JP2024022000A - granular magnesium oxide - Google Patents
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- 239000000395 magnesium oxide Substances 0.000 title claims abstract description 81
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 81
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims abstract description 53
- 239000002245 particle Substances 0.000 claims abstract description 59
- 239000006185 dispersion Substances 0.000 claims abstract description 21
- 238000000790 scattering method Methods 0.000 claims description 16
- 239000005871 repellent Substances 0.000 description 29
- 230000002940 repellent Effects 0.000 description 29
- 239000002002 slurry Substances 0.000 description 27
- 238000000034 method Methods 0.000 description 17
- 241000251468 Actinopterygii Species 0.000 description 16
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 15
- 239000000347 magnesium hydroxide Substances 0.000 description 15
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 15
- 239000013535 sea water Substances 0.000 description 15
- 238000010304 firing Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 9
- 238000009826 distribution Methods 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000001132 ultrasonic dispersion Methods 0.000 description 6
- 230000034994 death Effects 0.000 description 5
- 231100000517 death Toxicity 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 239000008187 granular material Substances 0.000 description 4
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 4
- 239000001095 magnesium carbonate Substances 0.000 description 4
- 235000014380 magnesium carbonate Nutrition 0.000 description 4
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 238000005507 spraying Methods 0.000 description 4
- 230000004083 survival effect Effects 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000005469 granulation Methods 0.000 description 3
- 230000003179 granulation Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- 241000894006 Bacteria Species 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 241000290272 Karenia mikimotoi Species 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 159000000003 magnesium salts Chemical class 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000000384 rearing effect Effects 0.000 description 2
- 239000013049 sediment Substances 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- IYLLULUTZPKQBW-UHFFFAOYSA-N Acrinol Chemical compound CC(O)C(O)=O.C1=C(N)C=CC2=C(N)C3=CC(OCC)=CC=C3N=C21 IYLLULUTZPKQBW-UHFFFAOYSA-N 0.000 description 1
- 102100026816 DNA-dependent metalloprotease SPRTN Human genes 0.000 description 1
- 101710175461 DNA-dependent metalloprotease SPRTN Proteins 0.000 description 1
- 241000206758 Heterosigma Species 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 241001600434 Plectroglyphidodon lacrymatus Species 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
- 241000700605 Viruses Species 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 239000012190 activator Substances 0.000 description 1
- 230000002353 algacidal effect Effects 0.000 description 1
- 239000003619 algicide Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 238000009360 aquaculture Methods 0.000 description 1
- 244000144974 aquaculture Species 0.000 description 1
- 238000010170 biological method Methods 0.000 description 1
- 238000009395 breeding Methods 0.000 description 1
- 230000001488 breeding effect Effects 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- SXYCCJAPZKHOLS-UHFFFAOYSA-N chembl2008674 Chemical compound [O-][N+](=O)C1=CC=C2C(N=NC3=C4C=CC=CC4=CC=C3O)=C(O)C=C(S(O)(=O)=O)C2=C1 SXYCCJAPZKHOLS-UHFFFAOYSA-N 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 230000003203 everyday effect Effects 0.000 description 1
- 210000002816 gill Anatomy 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 230000002147 killing effect Effects 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052901 montmorillonite Inorganic materials 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 235000015170 shellfish Nutrition 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 230000004936 stimulating effect Effects 0.000 description 1
- 230000000638 stimulation Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 230000009182 swimming Effects 0.000 description 1
- UEUXEKPTXMALOB-UHFFFAOYSA-J tetrasodium;2-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]acetate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]C(=O)CN(CC([O-])=O)CCN(CC([O-])=O)CC([O-])=O UEUXEKPTXMALOB-UHFFFAOYSA-J 0.000 description 1
Landscapes
- Farming Of Fish And Shellfish (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Agricultural Chemicals And Associated Chemicals (AREA)
Abstract
Description
本発明は、粒状酸化マグネシウムに関する。 The present invention relates to granular magnesium oxide.
近年、赤潮がより多くの漁業被害を伴うようになり、大きな社会問題となっている。これまで、一般的な赤潮対策としては、物理的手法（養殖用の筏を海底へ移動させる、海面の赤潮を回収する、海水を撹拌循環させ赤潮の濃度を下げるなど）や化学的手法（活性白土やモンモリロナイトなどの粘土及び粘土機能賦活剤、アクリノール、水酸化マグネシウムの投入など）や生物的手法（海洋において互いに影響を及ぼしあっている微細藻と従属栄養細菌の関係を応用した殺藻細菌や殺藻ウイルスなど）が提案されている。 In recent years, red tide has caused more damage to fisheries and has become a major social problem. Until now, general red tide countermeasures have included physical methods (such as moving aquaculture rafts to the seabed, collecting red tide from the sea surface, and stirring and circulating seawater to reduce the concentration of red tide) and chemical methods (activating Injection of clays such as white clay and montmorillonite, clay function activators, acrinol, magnesium hydroxide, etc.) and biological methods (algicidal bacteria that apply the relationship between microalgae and heterotrophic bacteria that influence each other in the ocean) algaecide viruses, etc.) have been proposed.
例えば、特許文献１には、即効性を有し、赤潮の駆除効率を大幅に向上させた赤潮駆除剤として、酸化マグネシウムを含有するものが開示されている。また、特許文献２には、苦土系粉粒体からなる底質改善剤が開示されている。 For example, Patent Document 1 discloses a red tide repellent containing magnesium oxide that has immediate effect and greatly improves red tide extermination efficiency. Further, Patent Document 2 discloses a sediment improving agent made of magnesium-based powder.
