JP4050052B2 - Coated granular fertilizer - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は被覆粒状肥料に関し、詳しくは施肥された環境下において肥料成分の溶出が制御され、且つ被覆材である皮膜が生分解することにより周辺環境への負荷を軽減した被覆粒状肥料に関する。
【０００２】
【従来の技術】
農作物の栽培には、その生長段階に応じた肥料が必要であり、その必要時期に合わせるために従来から元肥、追肥等、作物の収穫までに数回の施肥を行ってきた。近年、農業が近代化されまた農業人口の減少に伴い、より手間の掛からない、施肥回数が少なくて済む肥料の開発が求められ、肥料成分の溶出を、作物の養分要求特性に適合させるように制御すべく、様々な肥料が開発された。
【０００３】
例えば、土壌中に施肥された肥料成分の溶出を物理的に制御するために、粒状肥料の表面を高分子樹脂皮膜で被覆する検討が広く実施され、そのうち幾つかは実用化されている。例えば、皮膜材料として低透湿性のポリオレフィン樹脂を使用し、肥料成分の溶出曲線が直線となる直線型溶出タイプやＳ字曲線となるシグモイド型溶出タイプ等の様々な溶出タイプのものがあり、作物の生育に合わせた施肥管理が可能となった（特公昭５４−３１０４、特公昭６０−３０４０、特公昭６０−３７０７４等）。
【０００４】
しかしながら近年、かかるポリオレフィン樹脂が非分解性であるため、被覆粒状肥料が投入された圃場で皮膜殻が蓄積し、さらにはこの殻が圃場域外へ流出し、その結果生態系に蓄積するなどの環境負荷が懸念されている。そこでポリオレフィン樹脂に生分解性資材を添加し皮膜を崩壊に至らしめる技術が提案されている。
例えば、生分解性資材として糖重合体及びその誘導体を添加する方法（特開平６−８７６８４、特開平１１−３２２４７９）、脂肪族ポリエステルを添加する方法（特開平９−２６３４７６）などがある。しかしこれらは被覆材の多くを占めるポリオレフィン樹脂の分解を促進するものではなく、生分解性資材の増加に伴い土壌中の溶出制御性が不安定となる欠点がある。
【０００５】
皮膜材自体を何らかの作用によって分解できるような、分解性を有する被覆材を使用する技術も検討されているが、各々に問題があり、これを解決するに至っていない。
例えば、光分解性樹脂を皮膜の主成分とする技術が提案され、光分解性樹脂としてエチレン・一酸化炭素共重合体を用いるもの（特公平２−２３５１６）、ビニルケトン共重合体を用いるもの（特公平７−５０６）、オレフィン類・一酸化炭素・オレフィン性不飽和化合物共重合体を用いるもの（特開平６−５６５６８）などが挙げられる。これらは被覆粒状肥料が日光等に露光している条件下でのみ分解するため、皮膜殻の圃場での蓄積及び圃場域外への流出を回避できるものではなく、また保存中に皮膜が変質し、溶出制御性が変化してしまうという問題がある。
【０００６】
また、生分解性樹脂を皮膜の主成分とする技術も提案され、その生分解性樹脂として、変性天然ゴム（特開昭５９−９２９８９）や種々の脂肪族ポリエステル類（特公平２−２３５１７、特公平７−５０５、特開平４−８９３８４、特開平５−８５８７３、特開平７−３３５７７、特開平７−６１８８４、特開平７−３１５９７６、特開平８−１５７２９０、特開平９−２４９７７、特開平１０−７４８４）が知られているが、これらは樹脂の透湿性が高いため、溶出停滞期を有するシグモイド型の溶出タイプを創製できないことや、土壌中での生分解速度が大きく、溶出制御性が不安定である欠点がある。
【０００７】
