JP6679477B2 - Method for producing heat-resistant aluminum hydroxide - Google Patents

Description

This patent application claims priority under the Paris Convention with respect to Japanese Patent Application No. 2014-110909, which is incorporated herein by reference in its entirety.
The present invention relates to a method for producing heat-resistant aluminum hydroxide and heat-resistant aluminum hydroxide.

  Gibbsite type aluminum hydroxide utilizes the reaction of water contained in crystals to dehydrate when heated, making it difficult to use for various polymer materials used in electronic components such as printed wiring boards, wire coating materials, and insulating materials. It is used as a flame retardant. On the other hand, gibbsite type aluminum hydroxide starts dehydration at around 230 ° C., but this dehydration region corresponds to a processing temperature range depending on the type of resin, and thus it may be difficult to use as a flame retardant. .

It is known that the dehydration of gibbsite type aluminum hydroxide, which occurs when gradually heated in an air atmosphere, is caused by the following two factors.
(1) Al ₂ O ₃ · 3H ₂ O ⇒ Al ₂ O ₃ · H ₂ O + 2H ₂ O
_{(2) Al 2 O 3 ·} 3H 2 O ⇒ Al 2 O 3 + 3H 2 O
(1) is dehydration when producing boehmite which is a monohydrate from gibbsite type aluminum hydroxide, and (2) is dehydration when producing alumina from gibbsite type aluminum hydroxide. Generally, the dehydration of (1) is likely to occur from the low temperature side (about 220 ° C), and the (2) is started simultaneously with (1) or from the high temperature side (about 230 ° C). For this reason, in order to improve the heat resistance of gibbsite type aluminum hydroxide, heat treatment is performed under various conditions, and the dehydration of (1) and the dehydration of (2) that occur on the low temperature side are partially advanced. It has been done.

For example, in Patent Document 1, aluminum hydroxide having an average particle diameter of 0.3 to 4.5 μm is partially dehydrated in advance by heat treatment, and Al ₂ O ₃ .nH ₂ O (where n is water). It is described that it is possible to obtain aluminum hydroxide having excellent heat resistance, which is represented by the number of Japanese water).

  Patent Document 2 discloses a method in which aluminum hydroxide particles are subjected to a heat treatment at 230 to 270 ° C. in an air atmosphere to generate χ-alumina to improve heat resistance. Further, the example of Patent Document 2 describes that aluminum hydroxide was heat-treated in an air atmosphere at 260 ° C. for a residence time of 30 minutes using a disk dryer.

  On the other hand, the resin is often processed even in a temperature range that is difficult to achieve by improving the heat resistance only by heat treatment. Therefore, as a method for further improving heat resistance, heat treatment using various additives has been proposed.

  For example, in Patent Document 3, aluminum hydroxide is mixed with a reaction retarder that delays boehmite formation, and by hydrothermal treatment in a pressure vessel or pressurization / heating in a steam atmosphere, the boehmite is completely converted into the original boehmite. It is described that the heat history can be imparted while suppressing the boehmite formation to only a part while the environment undergoes the phase transition, and the heat resistance of aluminum hydroxide is improved.

  In Patent Document 4, aluminum hydroxide particles are subjected to a heat treatment at 200 ° C. to 270 ° C. in a gas atmosphere containing fluorine, or aluminum hydroxide particles are treated with a solution containing a fluorine ion to form particles. It describes a method of performing a heat treatment at 200 ° C. to 270 ° C. after substituting a part of the hydroxyl groups with fluorine.

JP 2002-219918 A JP, 2011-84431, A International Publication 2004/080897 pamphlet JP, 2013-10665, A

  However, in the method of Patent Document 3, pressurization is required, and heat treatment needs to be performed in an expensive pressure vessel.

  Further, in the method of Patent Document 4, since harmful fluorine gas or a solution containing fluorine ions is generated as waste, there is a problem of safety, and it is necessary to treat the waste.

  Therefore, it has been difficult to produce heat-resistant aluminum hydroxide with the conventional method safely and with high productivity.

  The present invention has been made to solve the above problems, and relates to a method for producing heat resistant aluminum hydroxide with high productivity without generating harmful exhaust gas or waste liquid.

