JP2008303110A - Low-soda fine particle aluminum hydroxide and its production method - Google Patents
Low-soda fine particle aluminum hydroxide and its production method Download PDFInfo
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この発明は、バイヤー法によって製造され、全ソーダ(T-Na2O)分の含有量が極めて低く、しかも、平均粒子径が極めて小さいギブサイト結晶（Al2O3・3H2O）からなる低ソーダ微粒水酸化アルミニウム及びその製造方法に係り、特に限定するものではないが、プリント配線基板等の電気・電子材、電線被覆材、絶縁材料、建築用の内装材や外装材等の用途に用いられる合成ゴム、天然ゴム、合成樹脂等の種々の高分子材料に配合され、耐熱性や難燃性を付与するための難燃材として特に有用な低ソーダ微粒水酸化アルミニウム及びその製造方法に関する。 This invention is produced by the Bayer method, has a very low content of total soda (T-Na 2 O), and is composed of gibbsite crystals (Al 2 O 3 .3H 2 O) having an extremely small average particle diameter. Although it relates to soda fine aluminum hydroxide and its manufacturing method, it is not particularly limited, but it is used for applications such as electrical / electronic materials such as printed wiring boards, wire coating materials, insulation materials, architectural interior materials and exterior materials. The present invention relates to a low soda fine aluminum hydroxide that is blended in various polymer materials such as synthetic rubber, natural rubber, and synthetic resin, and is particularly useful as a flame retardant for imparting heat resistance and flame retardancy, and a method for producing the same.
従来、この種の水酸化アルミニウムについては古くから多くの提案があり、例えば、米国特許第4,014,985号公報には、バイヤー法で得られたアルミン酸ソーダ溶液中のAl2O3／Na2O比を１．０４以下とし、平均粒子径５５μmの種子を添加して０．０３g-Al2O3／m2-種子・h以下の極めてゆっくりとした析出を行い、全ソーダ分０．１重量%以下の水酸化アルミニウムを製造することが記載されている。 Conventionally, there have been many proposals for this type of aluminum hydroxide. For example, US Pat. No. 4,014,985 discloses an Al 2 O 3 / Na 2 O ratio in a sodium aluminate solution obtained by the Bayer method. 1.04 or less, seeds with an average particle size of 55 μm were added, and 0.03 g-Al 2 O 3 / m 2 -seed · h or less was precipitated very slowly, with a total soda content of 0.1% by weight. The production of the following aluminum hydroxide is described.
また、特開昭59-204,632号公報には、平均粒子径が０．５〜６０μmであって全ソーダ分が０．１%以下、好ましくは０．０７%以下であるギブサイト型水酸化アルミニウムを添加して得られた耐熱性樹脂成形体が記載されており、また、その実施例及び比較例には、中心粒径が８．０〜８．５μmで全ソーダ分（T-Na2O）が０．０６〜０．２１%のギブサイト型水酸化アルミニウムを用いることが記載されている。 JP-A-59-204,632 discloses gibbsite-type aluminum hydroxide having an average particle size of 0.5 to 60 μm and a total soda content of 0.1% or less, preferably 0.07% or less. The heat-resistant resin moldings obtained by addition are described, and in the examples and comparative examples, the center particle size is 8.0 to 8.5 μm and the total soda content (T-Na 2 O). Describes that 0.06 to 0.21% of gibbsite type aluminum hydroxide is used.
更に、特開昭62-246,961号公報には、平均粒子径が０．５〜１５μm、窒素ガス吸着法によるBET比表面積が２．８m2/g以上、好ましくは３〜４．５m2/g、及び全ソーダ分が０．０８重量%以下であるギブサイト型水酸化アルミニウムを添加して得られた耐熱性樹脂組成物が記載されており、また、その実施例及び比較例には、平均粒子径０．８〜１４．３μm、BET比表面積１．５〜４．５m2/g、及び全ソーダ分０．０１５〜０．２１重量%のギブサイト型水酸化アルミニウムを用いることが記載されている。 Furthermore, Japanese Patent Application Laid-Open No. 62-246,961 discloses an average particle size of 0.5 to 15 μm and a BET specific surface area by nitrogen gas adsorption method of 2.8 m 2 / g or more, preferably 3 to 4.5 m 2 / g. , And a heat-resistant resin composition obtained by adding gibbsite-type aluminum hydroxide having a total soda content of 0.08% by weight or less, and examples and comparative examples show average particles. It is described that gibbsite type aluminum hydroxide having a diameter of 0.8 to 14.3 μm, a BET specific surface area of 1.5 to 4.5 m 2 / g, and a total soda content of 0.015 to 0.21 wt% is used. .
更にまた、特開平2-74,521号公報には、平均粒子径が１０μm以下、好ましくは５μm以下であって、全ソーダ分が０．１０重量%以下であり、２００℃以下の温度での低温脱水反応が抑制され、かつ、ベーマイト転移反応速度の小さいギブサイト型の耐熱性水酸化アルミニウムが記載されており、また、その実施例１には、平均粒子径１．７μm及び全ソーダ分０．０６重量%の水酸化アルミニウムを得たことが記載されている。 Furthermore, Japanese Patent Application Laid-Open No. 2-74,521 discloses an average particle size of 10 μm or less, preferably 5 μm or less, a total soda content of 0.10% by weight or less, and low temperature dehydration at a temperature of 200 ° C. or less. Gibbsite-type heat-resistant aluminum hydroxide having a low reaction rate and a low boehmite transfer reaction rate is described. In Example 1, the average particle size is 1.7 μm and the total soda content is 0.06 wt. % Aluminum hydroxide is obtained.
また、特開平3-28,121号公報には、平均粒子径が５μm以下であって、全ソーダ分が０．１０重量%以下であり、耐熱性に優れ、ゴムやプラスチックに充填した際に強度低下の少ない微粒の耐熱性水酸化アルミニウムが記載されており、そして、その実施例１には、平均粒子径が１．５μmで一次粒子径が０．５μmであり、全ソーダ分が０．０６重量%である耐熱性水酸化アルミニウムが記載されている。 Japanese Patent Laid-Open No. 3-28,121 discloses an average particle size of 5 μm or less and a total soda content of 0.10% by weight or less, excellent heat resistance, and reduced strength when filled in rubber or plastic. The heat-resistant aluminum hydroxide with a small particle size is described, and in Example 1, the average particle size is 1.5 μm, the primary particle size is 0.5 μm, and the total soda content is 0.06 wt. % Heat-resistant aluminum hydroxide is described.
