JP2012131682A - Aluminum hydroxide fine particle and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aluminum hydroxide fine particles and a method for producing the same for securing a sufficient filling amount and obtaining aluminum hydroxide mixture powder excellent in heat resistance.SOLUTION: In the aluminum hydroxide fine particles: an amount of NaO is 0.15 wt% or less; an average particle size Dis 0.5-2.0 μm; and a particle size distribution satisfies the following expression 0.2≤(log(D/D))/(log(D/D))≤3.8 wherein Dis a particle size giving a cumulative volume 10% from a fine particle portion, Dis a particle size giving a cumulative volume 90% from the fine particle portion, and Dis a mode diameter.

Description

  The present invention relates to fine aluminum hydroxide and a method for producing the same.

  Aluminum hydroxide has been widely used as a filler for filling a resin such as rubber or plastic. In particular, it is used as a flame retardant for imparting flame retardancy in various polymer materials used for electronic parts such as printed boards. Also, in the process of mounting electronic components on this printed circuit board, the solder bath temperature is increased to speed up the line, and reflow soldering technology is introduced for high-density mounting. Laminates have been exposed to higher temperatures than conventional processes. Therefore, the trouble that the aluminum hydroxide in a board | substrate decomposes | disassembles thermally and copper foil peels with the generate | occur | producing vapor | steam has arisen. For this reason, aluminum hydroxide having a low decomposition rate is desired even under conditions where the crystal water is stable up to a high temperature and heated to the decomposition start temperature or higher.

  As aluminum hydroxide used as a flame retardant filler, for example, aluminum hydroxide described in Patent Document 1 and Patent Document 2 is known.

JP 2009-184866 A JP 59-204632 A

  However, conventional fine aluminum hydroxide is not sufficient in terms of heat resistance and filling properties. An object of the present invention is to provide fine aluminum hydroxide capable of ensuring a sufficient filling amount as a filler to be filled in a resin and the like and obtaining an aluminum hydroxide mixed powder excellent in heat resistance characteristics, and a method for producing the same Is to provide.

  As a result of studying to find fine aluminum hydroxide capable of solving the above-mentioned problems, the present inventors have completed the present invention.

That is, the present invention provides the following [1] to [7].
[1] Na ₂ O amount is 0.15 wt% or less, an average particle diameter _{D 50} is at 0.5μm or 2.0μm or less, the particle diameter _{D 10} cumulative volume from the fine portion is 10%, Fine particle aluminum hydroxide satisfying the following formula when the particle diameter D ₉₀ is 90% and the mode diameter is D ₁ from the fine particle portion.
0.2 ≦ (log (D ₁ / D ₁₀ )) / (log (D ₉₀ / D ₁ )) ≦ 3.8
[2] The fine aluminum hydroxide (A) according to the above [1], an amount of Na ₂ O of 0.1% by weight or less, and an average particle diameter D ₅₀ of 5.0 μm or more and 15.0 μm or less Aluminum hydroxide mixture containing aluminum powder (B) and containing fine aluminum hydroxide (A) and aluminum hydroxide powder (B) in a weight ratio (A: B) of 1: 9 to 5: 5 powder.
[3] A resin composition comprising the fine aluminum hydroxide according to [1] and a resin.
[4] A resin composition comprising the aluminum hydroxide mixed powder according to [2] and a resin.
[5] The amount of Na ₂ O is 0.15 wt% or less, the average particle diameter D ₅₀ is 1.0 μm or more and 4.0 μm or less, and the particle size distribution is 1.0 μm or more and 2.0 μm or less and 2.5 μm or more. The maximum frequency in each range of 5 μm or less is 1.0% to 6.0% in the range of 1.0 μm to 2.0 μm, and 2.5 μm to 3.5 μm Production of fine aluminum hydroxide according to [1], including a step of adjusting the particle size of aluminum hydroxide having a maximum volume frequency of 4.0% to 11.0% in the following range using a crusher. Method.
[6] A printed board containing the fine aluminum hydroxide according to [1].
[7] A prepreg comprising the fine aluminum hydroxide according to [1].

