JPH1036705A - Surface treatment of inorganic particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating the surface of inorganic particles, not causing a discoloration and sufficiently making the surface of the inorganic particles hydrophobic in the surface treatment of the inorganic particles by a spray drying. SOLUTION: This method for treating the surface of inorganic particles is to disperse inorganic particles having 0.005-5μm mean particle diameter such as a silica, a silicatitania and a silicazirconia into a polar solvent such as water, methanol, ethanol and acetone, them mix the dispersion with a solution obtained by hydrolyzing a silane coupling agent in the presence of an assistant for hydrolysis such as hydrochloric acid, nitric acid, acetic acid and citric acid, and spray drying the mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for surface treatment of inorganic particles. Specifically, especially when the average particle diameter is 0.00
The present invention relates to a method for hydrophobizing inorganic particles of 5 to 5 μm with a silane coupling agent.

[0002]

2. Description of the Related Art Conventionally, in the case of a composite material produced by polymerizing and curing a paste-like composition comprising an inorganic filler and a polymerizable monomer, the surface of the inorganic filler is treated with an organic material to improve the mechanical strength of the composite material. Hydrophobizing with compounds,
A method of treating with a silane coupling agent having a polymerizable group is generally performed.

A method of treating the surface of an inorganic filler with a silane coupling agent includes spraying a silane coupling agent on a fluidized inorganic filler, adding an inorganic filler to an organic solvent such as alcohol or toluene, and further adding a silane coupling agent. After adding a ring agent and water, a method of evaporating and drying water and an organic solvent by an evaporator, and a method of adding ultrafine silica to a solution of a hydrolyzed silane coupling agent, homogenizing, and then spray drying. (U.S. Pat. No. 4,482,656) and the like.

[0004]

When the above-mentioned method of spray drying is applied to hydrophobizing inorganic particles having an average particle diameter in the range of 0.1 to 1 μm, the following problems arise. Inorganic particles having an average particle size in the range of 0.1 to 1 μm have lower dispersibility than particles larger than 1 μm, tend to aggregate in the dispersion, and precipitate easily in the dispersion when aggregated. Therefore, the inorganic particles were put into a solution containing the hydrolyzed silane coupling agent, dispersed with a homogenizer and spray-dried. Did not.

[0005] Therefore, there has been a demand for a method of causing no coloring and sufficiently hydrophobizing the particle surface in the surface treatment of the inorganic particles with the silane coupling agent.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above-mentioned object. As a result, the present inventors did not mix the inorganic particles with the hydrolyzate of the silane coupling agent but homogenize the mixture. After homogenizing the particles, they were mixed with a hydrolyzate of a silane coupling agent and spray-dried, whereby they were found to be able to obtain sufficiently hydrophobic inorganic particles without coloring.

That is, according to the present invention, the average particle diameter is 0.005.
５5 μm of inorganic particles are dispersed in a solvent, and then a solution obtained by hydrolyzing a silane coupling agent in the presence of a hydrolysis aid is mixed with a dispersion of the inorganic particles, followed by spray drying. Surface treatment method for the inorganic particles.

The inorganic particles used in the present invention have an average particle size of 0.005 to 5 μm. Known inorganic particles having an average particle diameter within the above range can be used without any particular limitation. Inorganic particles having an average particle diameter of less than 0.005 μm are difficult to disperse even by the method of the present invention,
In addition, even if inorganic particles having an average particle diameter exceeding 5 μm are dispersed by the method of the present invention, the inorganic particles immediately settle, and a stable dispersion cannot be obtained.

In the present invention, the inorganic particles may have an average particle diameter of 0.005 to 5 μm, but the effect is particularly remarkable when inorganic particles having an average particle diameter in the range of 0.1 to 1 μm are used. is there. In this case, the particle diameter of all particles is 0.
It is not necessary that the particle diameter is in the range of 1 to 1 μm.
Wt% or less, or inorganic particles larger than 1 μm may be present at 20 wt% or less.

Specific examples of the inorganic particles suitably used in the present invention include, for example, amorphous silica, silica-zirconia, silica-titania, silica-titania-
Spherical particles or irregular particles such as barium oxide, quartz, alumina, and glass can be used. For dental crown materials, for dental filling and restoration materials, spherical inorganic particles of composite oxides containing silica and zirconia or silica and barium oxide as main components have X-ray contrast properties,
It is particularly preferably used because a cured product of the composite composition having more excellent wear resistance and surface lubricity can be obtained.