更に、特開平11-278,829号公報には、平均粒子径１〜６μm及び全ソーダ分０．１質量%以下の高純度水酸化アルミニウムや、平均粒子径１５〜４０μm及び全ソーダ分０．１質量%以下の高純度水酸化アルミニウムが記載されており、また、その比較例及び実施例には、平均粒子径１．８〜４２．２μm及び全ソーダ分０．０５〜０．３１質量%以下の水酸化アルミニウムが記載されている。 Further, JP-A-11-278,829 discloses high-purity aluminum hydroxide having an average particle size of 1 to 6 μm and a total soda content of 0.1% by mass or less, an average particle size of 15 to 40 μm and a total soda content of 0.1 mass. % Of high-purity aluminum hydroxide is described, and comparative examples and examples thereof have an average particle size of 1.8 to 42.2 μm and a total soda content of 0.05 to 0.31% by mass or less. Aluminum hydroxide is described.
更にまた、特開2002-348,408号公報には、SiO2含有量が０．０２重量%未満であり、BET比表面積が３m2/g未満であり、かつ、１１０℃から２１０℃まで昇温し保持したときの重量減少率が０．３%以下の樹脂充填用水酸化アルミニウム粉末が記載されており、また、その実施例にはNa2O含有率が０．０４重量%であって平均粒子径が５μmのギブサイト型水酸化アルミニウムを得たことが記載されている。 Furthermore, JP-A-2002-348,408 discloses that the SiO 2 content is less than 0.02% by weight, the BET specific surface area is less than 3 m 2 / g, and the temperature is raised from 110 ° C. to 210 ° C. An aluminum hydroxide powder for resin filling having a weight reduction rate of 0.3% or less when held is described, and the example has an Na 2 O content of 0.04% by weight and an average particle size Obtained 5 μm gibbsite-type aluminum hydroxide.
ところで、このような種々の高分子材料に耐熱性や難燃性を付与するための難燃材等として用いるギブサイト型水酸化アルミニウムについて検討してみると、その平均粒子径については、例えば半導体部品や積層板等において小型化や薄膜化に対応するという観点からは３μm以下、コンパウンドの粘度や成形作業性を考慮すると好ましくは０．５μm以上３μm以下であるのがよく、また、その全ソーダ(T-Na2O)分については、その含有量が多くなればなるほど２００℃付近から始まるベーマイト転移による初期脱水反応が起き易くなくなって耐熱性が低下するので、０．１質量%以下、好ましくは可及的により少ないものであるのがよく、更に、そのBET比表面積については、その値が大きくなると樹脂との混練性や成形性が悪化するので、１０m2/g以下、好ましくは５m2/g以下であるのがよい。 By the way, when examining gibbsite type aluminum hydroxide used as a flame retardant for imparting heat resistance and flame retardancy to such various polymer materials, the average particle diameter thereof is, for example, semiconductor components. From the standpoint of responding to miniaturization and thinning of laminated plates and the like, the thickness should be 3 μm or less, preferably 0.5 μm or more and 3 μm or less in consideration of the viscosity of the compound and molding workability. As for the content of T-Na 2 O), the higher the content, the easier the initial dehydration reaction due to the boehmite transition starting from around 200 ° C. does not occur and the heat resistance decreases, so 0.1% by mass or less, preferably The BET specific surface area should be as small as possible. Further, as the value increases, the kneadability and moldability with the resin deteriorate, so 10 m 2 / g or less, preferably 5 m 2 / g or less.
しかしながら、バイヤー法により平均粒子径が２μm以下と極めて小さく、しかも、全ソーダ分の含有量も０．０４質量%以下と極めて少ないギブサイト型水酸化アルミニウムを製造する方法については知られておらず、また、これまでに未粉砕であって平均粒子径２μm以下、全ソーダ分０．０４質量%以下及びBET比表面積１０m2/g以下という条件を満たすギブサイト型の低ソーダ微粒水酸化アルミニウムは製造されていない。 However, there is no known method for producing gibbsite-type aluminum hydroxide by the Bayer method, which has an extremely small average particle diameter of 2 μm or less and a very small content of soda of 0.04% by mass or less. In addition, a gibbsite-type low soda fine aluminum hydroxide that has not been pulverized and satisfies the conditions of an average particle diameter of 2 μm or less, a total soda content of 0.04 mass% or less, and a BET specific surface area of 10 m 2 / g or less has been produced. Not.
ところで、全ソーダ分の含有量が０．０４質量%以下で平均粒子径が２μmを超えるギブサイト型水酸化アルミニウムを製造し、次いで既知の手段で粉砕することによりその平均粒子径を細かくし、これによって平均粒子径２μm以下及び全ソーダ分０．０４質量%以下のギブサイト型水酸化アルミニウムを製造することは可能である。しかしながら、このような方法で製造されたギブサイト型水酸化ナトリウムは、粉砕により結晶自体がダメージを受け、また、チッピングが発生し易くなり、更に、BET比表面積も大きくなってしまうため、樹脂との混練性や成形性も悪化する。 By the way, a gibbsite-type aluminum hydroxide having a total soda content of 0.04% by mass or less and an average particle size exceeding 2 μm is produced, and then the average particle size is reduced by grinding by known means. Thus, it is possible to produce gibbsite type aluminum hydroxide having an average particle diameter of 2 μm or less and a total soda content of 0.04% by mass or less. However, the gibbsite-type sodium hydroxide produced by such a method is damaged by the crystal itself by pulverization, is likely to generate chipping, and further increases the BET specific surface area. Kneadability and moldability also deteriorate.