  According to the fine aluminum hydroxide of the present invention, it is possible to provide an aluminum hydroxide mixed powder that is excellent in filling into a resin and excellent in heat resistance.

  Hereinafter, the present invention will be described in detail.

The Na content of the fine aluminum hydroxide of the present invention is 0.15% by weight or less, preferably 0.10% by weight or less in terms of Na ₂ O. When the amount of Na ₂ O exceeds 0.15% by weight, fine aluminum hydroxide tends to be dehydrated and heat resistance is lowered. Moreover, the lower limit of the amount of Na ₂ O is not particularly limited, and is preferably as small as possible, but is usually about 0.01% by weight.

The water-soluble soda (hereinafter referred to as S-Na ₂ O) contained in the fine aluminum hydroxide of the present invention is preferably 300 ppm or less, more preferably 150 ppm or less in terms of Na ₂ O. When S-Na ₂ O exceeds 300 ppm, when added to the resin, S-Na ₂ O on the surface of the fine aluminum hydroxide particles may reduce the insulating properties of the resin composition and may cause a decrease in heat resistance. There is.

The average particle diameter D ₅₀ of the fine aluminum hydroxide of the present invention is 0.5 μm or more and 2.0 μm or less, preferably 1.0 μm or more and 1.7 μm or less. In the present invention where the average particle diameter D _50, the particle size distribution curve measured by a laser scattering method, refers to a particle diameter at 50% cumulative volume from fine part. The particle size distribution curve measured by the laser scattering method represents a volume-based frequency distribution with respect to the common logarithm of the particle diameter [log (particle diameter)], and the increment of [log (particle diameter)]. The value (class in the histogram) means herein a particle size distribution measured at 0.038. When the average particle diameter D ₅₀ of fine aluminum hydroxide is smaller than 0.5 μm, the BET specific surface area becomes large and dehydration from the particle surface is likely to occur. The heat resistance of the resulting aluminum hydroxide mixed powder is lowered. On the other hand, when the average particle diameter D ₅₀ exceeds 2.0 μm, the filling property of the aluminum hydroxide mixed powder obtained by mixing with the aluminum hydroxide powder decreases.

The fine particle aluminum hydroxide of the present invention has a particle size distribution satisfying 0.2 ≦ (log (D ₁ / D ₁₀ )) / (log (D ₉₀ / D ₁ )) ≦ 3.8, preferably 0.4. ≦ (log (D ₁ / D ₁₀ )) / (log (D ₉₀ / D ₁ )) ≦ 3.5 is satisfied. In the above formula, D ₁ represents a mode diameter, and indicates a particle diameter at which the volume frequency of the particle size distribution takes a maximum value. In this specification, when the volume frequency particle diameter showing the maximum value there is more than one, most of the small particle size and mode diameter D _1. D ₁₀ and D ₉₀ are particle diameters of 10% and 90%, respectively, by volume accumulation from the fine particle portion in the particle size distribution curve measured by the laser scattering method. When the particle size distribution satisfies the range of 0.2 ≦ (log (D ₁ / D ₁₀ )) / (log (D ₉₀ / D ₁ )) ≦ 3.8, the particle size distribution takes a value close to a normal distribution. If this range is not satisfied, the gap cannot be filled, and the high filling property is impaired.

The ratio _D 90 _{/ D 10} of _{D 10} and _{D 90} of fine aluminum hydroxide of the present invention is preferably in the range of 2.0 to 10.0, more preferably 2.0 to 8.0 range It is. The value of D ₉₀ / D ₁₀ is an index indicating how wide the particle size distribution has, and the smaller this value, the sharper the particle size distribution. It is preferable that D ₉₀ / D ₁₀ of the fine aluminum hydroxide is in the above-mentioned range because a highly filled aluminum hydroxide mixed powder can be obtained.