That is, the present invention includes the following preferred modes.
[1] 100 parts by weight of gibbsite type aluminum hydroxide powder and 0.05 parts by weight or more and 5 parts by weight or less of aluminum fluoride powder having a BET specific surface area of 10 m ² / g or more and 300 m ² / g or less are mixed to form a mixture. The step of obtaining
A method for producing heat-resistant aluminum hydroxide, comprising the step of subjecting the mixture to a heat treatment at a temperature of 180 ° C. or higher and 300 ° C. or lower under a pressure of atmospheric pressure or higher and 0.3 MPa or lower.
[2] The method according to [1], wherein the heat treatment is performed in an atmosphere having a water vapor mole fraction of 0.03 or more and 1 or less.
[3] The method according to [1] or [2] above, wherein the heat treatment time is 1 minute or longer and 360 minutes or shorter.
[4] The method according to any one of [1] to [3] above, wherein the gibbsite type aluminum hydroxide powder is manufactured by the Bayer method.
[5] The method according to any one of [1] to [4] above, wherein the gibbsite type aluminum hydroxide powder has an average particle size of 0.5 μm or more and 10 μm or less.
[6] To a mixed powder of a gibbsite type aluminum hydroxide powder and an aluminum fluoride powder, 0.1 part by weight or more and 5 parts by weight or less of a silicon compound in terms of SiO ₂ is added and heat treatment is performed. The method according to any one of 1] to [5].
[7] The method according to [6] above, wherein the silicon compound is a silicate monomer represented by the following composition formula or a polymer thereof, or a hydrolysis product or a condensation product thereof.
Si (OR) ₄
[In the formula, R represents an alkyl group having 1 to 2 carbon atoms]
[8] A heat-resistant aluminum hydroxide produced by the method according to any one of [1] to [7].
[9] A heat-resistant aluminum hydroxide having a peak top of F1s binding energy measured by X-ray photoelectron spectroscopy of 684.0 eV or more and 685.5 eV or less and a boehmite content of 3% or more and 15% or less.
[10] The heat-resistant aluminum hydroxide according to the above [9], wherein the dehydration start temperature is 245 ° C. or higher and the dehydration amount is 27% or higher and 30% or lower.
[11] The heat-resistant aluminum hydroxide according to the above [9] or [10], which has a BET specific surface area of 0.5 m ² / g or more and 8.0 m ² / g or less.
[12] A resin composition containing the heat-resistant aluminum hydroxide according to any one of [8] to [11].

  According to the method of the present invention, in the step of heat treatment at 300 ° C. or lower, by using aluminum fluoride that can stably exist without generating fluorine gas as an additive, the heat-resistant hydroxylation that can withstand the processing temperature of the resin. Aluminum can be manufactured safely and with high productivity.

  Hereinafter, embodiments of the present invention will be described in detail.

The method for producing heat-resistant aluminum hydroxide of the present invention (hereinafter, also referred to as “method of the present invention”) comprises 100 parts by weight of gibbsite type aluminum hydroxide powder and a BET specific surface area of 10 m ² / g or more and 300 m ² / or less. Mixing 0.05 part by weight or more and 5 parts by weight or less of aluminum fluoride powder to obtain a mixture, and heat-treating the mixture at a temperature of 180 ° C. or more and 300 ° C. or less under a pressure of atmospheric pressure or more and 0.3 MPa or less. Including steps.

The aluminum fluoride powder used in the present invention is preferably an anhydride represented by AlF ₃ . A hydrate may be used, but in that case, it is necessary to convert the added amount as an anhydride so that the converted value satisfies the above range. Aluminum fluoride powder does not generate fluorine gas at atmospheric pressure at least at 300 ° C. or lower. Further, the solubility in water is 0.6 g / 100 mL or less, and the solubility is low. Furthermore, aluminum fluoride dissolved in water forms stable fluoroaluminate ions and does not decompose at room temperature.

  The aluminum fluoride powder generally contains impurities such as alkali metals and alkaline earth metals, but preferably has a purity of 90% or more, more preferably 99% or more. When a large amount of impurities such as alkali metals and alkaline earth metals are contained, the impurities may accelerate the dehydration of the aluminum hydroxide powder and reduce the heat resistance.

  In the present invention, the aluminum fluoride powder is preferably crushed before use. By pulverizing, the activity of aluminum fluoride can be increased, and the heat resistance of the obtained aluminum hydroxide can be further improved. The pulverization method is not particularly limited, and either dry or wet treatment methods can be used.

  Specific examples of the pulverizing method include, but are not limited to, a method of causing the target particles and the pulverizing medium to collide with each other using a ball mill, a bead mill, or the like, and a method of causing the particles to collide with each other using a jet mill or the like.