酸化マグネシウムとしては、粗粒または顆粒のものが提案されている（例えば、特許文献３，４参考）。これらにおいては、ＢＥＴ比表面積は最大でも６０ｍ２／ｇである。また、所定の粒子形態とすることで、樹脂やゴムに配合した際に材料物性の低下をきたさない高活性の酸化マグネシウム粒子が提案されている（例えば、特許文献５，６参照）。これらに記載されている酸化マグネシウム粒子は、平均粒子径が１０μｍ以下の粉末状である。 As magnesium oxide, coarse particles or granules have been proposed (for example, see Patent Documents 3 and 4). In these, the BET specific surface area is at most 60 m 2 /g. In addition, highly active magnesium oxide particles have been proposed that do not cause deterioration of material properties when blended into resins or rubbers by forming them into a predetermined particle form (see, for example, Patent Documents 5 and 6). The magnesium oxide particles described in these documents are in powder form with an average particle diameter of 10 μm or less.
酸化マグネシウムは、底質の改善や赤潮駆除などを目的として海洋、湖沼、河川などに散布されるが、水生生物に悪影響を及ぼさないこと、特に毒性抵抗の低い稚魚や稚貝の斃死を引き起こさないことが求められる。 Magnesium oxide is sprayed into oceans, lakes, rivers, etc. for the purpose of improving bottom sediment and eliminating red tide, but it does not have a negative effect on aquatic organisms, and in particular does not cause the death of young fish and shellfish with low toxicity resistance. That is required.
そこで本発明は、稚魚に対する安全性を備えた粒状酸化マグネシウムを提供することを目的とする。本発明の粒状酸化マグネシウムは、特に赤潮駆除剤として好適に用いることが出来る。 Therefore, an object of the present invention is to provide granular magnesium oxide that is safe for young fish. The granular magnesium oxide of the present invention can be particularly suitably used as a red tide repellent.
本発明に係る粒状酸化マグネシウムは、前処理として分散処理を行わないでレーザー回折散乱法により測定した平均粒子径（Ａ）が１００～７００μｍであり、前処理として分散処理を行った後にレーザー回折散乱法により測定した平均粒子径（Ｂ）が０．１～１０μｍであって、ＢＥＴ比表面積が７０ｍ２／ｇ以上であることを特徴とする。 The granular magnesium oxide according to the present invention has an average particle diameter (A) of 100 to 700 μm measured by a laser diffraction scattering method without performing a dispersion treatment as a pretreatment, and a laser diffraction scattering after performing a dispersion treatment as a pretreatment. The average particle diameter (B) measured by the method is 0.1 to 10 μm, and the BET specific surface area is 70 m 2 /g or more.
本発明によれば、稚魚に対する安全性を備えた粒状酸化マグネシウムを提供することができる。本発明の粒状酸化マグネシウムは、特に赤潮駆除剤として好適に用いることが出来る。 According to the present invention, it is possible to provide granular magnesium oxide that is safe for young fish. The granular magnesium oxide of the present invention can be particularly suitably used as a red tide repellent.
本発明者らは鋭意検討の結果、高活性かつ前処理として分散処理を行わないで測定した平均粒子径の大きい粒状酸化マグネシウムが、赤潮に対する駆除効果と稚魚に対する安全性を兼ね備えた赤潮駆除剤として好適に用い得ることを見出し、本発明を完成させるに至った。
以下、本発明の実施形態を詳細に説明する。
As a result of intensive studies, the present inventors found that granular magnesium oxide, which is highly active and has a large average particle diameter measured without performing dispersion treatment as a pretreatment, can be used as a red tide repellent that has both a red tide extermination effect and safety for young fish. The present inventors have found that the present invention can be suitably used, and have completed the present invention.
Embodiments of the present invention will be described in detail below.
本発明の粒状酸化マグネシウムは造粒物であり、前処理として分散処理を行わないで測定した、レーザー回折散乱法による平均粒子径（Ａ）が、１００～７００μｍの範囲内である。 The granular magnesium oxide of the present invention is a granulated product, and the average particle diameter (A) measured by a laser diffraction scattering method without performing a dispersion treatment as a pretreatment is within the range of 100 to 700 μm.
本明細書における分散処理とは、液中での超音波分散処理をさす。通常、レーザー回折散乱法により粒度分布を測定する際には、前処理として超音波分散装置にて分散処理を行う。超音波分散装置は粒度分布測定装置に内蔵されているものを使っても良いし、別の超音波分散装置を使うこともできる。レーザー回折散乱法による粒度分布の測定においては、特筆しない限り、分散処理を行った後に粒度分布を測定したものである。 Dispersion treatment in this specification refers to ultrasonic dispersion treatment in a liquid. Usually, when measuring particle size distribution by laser diffraction scattering method, dispersion treatment is performed using an ultrasonic dispersion device as a pretreatment. As the ultrasonic dispersion device, one built in the particle size distribution measuring device may be used, or a separate ultrasonic dispersion device may be used. In the measurement of particle size distribution by laser diffraction scattering method, unless otherwise specified, the particle size distribution was measured after performing a dispersion treatment.
本発明における平均粒子径（Ａ）は、前処理として通常行われる分散処理を行わないでレーザー回折散乱法により測定した平均粒子径であり、造粒物の平均粒子径（造粒径）ということができる。造粒物は、海域に投入された際にある程度の造粒径を保持し、その後、海中で徐々に崩壊する。 The average particle diameter (A) in the present invention is the average particle diameter measured by a laser diffraction scattering method without performing a dispersion treatment that is usually performed as a pretreatment, and refers to the average particle diameter (granulation diameter) of the granulated product. Can be done. When the granules are put into the sea, they maintain a certain granule size and then gradually disintegrate in the sea.