The fine aluminum hydroxide of the present invention is a fine aluminum hydroxide (hereinafter referred to as “raw fine aluminum hydroxide”) characterized by a specific amount of Na ₂ O, an average particle diameter, and a maximum volume frequency. Can be produced by adjusting the particle size. As the raw material fine aluminum hydroxide in the present invention, the amount of Na ₂ O is 0.15 wt% or less, the average particle diameter D ₅₀ is 1.0 μm or more and 4.0 μm or less, and the particle size distribution is 1.0 μm or more and 2.0 μm. And maximum frequency in the range of 1.0 μm or more and 2.0 μm or less is 1.0% or more and 6.0% or less, and The maximum volume frequency in the range of 2.5 μm to 3.5 μm is 4.0% to 11.0%. In addition, it is preferable to use fine aluminum hydroxide that has a maximum volume frequency of 2.5 μm or more and 3.5 μm or less and a maximum volume frequency of 1.0 μm or more and 2.0 μm or less.

The amount of Na ₂ O in the raw material fine aluminum hydroxide is 0.15% by weight or less, and preferably 0.10% by weight or less. The lower limit of the amount of Na ₂ O is not particularly limited and is preferably as small as possible, but is usually about 0.01% by weight.

The average particle diameter D ₅₀ of the raw material fine aluminum hydroxide is 1.0 μm or more and 4.0 μm or less, and preferably 1.5 μm or more and 3.5 μm or less. When the average particle diameter D ₅₀ is smaller than 1.0 μm, the average particle diameter D ₅₀ is smaller than 0.5 μm when the particle size is adjusted using a crusher, and the particle size distribution is 0.2 ≦ (log (D ₁ / D ₁₀ )) / (log (D ₉₀ / D ₁ )) ≦ 3.8 There is a possibility that an aluminum hydroxide powder satisfying the formula may not be obtained. On the other hand, when the average particle diameter D ₅₀ is larger than 4.0 μm, the average particle diameter D ₅₀ does not become 2.0 μm or less when the particle size is adjusted using a crusher, and 0.2 ≦ (log (D ₁ / D ₁₀ )) / (log (D ₉₀ / D ₁ )) ≦ 3.8 There is a possibility that an aluminum hydroxide powder satisfying the formula may not be obtained. Thereby, there exists a possibility that the filling property to resin of the aluminum hydroxide mixed powder obtained by mixing with aluminum hydroxide powder may fall.

  Furthermore, the raw material fine aluminum hydroxide has a maximum frequency in the particle size distribution in the range of 1.0 μm to 2.0 μm and 2.5 μm to 3.5 μm. The maximum volume frequency in the range of 1.0 μm or more and 2.0 μm or less is 1.0% or more and 6.0% or less, preferably 2.0% or more and 5.0% or less, and 2.5 μm. The maximum volume frequency in the range of 3.5 μm or less is 4.0% or more and 11.0% or less, preferably 5.0% or more and 10.0% or less. When the maximum volume frequency of the raw material fine aluminum hydroxide at 1.0 μm or more and 2.0 μm or less and 2.5 μm or more and 3.5 μm or less is not within the above range, the raw material fine aluminum hydroxide is crushed using a pulverizer. When performing this, there is a possibility that a desired particle size distribution cannot be obtained. Moreover, it is preferable that the maximum volume frequency in 2.5 micrometer or more and 3.5 micrometers or less of raw material aluminum hydroxide is more than the maximum volume frequency in 1.0 micrometer or more and 2.0 micrometers or less.

Although the manufacturing method of the raw material fine particle aluminum hydroxide used in this invention is not specifically limited, It is preferable to manufacture by a buyer method. Specifically, it can be produced by adding seed aluminum hydroxide to a supersaturated sodium aluminate solution and depositing it.
Specifically, neutralized gel obtained by mixing a supersaturated sodium aluminate solution and an acid as seed aluminum hydroxide was added to a heated supersaturated sodium aluminate solution with stirring, and the sodium aluminate solution was added. By hydrolyzing, it can be obtained as a slurry containing raw material fine aluminum hydroxide. By using the neutralized gel, it is possible to produce fine aluminum hydroxide having a fine particle size and having a predetermined double peak as described above. When the average particle diameter of the raw material fine aluminum hydroxide is smaller than 1.0 μm, it can be produced by gradually adding a supersaturated sodium aluminate solution to the slurry to increase the particle diameter.

