JP2003183516A - Dispersible fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of dispersing fine particles into a single particle state. <P>SOLUTION: This dispersible particles comprise organic and/or inorganic fine particles and an expandable additive. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a highly dispersible fine powder.

[0002]

2. Description of the Related Art Conventionally, fine powder dispersions in which non-expandable fine powders are dispersed in a dispersion medium have been used in various fields such as filler-containing adhesives and conductive filler-containing anisotropic conductive films. It is used. It is generally known that these dispersions exhibit a particularly high effect when the fine powder to be added is dispersed in a dispersion medium in a single particle state.

As a method for dispersing the fine powder, for example, the fine powder is added to the polymer matrix and then kneaded with a mixer or the like; the fine powder is uniformly dispersed in a solvent or the like by a homogenizer or the like and then added to the polymer matrix. A dispersion method using mechanical shearing such as diluting a polymer matrix with a solvent or the like and then adding fine powder and kneading is widely used.

However, when the specific gravity of the fine powder or the specific gravity of the dispersion medium is large, the viscosity of the dispersion medium is high, or the dispersion medium is a polymer matrix, agglomeration occurs at the time of addition, and single particles cannot be dispersed even after kneading. In many cases, it was extremely difficult to disperse the fine powder in a single particle state. Further, even when diluted with a solvent or the like, there is a problem that secondary aggregation occurs in the step of drying the solvent after dispersion.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above problems and an object thereof is to provide a highly dispersible fine powder in which fine powder can be dispersed in a single particle state.

[0006]

The highly dispersible fine powder of the present invention is characterized by comprising an organic and / or inorganic fine powder and an expansive additive.

The present invention will be described in detail below. The fine powder is not particularly limited as long as it does not dissolve in the dispersion medium, and organic and / or inorganic fine powder can be used. Examples of the organic fine powder include fine powders of polystyrene, polymethylmethacrylate, polyethylene, polypropylene, nylon and the like. Examples of the inorganic fine powder include inorganic substances such as carbon black; inorganic oxides such as silicic acid; gold, platinum, silver, copper,
Metals such as iron, nickel, aluminum and chrome; ITO
Examples thereof include metal oxides; and fine powders of metal compounds such as solder. These fine powders may be used alone or in combination of two or more kinds. Further, it may be an organic and inorganic composite. The average particle size of the fine powder is preferably 1 mm or less.

As the expansive additive, those which do not dissolve in the dispersion medium and have self-expansion property are preferably used. For example, a resin containing a material which expands by heat therein;
Examples thereof include a resin and the like that internally contains a material that is foamed or expanded by heat, light, an electron beam or the like.

As the material that expands by the heat, the softening point of the resin used (generally about 120 to 150).
(° C) or less, a substance which becomes a gas at a temperature of not more than, for example, butene, normal butane, isobutane, isopentane, normal pentane, neopentane, hexane, heptane,
Examples include low boiling point liquids such as petroleum ether, methane halides (methyl chloride, methylene chloride, etc.), and tetraalkylsilanes (tetramethylsilane, trimethylethylsilane, etc.). Among these, low boiling point liquids such as isobutane, normal butane, normal pentane, isopentane, and petroleum ether are particularly preferable.

Examples of the material which is foamed or expanded by the heat, light, electron beam or the like include dinitrosopentamethyltetramine, N, N'-dimethyl-N, N'-dinitrosoterephthalamide, benzenesulfonyl hydrazide, p
-Toluenesulfonyl hydrazide, p, p'-oxybis (benzenesulfonylhydrazide), 3,3'-disulfone hydrazide diphenylsulfone, toluenedisulfonyl hydrazide, p-toluenesulfonyl semicarbazide, azobisisobutyronitrile, azodicarbonamide , Diethylazodicarboxylate and the like.