平均粒子径（Ａ）が１００μｍ未満の場合には、赤潮プランクトンの細胞に作用して殺滅効果は期待できるが、他の生物への刺激による斃死を引き起こすおそれがある。海洋生物の中でも脆弱な稚魚などは、わずかな刺激により斃死する可能性が高い。一方、７００μｍより大きい場合には、海中での沈降速度が速すぎて赤潮内の滞留時間が短くなり、赤潮駆除効果が小さくなる。平均粒子径（Ａ）は、１５０～５００μｍの範囲内であることが好ましい。 If the average particle size (A) is less than 100 μm, it can be expected to have a killing effect by acting on red tide plankton cells, but there is a risk of stimulating other organisms and causing death. Among marine creatures, young fish and other vulnerable creatures are likely to die from even the slightest stimulation. On the other hand, if it is larger than 700 μm, the sedimentation speed in the sea is too fast and the residence time in the red tide becomes short, reducing the red tide extermination effect. The average particle diameter (A) is preferably within the range of 150 to 500 μm.
本発明の粒状酸化マグネシウムは、前処理として分散処理を行った後にレーザー回折散乱法により測定した平均粒子径（Ｂ）が、０．１～１０μｍの範囲内である。平均粒子径（Ｂ）は、レーザー回折散乱法による粒度分布測定装置を用いて測定することができる。平均粒子径（Ｂ）が大きすぎる場合には、海中で粒状物が徐々に拡散した後の粒子の存在密度が小さくなることから赤潮防除効果が低下する。一方、小さすぎると粒子が嵩高くなり粒状物の製造効率が悪くなる。平均粒子径（Ｂ）は、０．５～６．０μｍの範囲内であることが好ましい。 The granular magnesium oxide of the present invention has an average particle diameter (B) in the range of 0.1 to 10 μm as measured by a laser diffraction scattering method after performing a dispersion treatment as a pretreatment. The average particle diameter (B) can be measured using a particle size distribution measuring device using a laser diffraction scattering method. If the average particle diameter (B) is too large, the density of the particles after they are gradually diffused in the sea becomes small, resulting in a decrease in the red tide control effect. On the other hand, if it is too small, the particles will become bulky and the production efficiency of granules will deteriorate. The average particle diameter (B) is preferably within the range of 0.5 to 6.0 μm.
粒状酸化マグネシウムの平均粒子径（Ｂ）は、原料として用いる水酸化マグネシウムの平均粒子径に起因する。一方、粒状酸化マグネシウムの平均粒子径（Ａ）は、焼成前の水酸化マグネシウムなどの造粒条件を調整することによって所望の範囲に制御することができる。粒状酸化マグネシウムの平均粒子径の制御法については、追って詳細に説明する。 The average particle size (B) of the granular magnesium oxide is determined by the average particle size of magnesium hydroxide used as a raw material. On the other hand, the average particle diameter (A) of granular magnesium oxide can be controlled within a desired range by adjusting the granulation conditions of magnesium hydroxide and the like before firing. A method for controlling the average particle diameter of granular magnesium oxide will be described in detail later.
本発明の粒状酸化マグネシウムは、ＢＥＴ比表面積が７０ｍ2／ｇ以上に規定されるので高活性である。ＢＥＴ比表面積が７０ｍ2／ｇ未満の場合には、赤潮防除効果が低下する。粒状酸化マグネシウムのＢＥＴ比表面積は、好ましくは８０ｍ2／ｇ以上であり、より好ましくは１２０ｍ2／ｇ以上である。なお、酸化マグネシウムの生産効率を考慮すると、ＢＥＴ比表面積の上限は、３００ｍ2／ｇ程度である The granular magnesium oxide of the present invention has a BET specific surface area of 70 m 2 /g or more, so it is highly active. When the BET specific surface area is less than 70 m 2 /g, the red tide control effect decreases. The BET specific surface area of the granular magnesium oxide is preferably 80 m 2 /g or more, more preferably 120 m 2 /g or more. In addition, considering the production efficiency of magnesium oxide, the upper limit of the BET specific surface area is about 300 m 2 /g.
粒状酸化マグネシウムのＢＥＴ比表面積は、原料となる水酸化マグネシウムの焼成温度によって所望の範囲に制御することができる。焼成温度が低いほどＢＥＴ比表面積は増大する傾向にある。 The BET specific surface area of the granular magnesium oxide can be controlled within a desired range by the firing temperature of the raw material magnesium hydroxide. The BET specific surface area tends to increase as the firing temperature decreases.
本発明の粒状酸化マグネシウムは、目開き０．１５ｍｍの篩下質量の割合が６０％以下であることが好ましい。目開き０．１５ｍｍの篩下質量の割合が６０％以下であることは、粉状物が少ないことを意味し、これによって稚魚の捕食による鰓への詰りに対する安全性がよりいっそう高められる。目開き０．１５ｍｍの篩下質量の割合は、５０％以下であることがより好ましく、４０％以下であることがさらに好ましい。 In the granular magnesium oxide of the present invention, it is preferable that the proportion of the mass under the sieve with a mesh size of 0.15 mm is 60% or less. A ratio of 60% or less of the mass under the sieve with a mesh size of 0.15 mm means that there is little powdery matter, which further increases the safety against clogging of the gills due to predation by young fish. The proportion of the mass under the sieve with a mesh opening of 0.15 mm is more preferably 50% or less, and even more preferably 40% or less.
本発明の粒状酸化マグネシウムは、例えば、粒状の水酸化マグネシウムを焼成して製造することができる。粒状の水酸化マグネシウムは、篩別粒度が、５．０～０．５ｍｍ、好ましくは２．０～０．５ｍｍの範囲内に調製したものが好ましい。水酸化マグネシウムとしては、海水中のマグネシウム塩と水酸化カルシウムとを反応させた、所謂海水法による水酸化マグネシウムなどを使用することができる。 The granular magnesium oxide of the present invention can be produced, for example, by firing granular magnesium hydroxide. The granular magnesium hydroxide is preferably prepared to have a sieved particle size of 5.0 to 0.5 mm, preferably 2.0 to 0.5 mm. As magnesium hydroxide, magnesium hydroxide produced by the so-called seawater method, in which magnesium salt in seawater and calcium hydroxide are reacted, can be used.