そこで、本発明者らは、平均粒子径、全ソーダ(T-Na2O)分、及びBET比表面積が何れも小さいギブサイト型水酸化アルミニウムの開発について鋭意検討した結果、意外なことには、Na2O濃度３０g/L以下及びAl2O3濃度３０g/L以下の初期媒体中に種子として全ソーダ分０．０５質量%以下及び平均粒子径１μm以下の水酸化アルミニウムを添加して初期溶液を調製し、この初期溶液中に添加溶液としてバイヤー法で得られたアルミン酸ナトリウム溶液を連続的又は間欠的に添加して析出溶液とし、この析出溶液から水酸化アルミニウムを析出させる際の析出温度と析出開始から析出終了までの平均過飽和Al2O3濃度とを所定の範囲に制御し、また、必要に応じて析出溶液から回収した水酸化アルミニウムを解砕することにより、目標とする平均粒子径２μm以下、全ソーダ分０．０４質量%以下、及びBET比表面積１０m2/g以下のギブサイト型水酸化アルミニウムを製造できることを突き止め、本発明を完成した。 Therefore, as a result of earnestly examining the development of gibbsite-type aluminum hydroxide in which the average particle size, the total soda (T-Na 2 O) content, and the BET specific surface area are all small, surprisingly, The initial solution is prepared by adding aluminum hydroxide having a total soda content of 0.05% by mass or less and an average particle diameter of 1 μm or less as seeds to an initial medium having an Na 2 O concentration of 30 g / L or less and an Al 2 O 3 concentration of 30 g / L or less. In this initial solution, a sodium aluminate solution obtained by the Bayer method as an additive solution is added continuously or intermittently to form a precipitation solution, and the precipitation temperature when aluminum hydroxide is precipitated from this precipitation solution And the average supersaturated Al 2 O 3 concentration from the start of precipitation to the end of precipitation within a predetermined range, and if necessary, by crushing the aluminum hydroxide recovered from the precipitation solution, the target average particle Diameter 2 m or less, the total soda content 0.04 wt% or less, and ascertained that can produce a BET specific surface area of 10 m 2 / g or less of gibbsite type aluminum hydroxide, and have completed the present invention.
従って、本発明の目的は、平均粒子径２μm以下、全ソーダ(T-Na2O)分０．０４質量%以下、及びBET比表面積１０m2/g以下のギブサイト型水酸化アルミニウムを提供することにある。 Accordingly, an object of the present invention is to provide a gibbsite-type aluminum hydroxide having an average particle diameter of 2 μm or less, a total soda (T—Na 2 O) content of 0.04% by mass or less, and a BET specific surface area of 10 m 2 / g or less. It is in.
また、本発明の他の目的は、このように平均粒子径２μm以下、全ソーダ(T-Na2O)分０．０４質量%以下、及びBET比表面積１０m2/g以下であるギブサイト型低ソーダ微粒水酸化アルミニウムを容易に製造することができる低ソーダ微粒水酸化アルミニウムの製造方法を提供することにある。 Another object of the present invention is to provide a gibbsite-type low particle having an average particle size of 2 μm or less, a total soda (T—Na 2 O) content of 0.04% by mass or less, and a BET specific surface area of 10 m 2 / g or less. An object of the present invention is to provide a method for producing low-soda fine aluminum hydroxide, which can easily produce soda-fine aluminum hydroxide.
すなわち、本発明は、バイヤー法によって製造されたギブサイト型水酸化アルミニウムであり、平均粒子径が２μm以下であって、全ソーダ(T-Na2O)分が０．０４質量%以下であり、ＢＥＴ比表面積が１０m2/g以下であることを特徴とする低ソーダ微粒水酸化アルミニウムである。 That is, the present invention is a gibbsite-type aluminum hydroxide produced by the Bayer method, having an average particle size of 2 μm or less and a total soda (T—Na 2 O) content of 0.04% by mass or less, A low soda fine aluminum hydroxide characterized by having a BET specific surface area of 10 m 2 / g or less.
また、本発明は、バイヤー法により低ソーダ微粒水酸化アルミニウムを製造するに際し、Na2O濃度３０g/L以下及びAl2O3濃度３０g/L以下の初期媒体中に種子として全ソーダ(T-Na2O)分０．０５質量%以下及び平均粒子径１μm以下の水酸化アルミニウムを添加して初期溶液を調製し、次いでこの初期溶液中にアルミン酸ナトリウム溶液からなる添加溶液を連続的又は間欠的に添加して水酸化アルミニウムの析出溶液を調製すると共に、この析出溶液からは析出温度６０〜９０℃で析出開始から析出終了までの平均過飽和Al2O3濃度が１５g/Lを超えない範囲で水酸化アルミニウムを析出させ、必要に応じて上記析出溶液から回収した水酸化アルミニウムを解砕することを特徴とする低ソーダ微粒水酸化アルミニウムの製造方法である。 In addition, when producing low-soda fine aluminum hydroxide by the Bayer method, the present invention provides all soda as seeds in an initial medium having a Na 2 O concentration of 30 g / L or less and an Al 2 O 3 concentration of 30 g / L or less. An initial solution is prepared by adding aluminum hydroxide having a Na 2 O content of 0.05% by mass or less and an average particle size of 1 μm or less, and then an added solution comprising a sodium aluminate solution is continuously or intermittently added to the initial solution. To prepare a precipitation solution of aluminum hydroxide, and from this precipitation solution, the average supersaturated Al 2 O 3 concentration from the start of precipitation to the end of precipitation at a precipitation temperature of 60 to 90 ° C. does not exceed 15 g / L. In this method, aluminum hydroxide is precipitated by crushing and, if necessary, aluminum hydroxide recovered from the precipitation solution is crushed.
本発明において、初期溶液を調製するのに用いられる初期媒体としては、それがNa2O濃度３０g/L以下及びAl2O3濃度３０g/L以下であればよいが、最も好ましくは純水であるのがよい。この初期媒体のNa2O濃度及びAl2O3濃度が３０g/Lより高いと、水酸化アルミニウムが析出し難くなる。一定の析出速度を得ようとして添加溶液の供給流量増やしても、析出溶液の過飽和Al2O3濃度が高くなって、析出溶液から水酸化アルミニウムを析出させる際の析出条件、すなわち析出開始から析出終了までの平均過飽和Al2O3濃度を１５g/Lを超えない範囲に維持することが難しくなり、目標とする平均粒子径、全ソーダ分、及びBET比表面積を有するギブサイト型水酸化アルミニウムの製造が困難になる。 In the present invention, the initial medium used to prepare the initial solution may be any Na 2 O concentration of 30 g / L or less and Al 2 O 3 concentration of 30 g / L or less, but most preferably pure water. There should be. When the Na 2 O concentration and Al 2 O 3 concentration of the initial medium are higher than 30 g / L, aluminum hydroxide is difficult to precipitate. Even if the supply flow rate of the additive solution is increased in order to obtain a constant deposition rate, the concentration of supersaturated Al 2 O 3 in the deposition solution increases, so that the deposition conditions for depositing aluminum hydroxide from the deposition solution, that is, deposition from the start of deposition Production of gibbsite-type aluminum hydroxide having a target average particle size, total soda content, and BET specific surface area becomes difficult to maintain the average supersaturated Al 2 O 3 concentration in the range not exceeding 15 g / L until completion. Becomes difficult.