  The average particle diameter of the aluminum fluoride powder is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.05 μm or more and 1 μm or less. In the present invention, the average particle size refers to a particle size of 50% on a volume basis in a particle size distribution measured by a laser scattering method. If the average particle size is too small, the aluminum fluoride powder is strongly aggregated and becomes difficult to disperse when mixed with the gibbsite powder. If the average particle size is too large, surface contact is reduced when mixed with gibbsite powder, and it becomes difficult to improve heat resistance.

The BET specific surface area of the aluminum fluoride powder, ^{10 m} 2 / g or more 300 meters ² / less, preferably, ^{20 m} 2 / g or more 200 meters ² / g or less, more preferably ^{30 m} 2 / g or more 100 m ² / g or less, more preferably Is 35 m ² / g or more and 70 m ² / g or less. If the BET specific surface area is too small, it may be necessary to mix a large amount of aluminum fluoride powder in order to secure a contact area with the gibbsite type aluminum hydroxide powder. If the BET specific surface area is too large, the amount of water adsorbed on the surface of aluminum fluoride increases, and water may be released and bubbles may be generated when blended with the polymer material.

  The mixing amount of the aluminum fluoride powder is 0.05 parts by weight or more and 5 parts by weight or less, preferably 0.1 parts by weight or more and 3 parts by weight or less, and more preferably 100 parts by weight of the gibbsite type aluminum hydroxide powder. It is 1 part by weight or less. If the mixing amount is too small, it may be difficult to secure the contact area between the gibbsite type aluminum hydroxide and the aluminum fluoride surface. If the mixing amount is too large, the proportion of the gibbsite powder in the mixed powder decreases, and the flame retardancy may decrease when blended with the polymer material.

The gibbsite type aluminum hydroxide powder to be mixed with the aluminum fluoride powder in the method of the present invention is generally produced by the Bayer method. The Bayer method is a method in which a supersaturated sodium aluminate aqueous solution is produced, and seeds are added to the aqueous solution to precipitate the aluminum component contained in the aqueous solution. The obtained slurry is washed and dried to precipitate. A powder of the product is obtained. The obtained powder has a crystal structure of gibbsite type aluminum hydroxide represented by the formula of Al (OH) ₃ or Al ₂ O ₃ .3H ₂ O. The gibbsite type aluminum hydroxide used as a raw material can be introduced not only in powder form but also in a cake or water slurry containing water into a heat treatment facility to continuously perform drying and heat treatment.

  The gibbsite type aluminum hydroxide powder preferably has an average particle size of 0.5 μm or more and 10 μm or less, more preferably 1.0 μm or more and 7.0 μm or less. If the average particle size of the gibbsite type aluminum hydroxide powder is larger than 10 μm, the flame retardancy when filled with resin will not be sufficiently improved, and the smoothness of the surface will be improved when used as a wire coating material or printed circuit board. Tends to get worse. On the other hand, when it is less than 0.5 μm, the viscosity of the resin when it is filled becomes high, and it tends to be difficult to produce a resin composition. Further, since the surface area becomes large, the amount of moisture adsorbed from the atmosphere after the heat treatment increases, and not only the insulating property of the resin composition when it is filled into the resin is lowered, but also this slight amount of moisture fills the resin. Desorption may occur at the processing temperature to be performed, which may lead to poor appearance.

  The method for mixing the gibbsite type aluminum hydroxide powder and the aluminum fluoride powder is not particularly limited, and any of dry and wet treatment methods can be used.

As the dry treatment method, for example, a method of mixing in a Henschel mixer or a Loedige mixer, and a method of throwing a mixture of a gibbsite type aluminum hydroxide powder and an aluminum fluoride powder into a pulverizer and pulverizing for further uniform mixing And so on.
Examples of the wet treatment method include a method in which aluminum fluoride powder is dispersed in a liquid, the obtained aluminum fluoride slurry is sprayed on gibbsite type aluminum hydroxide powder, and the obtained wet cake is dried. The liquid serving as the dispersion medium is not particularly limited, but water that can be easily removed by drying is preferable.

  The pressure when performing the heat treatment is not less than atmospheric pressure and not more than 0.3 MPa. If the pressure during heating is high, the transition to boehmite may proceed, so it is preferable that the pressure be as low as possible. Therefore, the pressure is 0.3 MPa or less, preferably 0.2 MPa or less.