なお、篩別粒度が５．０～０．５ｍｍの粒状の水酸化マグネシウムは、例えば、レーザー回折散乱法による平均粒子径が０．１～１０μｍの水酸化マグネシウム粒子を造粒して製造することができる。造粒物の平均粒子径は、造粒条件を調整して制御することができる。 Note that granular magnesium hydroxide with a sieved particle size of 5.0 to 0.5 mm can be produced, for example, by granulating magnesium hydroxide particles with an average particle size of 0.1 to 10 μm by laser diffraction scattering method. Can be done. The average particle diameter of the granulated product can be controlled by adjusting the granulation conditions.
水酸化マグネシウムの焼成温度は、４５０～８００℃の範囲が好ましい。焼成温度が４５０℃未満の場合には、焼成が不十分となり未分解の水酸化マグネシウムが増加する。一方、焼成温度が８００℃を超えると、ＢＥＴ比表面積が小さくなる。例えば、箱型焼成炉やロータリー式の焼成炉等を用いて、６０～１８０分程度、水酸化マグネシウムを焼成することにより、所望の粒状酸化マグネシウムを製造することができる。得られた粒状酸化マグネシウムは、必要に応じて分級を行って所定の粒度に調整してもよい。 The firing temperature of magnesium hydroxide is preferably in the range of 450 to 800°C. If the firing temperature is less than 450°C, the firing will be insufficient and undecomposed magnesium hydroxide will increase. On the other hand, when the firing temperature exceeds 800°C, the BET specific surface area becomes small. For example, desired granular magnesium oxide can be produced by firing magnesium hydroxide for about 60 to 180 minutes using a box-shaped firing furnace, rotary-type firing furnace, or the like. The obtained granular magnesium oxide may be classified to have a predetermined particle size, if necessary.
本発明の粒状酸化マグネシウムは、水酸化マグネシウム以外の原料を用いて製造することもできる。例えば、炭酸マグネシウム、塩基性炭酸マグネシウムなどのマグネシウム塩を焼成して熱分解する方法などが挙げられる。炭酸マグネシウムとしては、マグネサイト鉱石などを使用することができる。 The granular magnesium oxide of the present invention can also be produced using raw materials other than magnesium hydroxide. For example, a method of thermally decomposing a magnesium salt such as magnesium carbonate or basic magnesium carbonate by firing may be mentioned. As magnesium carbonate, magnesite ore or the like can be used.
本発明の粒状酸化マグネシウムは、以下の条件を満たしているので、稚魚に対する安全性を備えた赤潮駆除剤として用いることができる。
・前処理として分散処理を行わないでレーザー回折散乱法により測定した平均粒子径（Ａ）が１００～７００μｍ
・分散処理を行った後にレーザー回折散乱法により測定した平均粒子径（Ｂ）が０．１～１０μｍ
・ＢＥＴ比表面積が７０ｍ２／ｇ以上
Since the granular magnesium oxide of the present invention satisfies the following conditions, it can be used as a red tide repellent that is safe for young fish.
- Average particle diameter (A) measured by laser diffraction scattering method without dispersion treatment as pretreatment is 100 to 700 μm
- Average particle diameter (B) measured by laser diffraction scattering method after dispersion treatment is 0.1 to 10 μm
・BET specific surface area is 70m 2 /g or more
駆除対象となる赤潮は特に制限されないが、一般に赤潮の原因となるプランクトンとして知られているシャトラネ・マリナ、ヘテロシグマ・アカシオ、カレニア・ミキモトイなどの種々の植物性プランクトンに特に効果を奏する。 Although there are no particular restrictions on the red tide that can be exterminated, it is particularly effective against various phytoplankton such as Chatelaine marina, Heterosigma acacio, and Karenia mikimotoi, which are generally known as plankton that cause red tide.
本発明の粒状酸化マグネシウムは、原料に由来して含まれる不純物や原料の一部が残留していてもよい。酸化マグネシウムの含有量としては、７０質量％以上であることが好ましく、８０質量％以上であることがより好ましく、８５質量％以上であることが更に好ましい。 In the granular magnesium oxide of the present invention, impurities derived from the raw materials and a part of the raw materials may remain. The content of magnesium oxide is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more.
粒状酸化マグネシウムは、必要に応じて界面活性剤、固着剤、分散剤及び／又は安定剤などを添加してもよい。 A surfactant, a sticking agent, a dispersing agent, and/or a stabilizer may be added to the granular magnesium oxide as necessary.
本発明の粒状酸化マグネシウムを赤潮駆除剤として用いる場合は、任意の方法により赤潮を駆除することができる。例えば、赤潮が発生している海域若しくは発生傾向のある海域（赤潮発生海域）に、赤潮駆除剤をそのまま散布することができる。赤潮駆除剤は、水又は海水へ分散させたスラリーとして用いてもよい。分散性と作業性の観点からは、赤潮駆除剤スラリーが好ましく、スラリー中のＭｇＯ濃度は、０．１～２０％程度であることがより好ましい。散布方法としては、ひしゃく、散布機などによる散布、移動しながらの船上や動力式散水機を使用した散水、ドローンやヘリコプターなどによる空中散布などが挙げられる。 When the granular magnesium oxide of the present invention is used as a red tide exterminating agent, red tide can be exterminated by any method. For example, a red tide repellent can be directly sprayed in a sea area where red tide is occurring or a sea area where red tide tends to occur (a sea area where red tide occurs). The red tide repellent may be used as a slurry dispersed in water or seawater. From the viewpoint of dispersibility and workability, a red tide repellent slurry is preferred, and the MgO concentration in the slurry is more preferably about 0.1 to 20%. Spraying methods include spraying with a ladle or sprayer, watering on a moving boat or using a powered water sprinkler, and aerial spraying using a drone or helicopter.
