particle diameter D50 value measured by laser diffraction in a range of 5 to 20 μm.
[3] The hydrophobic silica gel according to [1] or [2], wherein the hydrophobic silica gel has a DBA adsorption amount in the range of 30 to 180 mmol/kg.
[4] The hydrophobic silica gel according to any one of [1] to [3], wherein the hydrophobic silica gel has a maximum particle diameter in the range of 15 to 70 μm as measured by laser diffraction.
[5] The hydrophobic silica gel according to any one of [1] to [4], wherein the ratio of the D90 value to the D50 value (D90/D50) measured by laser diffraction method is less than 1.8. hydrophobic silica gel.

According to the present invention, it is possible to provide a hydrophobic silica gel for energy beam-curable paint matting that has excellent chemical resistance, scratch resistance, and sedimentation stability in addition to matting performance.

FIG. 1 shows the mercury pore distribution of the hydrophobic silica gel of Example 1. FIG. 2 shows the mercury pore distribution of the hydrophobic silica gel of Comparative Example 1.

<Hydrophobic silica gel>
The present invention is a hydrophobic silica gel surface-treated with silicone oil, comprising:
(1) The pore volume measured by nitrogen adsorption/desorption method is in the range of 0.6 to 2 ml/g,
(2) the M value is in the range of 5 to 40 vol%, and (3) the ratio of the pore volume of 109 nm or less after compression to the pore volume of 109 nm or less before compression at a pressure of 260 MPa (pore volume after compression volume/pore volume before compression) is in the range of 0.8 to 1.5.
This invention relates to hydrophobic silica gel for energy beam-curable paint matting.

The hydrophobic silica gel of the present invention is silica whose surface is treated with silicone oil, and is obtained by treating the surface of silica gel with silicone oil. The silica gel is a known silica gel produced by a known method, and the silicone oil for surface treatment can also be a known silicone oil. However, the hydrophobic silica gel having the properties (1) to (3) above is a new hydrophobic silica gel, and by satisfying these physical properties, it can become a silica suitable for energy beam-curable paint matting. .

(1) The hydrophobic silica gel of the present invention has a pore volume in the range of 0.6 to 2 ml/g as measured by a nitrogen adsorption/desorption method. Within this range, excellent matting performance and scratch resistance can be achieved. When the pore volume is smaller than 0.6 ml/g, the silica has too few pores and the matting performance is greatly reduced. As the pore volume increases, the pore size tends to increase, and if the pore volume exceeds 2 ml/g, the pores become too large, weakening the silica secondary particle aggregate structure and worsening scratch resistance. do. It is preferably in the range of 0.7 to 1.8 ml/g, more preferably 0.8 to 1.6 ml/g. A method for measuring pore volume by nitrogen adsorption/desorption method will be explained in Examples.

(2) The hydrophobic silica gel of the present invention has an M value in the range of 5 to 40 vol%. The method for measuring the M value will be explained in Examples, and the M value is an index that indicates the degree of hydrophobicity of the hydrophobic silica gel based on the methanol concentration of the methanol aqueous solution in which the hydrophobic silica gel can be suspended. Since the M value is in this range, that is, the degree of hydrophobicity is in this range, it has excellent chemical resistance and is less likely to become a hard cake and has better redispersibility than the wax-treated silica described in Patent Documents 1 and 2. Excellent. When the M value is less than 5 vol%, the desired chemical resistance cannot be obtained, and when the M value exceeds 40 vol%, precipitation tends to occur over time, making redispersion difficult. When the M value is 40 vol% or less, the amount of silanol groups remaining is large compared to existing hydrophobic silica gels with an M value of over 40 vol%, and flocculates are formed in the paint, making it difficult to form a hard cake. The M value is preferably 10 to 35 vol%, more preferably 15 to 30 vol%.