  The temperature for the heat treatment is 180 ° C. or higher and 300 ° C. or lower, preferably 200 ° C. or higher and 280 ° C. or lower, and more preferably 220 ° C. or higher and 260 ° C. or lower. By heating under this temperature condition, the temperature of the powder which is a mixture is raised to 180 ° C. or higher and 300 ° C. or lower. When the heat treatment temperature is less than 180 ° C., there is a limit to improvement in heat resistance even if heat treatment is performed for a long time. On the other hand, when the temperature exceeds 300 ° C., dehydration to alumina proceeds, which leads to an increase in BET specific surface area and a decrease in heat resistance, and at the same time, the flame retardancy decreases when compounded with a polymer material.

The atmosphere in which the heat treatment is performed is not particularly limited, but the heat treatment is preferably performed under an inert gas. Examples of the inert gas include air and nitrogen. Particularly preferred is air.
The atmosphere for heat treatment is preferably an inert gas atmosphere with a water vapor mole fraction of 0.03 or more and 1 or less, preferably 0.1 or more, more preferably 0.2 or more, The heat resistance can be further improved. When the water vapor mole fraction is 1, heat treatment is performed in 100% water vapor. The water vapor mole fraction may be 0.03 or more after the powder temperature of the gibbsite type aluminum hydroxide reaches 180 ° C. or more, or before the heating. By setting the water vapor mole fraction to 0.03 or more, dehydration of gibbsite type aluminum hydroxide particles to alumina can be suppressed, and an increase in BET specific surface area can be prevented.

  The water vapor mole fraction is calculated from the formula of (molar concentration of water vapor) / [(molar concentration of water vapor) + (molar concentration of inert gas)], and the volume of water vapor and inert gas supplied at a predetermined heat treatment temperature and It can be calculated from the molecular weights of water and inert gas. When air is used as the inert gas, the molecular weight is 29.

  As a method for adjusting the water vapor mole fraction, a known method may be used. For example, a method in which steam heated to 100 ° C. or higher is mixed with hot air to be introduced into the apparatus, or water is continuously introduced in a liquid state into the heating apparatus and dried while being evaporated in the heating apparatus. And a method of mixing in a device.

  The heat treatment time is usually 1 minute or more and 360 minutes or less, preferably 10 minutes or more and 240 minutes or less. Since the optimum time for the heat treatment varies depending on the heating temperature and the water vapor mole fraction, it may be appropriately adjusted.

  The method of the heat treatment is not particularly limited, and for example, the heat treatment can be performed using a hot air dryer or an electric furnace in the case of a stationary type and a rotary kiln or a paddle dryer in the case of a fluid type. In addition, a cake or water slurry obtained by filtering and washing a slurry containing gibbsite type aluminum hydroxide as a raw material is introduced into equipment used in the above heat treatment, and drying and subsequent heat treatment are continuously performed. You can also

  In the heat treatment, sodium may migrate from the inside of the gibbsite type aluminum hydroxide particles to the surface of the particles to become soluble sodium. The presence of soluble sodium on the surface of the particles may react with the aluminum fluoride particles on the surface to produce highly soluble sodium fluoride. The production of sodium fluoride tends to increase the conductivity of the heat-resistant aluminum hydroxide. In applications where insulation is required, it is preferable to suppress the generation of sodium fluoride and reduce the conductivity. In this case, by adding a silicon compound and heat-treating the mixed powder of gibbsite type aluminum hydroxide powder and aluminum fluoride powder, the soluble sodium is captured by the silicon compound, and as a result, the generation of sodium fluoride is suppressed. Therefore, the conductivity can be reduced.

The addition amount of the silicon compound is suitably 0.1 part by weight or more and 5 parts by weight or less, preferably 3 parts by weight or less, in terms of SiO _{2 with} respect to 100 parts by weight of aluminum hydroxide. If the amount is less than 0.1 part by weight, the effect of lowering the conductivity tends to be small. On the other hand, if the amount is more than 5 parts by weight, depending on the type of the silicon compound, it may act as a binder during mixing and form an aggregate.

  The timing of adding the silicon compound is not particularly limited. For example, a method of adding in advance before mixing the gibbsite type aluminum hydroxide powder and the aluminum fluoride powder, or a method of adding simultaneously when mixing the gibbsite type aluminum hydroxide powder and the aluminum fluoride powder are mentioned. In particular, a method of adding a silicon compound later to a mixed powder of gibbsite type aluminum hydroxide powder and aluminum fluoride powder is preferable.

  Examples of the silicon compound include powdery silicon compounds such as silica, sodium hexafluorosilicate and potassium hexafluorosilicate, and liquid silicon compounds such as silicates, silicones and silane coupling agents. These may be used alone or in combination of two or more.