As the resin containing the above or, depending on the dispersion medium, a conventionally known material can be used, and examples thereof include (un) saturated hydrocarbons, aromatic hydrocarbons,
(Un) saturated fatty acid, aromatic carboxylic acid, (un) saturated aliphatic ketone, aromatic ketone, (un) saturated alcohol, aromatic alcohol, (un) saturated amine, (un) saturated thiol, aromatic thiol, organic Examples thereof include condensates or polymers of one or more compounds selected from the group consisting of silicon compounds and their derivatives. In addition, (un) saturation means
Means both saturated and unsaturated.

The above-mentioned condensate or polymer is, for example,
Polyolefins such as polyethylene and polybutadiene; polyethers such as polyethylene glycol and polypropylene glycol; polystyrene, poly (meth) acrylic acid, poly (meth) acrylic acid ester, polyacrylamide, polyacrylonitrile, polyvinyl alcohol,
Polyvinyl ester, phenol resin, melamine resin,
Allyl resin, furan resin, polyester, epoxy resin, silicone resin, polyimide resin, polyurethane,
Examples thereof include Teflon (registered trademark), acrylonitrile / styrene resin, styrene / butadiene resin, vinyl resin, polyamide resin, polycarbonate, polyacetal, polyether sulfone, polyphenylene oxide, sugar, starch, cellulose, polypeptide and the like. These may be used alone or in combination of two or more.

The structure of the resin containing the material which expands or expands by the above heat, light, electron beam or the like is not particularly limited, and for example, 1) heat-expandable microcapsules,
2) A resin composition containing a thermal decomposition type chemical foaming agent may be mentioned.

As a specific example of the above 1), a polymer obtained from a nitrile-based monomer component or a non-nitrile-based monomer component is used, and becomes a gas at a temperature below the softening point of the polymer, butane, isobutane, pentane. Examples thereof include heat-expandable microcapsules obtained by encapsulating a volatile liquid expander such as hexane.

Specific examples of the above 2) include vinyl chloride resin, vinyl acetate resin, acrylic resin, urethane resin,
Examples thereof include synthetic rubber and the like to which a thermally decomposable chemical foaming agent is added. Examples of the thermally decomposable chemical foaming agent include dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitrosoterephthalamide, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, p, p′-oxybis. (Benzenesulfonyl hydrazide), 3,3′-disulphone hydrazide diphenyl sulfone, toluene disulphonyl hydrazide, p-toluene sulphonyl semicarbazide, azobisisobutyronitrile, azodicarbonamide, diethyl azodicarboxylate and the like. it can.

The expansion ratio of the expansive additive varies depending on the size of the fine powder, the properties of the dispersion medium, the use, etc., but is generally preferably 2 to 30 times, more preferably 2 to 30 times.
It is 10 times. Further, as the expansive additive, one that expands by heat and / or light is preferably used.

As the shape of the expansive additive, it is preferable to use a particulate form including an ellipsoidal sphere, a sphere, etc.
Among these, spherical ones that areotropically expand are more preferable. As a method for producing the spherical additive, a conventionally known method can be used, for example, a mini emulsion polymerization method, an emulsion polymerization method, a phase inversion emulsion polymerization method, a microsuspension polymerization method, a suspension polymerization method, a dispersion weight method. Examples thereof include a synthesis method, a soap-free precipitation polymerization method, a seed polymerization method, a droplet polymerization method and a microcapsule method. Among these, the soap-free precipitation polymerization method, which is excellent in particle size controllability, is preferably used.

The expandable additive is preferably physically adsorbed or chemically bonded to the surface of the fine powder. If the surface of the fine powder is coated with an additive, even if secondary aggregation occurs, the additive existing between the fine powders expands due to external stimulus, and the distance between the fine powders can be efficiently expanded. Is possible.

The physical adsorption method is not particularly limited, and examples thereof include a heterocoagulation method, an electrostatic interaction method, a dry blending method and the like. Further, examples of the method of chemically bonding include a method of chemically bonding after introducing a reactive functional group to the surface of the additive and / or the surface of the fine powder. As the chemical bond, ionic bond, covalent bond, coordinate bond and the like are preferably used.