(3) The hydrophobic silica gel of the present invention has a ratio of the pore volume of 109 nm or less after compression to the pore volume of 109 nm or less before compression at a pressure of 260 MPa (pore volume after compression/pore volume before compression). is in the range of 0.80 to 1.5. When hydrophobic silica gel is compressed using a press, the secondary particle aggregate structure of the silica particles collapses and disappears from large pores, depending on the type of silica and the compression pressure. When the hydrophobic silica gel of the present invention is compressed at a pressure of 260 MPa, the ratio of the pore volume of 109 nm or less after compression to the pore volume of 109 nm or less before compression is within the above range. The pore volume of 109 nm or less indicates the pore structure from the surface to the inside of the silica secondary particle aggregate, and the higher the value, the more voids there are in the secondary particle aggregate. As the pore volume of silica increases, the density per secondary silica particle decreases, and the number of secondary silica particles per unit weight increases. In other words, when the same amount of silica with the same particle size is mixed into a paint, the larger the pore volume of the silica, the higher the matting performance. On the other hand, as the pore volume increases, the number of points of contact between silica primary particles decreases, and thus the secondary particle aggregate structure weakens.

By setting the compression pressure to 260 MPa, the strength of the secondary particle aggregate structure that constitutes pores of 109 nm or less can be evaluated. The pore volume of 109 nm or less is measured by mercury intrusion porosimetry when the pressure is increased from 0 MPa to 400 MPa. A method for measuring pore volume of 109 nm or less by mercury porosimetry will be explained in Examples.

The fact that the pore volume ratio before and after compression is 0.8 to 1.5 indicates that the secondary particle aggregate structure of the silica particles is maintained and strong even after compression at 260 MPa. In other words, hydrophobic silica gel with a pore volume ratio before and after compression of 0.8 to 1.5 has excellent scratch resistance. The lower limit of the pore volume ratio before and after compression is preferably 0.85, more preferably 0.9. The upper limit of the pore volume ratio before and after compression is 1.5, and it is practically difficult to provide a hydrophobic silica gel with a ratio exceeding 1.5. The upper limit of the pore volume ratio before and after compression is preferably 1.4, more preferably 1.3, even more preferably 1.2, and most preferably 1.1.

(4) The hydrophobic silica gel of the present invention preferably has a D50 value measured by laser diffraction in the range of 5 to 20 μm. When the D50 value measured by the laser diffraction method is in the range of 5 to 20 μm, the coating film can be provided with appropriate unevenness and exhibit matte performance for a typical coating film thickness. A method for measuring the volume average particle diameter by laser diffraction method will be explained in Examples. Hydrophobic silica gels with a D50 value of less than 5 μm tend to have poor matte performance, while those with a D50 value of more than 20 μm may be unsuitable for matte applications because the coating surface becomes rough and the design is impaired.

(5) The hydrophobic silica gel of the present invention preferably has a DBA adsorption amount in the range of 30 to 180 mmol/kg. By having the DBA adsorption amount within the above range, precipitation in the paint can be controlled while improving chemical resistance, which is a characteristic of hydrophobic silica gel. When it is less than 30 mmol/kg, there are few silanol groups on the surface of the hydrophobic silica gel, and flocculate of silica particles is not formed, so that the silica particles precipitate and cannot be redispersed. When it is larger than 180 mmol/kg, the hydrophobic state of the hydrophobic silica gel becomes weak and the effect of improving chemical resistance becomes small. The amount of DBA adsorbed is preferably 40 to 170 mmol/kg, more preferably 50 mmol/kg to 160 mmol/kg, and even more preferably 60 to 140 mmol/kg.

(6) The hydrophobic silica gel of the present invention preferably has a maximum particle diameter in the range of 15 to 70 μm as measured by laser diffraction. When the maximum particle size is within this range, appropriate unevenness can be imparted to the matte coating film. When the maximum particle diameter measured by laser diffraction is less than 15 μm, the matting performance tends to be low. If it is larger than 70 μm, the surface of the coating film becomes rough and the design is impaired, so it may not be suitable for matte applications. The maximum particle size measured by laser diffraction is more preferably in the range of 15 to 65 μm.

(7) In the hydrophobic silica gel of the present invention, the ratio D90/D50 between the D90 value and the D50 value of the particle diameter measured by laser diffraction is preferably in a range of less than 1.8. When D90/D50 is in a range of less than 1.8, it has a sharp particle size distribution and better matte performance. When the ratio D90/D50 between the D90 value and the D50 value of the particle size measured by laser diffraction method is 1.8 or more, the particle size becomes broad and the matting performance is relatively low. More preferably, D90/D50 is less than 1.7.