The method for producing the inorganic particles is not particularly limited, and any method may be used as long as it has the above-mentioned particle size. Generally, industrially, a method of producing by hydrolysis of a metal alkoxide is suitably employed. Further, it is preferable to reduce the number of OH groups on the surface in order to maintain the surface stability of the inorganic particles. For that purpose, a means for baking at a temperature of 500 to 1000 ° C. after drying the inorganic particles is often suitably adopted.

As the solvent used in the present invention, known solvents can be used without particular limitation as long as they can disperse the inorganic particles. Preferably, water or an organic solvent containing a small amount of water dissolved therein, for example, methanol, ethanol, propanol, butanol, acetone or the like, or
Polar solvents such as a mixed solvent thereof can be exemplified.

In the present invention, it is necessary to add and disperse the inorganic particles to the solvent. The term “dispersion” as used herein refers to a state in which the dispersion is allowed to stand, and the inorganic particles do not precipitate after standing for one hour. If the inorganic particles are not dispersed, a uniform surface treatment cannot be performed at the stage of spray drying in a later step, and the contact angle of the surface-treated inorganic particles will vary. In order to disperse the inorganic particles, a generally known homogenizer is used. If a homogenizer is specifically illustrated, it is crushed and dispersed while stirring with a stirring rod in a cylindrical container containing a spherical ceramic ball, an ultrahigh pressure impact type emulsifying and dispersing device, crushing with a chopper, Dispersing devices and the like can be mentioned.

The above-mentioned dispersion does not need to be performed at a particularly limited temperature, and may be performed within a range in which the solvent does not volatilize or coagulate. In general, it may be performed at around room temperature, for example, in the range of 10 to 60 ° C.

The mixing ratio between the inorganic particles and the solvent may be within the range of slurry. Generally, the solvent is used in the range of 200 to 1000 parts by weight based on 100 parts by weight of the inorganic particles.

As the silane coupling agent used in the present invention, conventionally known silane coupling agents can be used without limitation. Examples of suitable silane coupling agents include vinyltriethoxysilane, vinyl-tris (β-methoxyethoxy) silane, γ-methacryloyloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxy Silane, γ-glycidoxypropyl-trimethoxysilane, N-β- (aminoethyl) -γ-aminopropyl-trimethoxysilane, γ-ureidopropyl-triethoxysilane, γ-chloropropyltrimethoxysilane, vinyltri Methoxysilane, κ-methacryloyloxidedecyltrimethoxysilane, and the like.

The addition amount of these silane coupling agents is
Any amount is sufficient as long as it is necessary to coat the surface of the inorganic particles.
Generally, the silane coupling agent is used in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the inorganic particles.

The silane coupling agent used in the present invention is hydrolyzed. The hydrolysis of the silane coupling agent is generally performed by adding a hydrolysis aid to water or an organic solvent containing water dissolved therein. Known solvents can be used without particular limitation as long as they are compatible with a small amount of water. Examples of commonly used solvents include methanol, ethanol, propanol, butanol, acetone and the like, and mixed solvents thereof.
The hydrolysis aid is used for adjusting the pH value of the solvent to the range of 3 to 5.5, and a known one is used without any limitation. Specific examples of the hydrolysis aid used for this hydrolysis include mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and carboxylic acids such as acetic acid, citric acid, malic acid and lactic acid. Among these acids, carboxylic acids are particularly preferably used because they hardly remain on the inorganic particles in spray drying in a later step.

The hydrolysis may be carried out generally at a temperature around room temperature, for example, in the range of 10 to 60 ° C. The silane coupling agent is used in an amount of 1 to 10 based on 100 parts by weight of the solvent.
The mixture is mixed in parts by weight, and the amount of the hydrolysis aid added is adjusted so that the pH of the solution becomes 3 to 5.5.

In the present invention, the inorganic particles are dispersed in a solvent, and then mixed with a solution obtained by hydrolyzing the silane coupling agent. The dispersion obtained by dispersing the inorganic particles in the solvent may be added to the solution obtained by hydrolyzing the silane coupling agent, or the solution may be added to the dispersion.

In the present invention, the dispersion and the solution are mixed, and the mixture is spray-dried. Spray drying is 150 ° -30
If it can be dried at 0 ° C., a general known method is employed. As a method of spraying, a method of spraying from a nozzle having fine pores, or an atomizer method of dropping and spraying the above mixture onto a high-speed rotating body is adopted.

The inorganic particles obtained by the spray drying may be used as they are as the inorganic filler of the composite material. However, in order to sufficiently remove the residue on the surface of the inorganic particles obtained by the spray drying, the temperature is further increased to 80 ° C. to 150 ° C. It is better to perform vacuum drying in the range of ° C.

