JP2665737B2 - Production method of fine particle inorganic filler dispersion - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a particulate inorganic filler dispersion. More specifically, the present invention relates to a method for preparing a composition having a viscosity (normal temperature, that is, 25 ° C.).
A low-viscosity organic dispersion medium having a viscosity of 0.1 to 10 centipoise in the range of 0.1 to 10 centipoise, and an agglomerated particulate inorganic filler having a primary particle diameter of 20% by weight or less based on the organic dispersion medium of 0.1 μm or less. The present invention relates to a method for producing a particulate inorganic filler dispersion in which the state of aggregation of the filler has been reduced from a mixture obtained by mixing the particles. BACKGROUND OF THE INVENTION In the case of preparing a fine inorganic filler dispersion by dispersing a fine inorganic filler such as fine titanium dioxide and silica in an organic dispersion medium, conventionally, a mechanical dispersing apparatus such as a ball mill and a sand mill is used. Has been used. That is, a method in which a mixture of a particulate inorganic filler and an organic dispersion medium is introduced into the above-described mechanical dispersion apparatus to obtain a dispersion liquid has been generally used. Ordinary powder dispersion can be easily realized by using a mechanical dispersion device as described above and performing a dispersion operation until the desired uniformity is achieved. However, according to the study of the present inventor, when the primary particle diameter is dispersed in an organic solvent having an extremely small particle size in a low-viscosity organic solvent having a viscosity in the range of 0.1 to 10 centipoise, the above-described case is considered. It has been found that it is difficult to sufficiently disperse by ordinary dispersing operation using a mechanical dispersing device. That is, for example, fine particle inorganic fillers such as titanium dioxide and silica having a primary particle diameter of 0.1 μm or less exist as aggregates of secondary particles, tertiary particles, and the like in a normal powder state. The agglomerate is introduced into the dispersion as an almost intact agglomerate with little or no loosening by a normal dispersion operation. For this reason, the conventional dispersion method is sufficiently effective for preparing a dispersion in which such aggregates are simply dispersed, but in order to obtain a dispersion in which the aggregate state of the aggregates is clearly reduced, the conventional dispersion method is required. The method is not effective. Of course, even when a conventional dispersion method using a mechanical dispersing apparatus is used, the degree of dispersion can be increased by making the dispersion conditions (eg, applied shear stress and dispersion time) more severe than usual. Can be improved, but the dispersion is only slightly improved and is not sufficient. Further, when the mechanical dispersion operation is performed under such severe conditions, there is also a problem that the mixing of the abrasion powder from the dispersion device becomes a nonnegligible amount. The insufficient dissociation of the aggregate in the dispersion operation of the fine-particle inorganic filler becomes remarkable particularly when the amount of the inorganic filler is small. That is, for example, when the amount of the inorganic filler is as small as about 20% by weight or less based on the dispersion medium, the shear stress applied to the inorganic filler aggregate by the mechanical dispersion operation is kept at a low level. Dissociation becomes more difficult. The fine-particle inorganic filler having a small primary particle diameter as described above is filled in, for example, a plastic film, and the surface thereof is formed into a moderately rough surface (in other words, the surface is formed with irregularities of an appropriate size). Used for
The plastic film filled with the particulate inorganic filler, for example, after preparing an organic solvent dispersion of the particulate inorganic filler, a polymer, a polymer precursor,
After adding a raw material for producing a polymer and performing a reaction treatment such as polymerization as required, the resulting inorganic filler-dispersed polymer solution is formed into a plastic film. In this case, even if a very small particulate inorganic filler having a primary particle diameter is used as the inorganic filler, if the aggregated state is introduced into the dispersion without unraveling, the filler is equivalent to the plastic film. Since it is introduced in an agglomerated state, the unevenness formed on the surface of the plastic film becomes large, and is not suitable for the purpose of filling. [Constitution of the Invention] The present invention provides a method for producing a dispersion having high dispersibility by dispersing at least a part of a particulate inorganic filler in an aggregated state in an organic dispersion medium while unwinding the aggregated state. The purpose is to provide. In particular, the present invention is a method for producing an organic solvent dispersion of a low-concentration particulate inorganic filler using a particulate inorganic filler that is at least partially in an aggregated state. An object of the present invention is to provide a method for producing a dispersion having high dispersibility by dispersing in water. That is, the present invention has a viscosity of 0.1 to 10 centipoise (2
5 ° C.), and a mixture obtained by mixing an organic dispersion medium having a primary particle diameter of 20% by weight or less with respect to the organic dispersion medium and an aggregated particulate inorganic filler having a primary particle diameter of 0.1 μm or less. In preparing a dispersion, there is provided a method for producing a particulate inorganic filler dispersion, which comprises subjecting the mixture to a mechanical dispersion operation using a rotor in advance, and then performing an ultrasonic dispersion operation. Next, the present invention will be described in detail. The fine particle inorganic filler to be dispersed in the present invention is an aggregated fine particle inorganic filler having a primary particle diameter of 0.1 μm or less, and examples thereof include fine particle copper powder, zinc powder, aluminum powder, and iron powder. Powders, metal powders such as cobalt powder and nickel powder, inorganic oxide powders such as fine titanium dioxide powder, silicon dioxide (silica) powder, magnesium oxide powder, aluminum oxide (alumina) powder, and zinc oxide powder; Inorganic nitride powder such as silicon nitride powder, titanium nitride powder, inorganic carbide powder such as silicon carbide powder, titanium carbide powder, tungsten carbide powder, and fine-particle calcium carbonate powder,