<Energy ray curable paint>
Hydrophobic silica gels are known in fields other than energy beam curable paints. However, these conventional hydrophobic silica gels have large particle diameters and a strong secondary particle aggregation structure, so they precipitate in a relatively short time, especially in paints containing weak solvents or reactive monomers with polar groups. Therefore, conventional hydrophobic silica gels have not been used in energy beam-curable paints.

The energy ray-curable paint in the present invention is a paint containing a reactive monomer, an organic solvent, and a photopolymerization initiator. There are no limitations on the reactive monomer, organic solvent, and photopolymerization initiator, and known materials can be used. Furthermore, components other than the reactive monomer, organic solvent, and photopolymerization initiator may also be contained as appropriate.

The reactive monomer is, for example, a reactive monomer having a polar group, and examples of the reactive monomer having a polar group include methyl carbitol acrylate, 2-ethylhexyl acrylate, phenyl acrylate, C9-phenylacrylate, and 1,9-nonane. Examples include diol diacrylate, tripropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

Typical examples of organic solvents include weak solvents with polar groups, such as esters such as ethyl acetate and butyl acetate, alcohols such as ethanol and methanol, ketones such as acetone and methyl ethyl ketone, dimethyl ether, diethyl ether, etc. There are ethers, etc.

The main feature of the present invention is that it maintains a good precipitation state even in energy beam-curable paints by imparting an optimal hydrophobic state to silica particles that have a large particle size and a strong secondary particle agglomeration structure. It is said that

The hydrophobic silica gel for matting energy ray curable paints of the present invention is suitably used as a matting agent for energy ray curable paints. Among these, energy ray-curable paints containing weak solvents that have low viscosity and tend to precipitate are highly effective, but are not limited thereto.

<Silicone oil>
The silicone oil for surface treatment of the hydrophobic silica gel of the present invention is not particularly limited as long as it can be mixed with the silica gel. It is common to use commercially available dimethyl silicone oil (commonly known as straight silicone oil) that has only methyl and phenyl groups, but there are also modified types that have organic substituents on the silicon atom. Silicone oil can also be used. Examples of substituents include polyether, epoxy, amines, and carboxyl groups, and many modified silicone oils are commercially available. Examples of modified silicone oil include the following products.

<Modified silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.>
KF-868, 865, 859, 393, 250, 889, 2001, 2004, 99, 9901, 8010, 8012, 8008, 105, 6000, 6001, 6002, 6003, 6123, 2200, 9701, 20 12, 857, 8001, 858, 351A, 353, 354L, 355A, 945, 640, 642, 643, 644, 6020, 6204, 6011, 6015, 6017, 412, 413, 414, 4003, 4917, 7235B, 50, 53, 54, 54SS, X-22-343, 2000, 2046, 4741, 4039, 4015, 161A, 161B, 9490, 163, 163A, 163B, 163C, 169AS, 169B, 164, 164AS, 164A, 164B, 164C, 164E, 4952, 4272, 167B, 167C, 162C, 5841, 2445, 1602, 168AS, 168A, 168B, 173BX, 173DX, 170BX, 170DX, 176DX, 176GX-A, 174ASX, 174BX, 2426, 2475, 3710, 2516, 821, 822, 7322, 3265

<Modified silicone oil manufactured by Dow Corning Toray>
SF 8417, BY 16-205, BY 16-213, BY 16-871, BY 16-893, SF 8411, BY 16-880, SF 8427, BY 16-201, SF 8428, BY 16-846, SF 8419, FS 1265, SH 510, SH 550, SH 710, SH 8400, FZ-77, L-7604

<Momentive Performance Materials modified silicone oil>
TSF4440, 4441, 4445, 4446, 4452, 4460, 4700, 4701, XF42-B0970

<Modified silicone oil manufactured by Wacker Chemie>
L03, 033, 066, L653, 655, 656, 662, WT1250, 65000VP, AP100, 150, 200, 500, AR20, 200

When using a silicone oil with high viscosity, it is necessary to dilute it with a solvent or the like, so silicone oil with a kinematic viscosity of about 1 to 500 centistokes is generally preferably used. Examples of silicone oils having a kinematic viscosity of 1 to 500 centistokes include the following products.

<Silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.>
KF-96-1cs, 1.5cs, 2.0cs, 5.0cs, 10cs, 20cs, 30cs, 50cs, 100cs, 200cs, 300cs, 350cs, 500cs

<Silicone oil manufactured by Toray Dow Corning>
SH200-1cs, 1.5cs, 2cs, 3cs, 5cs, 10cs, 20cs, 50cs, 100cs, 200cs, 350cs, 500cs

<Silicone oil manufactured by Momentive Performance Materials>
TSF451-5A, 10, 20, 30, 50, 100, 200, 300, 350, 500

<Silicone oil manufactured by Wacker Chemie>
AK 1, 10, 35, 50, 100, 350, 500

<Silica gel>
The method for producing the raw material silica gel for the hydrophobic silica gel of the present invention will be explained. In order to provide a hydrophobic silica gel having a desired pore volume and pore volume after compression/pore volume before compression, the silica gel used in the present invention has a pore structure that is is controlled. First, the silica hydrogel used in the production method of the present invention may be obtained by a conventional method. That is, a homogeneous silica hydrosol is obtained by reacting an aqueous solution of an alkali metal silicate such as sodium silicate, potassium silicate, or lithium silicate with a mineral acid such as sulfuric acid, hydrochloric acid, or nitric acid in an acidic excess. Next, the obtained silica hydrosol is gelled, then crushed and washed with water. In the water washing step, a hydrothermal treatment may be performed by adding and heating an aqueous solution of sodium hydroxide or ammonia for the purpose of removing by-product salts and, if necessary, lowering the specific surface area.

For drying, a stationary dryer, a band dryer, a paddle dryer, a fluidized dryer, etc. are generally used, but the dryer is not limited thereto. Although the drying temperature is not particularly limited, when uniform drying is to be carried out at an average drying rate within the above range, it is appropriate to carry out the drying at a temperature of 100 to 300°C.

Drying of the silica hydrogel is carried out in consideration of pore structure control in order to provide a hydrophobic silica gel having a desired pore volume and pore volume after compression/pore volume before compression. From this point of view, it is preferable to dry the silica hydrogel to obtain silica gel using a dryer that can control the drying speed, such as a static dryer or a fluidized dryer. The water content of the silica gel after drying is, for example, suitably in the range of 3 to 10% (based on mass).

The silica gel thus obtained can be further pulverized and classified for the purpose of adjusting the average particle size. The pulverization can be carried out by a known method, for example, using a roll mill, ball mill, hammer mill, pin mill, jet mill, or the like. Furthermore, classification can be performed using a wind classifier such as a micron separator, a centrifugal classifier, or the like to obtain silica gel having a desired average particle size. At this time, it is not necessary to match the target average particle size, but by keeping it close to the target particle size, it becomes easier to adjust the particle size after hydrophobization.

As the surface treatment method for silica gel using a surface treatment agent to obtain the hydrophobic silica gel for matting energy beam-curable paint of the present invention, a method using a high-speed fluid mixer such as a Henschel mixer is preferred in order to achieve uniform treatment. . However, the method is not limited to this method. The amount of surface treatment agent used to treat silica gel is adjusted to obtain the desired M value. Furthermore, in order to adjust the amount of DBA adsorption, the amount of surface treatment agent used for treating the silica gel is adjusted.

After mixing the surface treatment agent and silica gel, heat treatment is performed at 200 to 600°C to make the mixture hydrophobic. Any heat treatment method may be used as long as uniform heat treatment can be performed for a certain period of time. The heat treatment time may be as long as a desired hydrophobic state can be obtained, and as a guide, 1 to 24 hours is exemplified. After the heat treatment, pulverization and classification can be performed if necessary.

Hereinafter, the present invention will be explained in more detail based on examples. However, the examples are illustrative of the present invention, and the present invention is not intended to be limited to the examples.

Physical property measurement method M value A mixed solution of methanol and water with varying concentrations at 5 vol % intervals is prepared, and 5 ml of this is placed in a 10 ml test tube. Next, 0.1 to 0.2 g of a hydrophobic silica gel sample, which is a test powder, is added, shaken, and left to stand. The minimum concentration of methanol at which the powder is suspended is observed, and this is taken as the M value.