一方、皮膜材料に生分解性を付与させ、かつ長期間にわたる溶出制御性を維持する目的で、低分子量のポリエチレン、石油ワックス類およびパラフィンワックスなどを皮膜の主成分とする技術が提案されている（特公昭４９−３３３９、特開平９−２６３４７６、特開平１０−２３１１９０、特開平１０−２９１８８０、特開平１１−７１１９２、特開平１１−２６３６８９等）。しかしこれらは皮膜材料の融点が低く、成膜中に肥料の粒子同志が融着して成膜が困難となり、皮膜の力学的強度、つまり耐衝撃性、耐磨耗性に乏しい。そのために物理的な衝撃により皮膜が損傷しやすくなる結果、溶出制御性が不安定となり、本来期待した溶出制御ができないなどの欠点がある。
【０００８】
上記の欠点を補うために、さらに外層に高分子物質を有する皮膜で被覆する技術が開示されている（特開平７−３３５７６、特開平７−２１５７８９、特開平８−１５１２８６、特開平９−３０８８３、特開平９−２４１０９０、特開平１０−２３１１９１等）が、外層被覆後のハンドリング性は改良されている反面、内層の被覆時の欠点を本質的に改善できるものではなく、また内層と外層の両皮膜層で溶出制御機能を持たせようとすると、溶出制御が煩雑となるなどの問題がある。
【０００９】
【発明が解決しようとする課題】
本発明の目的は、力学的強度に優れた皮膜を有し、且つ皮膜の変質・破損等により溶出制御性が変化することなく、長期間にわたり施肥環境下における溶出制御性が良好であり、最終的にコーティング材の皮膜が土壌内外で分解することにより、環境への負荷を軽減した被覆粒状肥料を提供することである。
【００１０】
【発明を解決するための手段】
本発明者らは上述の課題を解決するために鋭意検討した結果、被覆粒状肥料における皮膜材料として、分岐鎖の含有率が特定量以下の特定分子量の直鎖状炭化水素を用いることによって、被覆粒状肥料が、従来単一皮膜層では実現できなかったシグモイド型溶出曲線を有する緩効性肥料となり、且つ皮膜強度に優れ、皮膜の分解性も付与できるという、上述したような課題を解決する被覆粒状肥料となることを見い出し、本発明に至った。
【００１１】
即ち本願発明は、分岐鎖含有率が１０重量％以下で、重量平均分子量が３００以上である直鎖状炭化水素を含む皮膜で被覆してなる被覆粒状肥料を、さらに生分解性樹脂を含む外層皮膜で被覆してなることを特徴とする被覆粒状肥料に存する。
【００１２】
【発明の実施の形態】
以下、本発明につき詳細に説明する。
本発明における直鎖状炭化水素は、分岐鎖の含有量が１０重量％以下の直鎖状（線状）化合物であり、且つ重量平均分子量が３００以上である。このように分岐鎖の含有量及び重量平均分子量を同時に特定することによって、結晶性、融点、及び材料強度が高くなり、また水蒸気の透過性も低くなることから被覆粒状肥料の皮膜材料として好ましい。この観点から、本発明における直鎖状炭化水素の分岐鎖の含有量は少ない程良く、中でも分岐鎖を全く含有しない直鎖状炭化水素が理想的である。
【００１３】
尚、本発明における分岐鎖とは、鎖状炭化水素における最長の炭素鎖（主鎖）より枝分かれした炭素鎖（側鎖）を示すものであって、この分岐鎖から更に枝分かれした側鎖をも含む。また分岐鎖の含有率とは、被覆粒状肥料の皮膜を構成する鎖状炭化水素の全重量に対する分岐鎖部分の重量割合（％）を示す。しかして、本発明における分岐鎖含有量は、尿素付加法により測定されるものと定義する。
【００１４】
直鎖状炭化水素の分岐鎖含有量の値は、１０重量％以下、好ましくは５重量％以下であればよく、更には、分岐鎖含有量は少ない程好ましい。しかし分岐鎖含有量が極めて低い鎖状炭化水素は工業的に入手困難であり、理想的に完全な直鎖状であっても、それ以上特段の効果は期待しがたいので、通常は、分岐鎖含有量は０．００１〜５重量％、好ましくは、０．００１〜１重量％の範囲から選択される。
【００１５】