また、初期溶液を調製する際に種子として用いる水酸化アルミニウムについては、少なくとも全ソーダ分が０．０５質量%以下、好ましくは０．０４質量%以下であって、平均粒子径が１μm以下、好ましくは０．９μm以下である必要がある。この種子として用いる水酸化アルミニウムの全ソーダ分が０．０５質量%を超えると得られた低ソーダ微粒水酸化アルミニウムの粒子中に全ソーダ分０．０４質量%を超える部分が局部的に生じて熱分解開始温度が低下する虞があり、また、平均粒子径が１μmを超えると目標とする平均粒径２μm以下及び全ソーダ分０．０４質量%以下の微粒水酸化アルミニウムを調製するのが難しくなる。このような種子として用いる水酸化アルミニウムは、バイヤー法により全ソーダ分０．０５質量%以下の水酸化アルミニウムを調製し、得られた水酸化アルミニウムを平均粒子径１μm以下まで湿式粉砕することにより調製することができる。 In addition, regarding aluminum hydroxide used as a seed in preparing the initial solution, at least the total soda content is 0.05% by mass or less, preferably 0.04% by mass or less, and the average particle size is 1 μm or less, preferably Needs to be 0.9 μm or less. When the total soda content of aluminum hydroxide used as seed exceeds 0.05% by mass, a portion exceeding 0.04% by mass of total soda content is locally generated in the particles of low soda fine aluminum hydroxide obtained. There is a risk that the thermal decomposition starting temperature may be lowered, and when the average particle diameter exceeds 1 μm, it is difficult to prepare fine aluminum hydroxide having an average particle diameter of 2 μm or less and a total soda content of 0.04% by mass or less. Become. Aluminum hydroxide used as such seeds is prepared by preparing aluminum hydroxide having a total soda content of 0.05% by mass or less by the Bayer method and wet-pulverizing the resulting aluminum hydroxide to an average particle size of 1 μm or less. can do.
更に、初期溶液における種子としての水酸化アルミニウムについては、そのBET比表面積が１０m2/g以上、好ましくは１０m2/g以上２０m2/g以下とするのがよく、また、初期溶液における種子の添加量については、種子添加率（m2/L）に換算して、通常３００m2/L以上、好ましくは３００m2/L以上１０００m2/L以下とするのがよい。この種子として用いる水酸化アルミニウムのBET比表面積が１０m2/gより低いと種子添加率を３００m2/L以上にするために多量の種子を添加する必要が生じて経済的でなく、また、この種子添加率が３００m2/Lより少ないと、場合によっては生産性が低下する、あるいは、粒径が粗くなるという問題が生じ、また、１０００m2/Lより多くしても、種子添加量の割に生産量が延びず、コスト高となる。 Furthermore, the aluminum hydroxide as the seed in the initial solution has a BET specific surface area of 10 m 2 / g or more, preferably 10 m 2 / g or more and 20 m 2 / g or less. The amount added is usually 300 m 2 / L or more, preferably 300 m 2 / L or more and 1000 m 2 / L or less, in terms of seed addition rate (m 2 / L). If the BET specific surface area of aluminum hydroxide used as the seed is lower than 10 m 2 / g, it is necessary to add a large amount of seed in order to increase the seed addition rate to 300 m 2 / L or more. when the seed addition rate is less than 300 meters 2 / L, when productivity is reduced by, or caused a problem that the particle size becomes coarse, also be more than 1000 m 2 / L, seed amount split However, the production volume does not increase and the cost becomes high.
本発明において、上記初期溶液に連続的又は間欠的に添加して析出溶液を調製するのに用いられる添加溶液は、バイヤー法によって得られるアルミン酸ナトリウム溶液であり、そのAl2O3濃度については、上記の初期溶液に添加して水酸化アルミニウムを析出するのに十分な濃度を達成できるものであれば特に制限はなく、例えば通常１００g/L以上２００g/L以下、好ましくは１４０g/L以上１７０g/L以下のものが用いられ、また、その溶解Na2O分と溶解Al2O3分とのモル比（Na2O／Al2O3）については、例えば通常３．０以下、好ましくは１．４以上１．７以下のものが用いられる。この添加溶液のモル比が１．４より低いと添加溶液が不安定になるという問題があり、反対に、３．０より高くなるとほとんど析出しなくなるという問題が生じる。 In the present invention, the additive solution used to prepare the precipitation solution by continuously or intermittently adding to the initial solution is a sodium aluminate solution obtained by the Bayer method, and the Al 2 O 3 concentration is about There is no particular limitation as long as it can be added to the above initial solution to achieve a concentration sufficient to precipitate aluminum hydroxide. For example, it is usually 100 g / L or more and 200 g / L or less, preferably 140 g / L or more and 170 g. The molar ratio of dissolved Na 2 O and dissolved Al 2 O 3 (Na 2 O / Al 2 O 3 ) is, for example, usually 3.0 or less, preferably Those of 1.4 or more and 1.7 or less are used. If the molar ratio of the additive solution is lower than 1.4, there is a problem that the additive solution becomes unstable.
また、この添加溶液については、溶液中の全有機物濃度（TOC）が１g/L以下、好ましくは可及的により少ないことが望ましい。この全有機物濃度（TOC）が１g/Lを超えると、析出し難くなり、全ソーダ分が高くなる傾向がある。 Further, for this added solution, it is desirable that the total organic matter concentration (TOC) in the solution is 1 g / L or less, preferably as low as possible. When this total organic matter concentration (TOC) exceeds 1 g / L, it becomes difficult to precipitate and the total soda content tends to increase.