DBA adsorption amount Accurately weigh 250 mg of a dry hydrophobic silica gel sample, add 50 ml of N/500 di-n-butylamine solution (petroleum benzine solvent), and leave it at 20° C. for about 2 hours. Add 5 ml of chloroform and 2 to 3 drops of an indicator (crystal violet) to 25 ml of this supernatant liquid, and titrate with N/100 perchloric acid solution (acetic anhydride solvent) until the purple color changes to blue. A ml.
Separately, a blank was prepared to obtain B ml, and the amount of DBA adsorption was calculated using the following formula.
DBA adsorption amount (mmol/kg) = 80 (B-A) f
However, f is the titer of perchloric acid solution of N/100

Particle size (D50 value, D90 value, maximum particle size)
Using Microtrac MT-3000II, a laser diffraction particle size distribution analyzer manufactured by Microtrac Bell Co., Ltd., we measured the 50% value (D50 value) and the lowest 90% value (D50 value) of the volume integrated value in the particle size distribution of a hydrophobic silica gel sample. D90 value) and the maximum detected particle size (maximum particle size) were determined. Note that isopropyl alcohol (refractive index: 1.38) was used as a solvent.

Pore volume measured by nitrogen adsorption/desorption method Pore radius in the range of 1.6 to 100 nm by Barret-Joyner-Halenda method (BJH method) using Belsorp MAX, a high-precision gas/vapor adsorption measuring device manufactured by Nippon Bell Co., Ltd. The total pore volume (V _P ) of the sample was measured. Note that the measurement result is the pore volume on the desorption side (measured from the side with the largest pore volume).

Pore volume measured by mercury porosimetry Using a mercury porosimeter PASCAL440 manufactured by Thermo, the pore volume is measured by increasing the pressure from 0 MPa to 400 MPa. The pressure and amount of mercury introduced are measured, and the respective values are output. A contact angle of 140° between mercury and silica was used. The volume of pores with a pore radius of 109 nm or less was determined by the mercury intrusion method under these measurement conditions.

Pretreatment of samples for mercury pore volume measurement (compression using a press machine)
A briquetting press manufactured by Maekawa Test Equipment Seisakusho Co., Ltd. was used.

Compression method using a press Approximately 2 g of a hydrophobic silica gel sample is packed into a 40 mm diameter die, and a load of approximately 5 tons is applied using a hydraulic press to perform preliminary compression. The pre-compressed sample is removed from the die and lightly ground in a mortar. The crushed sample was packed in a 31 mmφ PVC frame, a load of 20 tons was applied, and the sample was compressed for 10 seconds to obtain a compressed hydrophobic silica gel sample.

Paint film preparation method (UV paint test)
Table 1 shows the formulation of the UV paint.
combination

Oligomer: NK Oligo UA-1100H manufactured by Shin-Nakamura Chemical Industry Co., Ltd.
Monomer: DPHA manufactured by Daicel Allnex
Photoinitiator 1: Ormirad 184 manufactured by BASF
Photoinitiator 2: Ormirad TPO H manufactured by BASF
Leveling agent: BYK Chemie BYK-UV-3570

Mixer: Made by Primix Co., Ltd. Labo Solution Spray gun: Made by Anest Iwata Co., Ltd. Gravity type spray gun W-101-132G
UV irradiation device: Eye Grandage ECS-4011GX manufactured by Eye Graphics
A mercury lamp was used as the light source.

Blending procedure (1) Weigh out the blend (a) into a 200 ml disposable cup and mix at 500 rpm for 5 minutes.
(2) Mixture (b) is weighed and added to (a) while stirring at 500 rpm.
(3) Once the powder has entered the paint, increase the rotation speed to 1,000 rpm and stir for 30 minutes.

Painting procedure (1) Fill the spray gun with the mixed paint.
(2) Paint on the ABS resin board (black).
(3) Let stand (set) at room temperature for 5 minutes.
(4) Dry in an oven at 80°C for 5 minutes.
(5) UV irradiation was performed twice using a UV irradiation device under the conditions of an output of 2 kW, an irradiation distance of 200 mm, and a conveyor speed of 210 cm/min to obtain a coating film with a coating thickness of 15 μm.