The size of the expansive additive varies depending on the amount of the additive added and the use of the highly dispersible fine powder of the present invention. Since the physical properties are controlled by the additive, the size is preferably 100% or less of the fine powder.

When the expandable additive is in the form of particles and is physically adsorbed or chemically bonded to the surface of the fine powder to be used, the average particle diameter of the additive varies depending on the size of the fine powder and the application. However, 1/2 or less of the average particle diameter of the fine powder is preferable. If the average particle size of the fine powder exceeds 1/2, the particle size of the highly dispersible fine powder of the present invention becomes unnecessarily large,
The characteristics of the highly dispersible fine powder cannot be expected.

When the highly dispersible fine powder of the present invention is used as the anisotropic conductive filler, the average particle size of the fine powder used is preferably 5 to 1000 nm. When the average particle size is smaller than 5 nm, the distance between adjacent particles becomes smaller than the hopping distance of electrons, and leakage occurs. Further, when the average particle diameter is larger than 1000 nm, excessive pressure or heat is required for pressure bonding. More preferably 10-5
00 nm.

When the expandable additive is in the form of particles,
Since the additive having a small particle diameter enters the gap covered with the additive having a large particle diameter, the coating density can be improved by using two or more kinds having different particle diameters in combination. At this time, the particle size of the small particulate additive is preferably 1/2 or less of the particle size of the large particulate additive, and the addition amount of the small particulate additive is 1/100 of that of the large particulate additive. It is preferably 4 or less.

The dispersion medium is preferably at least one selected from the group consisting of water, an organic solvent, an organic polymer and a monomer forming a polymer by a reaction. Examples of the monomer forming the polymer include a vinyl monomer that performs a polymerization reaction with heat, light, an electron beam, a radical polymerization initiator, a polymerization catalyst, and the like, and a monomer that performs a polycondensation reaction or a polyaddition reaction.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Examples are shown below, but the present invention is not limited thereto. Preparation of expandable additive (a) 1.75 g of a 50% aqueous solution of adipic acid diethanolamine condensate, which is a water-soluble polymer, was dissolved in 300 g of ion-exchanged water, and 45 g of a 20% aqueous solution of colloidal silica was added, and then this aqueous solution was adjusted to pH 4 To prepare an aqueous layer. Next, methyl methacrylate 75 mmol, acrylonitrile 1700 mmol, methacrylonitrile 670 mm
ol, trimethylolpropane trimethacrylate 2m
An oil layer was prepared by mixing mol, 42 mmol of isopentane, and 4.5 mmol of azobisisobutyronitrile. After mixing the water layer and the oil layer, the mixture is stirred and dispersed for 120 seconds at a rotation speed of 6000 rpm using a homomixer, and polymerized in a nitrogen-substituted 1 liter autoclave at a pressure of 300 to 400 kPa and a temperature of 60 ° C. for 20 hours, An expandable additive (a) consisting of isopentane-encapsulated microcapsules having an average particle size of 16.9 μm was obtained.

Preparation of expandable additive (b) In a 1000 ml separable flask equipped with a three-neck separable cover, a stirring blade, a three-way cock, a cooling tube and a temperature probe, glycidyl methacrylate 60 mmo.
1, styrene 50 mmol, 2,2′-azobis (2-aminodipropane) dihydrochloride 1 mmol, azoamide compound (“Uniform AZ EVA manufactured by Otsuka Chemical Co., Ltd.
-14) After weighing 1 mmol and 500 g of distilled water,
70 ° C under nitrogen atmosphere while stirring at a rotation speed of 200 rpm
By carrying out polymerization for 24 hours, an aqueous dispersion (solid content concentration 5%) of the expansive additive (b) containing a thermal foaming agent having an epoxy group on the surface and having an average particle diameter of 0.3 μm was obtained. Furthermore, the dispersion medium was replaced with acetone from the water by centrifugation to obtain an acetone dispersion having a solid content concentration of 5%.