上記初期溶液に上記添加溶液を連続的又は間欠的に添加して水酸化アルミニウムの析出溶液を調製する際には、少なくとも析出溶液から水酸化アルミニウムを析出させる際の析出条件、すなわち析出温度が６０℃以上９０℃以下、好ましくは７０℃以上８０℃以下であって、析出開始から析出終了までの平均過飽和Al2O3濃度が１５g/L、好ましくは１０g/L、より好ましくは５g/Lを超えない範囲に維持される必要があり、この析出条件が維持されれば初期溶液に添加溶液を添加する方法に制限はない。析出温度が６０℃より低いと析出する水酸化アルミニウムの全ソーダ分が高くなるという問題があり、反対に、９０℃より高くなると生産性が悪化するという問題が生じ、また、平均過飽和Al2O3濃度が１５g/Lより高くなると析出する水酸化アルミニウムの全ソーダ分が高くなるという問題が生じる。ここで、析出開始から析出終了までの平均過飽和Al2O3濃度とは、初期溶液に添加溶液を添加し始めて水酸化アルミニウムの析出を開始してから添加溶液の添加を終了して水酸化アルミニウムの析出を終了するまでの間に析出溶液の過飽和Al2O3濃度が徐々に上昇するが、この間に経時的に測定された複数の過飽和Al2O3濃度の単純平均値として求められる。 When preparing the aluminum hydroxide precipitation solution by continuously or intermittently adding the additive solution to the initial solution, at least the precipitation conditions for precipitation of aluminum hydroxide from the precipitation solution, that is, the precipitation temperature is 60. The average supersaturated Al 2 O 3 concentration from the start of precipitation to the end of precipitation is 15 g / L, preferably 10 g / L, more preferably 5 g / L. There is no limitation on the method of adding the additive solution to the initial solution as long as the deposition conditions are maintained. When the precipitation temperature is lower than 60 ° C., there is a problem that the total soda content of the precipitated aluminum hydroxide is increased. On the other hand, when the precipitation temperature is higher than 90 ° C., the productivity is deteriorated, and the average supersaturated Al 2 O 3 When the concentration is higher than 15 g / L, there arises a problem that the total soda content of the precipitated aluminum hydroxide is increased. Here, the average supersaturated Al 2 O 3 concentration from the start of the precipitation to the end of the precipitation means that the addition of the additive solution to the initial solution starts the precipitation of the aluminum hydroxide and then finishes the addition of the additive solution, and then finishes the aluminum hydroxide. The supersaturated Al 2 O 3 concentration of the precipitation solution gradually rises until the precipitation is completed, and it is obtained as a simple average value of a plurality of supersaturated Al 2 O 3 concentrations measured over time during this period.
そして、初期溶液に添加溶液を添加して析出溶液を調製し水酸化アルミニウムを析出させる析出操作に際しては、好ましくは添加溶液の添加前に初期溶液の溶液温度を７０℃以上、好ましくは７０℃以上９０℃以下に調整し、添加溶液が添加された直後から析出溶液の溶液温度が６０〜９０℃の範囲内に維持されるようにするのがよく、溶液温度が６０℃より低くなると、析出する水酸化アルミニウムの全ソーダ分が高くなる傾向にあるので好ましくない。 In addition, in the precipitation operation in which the additive solution is added to the initial solution to prepare a precipitation solution and aluminum hydroxide is precipitated, the solution temperature of the initial solution is preferably 70 ° C. or higher, preferably 70 ° C. or higher before the addition solution is added. The temperature is adjusted to 90 ° C. or less, and the solution temperature of the precipitation solution is preferably maintained within the range of 60 to 90 ° C. immediately after the addition solution is added. When the solution temperature is lower than 60 ° C., the solution is precipitated. This is not preferable because the total soda content of aluminum hydroxide tends to increase.
また、この水酸化アルミニウムの析出操作中は、添加溶液の添加に応じて、また、水酸化アルミニウムの析出経過に応じて、析出溶液の過飽和Al2O3濃度が変化して一時的に過飽和Al2O3濃度１５g/Lを超える場合が生じてもよいが、好ましくは、過飽和Al2O3濃度が１５g/Lを超えないようにして析出開始から析出終了までの平均過飽和Al2O3濃度を１５g/L以下に維持するのがよく、また、その析出操作途中から析出操作終了までの間における降温速度調整操作により析出開始から析出終了までの平均過飽和Al2O3濃度を１５g/L以下に維持してもよい。 In addition, during the precipitation of aluminum hydroxide, the supersaturated Al 2 O 3 concentration in the precipitation solution changes temporarily depending on the addition of the additive solution and the precipitation of aluminum hydroxide. Although the case where the 2 O 3 concentration exceeds 15 g / L may occur, preferably, the average supersaturated Al 2 O 3 concentration from the start of precipitation to the end of precipitation so that the supersaturated Al 2 O 3 concentration does not exceed 15 g / L. Is preferably maintained at 15 g / L or less, and the average supersaturated Al 2 O 3 concentration from the start of precipitation to the end of precipitation is adjusted to 15 g / L or less by adjusting the temperature drop rate during the precipitation operation to the end of the precipitation operation. May be maintained.
この析出操作は、従来の方法における場合と特には変わりなく、析出槽内で初期溶液を調製し、次いでこの析出槽内の初期溶液中に攪拌下に連続的又は間欠的に添加溶液を添加し、析出槽内で析出溶液としながら所定の析出条件下に水酸化アルミニウムを析出させ、析出槽内が所定の液量に達した時点で添加溶液の添加を停止し、その後、析出温度６０〜９０℃で所定時間、通常は添加溶液の添加に要した時間の０．０２〜０．２５倍程度であって０〜２時間程度保持し、最終的に析出温度６０〜９０℃を維持しながら析出操作を終了する。 This precipitation operation is not particularly different from that in the conventional method, and an initial solution is prepared in a precipitation tank, and then the added solution is continuously or intermittently added to the initial solution in the precipitation tank with stirring. Then, aluminum hydroxide is precipitated under a predetermined precipitation condition while forming a precipitation solution in the precipitation tank. When the inside of the precipitation tank reaches a predetermined liquid amount, the addition of the addition solution is stopped, and then the precipitation temperature is 60 to 90. Precipitation for a predetermined time at ℃, usually about 0.02 to 0.25 times the time required for the addition of the addition solution, for about 0 to 2 hours, and finally maintaining the precipitation temperature of 60 to 90 ° C End the operation.
このようにして析出操作終了後、フィルタープレス等による濾過、スクリューデカンター等による遠心分離等の手段で固液分離し、次いで常温から７０〜９０℃程度の温度の純水でリパルプした後に再度固液分離する水洗操作を複数回繰り返し、洗浄除去可能なフリーのソーダ(f-Na2O)分〔フリーソーダ(f-Na2O)分の含有量の測定は試料を温水に浸漬して溶出させた後、JIS R9301-3-9に準じた原子吸光法で行う。〕を０．００２質量%以下、好ましくは可及的により低減せしめるのがよい。 In this way, after the precipitation operation is completed, solid-liquid separation is performed by means such as filtration with a filter press or centrifugal separation with a screw decanter, etc., and then repulped with pure water at a temperature of about 70 to 90 ° C. from room temperature to solid-liquid again. Repeat the washing operation several times to separate the free soda (f-Na 2 O) content that can be removed by washing (measure the content of free soda (f-Na 2 O) content by immersing the sample in warm water and eluting it). After that, the atomic absorption method according to JIS R9301-3-9 is performed. ] Is 0.002% by mass or less, preferably as much as possible.