粒状酸化マグネシウムの海への散布量は、海域における赤潮の発生の状況や目的（予防又は発生制御）などによっても異なるが、通常、海域の単位面積に対して粒状酸化マグネシウムが５０～２００ｇ／ｍ２程度となるような割合で、１～３日に１回程度供することができる。 The amount of granular magnesium oxide sprayed into the ocean varies depending on the situation and purpose (prevention or control) of red tide occurrence in the ocean area, but usually 50 to 200 g/m of granular magnesium oxide per unit area of the ocean area. It can be served about once every 1 to 3 days at a rate of about 2 servings.
本発明の粒状酸化マグネシウムは、赤潮を構成するプランクトンに付着してプランクトンを沈降させるとともに、プランクトンの細胞を損傷する効果を有している。このため、通常赤潮が発生している海域の単位面積あたりの散布量として施工される。なお、赤潮が発生している場合や発生傾向がある場合は、毎日使用することが好ましい。 The granular magnesium oxide of the present invention has the effect of adhering to plankton constituting red tide and causing the plankton to settle, as well as damaging plankton cells. For this reason, the amount of spraying is usually applied per unit area of sea areas where red tide occurs. In addition, if red tide is occurring or has a tendency to occur, it is preferable to use it every day.
いずれの方法で海域に散布した場合でも、本発明の粒状酸化マグネシウムを用いることによって、稚魚の斃死を顕著に抑制しつつ赤潮駆除という効果が得られる。 No matter which method is used to spray the sea area, by using the granular magnesium oxide of the present invention, the effect of eliminating red tide can be obtained while significantly suppressing the mortality of young fish.
以下、本発明を実施例に基づいて具体的に説明するが、これらは本発明の目的を限定するものではなく、また、本発明は、これら実施例に限定されるものではない。 Hereinafter, the present invention will be specifically explained based on Examples, but these do not limit the purpose of the present invention, and the present invention is not limited to these Examples.
（酸化マグネシウムの製造）
まず、サンプルとなる酸化マグネシウム（ＭｇＯ（Ａ）、ＭｇＯ（Ｂ）、ＭｇＯ（Ｃ）を準備した。
粒状の水酸化マグネシウム（宇部マテリアルズ株式会社製、ＵＤ６５、篩別粒度２．０～０．５ｍｍ）を、電気加熱外熱式ロータリーキルンを用いて、電気炉温度７１５℃、滞留時間３０分にて焼成した。こうして得られた高活性粒状酸化マグネシウムを、ＭｇＯ（Ａ）とした。
微粉状中活性酸化マグネシウム（宇部マテリアルズ株式会社製、ＵＣ８０、ＢＥＴ比表面積、２６ｍ2／ｇ）を、ＭｇＯ（Ｂ）とした。
微粉状高活性酸化マグネシウム（宇部マテリアルズ株式会社製、ＵＣＭ１５０、ＢＥＴ比表面積、１７４ｍ2／ｇ）を、ＭｇＯ（Ｃ）とした。
(Manufacture of magnesium oxide)
First, samples of magnesium oxide (MgO (A), MgO (B), and MgO (C)) were prepared.
Granular magnesium hydroxide (manufactured by Ube Materials Co., Ltd., UD65, sieved particle size 2.0 to 0.5 mm) was heated using an electrically heated external heating rotary kiln at an electric furnace temperature of 715°C and a residence time of 30 minutes. Fired. The highly active granular magnesium oxide thus obtained was designated as MgO(A).
Finely powdered medium active magnesium oxide (manufactured by Ube Materials Co., Ltd., UC80, BET specific surface area, 26 m 2 /g) was used as MgO (B).
Finely powdered highly active magnesium oxide (manufactured by Ube Materials Co., Ltd., UCM150, BET specific surface area, 174 m 2 /g) was used as MgO(C).
各酸化マグネシウムについて、篩による粒度、平均粒子径（Ａ）、平均粒子径（Ｂ）、およびＢＥＴ比表面積、酸化マグネシウム含有量を求めた。それぞれの測定方法は、以下のとおりである。 For each magnesium oxide, the particle size by sieving, average particle diameter (A), average particle diameter (B), BET specific surface area, and magnesium oxide content were determined. The respective measurement methods are as follows.
＜篩による粒度＞
目開き０．５ｍｍ、０．３ｍｍ、０．１５ｍｍの円形標準篩を、上から目開きが大きい順に積み重ね、上からサンプルの酸化マグネシウム５０ｇを投入した。積み重ねた円形標準篩を、電磁式振盪機（ＡＮＡＬＹＳＥＴＴＥ ３ ＳＰＡＲＴＡＮ ＦＲＩＴＳＨ製）を用い、振幅２ｍｍの条件にて５分間振盪して、サンプルの篩分けを行った。振盪後、＋０．５ｍｍ、－０．５ｍｍ＋０．３ｍｍ、－０．３ｍｍ＋０．１５ｍｍ、－０．１５ｍｍそれぞれの質量を測定し、全量に対する割合を求めて篩による粒度とした。
<Particle size by sieve>
Circular standard sieves with mesh openings of 0.5 mm, 0.3 mm, and 0.15 mm were stacked in descending order of mesh opening from the top, and 50 g of magnesium oxide as a sample was poured from above. The stacked circular standard sieves were shaken for 5 minutes at an amplitude of 2 mm using an electromagnetic shaker (ANALYSETTE 3 manufactured by SPARTAN FRITSH) to sieve the samples. After shaking, the mass of each of +0.5 mm, -0.5 mm +0.3 mm, -0.3 mm +0.15 mm, and -0.15 mm was measured, and the ratio to the total amount was determined to determine the particle size by sieving.