In the present invention, the average particle size is 0.1 to 1 μm
A solution obtained by dispersing at least one inorganic oxide particle selected from silica, silica-titania, and silica-zirconia in a polar solvent, and hydrolyzing a silane coupling agent in the presence of an organic acid; A particularly preferred embodiment is a method of mixing with a dispersion of the product and spray-drying.

[0024]

According to the surface treatment method of the present invention, the surface-treated inorganic particles have a uniform contact angle without coloring. In addition, when the inorganic particles are used as a filler for a composite material, the composite material is not colored, the mechanical strength is less varied, and high mechanical strength and wear resistance can be obtained.

[0025]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The paste preparation methods, bending strength, wear depth, and contact angle shown in the following Examples and Comparative Examples were measured according to the following methods.

The abbreviations of compounds such as a polymerization monomer and a polymerization catalyst are shown below.

Bis-GMA: 2,2-bis (4- (3-methacryloyloxy) -2-hydroxypropoxyphenyl) propane TEGDMA: triethylene glycol dimethacrylate CQ: camphorquinone DMEM: dimethylaminoethyl methacrylate 1) Contact Corner The inorganic particles having been subjected to the surface treatment are put into a metal ring having a hole having a diameter of 10 mm and a depth of 1 mm, a load of 50 MPa is applied for 5 minutes, a pellet is produced, a drop of water is dropped on the pellet with a syringe, and the contact angle is measured. Was measured.

2) Method for preparing paste-like composition A paste-like composition having the following composition was prepared by kneading in a mortar.

Surface-treated inorganic particles 75 parts by weight Bis-GMA 15 parts by weight TEGDMA 10 parts by weight CQ 0.125 parts by weight DMEM 0.25 parts by weight 3) Method of measuring bending strength Paste containing surface-treated inorganic particles Composition 2 ×
A split mold having a hole of 2 × 25 mm was filled and uniformly irradiated to three places on the upper surface using a visible light irradiator power light (manufactured by Tokuyama Corporation) to produce a cured product. Thereafter, the cured product was immersed in water at 37 ° C. for 24 hours to obtain a test piece. This test piece was tested with a testing machine (UTM-5, manufactured by Toyo Board Win).
T), and the bending strength was measured at a crosshead speed of 0.5 mm / min. The number of test pieces was 10, and the average value and standard deviation were shown.

4) Method of measuring abrasion depth 6 m of paste-like composition containing surface-treated inorganic particles
Fill into a split mold having a hole with a diameter of 12 mm and a diameter of 12 mm.
The sample was irradiated for 2 seconds to produce a test piece. The test piece was mounted at a position of 6 cm from the center of the disc to the outer circumference so that the bottom surface of the test piece was in contact with a rotary polishing machine equipped with a number 1000 diamond disc, a load of 800 g was applied, and the disc was rotated at 150 rpm. After rotating the disk for one minute, the wear depth was measured with a micrometer.

Example 1 100 g of spherical silica inorganic particles (average particle diameter 0.6 μm)
m, specific surface area 4.5 m ² / g) in 150 g of water, and a processing pressure of 6 using an ultra-high pressure impact-type emulsifying and dispersing machine Nanomizer.
A dispersion in which the inorganic particles were dispersed at 0 MPa was obtained. Even when this dispersion was allowed to stand for 1 hour, no precipitate of inorganic particles was observed.

Then, 3 g of γ-methacryloyloxypropyltrimethoxysilane and 0.003 g of acetic acid were added to 7
The mixture was added to 0 g of water and stirred for 1 hour and 30 minutes to obtain a uniform solution having a pH of 4. This solution was added to the above dispersion and mixed uniformly. Thereafter, the solution is spray-dried while being mixed lightly (spray dryer TSR-2W manufactured by Sakamoto Giken Co., Ltd.).
The temperature of the air was set to 200 ° C. and spray-dried. Thereafter, the spray-dried inorganic particles were vacuum-dried at 90 ° C. for 12 hours.

The inorganic particles obtained by the above surface treatment had no coloration and a contact angle of 110 ° C. A paste was prepared using the inorganic particles, and 10 test pieces were further prepared, and the bending strength and the wear depth were measured. as a result,
The average bending strength was 150 MPa, the standard deviation was 20 MPa, and the wear depth was 1.85 mm.