本発明においては、析出操作で得られた水酸化アルミニウムは緩く凝集している。そこで、必要に応じて、析出操作で得られた水酸化アルミニウムを部分的に溶解させたり、あるいは、上記の水洗前又は水洗後に、好ましくは水洗後に、湿式解砕により析出操作で得られた水酸化アルミニウムの二次粒子を一次粒子にまで解砕する。この二次粒子を一次粒子に解砕する解砕操作は、具体的には例えば、得られた水酸化アルミニウムに純水を添加してスラリーを調製し、このスラリーを湿式解砕機（ビーズミル等）中に供給して行なわれる。 In the present invention, the aluminum hydroxide obtained by the precipitation operation is loosely agglomerated. Therefore, if necessary, the aluminum hydroxide obtained by the precipitation operation is partially dissolved, or the water obtained by the precipitation operation by wet crushing before or after the above water washing, preferably after water washing. The secondary particles of aluminum oxide are crushed to primary particles. Specifically, the crushing operation for crushing the secondary particles into primary particles is, for example, preparing a slurry by adding pure water to the obtained aluminum hydroxide, and then removing the slurry from a wet crusher (bead mill, etc.) It is done by feeding in.
上記のようにして、必要に応じて二次粒子を解砕して得られた水酸化アルミニウムは、乾燥機等により乾燥した後、製品の低ソーダ微粒水酸化アルミニウムとされる。この低ソーダ微粒水酸化アルミニウムは、通常その平均粒子径が２μm以下、好ましくは１．０μm以上２．０μm以下であり、また、全ソーダ分が０．０４質量%以下であり、更に、BET比表面積が１０m2/g以下である。 As described above, the aluminum hydroxide obtained by crushing the secondary particles as necessary is dried with a drier or the like, and then used as the low-soda fine aluminum hydroxide of the product. This low soda fine aluminum hydroxide usually has an average particle size of 2 μm or less, preferably 1.0 μm or more and 2.0 μm or less, and a total soda content of 0.04% by mass or less. The surface area is 10 m 2 / g or less.
そして、この低ソーダ微粒水酸化アルミニウムについては、必要によりシランカップリング剤、チタネートカップリング剤、ステアリン酸等の表面処理剤による表面処理が施されてもよい。 The low soda fine aluminum hydroxide may be subjected to a surface treatment with a surface treatment agent such as a silane coupling agent, a titanate coupling agent, or stearic acid, if necessary.
本発明の低ソーダ微粒水酸化アルミニウムは、平均粒子径２μm以下、全ソーダ分０．０４質量%以下、及びBET比表面積１０m2/g以下と何れも小さいギブサイト型水酸化アルミニウムであり、特に種々の高分子材料に耐熱性や難燃性を付与するための難燃材として優れた性能を発揮するものである。 The low soda fine aluminum hydroxide of the present invention is a gibbsite type aluminum hydroxide having an average particle size of 2 μm or less, a total soda content of 0.04% by mass or less, and a BET specific surface area of 10 m 2 / g or less. It exhibits excellent performance as a flame retardant for imparting heat resistance and flame resistance to the polymer material.
また、本発明の低ソーダ微粒水酸化アルミニウムの製造方法によれば、このような平均粒子径、全ソーダ分、及びBET比表面積が何れも小さくて種々の高分子材料用の難燃材として優れた性能を発揮するギブサイト型水酸化アルミニウムをバイヤー法によって容易に製造することができる。 In addition, according to the method for producing low-soda fine aluminum hydroxide of the present invention, the average particle diameter, the total soda content, and the BET specific surface area are all small and excellent as a flame retardant for various polymer materials. Gibbsite-type aluminum hydroxide exhibiting excellent performance can be easily produced by the Bayer method.
以下、実施例及び比較例に基づいて、本発明の好適な実施の形態を具体的に説明する。 Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.
［実施例１］
〔種子用水酸化アルミニウムの調製〕
バイヤー法で調製した平均粒子径１．２μm、全ソーダ(T-Na2O)分０．０４０質量%及びBET比表面積１２m2/gの水酸化アルミニウムを純水と混合して５００g/Lのスラリーを調製し、湿式粉砕機（WAB社製ダイノーミルKDL-PILOT）を用いて湿式粉砕し、平均粒子径１．０μm、全ソーダ分０．０４７質量%及びBET比表面積１４．８m2/gの水酸化アルミニウムを調製し、種子用水酸化アルミニウムとした。
[Example 1]
[Preparation of aluminum hydroxide for seeds]
An aluminum hydroxide having an average particle diameter of 1.2 μm, a soda (T—Na 2 O) content of 0.040% by mass and a BET specific surface area of 12 m 2 / g prepared by the Bayer method was mixed with pure water to give 500 g / L. A slurry was prepared, and wet pulverized using a wet pulverizer (Dynomill KDL-PILOT manufactured by WAB). The average particle size was 1.0 μm, the total soda content was 0.047% by mass, and the BET specific surface area was 14.8 m 2 / g. Aluminum hydroxide was prepared and used as seed aluminum hydroxide.
〔初期溶液の調製〕
初期媒体として純水を用い、また、上記の種子用水酸化アルミニウム１２０gを用い、容積５Lの析出槽内で７０℃に加温した純水と上記種子用水酸化アルミニウムとを混合してスラリー濃度６０g/Lの初期溶液２Lを調製した。
(Preparation of initial solution)
Pure water was used as an initial medium, and 120 g of the above-mentioned aluminum hydroxide for seeds was mixed with pure water heated to 70 ° C. in a precipitation tank having a volume of 5 L and the above-mentioned aluminum hydroxide for seeds to give a slurry concentration of 60 g / 2 L of an initial solution of L was prepared.