＜前処理として分散処理を行わないで測定した平均粒子径（Ａ）＞
レーザー回折式粒度分布測定装置（ＭＩＣＲＯＴＲＡＣ ＭＴ３３００ＥＸII マイクロトラック・ベル（株）製）を使用した。イオン交換水５０ｍＬとサンプル０．５ｇをビーカーに収容し、手で軽くビーカーを振って混ぜ合わせた。その後、直ちに粒度分布測定装置に投入し体積基準の平均粒子径（Ａ）を測定した。
<Average particle diameter (A) measured without dispersion treatment as pretreatment>
A laser diffraction particle size distribution analyzer (MICROTRAC MT3300EXII manufactured by Microtrac Bell Co., Ltd.) was used. 50 mL of ion-exchanged water and 0.5 g of sample were placed in a beaker and mixed by shaking the beaker lightly by hand. Thereafter, it was immediately put into a particle size distribution measuring device and the volume-based average particle diameter (A) was measured.
＜前処理として分散処理を行った後に測定した平均粒子径（Ｂ）＞
レーザー回折式粒度分布測定装置（ＭＩＣＲＯＴＲＡＣ ＭＴ３３００ＥＸII マイクロトラック・ベル（株）製）を使用した。イオン交換水５０ｍＬとサンプル０．５ｇをビーカーに収容し、手で軽くビーカーを振って混ぜ合わせた。その後、粒度分布測定装置に投入したのち装置内蔵の超音波分散装置にて、出力４０Ｗで３分間の超音波分散処理を施してから、体積基準の平均粒子径（Ｂ）を測定した。
<Average particle diameter (B) measured after performing dispersion treatment as pretreatment>
A laser diffraction particle size distribution analyzer (MICROTRAC MT3300EXII manufactured by Microtrac Bell Co., Ltd.) was used. 50 mL of ion-exchanged water and 0.5 g of sample were placed in a beaker and mixed by shaking the beaker lightly by hand. After that, it was put into a particle size distribution measuring device, and then subjected to ultrasonic dispersion treatment for 3 minutes at an output of 40 W using an ultrasonic dispersion device built into the device, and then the volume-based average particle diameter (B) was measured.
＜ＢＥＴ比表面積の測定＞
ＢＥＴ比表面積測定装置（ＭＯＵＮＴＥＣＨ社製、Ｍａｃｓｏｒｂ ＨＭ ｍｏｄｅｌ－１２１０）にて、サンプルセルに、サンプルを約０．１ｇ入れ、１８０℃で１０分間の前処理により脱気後、ＢＥＴ１点法により測定した。
<Measurement of BET specific surface area>
Approximately 0.1 g of the sample was placed in a sample cell using a BET specific surface area measurement device (Macsorb HM model-1210, manufactured by MOUNTECH), and after degassing by pretreatment at 180°C for 10 minutes, measurement was performed using the BET 1-point method. .
＜酸化マグネシウム含有量＞
試料１．０ｇを量り取り、濃塩酸１０ｍＬと純水２０ｍＬを加えて加熱溶解した後、純水で２５０ｍＬにメスアップした。５ｍＬを分取し、さらに純水で１５０ｍＬに希釈し、不純物金属イオンをマスクするため、５０体積％トリエタノールアミン水溶液５ｍＬを添加した。塩化アンモニウム・アンモニア緩衝液でｐＨを９．８～１０．２に調整し、指示薬としてエリオクロムブラックＴ溶液を少量加え、０．０５規定のエチレンジアミン四酢酸ナトリウム水溶液で滴定し、以下の式からＭｇＯ含有量を求めた。
<Magnesium oxide content>
1.0 g of a sample was weighed out, 10 mL of concentrated hydrochloric acid and 20 mL of pure water were added, and the solution was heated and dissolved, and then the volume was made up to 250 mL with pure water. 5 mL was collected and further diluted to 150 mL with pure water, and 5 mL of a 50% by volume triethanolamine aqueous solution was added to mask impurity metal ions. Adjust the pH to 9.8 to 10.2 with ammonium chloride/ammonia buffer, add a small amount of Eriochrome Black T solution as an indicator, titrate with 0.05N aqueous solution of sodium ethylenediaminetetraacetate, and use the following formula to determine MgO The content was determined.
得られた結果を、下記表にまとめる。 The results obtained are summarized in the table below.
＜赤潮駆除剤の調製＞
サンプルとしての酸化マグネシウムは、殺菌した濾過海水に添加して、所定のＭｇＯ濃度の赤潮駆除剤スラリーを調製する。ＭｇＯ濃度は、１００～１０００ｐｐｍの範囲内で適宜選択することができる。
<Preparation of red tide repellent>
Magnesium oxide as a sample is added to sterilized filtered seawater to prepare a red tide repellent slurry having a predetermined MgO concentration. The MgO concentration can be appropriately selected within the range of 100 to 1000 ppm.
＜安全性評価方法＞
所定濃度に希釈された赤潮駆除剤スラリーを収容した水槽に、平均尾叉長５５．５ｍｍ、平均体重２．７ｇのブリの稚魚を５匹入れて、経過時間ごとの生残数を調査する。飼育開始から６時間経過後の斃死数がゼロであれば安全性は合格とする。６時間未満に斃死が確認された場合には、安全性は不十分であり、例えば３時間で斃死が確認された場合には、安全性を有していない。
<Safety evaluation method>
Five young yellowtail fish with an average fork length of 55.5 mm and an average weight of 2.7 g are placed in an aquarium containing a red tide repellent slurry diluted to a predetermined concentration, and the number of survivors is investigated at each elapsed time. If the number of deaths after 6 hours from the start of breeding is zero, the safety is passed. If death is confirmed in less than 6 hours, safety is insufficient; for example, if death is confirmed in 3 hours, safety is not achieved.