Gloss value measurement The 60° gloss value was measured using a gloss meter VG7000 manufactured by Nippon Denshoku Industries. A 60° gloss value of 39 or less was judged as excellent, 40 to 49 as good, 50 to 59 as acceptable, and 60 or more as poor.

Transparency Using the L* value of the coating film applied to the ABS board (black) using a spectrophotometer CM-5 manufactured by Konica Minolta, 13 or less is excellent, more than 13 and 15 or less is good, and 15 is Those exceeding 18 or less were allowed, and those exceeding 18 were unacceptable.

Abrasion Resistance Test Using a Gakushin abrasion fastness tester AB-301 manufactured by Tester Sangyo Co., Ltd., the state of the coating film was observed after 5000 reciprocations using a No. 6 canvas under a load of 500 g. The Rz value (10-point average surface roughness) of the coating film surface before and after the abrasion test was measured using an ultra-deep profile measurement microscope VK8500 manufactured by Keyence Corporation at a magnification of 50 times. The Rz values before and after the wear test were measured at three locations each, and the average difference in Rz was defined as |ΔRz|. The smaller the difference (|ΔRz|) before and after the abrasion test, the less scratched it is. 0.5 or less is excellent, more than 0.5 and 1 or less is good, more than 1 and 1.5 or less is acceptable. Those exceeding 5 were judged as unacceptable.

Chemical resistance The state of the coating film was observed after 2 hours of immersion in 5% NaOH.
Color difference measurement ΔE of the coating film before and after the chemical resistance test was measured using a spectrophotometer CM-5 manufactured by Konica Minolta. The formula for calculating ΔE is shown in Equation 1.
The smaller ΔE is, the better the chemical resistance is. A score of 4.0 or less was judged as acceptable, a score of more than 4.0 and 3.5 or less was judged as good, and a score of more than 3.5 was judged as excellent.

Redispersibility test 2 g of a hydrophobic silica gel sample was mixed with 50 g of a solvent of ethyl acetate:toluene = 1:1, and 50 ml of the mixture was poured into a 50 ml measuring cylinder and allowed to stand. After 30 minutes, redispersion was performed by turning the tube upside down once every second, and the number of times required for the precipitate to be redispersed was measured. 10 times or less was evaluated as excellent, 11 times or more and 30 times or less as good, 31 times or more and 50 times or less as acceptable, and more than 50 times as unacceptable.

Preparation of raw material silica gel Sodium silicate (SiO ₂ concentration 25 wt%, SiO ₂ /Na ₂ O molar ratio 3.3) and sulfuric acid (H ₂ SO ₄ 2 wt%) were mixed with sodium silicate at a flow rate of about 15 L/min and sulfuric acid with silica hydrochloride. A silica hydrosol was obtained by mixing using a mixing nozzle under conditions such that the amount of excess sulfuric acid in the sol was 6 wt%. This hydrosol was hydrothermally treated at pH 7.0 at 90°C for 3 to 5 hours, washed with water, dried, and pulverized to give a BET specific surface area of 470 to 530 m ² /g and a D50 measured by laser diffraction method. Silica gel with a value of 10.4-15.1 μm was obtained.

Example 1
Silica gel with a BET specific surface area of 500 m ² /g and a D50 value measured by laser diffraction method of 14.5 μm was used as the raw material silica, and silicone oil (KF96-50cs, manufactured by Shin-Etsu Chemical Co., Ltd.) was used to have a BET specific surface area of 100 m ² /g. 3.0 parts of the mixture was added to the solution, and mixed for 10 minutes using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) to homogenize. After mixing, the mixture was filled into a ceramic sagger with an internal volume of 10,000 cm ³ and heat-treated at 320° C. for 8 hours in a continuous heating furnace to obtain hydrophobic silica gel.

Example 2
Silica gel with a BET specific surface area of 530 m ² /g and a D50 value measured by laser diffraction method of 13.6 μm was used as the raw material silica, and silicone oil (KF96-50cs, manufactured by Shin-Etsu Chemical Co., Ltd.) was used to have a BET specific surface area of 100 m ² /g. 3.4 parts of the mixture was added, and mixed for 10 minutes using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) to homogenize.
After mixing, heat treatment was performed at 350° C. for 4 hours in a static heating furnace to obtain hydrophobic silica gel.