〔添加溶液の調製〕
バイヤー法により溶解Na2O分（Na2O濃度）１４８g/L、溶解Al2O3分（Al2O3濃度）１４９g/L、及びこれら溶解Na2O分と溶解Al2O3分とのモル比（Na2O／Al2O3）１．６のアルミン酸ナトリウム溶液を調製し、これを７０℃に加温して添加溶液とした。
(Preparation of additive solution)
According to the Bayer method, dissolved Na 2 O content (Na 2 O concentration) 148 g / L, dissolved Al 2 O 3 content (Al 2 O 3 concentration) 149 g / L, and these dissolved Na 2 O content and dissolved Al 2 O 3 content A sodium aluminate solution having a molar ratio (Na 2 O / Al 2 O 3 ) of 1.6 was prepared, and this was heated to 70 ° C. to obtain an added solution.
〔析出操作〕
析出槽内の上記初期溶液中に、攪拌下に上記添加溶液を連続的に添加し、析出槽内で水酸化アルミニウムの析出溶液を調製すると共に、析出溶液の過飽和Al2O3濃度を１５g/L以下に維持しながら水酸化アルミニウムを析出させ、添加溶液２Lが添加された時点で添加溶液の添加を終了し、引き続き７０℃に維持しながら２時間攪拌して水酸化アルミニウムを析出させ、析出操作を終了した。
(Deposition operation)
The additive solution is continuously added to the initial solution in the precipitation tank with stirring to prepare a precipitation solution of aluminum hydroxide in the precipitation tank, and the supersaturated Al 2 O 3 concentration of the precipitation solution is 15 g / While maintaining below L, aluminum hydroxide is precipitated. When 2 L of additive solution is added, the addition of the additive solution is terminated, and subsequently maintained at 70 ° C. for 2 hours to precipitate aluminum hydroxide. The operation has ended.
この析出操作の間、析出槽内の析出溶液は常に７０℃に維持され、また、水酸化アルミニウムの析出開始から析出終了までの平均過飽和Al2O3濃度は４．５g/Lであった。更に、添加溶液１L当りに析出した水酸化アルミニウム量（アルミナ換算）として求められた析出率は７４g/Lであった。 During this precipitation operation, the precipitation solution in the precipitation tank was always maintained at 70 ° C., and the average supersaturated Al 2 O 3 concentration from the start of precipitation of aluminum hydroxide to the end of precipitation was 4.5 g / L. Furthermore, the precipitation rate calculated | required as the amount of aluminum hydroxide (alumina conversion) precipitated per 1L of addition solutions was 74 g / L.
〔水洗・解砕操作〕
析出操作終了後、遠心分離機を用いて固液分離し、得られた個体について、７０℃の純水４．８m3でリパルプした後に固液分離する水洗操作を５回繰り返して行い、析出した水酸化アルミニウムを回収した。
[Washing and crushing operation]
After completion of the precipitation operation, solid-liquid separation was performed using a centrifuge, and the obtained solid was repulped with 4.8 m 3 of pure water at 70 ° C. and then subjected to a water-washing operation for solid-liquid separation 5 times to cause precipitation. Aluminum hydroxide was recovered.
次に、この回収した水酸化アルミニウムについて、純水を添加してスラリー濃度３００g/Lのスラリーを調製し、平均粒径が１．３μmとなるように解砕した。 Next, with respect to the recovered aluminum hydroxide, pure water was added to prepare a slurry having a slurry concentration of 300 g / L, and pulverized so that the average particle diameter became 1.3 μm.
次に、得られた水酸化アルミニウムを１３０℃の加熱下で約１時間乾燥して、実施例１の低ソーダ微粒水酸化アルミニウムを得た。 Next, the obtained aluminum hydroxide was dried for about 1 hour under heating at 130 ° C. to obtain low soda fine aluminum hydroxide of Example 1.
この実施例１で得られた低ソーダ微粒水酸化アルミニウムについて、平均粒子径、全ソーダ分、フリーソーダ(f-Na2O)分、及びBET比表面積をそれぞれ測定した。なお、平均粒子径はレーザー回折式粒度分布装置（日機装社製マイクロトラックX100）を用いて測定し、全ソーダ分及びフリーソーダ分はJIS R9301-3-9に準じた原子吸光法で測定し、また、BET比表面積は比表面積自動測定装置（マイクロメリテックス社製フローソーブII2300形）を用いて測定した。
結果を表１に示す。
With respect to the low soda fine aluminum hydroxide obtained in Example 1, the average particle size, the total soda content, the free soda (f-Na 2 O) content, and the BET specific surface area were measured. The average particle size was measured using a laser diffraction type particle size distribution device (Microtrack X100 manufactured by Nikkiso Co., Ltd.), the total soda content and the free soda content were measured by an atomic absorption method according to JIS R9301-3-9, The BET specific surface area was measured using a specific surface area automatic measuring device (Microsorbex, Flowsorb II2300 type).
The results are shown in Table 1.
［実施例２］
種子として使用した水酸化アルミニウムの平均粒子径、全ソーダ分、BET比表面積、添加量及び添加率と、添加溶液として用いたアルミン酸ナトリウム溶液の溶解Na2O分（Na2O濃度）、溶解Al2O3分（Al2O3濃度）、溶解Na2O分（Na2O濃度）と溶解Al2O3分（Al2O3濃度）とのモル比（Na2O／Al2O3）、添加量を表１に示す値に調整した以外は、上記実施例１と同様にして実施例２の低ソーダ微粒水酸化アルミニウムを得た。
[Example 2]
Average particle diameter of aluminum hydroxide used as seed, total soda content, BET specific surface area, addition amount and addition rate, dissolved sodium aluminate solution used as additive solution, Na 2 O content (Na 2 O concentration), dissolution Al 2 O 3 minutes (Al 2 O 3 concentration), molar ratio of dissolved Na 2 O components (Na 2 O concentration) to dissolved Al 2 O 3 minutes (Al 2 O 3 concentration) (Na 2 O / Al 2 O) 3 ) A low-soda fine aluminum hydroxide of Example 2 was obtained in the same manner as in Example 1 except that the addition amount was adjusted to the value shown in Table 1.
この析出操作の間、析出槽内の析出溶液は常に７０℃に維持され、また、水酸化アルミニウムの析出開始から析出終了までの平均過飽和Al2O3濃度は３．３g/Lであった。また、析出率は６９g/Lであった。 During this precipitation operation, the precipitation solution in the precipitation tank was always maintained at 70 ° C., and the average supersaturated Al 2 O 3 concentration from the start of precipitation of aluminum hydroxide to the end of precipitation was 3.3 g / L. The precipitation rate was 69 g / L.