直鎖状炭化水素における分岐鎖の構造は任意であり、具体的にはメチル基、エチル基、ｎ−ブチル基等のアルキル基；ビニル基、アリル基、１−プロペニル基、等のアルケニル基；エチニル基、プロパルギル基等のアルキニル基；フェニル基、トリル基、ナフチル基等のアリール基等が挙げられる。中でもアルキル基、アルケニル基等を有するものが好ましく、特にアルキル基を有するものが好ましい。また各炭素に結合した分岐鎖の位置は特に限定されない。なお鎖状炭化水素は単一種のもののみを使用しても、２種以上を混合して使用してもよい。
【００１６】
本発明における炭化水素とは、主鎖を構成する炭素原子が線状に配列した直鎖状の構造を有する化合物を示す。直鎖状炭化水素における炭素同志の結合は、単結合、二重結合またはその他の態様やこれら複数種を有するものであってもよい。中でも炭素同志の結合が全て単結合である飽和化合物は、結晶性、疎水性に優れるので好ましい。例えば、高密度ポリエチレン、直鎖状低密度ポリエチレン等の高分子量ポリエチレン；フィッシャー・トロプシュワックス、ポリエチレンワックス等の合成ワックス；パラフィンワックス、マイクロクリスタリンワックス、ペトロラタムに代表される石油ワックスなどが挙げられる。中でも分岐鎖が特に少なく、成膜性に優れ、かつ分解性が良好な合成ワックス、中でもフィッシャー・トロプシュワックスが特に好ましい。
【００１７】
本発明における直鎖状炭化水素の重量平均分子量は、３００以上の特定の範囲であり、通常、３００〜１００００、好ましくは５００〜５０００、さらに好ましくは６００〜１０００である。また、ＤＳＣ（示差走査型熱量計）法により測定される融点としては、４４〜１１０℃、好ましくは５０〜１００℃である。重量平均分子量が小さすぎると融点が低く、成膜中に肥料粒同志が融着して被覆成形性に問題が生じることがあり、土壌中での生分解速度が速すぎて溶出制御性が不安定となる。また、重量平均分子量が大きすぎると、肥料成分の初期の溶出抑制性は優れるが、皮膜の分解性及び崩壊性が低下することがある。
【００１８】
また、本発明における直鎖状炭化水素はある程度の分子量分布を有していてもよいが、この分布は小さい程よい。具体的には、数平均分子量（Ｍｎ）に対する重量平均分子量（Ｍｗ）の比、すなわちＭｗ／Ｍｎが１．０１〜３．００であるものが好ましい。尚、本発明における鎖状炭化水素の平均分子量は、高温ＧＣ（ガスクロマトグラフィー）−ＦＩＤ（水素炎イオン化検出器）法により測定したものをいう。
【００１９】
皮膜の膜厚は、所望の溶出制御性、皮膜強度、生分解性等によって適宜選択できる。膜厚が薄いと経済的に有利であるが、皮膜の強度が弱く、剥離や欠損が生じやすい。膜厚が厚いと皮膜の強度、初期の溶出防止性および長期間に亘る溶出制御性に優れるが、経済的に不利である。以上の理由から、一般的には３０〜２１０μｍ、中でも４５〜１７５μｍとするのが好ましく、特に水稲用の緩効性肥料としては５０〜１４０μｍとするのが最も好ましい。
【００２０】
本発明の被覆粒状肥料の皮膜の被覆率（被覆される肥料成分粒子重量に対する皮膜の重量％）は、通常、６〜２５重量％、好ましくは７〜２０重量％の範囲である。被覆粒状肥料の皮膜膜厚、肥料粒子径およびその比重を測定することにより計算により求まる。
【００２１】
本発明の被覆粒状肥料におけるその皮膜は、分岐鎖含有率が１０重量％以下で、重量平均分子量が３００以上である直鎖状炭化水素を含むものである。当該皮膜は、その全体が該直鎖状炭化水素から構成されていてもよいが、その効果を損なわない範囲で、皮膜中に種々の物質を配合することができる。例えば、高分子化合物、樹脂類、無機物、塩類およびその他の添加物を用いて皮膜の性質を変え、肥料成分の溶出を制御するとともに、皮膜の生分解性、透湿性を高めたり、低めたりすることができる。また、力学的強度を変えることもできる。
【００２２】