As the acid to be added to the supersaturated sodium aluminate solution, hydrochloric acid, sulfuric acid, nitric acid, an aluminum chloride aqueous solution, an aluminum sulfate aqueous solution or the like can be used, and preferably an aluminum-containing acidic aqueous solution such as an aluminum sulfate aqueous solution can be used. The amount of acid added (W) to the supersaturated sodium aluminate solution is the neutralization molar ratio (= W) expressed as the ratio of the amount of acid used to completely neutralize the sodium aluminate solution (W ₀ ). / W ₀ ), which is about 0.3 to 0.7.

The concentration of Na ₂ O in the sodium aluminate solution is preferably 100 g / l or more and 170 g / l or less, and more preferably 120 g / l or more and 160 g / l or less. Further, the Al ₂ O ₃ concentration in the sodium aluminate solution is preferably 100 g / l or more and 170 g / l or less, and more preferably 130 g / l or more and 160 g / l or less.

Further, the amount of the neutralizing gel added to the sodium aluminate solution is preferably 1.0% by weight or more and 4.0% by weight or less in terms of Al ₂ O _{3 with} respect to the amount of aluminum in the sodium aluminate solution. Preferably they are 2.0 weight% or more and 3.0 weight% or less.

  The heating temperature of the sodium aluminate solution when adding the neutralizing gel is preferably 50 ° C. or higher and 90 ° C. or lower, more preferably 60 ° C. or higher and 80 ° C. or lower. Further, the neutralization gel is preferably added so that the time from the start of addition to the end of addition is within 30 minutes. If the addition time exceeds 30 minutes, precipitation starts during the addition, and the particle diameter of the resulting aluminum hydroxide may increase.

  The particulate aluminum hydroxide of the present invention can be obtained by adjusting the particle size of the obtained raw material particulate aluminum hydroxide using a crusher.

In the step of producing the fine aluminum hydroxide of the present invention from the slurry containing the raw material fine aluminum hydroxide, the slurry containing the raw fine aluminum hydroxide is adjusted in particle size using a pulverizer, then washed and dried. Alternatively, after solid-liquid separation, washing, and drying, the particle size may be adjusted using a crusher. The crusher is not particularly limited as long as a predetermined fine aluminum hydroxide can be obtained, but is preferably one that can be used under conditions that generate a centrifugal force of 1000 G or more using a continuous centrifugal separator. The particle size adjustment in the present specification is such that D ₅₀ 2 / D ₅₀ 3 is 1.3 or more and 3.0 or less when the average particle size before treatment is D ₅₀ 2 and the average particle size after treatment is D ₅₀ 3. It means adjusting to the range. By using the raw material fine aluminum hydroxide and adjusting the particle size within the above range using a pulverizer, the fine aluminum hydroxide of the present invention having a predetermined Na ₂ O amount, average particle size, and particle size distribution is obtained. Can be manufactured.

  Cleaning of the raw material fine aluminum hydroxide in the present invention can be carried out by repeating the water washing operation of repulping the raw material fine aluminum hydroxide particles after solid-liquid separation with water and then again solid-liquid separating a plurality of times. As the water used for washing, it is preferable to use hot water of 60 to 90 ° C. because the dissolved sodium content adhering to the aluminum hydroxide surface can be efficiently removed.

  The drying of the raw material fine aluminum hydroxide in the present invention is not particularly limited, and can be performed by a commonly used method. When the raw material fine aluminum hydroxide contains 1% by weight or more of water, drying is preferably performed at a temperature range of 100 ° C. or higher and a temperature of the raw material fine aluminum hydroxide surface not exceeding 220 ° C.