Example 2 200 g of 100 g of spherical silica-zirconia inorganic particles (average particle diameter 0.52 μm, specific surface area 4.8 m ² / g)
And a dispersion liquid in which inorganic particles were dispersed at a processing pressure of 40 MPa using the same disperser as in Example 1 was obtained. Even when this dispersion was allowed to stand for 1 hour, no precipitation of inorganic particles was observed.

Then, 3 g of γ-methacryloyloxypropyltrimethoxysilane and 0.003 g of acetic acid were added to 8
The mixture was added to 0 ml of water and stirred for about 2 hours to obtain a uniform solution having a pH of 4. This solution was added to the above dispersion and mixed uniformly. Thereafter, the solution was dried at a drying temperature of 16 while mixing gently.
Spray dried at 0 ° C. Thereafter, the spray-dried inorganic particles were vacuum-dried at 100 ° C. for 10 hours.

The obtained spherical inorganic particles had no coloring and had a contact angle of 115 °. The bending strength and wear depth were measured in the same manner as in Example 1. The average bending strength is 1
It was 60 MPa, the standard deviation was 15 MPa, and the wear depth was 1.73 mm.

Example 3 80 g of spherical silica-zirconia inorganic particles (average particle diameter 0.42 μm, specific surface area 5.6 m ² / g) and 20 g of spherical silica-titania inorganic particles (average particle diameter 0.08 μm)
m, specific surface area: 33 m ² / g) was placed in 400 g of water, and a dispersion liquid in which inorganic particles were dispersed at a processing pressure of 50 MPa using the same disperser as in Example 1 was obtained. This dispersion did not produce a precipitate even after standing for 1 hour. Next, 7 g of γ-methacryloyloxypropyltrimethoxysilane and 0.0 g
04 g of citric acid was added to 100 ml of water to obtain a pH5 homogeneous solution. The above dispersion was added to this solution and mixed uniformly. The mixed solution was spray-dried at a drying temperature of 200 ° C. Thereafter, the spray-dried inorganic particles were heated at 90 ° C.
Vacuum dried for 24 hours.

The obtained spherical inorganic particles had no coloration and a contact angle of 115 °. As a result of measuring the bending strength and the wear depth in the same manner as in Example 1, the average bending strength was 2
30MPa, standard deviation 12MPa, wear depth 1.40m
m.

Example 4 100 g of irregularly shaped barium glass (average particle size 0.7
μm, the particle size range is 0.1 to 1.5 μm, of which 1 to
The particle size of 1.5 μm was 8% by weight.
(3 m ² / g) was placed in 300 g of water and dispersed in a vessel equipped with a chopper to obtain a dispersion. This dispersion did not show any precipitate even after standing for 1 hour. Next, 0.5 g of methyltrimethoxysilane and 2 g of γ-methacryloyloxypropyltrimethoxysilane, and 0.003 g
Acetic acid was added to 100 ml of water to obtain a homogeneous solution of pH5. The above dispersion was added to this solution and mixed uniformly.
The mixed solution was spray-dried at a drying temperature of 200 ° C. Thereafter, the spray-dried inorganic particles were vacuum-dried at 90 ° C. for 12 hours. The obtained amorphous barium glass had a white color and a contact angle of 118 °. The bending strength and the wear depth were measured in the same manner as in Example 1. As a result, the average bending strength was 145 MPa, the standard deviation was 15 MPa, and the wear depth was 1.41 mm.

COMPARATIVE EXAMPLE 1 A solution containing 3 g of γ-methacryloyloxypropyltrimethoxysilane, 0.03 g of acetic acid, and 70 g of water was mixed with 1 solution.
After mixing for 30 minutes, 100 g of the inorganic particles of Example 1 was added to this solution, dispersed by the same apparatus as in Example 1, and spray-dried. The obtained inorganic particles were slightly brownish.

Comparative Example 2 The solvent was removed from the dispersion of Example 1 using an evaporator. The obtained inorganic particles were white, but the contact angle was 95 °. A paste was prepared in the same manner as in Example 1, and the bending strength and the wear depth were measured. As a result, the average bending strength was 110 MPa, and the standard deviation was 50 MP.
a, the abrasion depth was 2.15 mm, and the bending strength was lower than that of Example 1, and the value was also large, the abrasion depth was large, and the abrasion resistance was low.

Claims (1)

[Claims] 1. A solution obtained by dispersing inorganic particles having an average particle diameter of 0.005 to 5 μm in a solvent, and then hydrolyzing a silane coupling agent in the presence of a hydrolysis aid, and a dispersion of the inorganic particles. And then spray-drying the mixture.