Example 3
Silica gel with a BET specific surface area of 470 m ² /g and a D50 value measured by laser diffraction method of 15.1 μm was used as the raw material silica, and silicone oil (KF96-50cs, manufactured by Shin-Etsu Chemical Co., Ltd.) was used to have a BET specific surface area of 100 m ² /g. 3.2 parts of the mixture was added, and mixed for 10 minutes using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) to homogenize. After mixing, heat treatment was performed at 380° C. for 7 hours in a static heating furnace to obtain hydrophobic silica gel.

Example 4
Silica gel with a BET specific surface area of 490 m ² /g and a D50 value measured by laser diffraction method of 11.0 μm was used as the raw material silica, and silicone oil (KF96-50cs, manufactured by Shin-Etsu Chemical Co., Ltd.) was used to have a BET specific surface area of 100 m ² /g. 3.1 parts of the mixture was added, and mixed for 10 minutes using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) to homogenize. After mixing, heat treatment was performed at 330° C. for 6 hours in a static heating furnace to obtain hydrophobic silica gel.

Example 5
Hydrophobic gel silica was obtained in the same manner as in Example 1 using silica gel having a BET specific surface area of 500 m ² /g and a D50 value of 10.4 μm measured by laser diffraction method as the raw material silica. Thereafter, the obtained hydrophobic gel silica was crushed and classified, and the particle size was adjusted so that the particle size distribution D50 value by laser diffraction method was 5.8 μm to obtain a hydrophobic silica gel.

The measurement results of Examples 1 to 5 are shown in Table 2. Further, the mercury pore volume distribution of Example 1 before and after compression is shown in FIG.

Reference example 1
Hydrophobic silica gel was obtained by the same procedure as in Example 1, except that silicone oil (KF96-50cs, manufactured by Shin-Etsu Chemical Co., Ltd.) was added in an amount of 5.0 parts per BET specific surface area of 100 m ² /g. . Hydrophobic silica gel with a large particle size and a high M value (55 vol%) had poor sedimentation stability.

Reference example 2
Commercial product Nipsil SS-50B (manufactured by Tosoh Silica)
Since the particle size was small, the sedimentation stability was excellent, but the matting performance was poor.

Comparative example 1
Commercial product NIPGEL AY-460 (manufactured by Tosoh Silica Co., Ltd.) WAX-treated gel silica This WAX-treated silica was inferior in transparency and chemical resistance compared to the hydrophobic silica gel of the present invention.

The measurement results of Reference Examples and Comparative Examples 1 and 2 are shown in Table 3. Further, the mercury pore volume distribution of Comparative Example 1 before and after compression is shown in FIG.

The present invention is useful in fields related to hydrophobic silica gel.

Claims (5)

A hydrophobic silica gel surface-treated with silicone oil,
The pore volume measured by nitrogen adsorption/desorption method is in the range of 0.6 to 2 ml/g,
The M value is in the range of 5 to 40 vol%, and the ratio of the pore volume with a pore radius of 109 nm or less after compression to the pore volume with a pore radius of 109 nm or less before compression at a pressure of 260 MPa (pore volume after compression) A hydrophobic silica gel for matting energy ray-curable paints containing a reactive monomer, an organic solvent, and a photopolymerization initiator and having a ratio (volume/pore volume before compression) of 0.8 to 1.5. The hydrophobic silica gel according to claim 1, wherein the hydrophobic silica gel has a volume average particle diameter D50 value measured by laser diffraction in a range of 5 to 20 μm. The hydrophobic silica gel according to claim 1 or 2, wherein the hydrophobic silica gel has a DBA adsorption amount in the range of 30 to 180 mmol/kg. The hydrophobic silica gel according to any one of claims 1 to 3, wherein the hydrophobic silica gel has a maximum particle diameter in the range of 15 to 70 μm as measured by laser diffraction. The hydrophobic silica gel according to any one of claims 1 to 4, wherein the hydrophobic silica gel has a ratio of D90 value to D50 value (D90/D50) measured by laser diffraction method of less than 1.8.