By mixing the fine aluminum hydroxide of the present invention with an aluminum hydroxide powder, the increase in viscosity when filling into a resin or the like is ensured to ensure a high filling amount, and the aluminum hydroxide that suppresses a decrease in heat resistance It becomes possible to obtain a mixed powder.
The aluminum hydroxide mixed powder of the present invention is the fine aluminum hydroxide of the present invention, the Na ₂ O amount is 0.1 wt% or less, and the average particle diameter D ₅₀ is in the range of 5.0 μm or more and 15.0 μm or less. And aluminum hydroxide powder.

Na content of an average particle diameter _{D 50} more than 5.0 .mu.m 15.0 .mu.m or less aluminum hydroxide powder contained in the aluminum hydroxide powder mixture of the present invention is 0.1 wt% or less in terms of Na ₂ O Yes, preferably 0.07% by weight or less. When the amount of Na ₂ O of the aluminum hydroxide powder is in the above range, it is preferable when the heat resistance of the mixed powder is suppressed when mixed with the fine aluminum hydroxide of the present invention. Further, the lower limit of the amount of Na ₂ O in the aluminum hydroxide powder is not particularly limited, and is preferably as small as possible, but is usually about 0.01% by weight.

The average particle diameter D ₅₀ of the aluminum hydroxide powder mixed with the fine aluminum hydroxide of the present invention is in the range of 5.0 μm to 15.0 μm, preferably in the range of 7.0 μm to 13.0 μm. . When the average particle diameter D ₅₀ of aluminum hydroxide is smaller than 5.0 μm, the effect of mixing with the fine aluminum hydroxide powder is reduced. That is, the space between the aluminum hydroxide particles having a large particle diameter cannot be sufficiently filled with the fine aluminum hydroxide particles of the present invention, and the high filling property is impaired. On the other hand, the average particle diameter D ₅₀ of aluminum hydroxide and 15.0μm larger, since the coarse particles of aluminum hydroxide powder mixture obtained is increased, is applied to the miniaturization, the printed circuit board or the like thinner is required It becomes difficult.

Fine aluminum hydroxide (A) of the present invention contained in the aluminum hydroxide mixed powder of the present invention, the amount of Na ₂ O is 0.1% by weight or less, and the average particle diameter D ₅₀ is 5.0 μm. The weight ratio of the aluminum hydroxide powder (referred to as B) in the range of 15.0 μm or less is such that A: B is in the range of 1: 9 to 5: 5, preferably 2: 8 to 4: 6. is there. When the mixing ratio of A to B is lower than 1: 9 by weight, the amount of fine aluminum hydroxide in the obtained aluminum hydroxide mixed powder is reduced, and the filling property of the aluminum hydroxide mixed powder into the resin is reduced. descend. On the other hand, when the mixing ratio of A to B is higher than 5: 5 by weight, the amount of fine aluminum hydroxide in the obtained aluminum hydroxide mixed powder increases, and the aluminum hydroxide mixed powder is filled into the resin. Not only lowers the heat resistance but also causes a decrease in heat resistance.

  There is no restriction | limiting in particular about the mixing method of a particulate aluminum hydroxide and aluminum hydroxide powder, For example, conventional methods, such as an air blender and a V-type blender, are applicable.

  The finely divided aluminum hydroxide and aluminum hydroxide mixed powder of the present invention can be used as a filler for filling a resin or the like. Examples of this resin include thermoplastic resins such as rubber and polypropylene, and thermosetting resins such as epoxy resins and phenol resins. Among these resins, epoxy resins, phenol resins, and the like that are used for printed boards that require high flame resistance and heat resistance, and prepregs that constitute the printed boards are suitable.

  The resin composition containing the fine aluminum hydroxide or aluminum hydroxide mixed powder of the present invention can be produced by, for example, a method of filling the resin with the fine aluminum hydroxide or aluminum hydroxide mixed powder of the present invention. . The filling method is not particularly limited, and can be appropriately selected according to the type of resin. For example, in the case of mixing with a thermoplastic resin, the resin and the fine aluminum hydroxide or aluminum hydroxide mixed powder of the present invention are mixed at a temperature lower than the melting temperature, and then charged into a kneader to melt the resin. The method of mixing etc. is mentioned. Kneading can be performed using a plast mill, a Banbury mixer, a single-screw or twin-screw extruder, and the like. In addition, when filling the thermosetting resin, the fine aluminum hydroxide or aluminum hydroxide mixed powder of the present invention is mixed below the curing temperature together with the thermosetting resin, the curing agent, the curing accelerator, the solvent, and the like. And the like.