＜生残細胞密度評価方法＞
赤潮プランクトン（K.mikimotoi強毒株）を含む海水をろ過海水にて希釈して、約１，０００ｃｅｌｌｓ／ｃｍ３～２０，０００ｃｅｌｌｓ／ｃｍ３に調整する。これを評価用の試料として用いる。
試料と赤潮駆除剤スラリー各１ｍＬを、それぞれ別のマイクロプレートへ収容する。マイクロピペットを用いて双方のマイクロプレートから供試液計２ｍＬを吸引し、マイクロプレートへの吐出とへの吸引を繰り返して混合する。その後、室温（２２℃）で静置する。所定の経過時間後、顕微鏡にてマイクロプレート中の赤潮プランクトンを観察し、遊泳している、もしくは容器の底で活動している赤潮プランクトンの数を計測して、生残赤潮プランクトン数（Ａ）とする。
ブランクとして、試料１ｍＬを殺菌したろ過海水１ｍＬにて希釈した後、赤潮プランクトンの数を計測して、初期赤潮プランクトン数（Ｂ）とし、下記により生残細胞密度を求める。
生残細胞密度（％）＝((Ａ)／(Ｂ))×１００
１２０分経過後の生残細胞密度が５０％以下であれば、所望の赤潮駆除効果を有する。
<Survival cell density evaluation method>
Seawater containing red tide plankton (a highly virulent strain of K. mikimotoi) is diluted with filtered seawater and adjusted to approximately 1,000 cells/cm 3 to 20,000 cells/cm 3 . This will be used as a sample for evaluation.
1 mL each of the sample and the red tide repellent slurry are placed in separate microplates. Aspirate a total of 2 mL of the sample liquid from both microplates using a micropipette, and mix by repeating ejection and suction into the microplate. Thereafter, it is allowed to stand at room temperature (22°C). After a predetermined period of time, observe the red tide plankton in the microplate with a microscope, count the number of red tide plankton swimming or active at the bottom of the container, and calculate the number of surviving red tide plankton (A). shall be.
As a blank, 1 mL of the sample is diluted with 1 mL of sterilized filtered seawater, and then the number of red tide plankton is counted to determine the initial red tide plankton count (B), and the surviving cell density is determined as follows.
Survival cell density (%) = ((A)/(B)) x 100
If the density of surviving cells after 120 minutes is 50% or less, it has the desired red tide extermination effect.
（実施例１）
ＭｇＯ（Ａ）をろ過海水に添加して、ＭｇＯ濃度１０００ｐｐｍ赤潮駆除剤スラリーを調製した。得られた潮駆除剤スラリーを海水で希釈して、ＭｇＯ濃度が５００ｐｐｍとなるように濃度を調整し、水槽に収容した。上記の方法により稚魚に対する安全性を調べたところ、飼育開始から６時間経過後も斃死はなく、安全性が確認された。
上述の赤潮駆除剤スラリーを用い、上記の方法によりＭｇＯ濃度５００ｐｐｍにおける生残細胞密度を測定した。１２０分経過後の生残細胞密度は５０％以下であり、所望の赤潮駆除効果を備えることが確認された。
(Example 1)
MgO(A) was added to filtered seawater to prepare a red tide repellent slurry with an MgO concentration of 1000 ppm. The obtained tide repellent slurry was diluted with seawater, the concentration was adjusted so that the MgO concentration was 500 ppm, and the slurry was placed in an aquarium. When the safety of young fish was investigated using the above method, there was no mortality even 6 hours after the start of rearing, and safety was confirmed.
Using the red tide repellent slurry described above, the density of surviving cells at an MgO concentration of 500 ppm was measured by the method described above. The density of surviving cells after 120 minutes was 50% or less, and it was confirmed that the desired red tide extermination effect was achieved.
（実施例２）
ＭｇＯ濃度を４００ｐｐｍとした以外は実施例１と同様にして、赤潮駆除剤スラリーを調製した。得られた赤潮駆除剤スラリーを海水で希釈して、ＭｇＯ濃度が２００ｐｐｍとなるように濃度を調整し、水槽に収容した。上記の方法により稚魚に対する安全性を調べたところ、飼育開始から６時間経過後も斃死はなく、安全性が確認された。
上述の赤潮駆除剤スラリーを用い、上記の方法によりＭｇＯ濃度２００ｐｐｍにおける生残細胞密度を測定した。１２０分経過後の生残細胞密度は５０％以下であり、所望の赤潮駆除効果を備えることが確認された。
(Example 2)
A red tide repellent slurry was prepared in the same manner as in Example 1 except that the MgO concentration was 400 ppm. The obtained red tide repellent slurry was diluted with seawater, the concentration was adjusted so that the MgO concentration was 200 ppm, and the slurry was placed in an aquarium. When the safety of the young fish was investigated using the above method, there was no mortality even 6 hours after the start of rearing, and safety was confirmed.
Using the red tide repellent slurry described above, the density of surviving cells at an MgO concentration of 200 ppm was measured by the method described above. The survival cell density after 120 minutes was 50% or less, and it was confirmed that the desired red tide extermination effect was achieved.