高分子化合物としては、分子量が１万以上で、その主鎖が主として共有結合からなる化合物を使用することができる。また、分子量が１０００〜１万からなるオリゴマーも本発明の目的を損なわない範囲で使用できる。例えば、その主鎖が炭素からなる、ポリエチレン、ポリプロピレン、エチレン・プロピレン共重合物、ポリブテン、ブテン・エチレン共重合物、ブテン・プロピレン共重合物、ポリスチレン等のオレフィン共重合物、エチレン・酢酸ビニル共重合物、エチレン・アクリル酸共重合物、エチレン・アクリル酸エステル共重合物、エチレン・メタアクリル酸共重合物、エチレン・アクリル酸エステル共重合物、エチレン・一酸化炭素共重合物等のオレフィンを含む共重合物、ブタジエン共重合物、イソプレン重合物、クロロプレン重合物、ブタジエン・スチレン共重合物、スチレン・イソプレン共重合物等のジエン系重合物、ポリ塩化ビニル等の合成高分子を使用できる。一方、皮膜の分解性および崩壊を促進させるのであれば、天然高分子を使用することもできる。これらは高分子化合物ではあるが、本発明においては、生分解性樹脂として把握したので、別途詳しく後述する。これらの有機系高分子は本発明の直鎖状炭化水素と相溶しやすく、かつ成膜性および被覆均一性が良好であるので好ましい。
【００２３】
有機系高分子化合物の他に、ケイ素、硫黄、リンなどからなる無機系高分子化合物も使用できる。また、これらの高分子化合物は、本発明の目的を損なわない範囲で一種または二種以上を任意の割合で併用してもよい。皮膜中におけるこれらの高分子化合物の添加量は、皮膜重量に対して、通常０．１〜５０重量％、好ましくは０．５〜４０重量％、特に好ましくは１〜３０重量％である。
【００２４】
本発明においては、先述の直鎖状炭化水素皮膜中に、無機充填材を含有させてもよい。無機充填材を皮膜中に含有させることで、被覆粒状肥料の溶出制御調整や、温度依存性低減を計れるので好ましい。無機充填材としては、例えば、タルク、クレー、マイカ、モンモリロナイト、ベントナイト、活性白土、セピオライト、イモゴライト、セリサイト、ガラス繊維、ガラスビーズ、ガラスフレーク、シリカ系バルン、シリカ、珪藻土、アルミナ、酸化亜鉛、酸化チタン、酸化カルシウム、酸化マグネシウム、酸化鉄、酸化スズ、フェライト類、水酸化カルシウム、水酸化マグネシウム、水酸化アルミニウム、炭酸カルシウム、炭酸マグネシウム、炭酸亜鉛、炭酸バリウム、ドーソナイト、ハイドロタルサイト、硫酸カルシウム、硫酸バリウム、石膏繊維、ケイ酸カルシウム、窒化アルミニウム、窒化ホウ素、窒化ケイ素、カーボンブラック、グラファイト、炭素繊維、炭素バルン、木炭粉末、各種金属粉、金属箔、弁柄、アルミニウムボレート、炭化ケイ素、ホウ酸亜鉛、ホウ酸アルミニウム、黒鉛、リサージ、イオウなどが挙げられる。
【００２５】
中でも皮膜強度を向上させる目的等で添加量を増加させても、被覆粒状肥料の溶出制御性への影響が小さいもの、例えばタルク、クレー、マイカ、シリカ、炭酸カルシウムなどが好ましい。皮膜中の無機充填材の添加量は、皮膜重量に対して、通常０．１〜７０重量％、好ましくは５〜６５重量％、特に好ましくは１０〜６０重量％である。無機充填材の添加量が多すぎると皮膜強度が低下し、溶出制御性が低下する場合があり、一方で添加量が少なすぎると充分な効果を得ることができない。また無機充填材は、直鎖状炭化水素皮膜の連続性を阻害せず、且つ無機充填材同志が凝集を起こさない程度の平均粒子径であることが好ましく、例えば膜厚の１／２以下の平均粒子径が好ましい。具体的には、２００μｍ以下、好ましくは５〜１００μｍ程度のものが用いられる。また、これらの無機充填材は、本発明の目的を損なわない範囲で一種または二種以上を任意の割合で併用してもよい。
【００２６】