Preparation of expandable additive (c) Glycidyl methacrylate 60 mmo in a 1000 ml separable flask equipped with a four-neck separable cover, a stirring blade, a three-way cock, a condenser and a temperature probe.
1, styrene 50 mmol, phenyl dimethyl dimethyl sulfonium methyl sulfate 2 mmol, 2,2'-
Azobis-2-N-2-carboxyethylaminodipropane 1 mmol, azoamide compound (“V manufactured by Wako Pure Chemical Industries, Ltd.
Am-111 ") 1 mmol and distilled water 500 g were weighed and then polymerized at 70 ° C. for 24 hours in a nitrogen atmosphere while stirring at a rotation speed of 200 rpm to give an epoxy group having an average particle diameter of 0.2 μm. An aqueous dispersion (solid content concentration 5%) of the expandable additive (c) containing a photo-foaming agent was obtained. Furthermore, the dispersion medium was replaced with acetone from the water by centrifugation to obtain an acetone dispersion having a solid content concentration of 5%.

Example 1 1 g of expandable additive (a) and cross-linked polymethylmethacrylate particles having an average particle size of about 50 μm (“PN beads MBX-50” manufactured by Sekisui Plastics Co., Ltd.) 1
0 g was put into a ball mill and mixed for a short time to obtain a highly dispersible fine powder (A) in which the surface of polymethyl methacrylate particles was coated with an expansive additive (a).

1 g of the highly dispersible fine powder (A), an epoxy resin ("Epicoat 828" manufactured by Yuka Shell Epoxy Co., Ltd.)
100 g and trisdimethylaminoethylphenol 5 g were sufficiently dispersed and mixed by using a planetary stirrer, and then coated on a glass plate having a thickness of 1 mm to have a film thickness of 120 μm. Further, a glass plate having a thickness of 1 mm was superposed on the coating film and then heated at 130 ° C. for 5 minutes to cure the epoxy resin. The cured sample was observed with an optical microscope to count the number of aggregated particles per 1 cm ^{2 of} the cured coating film, and the aggregation rate was calculated from the ratio of the aggregated particles to the total number of single particles. In addition, aggregates of 5 or more single particles were counted as aggregated particles.

Example 2 An aqueous dispersion of the expandable additive (b) was freeze-dried and powdered to give 1 g and an average particle size of about 5
10 g of silica particles having a diameter of 10 μm were introduced into a hybridization system and treated at 90 ° C. for 2 minutes to obtain highly dispersible fine powder (B) in which the surfaces of silica particles were coated with polymethylmethacrylate particles.

A cured epoxy resin sample was prepared in the same manner as in Example 1 except that the highly dispersible fine powder (A) was replaced with the highly dispersible fine powder (B). The aggregation rate was calculated in the same manner as 1 and shown in Table 1. The coating was applied on a glass plate so that the film thickness was 40 μm.

Example 3 In a 1000 ml separable flask equipped with a four-neck separable cover, a stirring blade and a three-way cock, 10 g of silica particles having an average particle size of about 5 μm was added to 500 ml of ethanol under a nitrogen atmosphere. After the dispersion, 10 mmol of 3-aminopropyltriethoxysilane was dispersed in the obtained dispersion under a nitrogen atmosphere, and the mixture was reacted at room temperature for 2 hours. Then, unreacted 3 by filtration
-Aminopropyltriethoxysilane was removed, washed with methanol and dried to obtain silica particles having an amino group which is a reactive functional group on the surface. The particles were dispersed in 500 ml of 2-butanone, 2 ml of an aqueous dispersion of the expansive additive (b) in acetone was added, and the mixture was stirred at room temperature for 12 hours, filtered with a 3 μm mesh filter, washed with acetone, and dried. Then, highly dispersible fine powder (C) in which the silica particle surface was coated with the expansive additive (b) was obtained.