The silicon compound is preferably in liquid form, and silicate is particularly preferably used. Specifically, a silicate monomer represented by the composition formula Si (OR) ₄ (wherein R is an alkyl group having 1 to 2 carbon atoms) or a polymer thereof is preferable. Examples of the monomer include methyl silicate and ethyl silicate, and methyl silicate is more preferable in terms of high reactivity. The polymer is preferably a dimer to 10-mer of methyl silicate or ethyl silicate, and more preferably a dimer to 10-mer of methyl silicate. When it is larger than the 10-mer, the viscosity of the silicate becomes high, and thus the dispersibility tends to decrease.

  The liquid silicon compound can be added to a mixed powder of gibbsite type aluminum hydroxide powder and aluminum fluoride powder at room temperature using a known mixer, and then subjected to heat treatment. For example, a method of mixing while heating using a stirring type mixer such as a Henschel mixer, adding a liquid silicon compound to a wet cake of a mixed powder of gibbsite type aluminum hydroxide powder and aluminum fluoride powder, It is also possible to mix the liquid silicon compound under heating, as in the method of mixing while heating in the step of drying the cake. When the silicate is heated to 100 ° C. or higher, hydrolysis proceeds, further the condensation of hydrolysis products proceeds, and a solid substance is deposited on the surface of aluminum hydroxide. The hydrolysis product of the liquid silicon compound thus obtained and / or the condensation product thereof can be used as a silicon compound for heat treatment. When mixing under heating, in order to remove the solvent component of the silicon compound, it is preferable to mix while heating so that the temperature of the silicon compound is 100 ° C. or higher and 140 ° C. or lower.

  In the present invention, the heat-resistant aluminum hydroxide contains a coupling agent such as a silane coupling agent or a titanate coupling agent; a fatty acid such as oleic acid or stearic acid in order to improve the affinity with the resin and the filling property. The surface treatment may be performed with a group carboxylic acid; an aromatic carboxylic acid such as benzoic acid and a fatty acid ester thereof; a surface treatment agent such as a colloidal silica particle, a silicon compound such as methyl silicate, ethyl silicate and the like. The surface treatment can be performed by either a dry treatment method or a wet treatment method.

As the dry surface treatment method, for example, a method of mixing the heat-resistant aluminum hydroxide powder and the surface treatment agent in a Henschel mixer or a Loedige mixer, and to uniformly coat the surface treatment agent, the heat-resistant aluminum hydroxide powder and the surface treatment agent are treated. Examples include a method in which a mixture of agents is put into a pulverizer and pulverized.
Examples of the wet surface treatment method include a method in which a surface treatment agent is dispersed or dissolved in a solvent, heat-resistant aluminum hydroxide powder is dispersed in the obtained solution, and the obtained dispersion is dried.

  In the present invention, the heat-resistant aluminum hydroxide preferably has a peak top of F1s binding energy measured by X-ray photoelectron spectroscopy of 684.0 eV or more and 685.5 eV or less. In addition, the peaks are 686.4 eV component attributed to aluminum fluoride, 683.8 eV component attributed to sodium fluoride as an impurity, and 684.0 eV or more 685. It is formed by superimposing three components of 5 eV or less, or by superimposing two components excluding the 683.8 eV component belonging to sodium fluoride as an impurity. Furthermore, the component of 684.0 eV or more and 685.5 eV or less is preferably 50% or more of the total peak area.

  In the present invention, the heat resistant aluminum hydroxide preferably has a content of boehmite having a higher heat resistance than that of gibbsite type aluminum hydroxide in the range of 3% to 15%, preferably 5% to 13%. If it is less than 3%, the heat resistance tends to decrease. When it is more than 15%, boehmite has less water of crystallization than gibbsite type aluminum hydroxide, so that the flame retardancy tends to decrease when compounded with a polymer material.

  In the present invention, the heat-resistant aluminum hydroxide preferably has a dehydration start temperature of 245 ° C. or higher. The dehydration start temperature is a temperature at which the weight is reduced by 0.5% with reference to the time point of holding at 100 ° C. for 10 minutes. When the dehydration start temperature is lower than 245 ° C, foaming may occur in the application of the resin composition in which even slight dehydration is unacceptable during processing and use. The dehydration start temperature is usually 255 ° C. or lower.