Examples thereof include inorganic salt powders such as calcium sulfate powder and barium sulfate powder. These particulate inorganic fillers may be used in combination of two or more kinds. The organic dispersion medium (organic solvent) used in the present invention has a viscosity (normal temperature, that is, a viscosity at 25 ° C.) of 0.1 to 10 centipoise. There is no particular limitation as long as the organic dispersion medium has a low viscosity, such as an alcohol solvent, a ketone solvent, an ether solvent, an ester solvent,
Various known organic solvents such as a hydrocarbon solvent, a halogenated hydrocarbon solvent, and an amide solvent are used alone or in combination. Further, the organic solvent may be an aqueous solvent mixed with water. The present invention is particularly effective when the organic dispersion medium to be used is an amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and the like. In the method for producing a dispersion of the present invention, first, an organic dispersion medium and 20% by weight or less of a particulate inorganic filler with respect to the organic dispersion medium are mixed to obtain a mixture, and then a specific dispersion operation is performed. It is performed by applying. The method for producing a dispersion of the present invention is particularly useful when a desired dispersion is prepared from a mixture of an effective dispersion medium and 1 to 15% by weight of a particulate inorganic filler with respect to the organic dispersion medium. It is valid. The mixture of the effective dispersion medium and the particulate inorganic filler can be obtained by a usual addition operation. In addition, a known dispersant may be added to this mixture if desired. The mixture of the organic dispersion medium and the particulate inorganic filler obtained as described above is then subjected to a mechanical dispersion operation according to the present invention. The mechanical dispersion operation using the above-described rotor is performed using a known mechanical dispersion device using a rotor. Examples of the mechanical dispersing device that can be used include a ball mill, a sand mill, an automatic mortar, a roll mill, an impeller mill, and a homogenizer. Such a mechanical dispersing device is generally a device that rotates at a rotation speed of 700 to 12000 rpm to disperse solid particles. The mechanical dispersion operation in the present invention is an operation mainly performed for roughly dispersing an inorganic filler in an organic dispersion medium, and in this operation, dissociation of aggregates hardly occurs,
Alternatively, it occurs only slightly. Therefore, this dispersion operation is desirably performed in a short time of about 30 minutes or less (preferably 30 seconds or more and 20 minutes or less). If this dispersion operation is performed for a long time, the abrasion powder of the dispersion device may be mixed in the dispersion in a considerable amount. The coarse dispersion subjected to the mechanical dispersion operation described above still contains a large amount of aggregates (secondary particles, tertiary particles, etc.).
Then, such a coarse dispersion is then subjected to a treatment by an ultrasonic dispersion operation to obtain a dispersion in which the amount of aggregates is clearly reduced. The ultrasonic dispersion operation used in the present invention is an operation already used for the purpose of ultrasonic cleaning, preparation of an emulsion, and the like. Such an operation is performed using a known ultrasonic transducer. Ultrasonic dispersion operation in the present invention,
It is desirable to perform at a low frequency of about 15 to 30 KHz to achieve a strong dispersion capability. The ultrasonic dispersion operation is desirably performed for an operation time in the range of about 15 minutes to 10 hours. Since the liquid temperature of the dispersion liquid tends to increase due to the ultrasonic dispersion operation, it is desirable that the apparatus to be subjected to the ultrasonic dispersion operation be placed under cooling. [Effect of the Invention] In preparing a filler dispersion from a mixture obtained by mixing a low-viscosity organic dispersion medium with a low-concentration particulate inorganic filler, the mixture was subjected to a mechanical dispersion operation according to the present invention in advance. Thereafter, by performing a two-stage dispersing operation including further performing an ultrasonic dispersing operation, it is possible to easily obtain a dispersion liquid in which uniform dispersion and reduction of aggregates are achieved. [Examples and Comparative Examples] [Example 1] 1140 g of dimethylacetamide (viscosity at 25 ° C: 0.92 centipoise) and 12 g of a polycarboxylic acid-based dispersant were placed in a container having a capacity of 2, and the rotation speed was 8,000 rpm using a homomixer. For 30 seconds. Further, 48 g of titanium dioxide having a primary particle size of 0.03 μm was added, and the mixture was preliminarily dispersed by stirring with a homomixer at a rotation speed of 8000 rpm for 15 minutes. The average particle diameter of titanium dioxide in the preliminary dispersion was 0.35 μm. Next, 100 ml of the above pre-dispersion liquid was dispensed into a 200-ml Erlenmeyer flask, and dispersed for 1 hour using an ultrasonic dispersing apparatus (an ultrasonic cleaner and an ultracleaner manufactured by Branson). The average particle diameter of titanium dioxide in the obtained dispersion (centrifugal sedimentation type particle size distribution analyzer CAPA manufactured by Horiba, Ltd.)