この実施例２で得られた低ソーダ微粒水酸化アルミニウムについて、実施例１と同様に、その平均粒子径、全ソーダ分、フリーソーダ分、及びBET比表面積をそれぞれ測定した。
結果を表１に示す。
For the low soda fine aluminum hydroxide obtained in Example 2, the average particle diameter, the total soda content, the free soda content, and the BET specific surface area were measured in the same manner as in Example 1.
The results are shown in Table 1.
［比較例１］
種子として使用した水酸化アルミニウムの平均粒子径、全ソーダ分、BET比表面積、添加量及び添加率と、添加溶液として用いたアルミン酸ナトリウム溶液の溶解Na2O分（Na2O濃度）、溶解Al2O3分（Al2O3濃度）、溶解Na2O分（Na2O濃度）と溶解Al2O3分（Al2O3濃度）とのモル比（Na2O／Al2O3）、添加量を表１に示す値に調整した以外は、上記実施例１と同様にして比較例１の低ソーダ微粒水酸化アルミニウムを得た。
[Comparative Example 1]
Average particle diameter of aluminum hydroxide used as seed, total soda content, BET specific surface area, addition amount and addition rate, dissolved sodium aluminate solution used as additive solution, Na 2 O content (Na 2 O concentration), dissolution Al 2 O 3 minutes (Al 2 O 3 concentration), molar ratio of dissolved Na 2 O components (Na 2 O concentration) to dissolved Al 2 O 3 minutes (Al 2 O 3 concentration) (Na 2 O / Al 2 O) 3 ) A low soda fine aluminum hydroxide of Comparative Example 1 was obtained in the same manner as in Example 1 except that the addition amount was adjusted to the value shown in Table 1.
この析出操作の間、析出槽内の析出溶液は常に５０℃に維持され、また、水酸化アルミニウムの析出開始から析出終了までの平均過飽和Al2O3濃度は７．１g/Lであった。また、析出率は９８g/Lであった。
結果を表１に示す。
During this precipitation operation, the precipitation solution in the precipitation tank was always maintained at 50 ° C., and the average supersaturated Al 2 O 3 concentration from the start of precipitation of aluminum hydroxide to the end of precipitation was 7.1 g / L. Moreover, the precipitation rate was 98 g / L.
The results are shown in Table 1.
［比較例２］
初期媒体としてNa2O濃度１３４g/L、Al2O3濃度８６g/L、モル比(Na2O/Al2O3)２．６及び添加量２Lのアルミン酸ナトリウム溶液を用い、また、種子として表１に示す平均粒子径、全ソーダ分、BET比表面積、添加量及び添加率の水酸化アルミニウムを使用し、更に、添加溶液として表１に示す溶解Na2O分（Na2O濃度）、溶解Al2O3分（Al2O3濃度）、溶解Na2O分（Na2O濃度）と溶解Al2O3分（Al2O3濃度）とのモル比（Na2O／Al2O3）、添加量のアルミン酸ナトリウム溶液を用いた以外は、上記実施例１と同様にして比較例２の低ソーダ微粒水酸化アルミニウムを得た。
[Comparative Example 2]
As an initial medium, a sodium aluminate solution having a Na 2 O concentration of 134 g / L, an Al 2 O 3 concentration of 86 g / L, a molar ratio (Na 2 O / Al 2 O 3 ) of 2.6 and an addition amount of 2 L was used. The average particle diameter, total soda content, BET specific surface area, addition amount and addition rate shown in Table 1 are used, and the dissolved Na 2 O content (Na 2 O concentration) shown in Table 1 is used as the addition solution. , Dissolved Al 2 O 3 minutes (Al 2 O 3 concentration), molar ratio of dissolved Na 2 O components (Na 2 O concentration) to dissolved Al 2 O 3 minutes (Al 2 O 3 concentration) (Na 2 O / Al 2 O 3 ), a low soda fine aluminum hydroxide of Comparative Example 2 was obtained in the same manner as in Example 1 except that the added amount of sodium aluminate solution was used.
この析出操作の間、析出槽内の析出溶液は常に７０℃に維持され、また、水酸化アルミニウムの析出開始から析出終了までの平均過飽和Al2O3濃度は１３．７g/Lであった。また、析出率は５８g/Lであった。
結果を表１に示す。
During this precipitation operation, the precipitation solution in the precipitation tank was always maintained at 70 ° C., and the average supersaturated Al 2 O 3 concentration from the start of precipitation of aluminum hydroxide to the end of precipitation was 13.7 g / L. The precipitation rate was 58 g / L.
The results are shown in Table 1.
この表１に示す結果から明らかなように、実施例１及び実施例２の場合は、そのいずれも、解砕後の平均粒子径が２μm以下であって、全ソーダ(T-Na2O)分が０．０４質量%以下であり、また、ＢＥＴ比表面積が１０m2/g以下であるのに対し、比較例１の場合には析出温度が５０℃であって全ソーダ分（T-Na2O）が０．０７４%と高く、また、比較例２の場合には初期媒体のNa2O濃度が１３４g/LでAl2O3濃度が８６g/Lであって全ソーダ分（T-Na2O）が０．０４９%と高く、しかも、析出率が５８g/Lであって実施例１及び２や比較例１の場合と比較してその生産性が低い。 As is apparent from the results shown in Table 1, in both cases of Example 1 and Example 2, the average particle size after pulverization was 2 μm or less, and total soda (T-Na 2 O) was used. In the case of Comparative Example 1, the precipitation temperature was 50 ° C. and the total soda content (T-Na) was 0.04% by mass or less and the BET specific surface area was 10 m 2 / g or less. 2 O) is as high as 0.074%, and in the case of Comparative Example 2, the Na 2 O concentration of the initial medium is 134 g / L, the Al 2 O 3 concentration is 86 g / L, and the total soda content (T- Na 2 O) is as high as 0.049%, and the precipitation rate is 58 g / L, which is lower in productivity than those in Examples 1 and 2 and Comparative Example 1.
本発明は、平均粒子径及び全ソーダ分、更には必要によりBET比表面積が何れも極めて小さいギブサイト型の低ソーダ微粒水酸化アルミニウムを提供するものであり、このような低ソーダ微粒水酸化アルミニウムは種々の高分子材料に耐熱性や難燃性を付与するための難燃材等の用途に極めて有用であり、その工業的価値の高いものである。 The present invention provides a gibbsite-type low soda fine aluminum hydroxide having an extremely small average particle size and total soda, and if necessary, a BET specific surface area, which is extremely small. It is extremely useful for uses such as flame retardants for imparting heat resistance and flame retardancy to various polymer materials, and has high industrial value.
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