  In the present invention, the heat-resistant aluminum hydroxide has a dehydration amount of preferably 27% or more and 30% or less, and more preferably 28% or more and 29% or less. The dehydration amount is the weight that was decreased while the temperature was raised to 400 ° C. with reference to the time point when the holding at 100 ° C. for 10 minutes was completed. In general, gibbsite type aluminum hydroxide starts abrupt dehydration at around 230 ° C and changes into a mixture of alumina and boehmite by 400 ° C. After that, through moderate dehydration, boehmite is converted to alumina by 600 ° C. In order to impart flame retardancy when heat-resistant aluminum hydroxide is mixed with a polymer material, rapid dehydration up to 400 ° C. is important. When the dehydration amount is less than 27%, the flame retardancy is lowered. On the other hand, when the dehydration amount is more than 30%, the flame resistance is high, but the heat resistance is lowered, and foaming may occur due to dehydration during processing and use.

In the present invention, the heat-resistant aluminum hydroxide has a BET specific surface area of 0.5 m ² / g or more and 8.0 m ² / g or less, preferably 0.7 m ² / g or more and 3.0 m ² / g or less, more preferably 1 It is 0.8 m ² / g or less. If it is more than 8.0 m ² / g, the amount of adsorbed water on the surface of the heat-resistant aluminum hydroxide increases, and foaming may occur due to dehydration during processing and use. On the other hand, if it is less than 0.5 m ² / g, flame retardancy may decrease.

In the present invention, heat-resistant aluminum hydroxide has the characteristics of high heat resistance and low adsorbed water content, and is suitable as a filler for various resins. Examples of the resin include rubber, thermoplastic resins such as polypropylene and polyethylene, and thermosetting resins such as epoxy resin.
The resin composition can be obtained by mixing the heat-resistant aluminum hydroxide and the resin by using a commonly known method.
Specific applications of resin compositions containing heat-resistant aluminum hydroxide mixed with various resins include, for example, printed wiring boards and members such as prepregs and other electronic components of electronic equipment, electric wire coating materials, and polyolefins. Molding materials, tires, building materials such as artificial marble, and the like, and particularly preferable applications include electronic equipment parts such as printed wiring boards and encapsulants that require high heat resistance during processing and use, and electric wires. A coating material can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
The physical properties of aluminum hydroxide in the examples and comparative examples were measured by the following methods.

(1) As an average particle size measuring device, a laser scattering type particle size distribution measuring device [“Microtrack MT-3300EXII” manufactured by Nikkiso Co., Ltd.] was used. Aluminum hydroxide powder was added to a 0.2 wt% sodium hexametaphosphate aqueous solution to adjust the concentration to a measurable level, and then ultrasonic waves with an output of 25 W were irradiated for 120 seconds, and then the number of samples was measured. And the particle size distribution curve was determined. The average particle diameter was determined as the particle diameter corresponding to 50% by weight (D50 (μm)). Further, when the average particle diameter obtained by the above method was 2 μm or less, the measurement conditions were changed, and the value measured after irradiating ultrasonic waves with an output of 40 W for 300 seconds was adopted.

(2) BET Specific Surface Area A BET specific surface area was determined by a nitrogen adsorption method using a fully automatic specific surface area measuring apparatus [“Macsorb HM-1201” manufactured by Mounttech Co., Ltd.] according to the method specified in JIS-Z-8830.

(3) Heat resistance and dehydration amount of aluminum hydroxide powder Using a differential thermogravimetric analyzer ["Thermo Plus TG8120" manufactured by Rigaku Co., Ltd.), a sample amount of about 10 mg and a dew point temperature of -20 [deg.] C. or less were used and the flow rate was 100 ml / min. The temperature was raised from room temperature to 100 ° C. at a temperature rising rate of 10 ° C./minute, held at 100 ° C. for 10 minutes, and then raised to 400 ° C. at a temperature rising rate of 10 ° C./minute. The heat resistance was evaluated by measuring the temperature at which the weight was reduced by 0.5% (“dehydration start temperature (° C.)” in Table 1 below) based on the time point at which the product was kept at 100 ° C. for 10 minutes. The amount of dehydration was evaluated as the weight that decreased during the temperature rising from 400 ° C. to 10 ° C. for 10 minutes.