また先述の無機充填材と同様に、本発明の被覆粒状肥料の溶出制御調整等の目的で鎖状炭化水素皮膜中に界面活性剤を含有させてもよい。界面活性剤としては、カチオン系、アニオン系、ノニオン系、及び両性界面活性剤の何れの任意のもの、およびこれらの混合物等を使用できる。中でも溶出制御の調整が容易で、且つ被覆粒状肥料の保存安定性に優れたノニオン系界面活性剤が好ましい。ノニオン系界面活性剤としては、例えば、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンポリスチリルフェニルエーテル、ポリオキシエチレンポリオキシプロピレンアルキルエーテル、ポリオキシエチレンポリオキシプロピレングリコール、ポリエチレングリコール、グリコールエーテル、ポリエチレングリコール脂肪酸エステル、アルキロールアマイド、ソルビタン脂肪酸エステル、蔗糖脂肪酸エステル等が挙げられる。中でも、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレンアルキルエーテルが、少量の添加で溶出制御が行えるので特に好ましい。
【００２７】
界面活性剤のＨＬＢは任意であるが、通常３〜２０であればよい。皮膜中の界面活性剤の添加量は、皮膜重量に対して通常０．０１〜２０重量％、好ましくは０．０５〜１５重量％、さらに好ましくは０．１〜１０重量％である。界面活性剤の添加量が多すぎると皮膜の親水性が高くなり、溶出制御性が低下する場合があり、一方添加量が少なすぎると、溶出制御の調整に充分な効果を得ることができない。
【００２８】
また、本発明においては、先述の直鎖状炭化水素皮膜中に、生分解性樹脂を含有させてもよい。これらは一種、または二種以上を任意の割合で使用できる。
生分解性樹脂としては、自然界において微生物が関与して低分子化合物に分解されるものであればよい。例えば、３−ヒドロキシブチレートと３−ヒドロキシバリレートからなる共重合ポリエステル、バクテリアセルロース等に代表される微生物生産型樹脂、ポリアミノ酸、ポリグルタミン酸、ポリリジン、セルロース、澱粉、キチン・キトサン、アルギン酸、グルテン、コラーゲン、カードラン、プルラン、デキストラン、ゼラチン、リグニン、キサンタンガム、天然ゴム、蛋白質、多糖、核酸等の天然化合物型樹脂、及びエチレングリコール、プロピレングリコール、ブタンジオール、ヘキサンジオール、ジプロピレングリコール等のジオール類から選ばれる１種とコハク酸、テレフタル酸、イソフタル酸、アジピン酸、セバシン酸等のジカルボン酸から選ばれる１種との脱水縮合により得られる脂肪族ポリエステル類、ポリε−カプロラクトン、ポリ乳酸、ポリグリコール酸等に代表される化学合成型樹脂が挙げられる。これらは一種又は二種以上を任意の割合で併用してもよい。また、生分解性樹脂としては、例えば、脂肪族ポリエステル、芳香族または環状エーテルが導入された脂肪族ポリエステル、糖重合体及びその誘導体、蛋白質及びその誘導体などが好ましい。
皮膜中の生分解性樹脂の添加量は、皮膜重量に対して通常０．１〜５０重量％、好ましくは０．５〜２０重量％、特に好ましくは１〜１０重量％である。
【００２９】
尚、本発明において被覆粒状肥料の皮膜が「生分解する」ということは、土壌中の微生物により皮膜中の高分子材料が低分子化され、最終的に水と二酸化炭素に分解される生物的メカニズムを示す。さらには紫外線を含む日光等に曝されて劣化したり、適当な温度と湿度の条件下で空気中の酸素により酸化される化学的メカニズム、農耕地土壌における土壌耕運・解砕時の皮膜への物理的衝撃、温度と湿度の変化による土壌の圧縮膨張および植物根の皮膜への侵入等による皮膜崩壊等の物理的メカニズムをも含む。例えばこの様な化学的、物理的メカニズムにより皮膜強度が粒子形状を維持できない程度まで減少し、さらには皮膜が極小片化に至る程度まで崩壊した状態であれば、粒子状態のままで土壌中に残留することがなく、また浮上等により系外へ流出することが抑制されるので、実質的には環境負荷の心配はなくなる。ここで極小片化した皮膜は、これらに微生物がより繁殖しやすくなるため生物的メカニズムによる分解が促進され、最終的に消失する。