A cured epoxy resin sample was prepared in the same manner as in Example 1 except that the highly dispersible fine powder (A) was replaced with the highly dispersible fine powder (C). The aggregation rate was calculated in the same manner as 1 and shown in Table 1. The coating was applied on a glass plate so that the film thickness was 40 μm.

Example 4 In a 1000 ml separable flask equipped with a four-neck separable cover, a stirring blade and a three-way cock, crosslinked polystyrene particles having an average particle size of about 5 μm (Sekisui Chemical Co., Ltd. Micro Pearl S
P ") was dispersed in 500 ml of ethanol under a nitrogen atmosphere, and then 10 mmol of 3-aminopropyltriethoxysilane was dispersed in the obtained dispersion under a nitrogen atmosphere and reacted at room temperature for 2 hours. Then, unreacted 3-aminopropyltriethoxysilane is removed by filtration,
After washing with methanol and drying, polystyrene particles having amino groups which are reactive functional groups on the surface were obtained. The particles were dispersed in 500 ml of 2-butanone, 2 ml of an aqueous acetone dispersion of the expansive additive (c) was added, the mixture was stirred at room temperature for 3 hours, and then filtered with a 3 μm mesh filter.
Highly dispersible fine powder (D) obtained by further washing with acetone and drying, and covering the surface of polystyrene particles with the expansive additive (c).
Got

1 g of the highly dispersible fine powder (D), an epoxy resin ("Epicoat 828" manufactured by Yuka Shell Epoxy Co., Ltd.)
100 g and a photocationic catalyst ("SP1 manufactured by Asahi Denka Co., Ltd."
70 ") was thoroughly dispersed and mixed by using a planetary stirrer, and then coated on a glass plate having a thickness of 1 mm to have a film thickness of 40 µm. Further, a glass plate having a thickness of 1 mm was superposed on the coating film, and then ultraviolet rays of 365 nm were irradiated for 3 minutes to cure the epoxy resin. The aggregation rate of this cured sample was calculated in the same manner as in Example 1 and is shown in Table 1.

Comparative Example 1 A cured sample was prepared in the same manner as in Example 1 except that the polymethylmethacrylate particles of Example 1 were used in place of the highly dispersible fine powder (A). The aggregation rate was calculated and shown in Table 1.

Comparative Example 2 A cured sample was prepared in the same manner as in Example 2 except that the silica particles of Example 2 were used in place of the above-mentioned highly dispersible fine powder (B), and the agglomeration rate was then measured. The calculated values are shown in Table 1.

Comparative Example 3 A cured sample was prepared in the same manner as in Example 4 except that the polystyrene particles of Example 4 were used in place of the above-mentioned highly dispersible fine powder (C), and then the agglomeration rate was determined. The calculated values are shown in Table 1.

[0039]

[Table 1]

In Examples 1 to 4, the agglomeration rate was 10% or less, showing good dispersibility. On the other hand, Comparative Examples 1 to 1
In No. 3, since no expansive additive was used, there were 25% or more of 5 or more aggregated particles, indicating that the dispersibility was low. Therefore, it was proved that the expansive additive was effective in developing good dispersibility.

[0041]

The highly dispersible fine powder of the present invention has the above-mentioned constitution and is well dispersed in the dispersion medium in a single particle state.
Therefore, it can be suitably used for applications such as a filler-containing pressure-sensitive adhesive and a conductive filler-containing anisotropic conductive film.

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Claims (4)

[Claims] 1. A highly dispersible fine powder comprising an organic and / or inorganic fine powder and an expandable additive. 2. The highly dispersible fine powder according to claim 1, wherein the expandable additive is physically adsorbed or chemically bonded to the surface of the fine powder. 3. The highly dispersible fine powder according to claim 1, wherein the expandable additive expands by heat and / or light. 4. The highly dispersible fine powder according to claim 1, wherein the expandable additive has a particulate shape.