(4) Boehmite content The powder X-ray diffraction measurement apparatus ["RINT-2000" manufactured by Rigaku Corporation) was used, Cu was used as the X-ray source, and measurement was performed under the following measurement conditions.
Step width: 0.02 deg
Scan speed: 0.04 deg / sec
Accelerating voltage: 40kV
Acceleration current: 30mA
The results of measurement under the above measurement conditions were compared with JCPDS card 70-2038 (corresponding to gibbsite type aluminum), and the area S (002) of the peak corresponding to the (002) plane of gibbsite type aluminum was calculated. Similarly, the measurement result was compared with JCPDS card 83-1505 (corresponding to boehmite), and the area S (020) of the peak corresponding to the (020) plane of boehmite was obtained. From these two peak areas, the boehmite content was calculated according to the following formula.
Boehmite content (%) = S (020) / [S (020) + S (002)] × 100

(5) Binding energy of F1s It was measured by using an X-ray photoelectron spectroscopy analyzer [“AXIS-ULTRA” manufactured by KRATOS]. The measurement conditions and analysis conditions are as shown below.
1) Measurement conditions X-ray: AlKα (monochrome) 15kV 15mA
Lens mode: LowMag
Pass Energy: 20 eV
Aperture: SLOT
Neutralization Gun Charge Balance: 3.5V
Step: 0.1 eV
Dwell time: 500ms
Measurement element: F1s
Electrification correction: C1s = 284.6 eV correction Sampling: A washer is fixed to the sample bar with carbon double-sided tape, and the sample is filled into the washer 2) Analysis conditions Analysis software: Casa XPS
Analysis procedure:
The energy position showing the maximum intensity of the F1s binding energy observed in the range of 680 to 690 eV was taken as the peak top.

(6) Conductivity 10 g of aluminum hydroxide powder was mixed with 50 g of pure water having a conductivity of less than 1 μS / cm, and ultrasonic irradiation was performed for 10 minutes to obtain a slurry. Using a conductivity measuring device [“CM-60S” manufactured by Toa Denpa Kogyo KK], the electrode was immersed in the slurry at 25 ° C. and left standing for 10 seconds, and the measured value was taken as the conductivity.

Example 1
100 parts by weight of gibbsite type aluminum hydroxide [“CL-303” manufactured by Sumitomo Chemical Co., Ltd.] powder having an average particle diameter of 5 μm, a BET specific surface area of 1 m ² / g, and a Na ₂ O content of 0.04% by weight, and aluminum fluoride [ Morita Chemical Industry Co., Ltd.] Powder was pulverized and mixed with 0.5 part by weight of fine powder having a BET specific surface area of 36 m ² / g in a plastic bag by dry shaking to obtain a mixed powder. 100 g of the mixed powder was charged into a hot-air dryer having an internal volume of 216 L and an ambient temperature of 230 ° C., no pure air was supplied, and pure water was supplied at a flow rate of 15 g / min using a tube pump. Heat treatment was performed for an hour. The steam mole fraction in the hot air dryer at 230 ° C. was 1. After the heat treatment, the product was taken out from the dryer to obtain aluminum hydroxide powder.

Example 2
In Example 1, 100 parts by weight of a gibbsite type aluminum hydroxide [“CL-303” manufactured by Sumitomo Chemical Co., Ltd.] powder having an average particle diameter of 5 μm, a BET specific surface area of 1 m ² / g, and a Na ₂ O content of 0.04% by weight. , Aluminum fluoride [Morita Chemical Industry Co., Ltd.] powder, 5 parts by weight of 10 wt% water slurry of fine powder having a BET specific surface area of 36 m ² / g was mixed by wet shaking in a plastic bag and dried at 120 ° C. Then, an aluminum hydroxide powder was obtained by the same method as in Example 1 except that the mixed powder was obtained.

Example 3
In Example 2, a 10% by weight aqueous slurry of fine powder having a BET specific surface area of 36 m ² / g obtained by crushing aluminum fluoride [manufactured by Morita Chemical Industry] powder was changed from 5 parts by weight to 10 parts by weight and wet shaken. Aluminum hydroxide powder was obtained in the same manner as in Example 2 except that the aluminum hydroxide powder was mixed.

Example 4
In Example 3, 0.7 parts by weight of methyl silicate (“MS-51” manufactured by Mitsubishi Chemical Corporation, silicon content 51% by weight in terms of SiO ₂ , weight average molecular weight 500 to 700) was added when wet-mixing. Aluminum hydroxide powder was obtained in the same manner as in Example 3 except that the aluminum hydroxide powder was added.

Example 5
In Example 2, 100 g of the obtained mixed powder was placed in a hot-air dryer having an internal volume of 216 L and an ambient temperature of 200 ° C., and heat treatment was performed under atmospheric pressure for 4 hours without supplying air or pure water. Except for the above, aluminum hydroxide powder was obtained by the same method as in Example 2.

Example 6
In Example 2, except that fine powder having a BET specific surface area of 58 m ² / g was used instead of the fine powder having a BET specific surface area of 36 m ² / g, aluminum fluoride [made by Morita Chemical Industry Co., Ltd.] was used. Aluminum hydroxide powder was obtained in the same manner as in Example 2.