  The compounding amount of the fine aluminum hydroxide or aluminum hydroxide mixed powder of the present invention with respect to the resin is appropriately determined according to the type of resin used and the required degree of flame retardancy. The amount is about 10 to 400 parts by weight, preferably about 50 to 200 parts by weight with respect to 100 parts by weight of the resin. If the blending amount is too small, it may not be possible to give a sufficient flame retardant effect to the resin. On the other hand, if it is too large, the strength of the molded product may be reduced or kneading may not be possible. There is sex.

  Since the fine aluminum hydroxide of the present invention is excellent in heat resistance, it can be suitably used for printed boards that require high flame retardancy and heat resistance, prepregs constituting the same, and the like. The prepreg containing the fine aluminum hydroxide of the present invention is, for example, after the resin composition containing the fine aluminum hydroxide of the present invention is impregnated or applied to a substrate such as glass cloth, aramid cloth, paper, or glass nonwoven fabric. It can be produced by semi-curing by a method of heating in a dryer. In addition, a plurality of the prepregs are stacked and pressed, and heat-cured to form a laminated board. A circuit is formed on the laminated board, and various electronic components are connected by soldering. Can be manufactured.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(1) Average particle diameter measurement The average particle diameter was measured using a laser scattering type particle size distribution measuring apparatus ["MICROTRACK HRA X-100" manufactured by Nikkiso Co., Ltd.].
The sample was added to a 0.2 wt% sodium hexametaphosphate aqueous solution, adjusted to a measurable concentration, and then irradiated with ultrasonic waves having an output of 40 W for 5 minutes. Then, it measured by the number of samples 2, and calculated | required the particle diameter and the particle diameter distribution curve from the average value. The refractive index of aluminum hydroxide particles at this time was measured using 1.57. With this particle size distribution curve, to obtain an average particle diameter D ₅₀ as particle diameter corresponding 50% by volume. Similarly, the particle diameter D ₉₀ of the cumulative volume from the fine portion is the particle diameter D _10, 90% of the 10%, was calculated from the particle size distribution curve. In the particle diameter distribution curve, the mode diameter D ₁ which is the particle diameter at which the volume frequency has the maximum value (when there are two or more particle diameters at which the volume frequency has the maximum value, the smallest particle diameter is the mode diameter D _1. The particle diameter Da showing the maximum frequency in the range of 1.0 to 2.0 μm and the particle diameter Db showing the maximum frequency in the range of 2.5 to 3.5 μm are expressed as [log (Particle size)] was determined from the value when the step width was 0.038.

(2) Weight reduction temperature measurement It measured using the differential thermogravimetric analyzer [Thermo Plus EVO TG8120 "by Rigaku.
The sample amount is about 10 mg, the air flow rate is 100 ml / min, the temperature is increased from room temperature to 100 ° C. at a rate of temperature increase of 10 ° C./min, and once held at 100 ° C. for 10 minutes, the temperature is increased to 400 ° C. The change in weight was measured, and the temperature at which the weight loss from 100 ° C. was 1.0% by weight was calculated.
The higher the weight reduction temperature, the higher the heat resistance of the resulting aluminum hydroxide.

(3) DOP oil absorption measurement In the method prescribed | regulated to JIS-K5101-13-1, it measured using dioctyl phthalate (henceforth, DOP). The DOP oil absorption is an index indicating the filling property to the resin, and the smaller the DOP oil absorption amount, the better the filling property to the resin, and it is possible to fill the resin per unit volume with more fine aluminum hydroxide. Means.

[Production of fine aluminum hydroxide powder]
Fine aluminum hydroxides A to E were prepared as follows.