【００３０】
また、本発明の被覆粒状肥料の皮膜中に、光分解性資材を含有させてもよい。光分解性資材としては、例えば、一酸化炭素とオレフィン類の共重合体、ジエン系重合体、ビニルケトン系共重合体、1,2−ポリブタジエン、ポリイソブチレンオキサイドなどの、感光性官能基が導入された樹脂が好ましい。これらは一種、または二種以上を任意の割合で使用できる。添加量としては、本発明の被覆粒状肥料の溶出制御性・分解性・保存安定性を考慮して適宜決定すればよいが、皮膜重量に対して通常０．１〜５０重量％、好ましくは０．５〜３０重量％、特に好ましくは１〜２０重量％である。
【００３１】
また、本発明の被覆粒状肥料の皮膜中に、酸化促進物質、光分解促進物質、昇華性物質等を含有させてもよい。これにより皮膜の酸化分解や光分解を促進させることができる。一方、またこれらと併せて、保存安定性を考慮して光安定剤や酸化防止剤を添加してもよい。これらは、相互に反対の作用を及ぼすので、製品の用途、目的に応じて適宜に使用することが肝要である。
【００３２】
酸化促進物質・光分解促進物質としては、例えば、炭素不飽和結合を有する不飽和脂肪酸、不飽和脂肪酸エステル、油脂類、遷移金属、遷移金属化合物、遷移金属錯体、芳香族ケトン類などが好ましい。添加量としては、溶出制御性・分解性・保存安定性を考慮して適宜決定されるが、皮膜重量に対して通常０．００１〜１０重量％、好ましくは０．００５〜５重量％、特に好ましくは０．０１〜１重量％である。
【００３３】
昇華性物質としては、例えば、ナフタリン、樟脳、硫黄などが好ましい。添加量としては、溶出制御性・分解性・保存安定性を考慮して適宜決定されるが、皮膜重量に対して通常０．０１〜３０重量％、好ましくは０．０５〜２０重量％、特に好ましくは０．１〜１０重量％である。
光安定剤や酸化防止剤としては、芳香族アミン系、フェノール系、例えば、チバスペシャリティケミカルズ製イルガノックス１０１０、サリシレート系、ベンゾフェノン系、ベンゾトリアゾール系、ニッケル系、シアノアクリレート系、オキザリックアシッドアニリド系、ヒンダードアミン系、例えば、チバスペシャリティケミカルズ製ＬＳ６２２ＬＤなどがあげられる。その添加量としては、溶出制御性、保存安定性を考慮して適宜決定される。皮膜重量に対して通常０．００１〜１０重量％、好ましくは０．０１〜１重量％程度である。
【００３４】
以上、分岐鎖含有率が１０重量％以下で、重量平均分子量が３００以上である直鎖状炭化水素と共に、皮膜を構成する補助的成分として使用される各種の配合物について説明した。これらの配合物の添加方法としては、先述の直鎖状炭化水素を含む高分子樹脂（溶液）に、必要に応じて相溶化剤又は分散剤を用いて均一に分散・溶解させるか、微粉末状で分散させて皮膜溶液としてもよい。相溶化剤としては、水、アルコール、炭化水素、ハロゲン化炭化水素等が使用されるが、詳しくは後述する。
【００３５】
本発明においては、上述の特定の直鎖状炭化水素で被覆された被覆粒状肥料（以下、「内層被覆肥料」ということがある。）上に、耐衝撃性向上等の観点から、さらに皮膜（以下、「外層皮膜」ということがある。）で被覆することが好ましい。外層皮膜としては、本発明の効果を損なわない範囲で被覆肥料としての保護効果を有するものが好ましく、特に施肥条件下において分解し消失するものがより好ましい。外層皮膜の膜厚は、その保護効果があればできる限り薄い方が好ましく、通常３〜２００μｍ、好ましくは５〜１５０μｍ、さらに好ましくは１０〜８０μｍである。また被覆率は、被覆される内層被覆肥料の重量に対して通常０．５〜２０重量％、好ましくは１〜１５重量％、さらに好ましくは３〜１０重量％の範囲である。