Example 7
In Example 1, gibbsite type aluminum hydroxide [Sumitomo Chemical Co., Ltd. “C-301N”] powder having an average particle diameter of 1.2 μm, a BET specific surface area of 4.3 m ² / g, and a Na ₂ O content of 0.2% by weight. 100 parts by weight and 20 parts by weight of a 10% by weight aqueous slurry of fine powder having a BET specific surface area of 36 m ² / g obtained by crushing aluminum fluoride [Morita Chemical Industry Co., Ltd.] powder were wet-mixed in a plastic bag, Aluminum hydroxide powder was obtained in the same manner as in Example 1 except that the mixed powder was obtained by drying at 120 ° C.

Comparative Example 1
The gibbsite type aluminum hydroxide powder [“CL-303” manufactured by Sumitomo Chemical Co., Ltd.] used as a raw material in Example 1 was directly used for evaluation.

Comparative Example 2
Aluminum hydroxide powder was obtained in the same manner as in Example 1 except that the aluminum fluoride powder was not mixed.

Comparative Example 3
Aluminum hydroxide powder was obtained in the same manner as in Example 2 except that the heat treatment was not performed.

Comparative Example 4
The gibbsite type aluminum hydroxide [“C-301N” manufactured by Sumitomo Chemical Co., Ltd.] powder used as a raw material in Example 7 was directly subjected to evaluation.

Comparative Example 5
Aluminum hydroxide powder was obtained in the same manner as in Example 7, except that the fine powder slurry obtained by crushing the aluminum fluoride powder was not mixed.

Comparative Example 6
Aluminum hydroxide powder was obtained in the same manner as in Example 7 except that the heat treatment was not performed.

[BET specific surface area of powder, heat resistance and F1s binding energy]
The evaluation results of the aluminum hydroxide powder obtained in the above Examples and Comparative Examples are shown in Tables 1, 2 and 3.

[Conductivity measurement of powder slurry]
Reference example 1
The aluminum hydroxide powder obtained in Example 3 was slurried and the conductivity was measured.

Reference example 2
The conductivity was measured by the same method as in Reference Example 1 except that the aluminum hydroxide powder obtained in Example 4 was used.

Reference Example 3
The conductivity was measured by the same method as in Reference Example 1 except that the aluminum hydroxide powder obtained in Comparative Example 2 was used.

  Table 4 shows the results of conductivity measurement in Reference Examples 1 to 3.

比較例２及び５については、６８０〜６９０ｅＶの範囲でピークは観測されなかった。

For Comparative Examples 2 and 5, no peak was observed in the range of 680 to 690 eV.

  From the above results, it was found that the method of the present invention can produce aluminum hydroxide powder having high heat resistance without generating toxic exhaust gas and waste liquid. It was also found that the heat treatment with the silicon compound can reduce the conductivity of the aluminum hydroxide powder.

Claims (7)

A step of mixing 100 parts by weight of gibbsite type aluminum hydroxide powder with 0.05 parts by weight or more and 5 parts by weight or less of aluminum fluoride powder having a BET specific surface area of 10 m ² / g or more and 300 m ² / g or less; ,
A method for producing heat-resistant aluminum hydroxide, comprising the step of subjecting the mixture to a heat treatment at a temperature of 180 ° C. or higher and 300 ° C. or lower under a pressure of atmospheric pressure or higher and 0.3 MPa or lower.   The method according to claim 1, wherein the heat treatment is performed in an atmosphere having a water vapor mole fraction of 0.03 or more and 1 or less.   The method according to claim 1, wherein the heat treatment is performed for 1 minute or longer and 360 minutes or shorter.   The method according to any one of claims 1 to 3, wherein the gibbsite type aluminum hydroxide powder is produced by the Bayer method.   The method according to claim 1, wherein the gibbsite type aluminum hydroxide powder has an average particle size of 0.5 μm or more and 10 μm or less. A heat treatment is performed by adding 0.1 part by weight or more and 5 parts by weight or less of a silicon compound in terms of SiO ₂ to a mixed powder of a gibbsite type aluminum hydroxide powder and an aluminum fluoride powder. The method described in any one of. The method according to claim 6, wherein the silicon compound is a silicate monomer represented by the following composition formula or a polymer thereof, or a hydrolysis product or a condensation product thereof.
Si (OR) ₄
[In the formula, R represents an alkyl group having 1 to 2 carbon atoms]