[Aluminum hydroxide A]
Neutralization of supersaturated sodium aluminate solution (Na ₂ O concentration in the liquid: 139 g / L, Al ₂ O ₃ concentration: 145 g / L) with stirring while adding aluminum sulfate with an Al ₂ O ₃ concentration of 8 wt% A gel (as seed aluminum hydroxide) was obtained. Thereafter, the neutralized gel was added to a sodium aluminate solution having a Na ₂ O concentration of 139 g / L and an Al ₂ O ₃ concentration of 145 g / L held at 70 ° C., with stirring, with respect to the amount of aluminum in the sodium aluminate solution. al ₂ O ₃ in terms of added so that 2.0 wt%, and stirred for 72 hours.

Thereafter, the temperature was lowered to 55 ° C. over 48 hours, the amount of Na ₂ O was 0.08 wt%, the average particle diameter D ₅₀ was 2.1 μm, and 1.0 μm or more and 2.0 μm or less and 2.5 μm or more. When the maximum frequency in each range of 5 μm or less has the maximum frequency, and the particle diameters of the maximum frequency in this range are Da and Db, Da is 1.2 μm, Db is 2.8 μm, and the volume frequency of Da is 3 9.9%, Db volume frequency 7.5%, D ₁₀ 0.9 μm, D ₉₀ 3.6 μm, BET specific surface area 3.7 m ² / g aluminum hydroxide 121 g as solid content concentration An aluminum hydroxide slurry was obtained, which was contained in / L, and had a Na ₂ O concentration of 138 g / L and an Al ₂ O ₃ concentration of 65 g / L.

  The obtained aluminum hydroxide slurry was subjected to solid-liquid separation with a screw decanter (“P-660” manufactured by Sakai Kogyo Co., Ltd.), and the same volume as the aluminum hydroxide slurry before solid-liquid separation was obtained in the obtained aluminum hydroxide cake. Then, warm water was added so that the solid-liquid separation was performed again using a screw decanter.

  This operation was repeated, and solid-liquid separation and washing with a screw decanter were performed four times. The screw decanter operating conditions were a centrifugal separation of 5000 rpm, a back drive of 4200 rpm, and a slurry flow rate of 2 L / min. Table 1 shows the transition of the particle size distribution when the screw decanter cleaning is performed.

By solid-liquid separation under the above conditions, aluminum hydroxide having an average particle diameter D ₅₀ of 1.3 μm, D ₁₀ of 0.7 μm, D ₉₀ of 2.2 μm, and mode diameter D ₁ of 1.3 μm is contained. An aluminum hydroxide cake was obtained. After the cake was dried at 120 ° C., the obtained dry powder was treated with a free crusher (“M-3” manufactured by Nara Machinery Co., Ltd.) to obtain fine aluminum hydroxide A. Table 2 shows the physical properties of the obtained fine aluminum hydroxide A.

[Aluminum hydroxide B]
Commercially available aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., trade name CL-310) was used. Table 2 shows the physical properties of aluminum hydroxide B.

[Aluminum hydroxide C]
Commercially available aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., trade name C-301) was used. Table 2 shows the physical properties of aluminum hydroxide C.

[Aluminum hydroxide D]
While stirring a supersaturated sodium aluminate solution (Na ₂ O concentration in the liquid: 140 g / L, Al ₂ O ₃ concentration: 145 g / L), aluminum sulfate having an Al ₂ O ₃ concentration of 8% by weight was added to the neutralized gel. After that, the neutralized gel was added to a sodium aluminate solution having a Na ₂ O concentration of 140 g / L and an Al ₂ O ₃ concentration of 145 g / L held at 55 ° C., with stirring, with respect to the amount of aluminum in the solution. al ₂ O ₃ was added in an amount of 0.5 wt% in terms of stirring was carried out for 72 hours. Thereafter, this aluminum hydroxide slurry is filtered, washed with warm water, dried at 120 ° C., and then the obtained dry powder is treated with a rotor speed mill (“P-14” manufactured by Fritsch) to obtain water. Aluminum oxide D was obtained. Table 2 shows the physical properties of the obtained aluminum hydroxide D.