-500, the same applies hereinafter) was 0.18 μm. [Comparative Example 1] 1140 g of dimethylacetamide and 12 g of a polycarboxylic acid-based dispersant were placed in a container having a capacity of 2, and stirred at a rotation speed of 8000 rpm for 30 seconds using a homomixer. Further, 48 g of titanium dioxide having a primary particle diameter of 0.03 μm was added, and the mixture was dispersed with a homomixer at a rotation speed of 8000 rpm for 2 hours. The average particle size of the particles in the obtained dispersion was 0.32 μm. The dispersion was colored gray due to impeller abrasion powder. Comparative Example 2 Dimethylacetamide 9 was placed in a 200 ml Erlenmeyer flask.
After mixing 5 g and 1 g of the polycarboxylic acid-based dispersant, 4 g of titanium dioxide having a primary particle size of 0.03 μm was added, and the mixture was dispersed for 1 hour using an ultrasonic cleaner. The oxidized average particle diameter in the obtained dispersion was 0.25 μm. [Comparative Example 3] 1140 g of dimethylacetamide and 12 g of a polycarboxylic acid-based dispersant were placed in a container having a capacity of 2 L, and mixed with a homomixer.
The mixture was stirred at a rotation speed of 000 rpm for 30 seconds. The resulting solution 100m
L was transferred to a beaker with a capacity of 300 mL, and the primary particle size was 0.03
After adding 4 g of titanium dioxide having a particle diameter of 4 μm, the same ultrasonic dispersing treatment as in Example 1 was carried out, and a homomixer was used.
The mixture was stirred at a rotation speed of 00 rpm for 15 minutes. The average particle diameter of the particles in the obtained dispersion was 0.25 μm. [Comparative Example 4] 1140 g of dimethylacetamide and 12 g of a polycarboxylic acid-based dispersant were placed in a container having a capacity of 2 L, and mixed with a homomixer.
The mixture was stirred at a rotation speed of 000 rpm for 30 seconds. The resulting solution 100m
L was transferred to a beaker with a capacity of 300 mL, and the primary particle size was 0.03
After adding 4 g of titanium dioxide of μm, the mixture was subjected to an ultrasonic dispersion treatment for 1 hour in the same manner as in Example 1, and then stirred at 8000 rpm for 15 minutes using a homomixer. The average particle size of the particles in the obtained dispersion was 0.28 μm. [Example 2] Preliminary dispersion was performed in the same manner as in Example 1 except that 1092 g of dimethylacetamide, 12 g of a polycarboxylic acid-based dispersant, and 96 g of titanium dioxide having a primary particle diameter of 0.03 µm were used. Prepare a container with a depth of 10 mm attached to the ultrasonic transducer,
The preliminary dispersion was dispersed for 4.5 hours using an ultrasonic disperser capable of continuously passing the preliminary dispersion while circulating in the container. The average particle diameter of titanium dioxide in the obtained dispersion is 0.08
μm, and particles having a particle size of 0.2 μm or less are mostly (99
%)Met.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yoshikazu Sasaki               3-10 Nakamiyakitamachi, Hirakata Ube Industries               Inside the company Hirakata Laboratory                (56) References JP-A-59-91123 (JP, A)                 JP-A-61-37816 (JP, A)                 JP-A-56-55424 (JP, A)                 JP-A-60-223639 (JP, A)                 Japanese Patent Publication No. 59-1415 (JP, B2)

Claims (1)

(57) [Claims] It was obtained by mixing an organic dispersion medium having a viscosity in the range of 0.1 to 10 centipoise and an agglomerated particulate inorganic filler having a primary particle size of 20% by weight or less based on the organic dispersion medium and 0.1 μm or less. A method for producing a particulate inorganic filler dispersion, comprising: before preparing a filler dispersion from a mixture, subjecting the mixture to a mechanical dispersion operation using a rotor in advance, and further performing an ultrasonic dispersion operation. 2. 2. The method for producing a particulate inorganic filler dispersion according to claim 1, wherein the amount of the aggregated particulate inorganic filler mixed is in the range of 1 to 10% by weight based on the organic dispersion medium. 3. 2. The method for producing a particulate inorganic filler dispersion according to claim 1, wherein the particulate inorganic filler is a particulate titanium dioxide powder, a silicon oxide powder, an alumina powder or a magnesium oxide powder. 4. The method for producing a particulate inorganic filler dispersion according to claim 1, wherein the organic dispersion medium is an amide solvent. 5. The organic dispersion medium is N, N-dimethylformamide, N, N
The method for producing a particulate inorganic filler dispersion according to claim 1, wherein the dispersion is -dimethylacetamide or N-methylpyrrolidone.