（比較例１）
ＭｇＯ（Ａ）を同量のＭｇＯ（Ｃ）に変更した以外は実施例１と同様にして、赤潮駆除剤スラリーを調製した。得られた赤潮駆除剤スラリーを海水で希釈して、ＭｇＯ濃度が５００ｐｐｍとなるように濃度を調整し、水槽に収容した。上記の方法により稚魚に対する安全性を調べたところ、３時間までに５匹とも斃死した。
(Comparative example 1)
A red tide repellent slurry was prepared in the same manner as in Example 1 except that MgO (A) was replaced with the same amount of MgO (C). The obtained red tide repellent slurry was diluted with seawater, the concentration was adjusted so that the MgO concentration was 500 ppm, and the slurry was placed in an aquarium. When the safety for young fish was investigated using the above method, all five died within 3 hours.
（比較例２）
ＭｇＯ濃度を２００ｐｐｍに変更した以外は比較例１と同様にして、赤潮駆除剤スラリーを調製した。得られた赤潮駆除剤スラリーを海水で希釈して、ＭｇＯ濃度が２００ｐｐｍとなるように濃度を調整し、水槽に収容した。上記の方法により稚魚に対する安全性を調べたところ、３時間までに５匹とも斃死した。
(Comparative example 2)
A red tide repellent slurry was prepared in the same manner as in Comparative Example 1 except that the MgO concentration was changed to 200 ppm. The obtained red tide repellent slurry was diluted with seawater, the concentration was adjusted so that the MgO concentration was 200 ppm, and the slurry was placed in an aquarium. When the safety for young fish was investigated using the above method, all five died within 3 hours.
（比較例３）
ＭｇＯ濃度を１００ｐｐｍに変更した以外は比較例１と同様にして、赤潮駆除剤スラリーを調製した。得られた赤潮駆除剤スラリーを海水で希釈して、ＭｇＯ濃度が１００ｐｐｍとなるように濃度を調整し、水槽に収容した。上記の方法により稚魚に対する安全性を調べたところ、３時間までに５匹とも斃死した。
(Comparative example 3)
A red tide repellent slurry was prepared in the same manner as in Comparative Example 1 except that the MgO concentration was changed to 100 ppm. The obtained red tide repellent slurry was diluted with seawater, the concentration was adjusted so that the MgO concentration was 100 ppm, and the slurry was placed in an aquarium. When the safety for young fish was investigated using the above method, all five died within 3 hours.
（比較例４）
ＭｇＯ（Ｃ）を同量のＭｇＯ（Ｂ）に変更した以外は比較例２と同様にして、赤潮駆除剤スラリーを調製した。得られた赤潮駆除剤スラリーを海水で希釈して、ＭｇＯ濃度が２００ｐｐｍとなるように濃度を調整し、水槽に収容した。上記の方法により稚魚に対する安全性を調べたところ、３時間までに５匹とも斃死した。
(Comparative example 4)
A red tide repellent slurry was prepared in the same manner as in Comparative Example 2 except that MgO (C) was replaced with the same amount of MgO (B). The obtained red tide repellent slurry was diluted with seawater, the MgO concentration was adjusted to 200 ppm, and the slurry was placed in an aquarium. When the safety for young fish was investigated using the above method, all five died within 3 hours.
比較例１～４の赤潮駆除剤スラリーを用い、上記の方法により生残細胞密度を測定した。１２０分経過後の生残細胞密度は５０％以下であった。 Using the red tide repellent slurries of Comparative Examples 1 to 4, the surviving cell density was measured by the method described above. The survival cell density after 120 minutes was less than 50%.
実施例の結果に示されるように、ＭｇＯ（Ａ）は、分散処理を行わないでレーザー回折散乱法により得られた平均粒子径が１００～７００μｍ、分散処理を行った後にレーザー回折散乱法により得られた平均粒子径が０．１～１０μｍ、かつＢＥＴ比表面積が７０ｍ２／ｇ以上の粒状酸化マグネシウムであるので、稚魚に対する安全性を備えた赤潮駆除剤を得ることができる。 As shown in the results of the examples, MgO(A) has an average particle diameter of 100 to 700 μm obtained by laser diffraction scattering method without dispersion treatment, and a mean particle diameter of 100 to 700 μm obtained by laser diffraction scattering method after dispersion treatment. Since the granular magnesium oxide has an average particle diameter of 0.1 to 10 μm and a BET specific surface area of 70 m 2 /g or more, it is possible to obtain a red tide repellent that is safe for young fish.
これに対し、分散処理を行わないでレーザー回折散乱法により得られた平均粒子径が１００～７００μｍという条件が欠ける場合には、分散処理を行った後にレーザー回折散乱法により得られた平均粒子径が０．１～１０μｍ、ＢＥＴ比表面積が７０ｍ２／ｇ以上であっても、稚魚に対する安全性を備えた赤潮駆除剤を得ることはできないことが、比較例の結果から明らかである。
On the other hand, if the condition that the average particle diameter obtained by laser diffraction scattering method without dispersion treatment is 100 to 700 μm is not met, then the average particle diameter obtained by laser diffraction scattering method after dispersion treatment is not satisfied. It is clear from the results of the comparative examples that even if the red tide is 0.1 to 10 μm and the BET specific surface area is 70 m 2 /g or more, it is not possible to obtain a red tide repellent that is safe for young fish.
Claims (3)
前処理として分散処理を行った後にレーザー回折散乱法により測定した平均粒子径（Ｂ）が０．１～１０μｍであって、
ＢＥＴ比表面積が７０ｍ２／ｇ以上であることを特徴とする粒状酸化マグネシウム。 The average particle diameter (A) measured by laser diffraction scattering method without dispersion treatment as pretreatment is 100 to 700 μm,
The average particle diameter (B) measured by a laser diffraction scattering method after performing a dispersion treatment as a pretreatment is 0.1 to 10 μm,
Granular magnesium oxide having a BET specific surface area of 70 m 2 /g or more.
The granular magnesium oxide according to claim 1 or 2, wherein the content of magnesium oxide is 70% by mass or more.
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