[Aluminum hydroxide E]
In the method for producing aluminum hydroxide A, an aluminum hydroxide slurry was obtained, and the aluminum hydroxide slurry before solid-liquid separation with a screw decanter was pulverized using an apex mill ("AM-1" manufactured by Kotobuki Giken Kogyo Co., Ltd.). . Thereafter, the ground aluminum hydroxide slurry is kept at 55 ° C. for 48 hours, followed by solid-liquid separation by filtration, the obtained cake is washed with warm water, dried at 120 ° C., and the obtained dry powder. The body was treated with a rotor speed mill ("P-14" manufactured by Fritsch) to obtain aluminum hydroxide E. Table 2 shows the physical properties of the obtained aluminum hydroxide E.

Example 1 and Comparative Example 1-3
[Preparation of aluminum hydroxide mixed powder]
Aluminum hydroxides A, B, C, D, and E were combined as shown in Table 3, mixed at a predetermined weight ratio, and then mixed for 10 minutes by shaking to obtain an aluminum hydroxide mixed powder. .

  Table 4 shows the 1.0 wt% weight loss temperature and DOP oil absorption of the obtained aluminum hydroxide mixed powder.

  As shown in Table 4, by mixing the fine aluminum hydroxide of the present invention, an aluminum hydroxide mixed powder having high heat resistance and high filling properties was obtained.

  The aluminum hydroxide mixed powder of the present invention is suitable for various fillers to be filled in a resin and the like, for example, a flame retardant filler when forming a printed circuit board, a semiconductor sealing material, and other electrical members, a kitchen counter, a bathtub, Heat dissipation when forming artificial marble filler when forming a washstand, etc., heat dissipation sheet that dissipates glass substrates that form flat panel displays such as PDP, heat dissipation sheet for IC chips, sealing materials for electrical components, etc. It can be used as various fillers including fillers. Especially, it uses suitably for the use as which a high filling and high heat resistance are desired like a flame-retardant filler.

Claims (7)

From the fine particle part, the particle diameter D ₁₀ having an Na ₂ O amount of 0.15 wt% or less, an average particle diameter D ₅₀ of 0.5 μm or more and 2.0 μm or less, and a volume accumulation from the fine particle part of 10%. A particulate aluminum hydroxide satisfying the following formula when the particle diameter D ₉₀ is 90% and the mode diameter is D ₁ .
0.2 ≦ (log (D ₁ / D ₁₀ )) / (log (D ₉₀ / D ₁ )) ≦ 3.8 A fine aluminum hydroxide (A) according to claim 1, Na ₂ O amount is 0.1 wt% or less, and the average particle diameter _{D 50} is less than 15.0μm or 5.0μm aluminum hydroxide powder ( An aluminum hydroxide mixed powder containing B) and containing fine aluminum hydroxide (A) and aluminum hydroxide powder (B) in a weight ratio (A: B) of from 1: 9 to 5: 5.   A resin composition comprising the fine aluminum hydroxide according to claim 1 and a resin.   A resin composition comprising the aluminum hydroxide mixed powder according to claim 2 and a resin. The amount of Na ₂ O is 0.15 wt% or less, the average particle diameter D ₅₀ is 1.0 μm or more and 4.0 μm or less, and the particle size distribution is 1.0 μm or more and 2.0 μm or less and 2.5 μm or more and 3.0 μm or less. Each range has a maximum frequency, and the maximum volume frequency in the range of 1.0 μm to 2.0 μm is 1.0% to 6.0%, and the range of 2.5 μm to 3.5 μm The manufacturing method of the fine-grain aluminum hydroxide of Claim 1 including the process of adjusting a particle size using the crusher for the aluminum hydroxide whose maximum volume frequency in this is 4.0% or more and 11.0% or less.   A printed circuit board comprising the particulate aluminum hydroxide according to claim 1.   A prepreg comprising the fine aluminum hydroxide according to claim 1.