【００３６】
この様な外層皮膜としては、先に述べた生分解性樹脂が使用できるほか、水溶性樹脂、直鎖状炭化水素等を使用することができる。外層皮膜の主たる構成成分は、これらの樹脂であるが、内層皮膜の場合と同様に、他の補助的配合物を併せ使用することができる。
【００３７】
水溶性樹脂としては、水（酸性水・アルカリ性水を含む）に溶解するものであって、各種植物に対して毒性のないものが使用される。水溶性樹脂の中には、先に述べた生分解性を有するものも含む。具体的には例えば、澱粉、寒天、アルギン酸ソーダ、アラビアゴム、トラガントゴム、トロロアオイー、コンニャク、にかわ、カゼイン、ゼラチン、卵白、プルラン、デキストラン等に代表される天然高分子型樹脂、可溶性澱粉、カルボキシル澱粉、ジアルデヒドデンプン、カチオン澱粉、ポリエーテル、ポリリンゴ酸、ブリティッシュゴム、デキストリン、ビスコース、メチルセルロース、エチルセルロース、カルボキシルメチルセルロース、ヒドロキシエチルセルロース等に代表される半合成高分子型樹脂、ポリビニルアルコール、ポリエチレングリコール、ポリプロピレングリコール、ポリアクリルアミド、ポリアクリル酸、ポリビニルアミン、ポリＮ−ビニルピロリドン、水溶性アルキッド、ポリビニルエーテル、ポリエチレンオキサイド、無水マレイン酸、ポリマレイン酸共重合体、ポリエチレンイミン、ポリビニルスルホン酸、ポリビニルアンモニウム、ポリスチレンスルホン酸、ポリメタクリル酸、ポリアミン、ポリイミン、ポリベタイン等に代表される合成高分子型樹脂、及びポリリン酸ソーダ、水ガラス等に代表される無機高分子型樹脂が挙げられる。
これらは一種又は二種以上を任意の割合で併用してもよい。
【００３８】
外層皮膜の形成方法、即ち、内層被覆肥料の被覆方法としては、通常は先述の直鎖状炭化水素と共に溶剤に溶解または分散させて使用するが、溶融させてもよい。また微粉末状で適当な溶剤に分散させたコロイダルディスパージョンや、乳化剤を添加したエマルジョンとしても使用できる。
【００３９】
以上の生分解性樹脂および水溶性樹脂の中でも、外層皮膜として保護効果を有し、且つ被覆性と分解性が良好であり、安価で且つ内層被覆肥料の溶出制御性に影響が少ないポリイソプレンを主成分とするものが好ましい。
ここでポリイソプレンを主成分とする生分解樹脂とは、その構造がイソプレンまたはイソプレン誘導体が鎖状に連なったポリマーであればよく、ゴムの樹（Hevea brasiliencis）に含まれるラテックスにギ酸を加えて凝固・乾燥して得られるもの、またはチーグラー−ナッタ触媒やアルキルリチウム触媒を用いた重合反応により得られるもので、重量平均分子量が１×１０5〜５×１０6程度のものが好ましい。また重合反応より異性構造を有する数種のポリイソプレンが得られるが、なかでもシス−1,4−ポリイソプレンを６０重量％以上含有するものは分解性が高いので好ましい。さらに、シス−1,4−ポリイソプレンの溶液に、硫黄を添加後加熱して得られる加硫ゴムや、塩素および塩化水素を通じて得られる塩化ゴムおよび塩酸ゴム、同様に硫酸、ｐ−トルエンスルホニルクロライドまたは重金属の塩化物を通じて得られる環化ゴム等に代表されるポリイソプレン誘導体も、本発明の目的を損なわない範囲で使用することができる。
【００４０】
本発明においては、外層皮膜の被覆性改良、皮膜強度の向上、および高価な樹脂の使用量を低減する目的で、外層皮膜中に無機充填材を添加することが好ましい。無機充填材としては、先述の内層被覆肥料の皮膜中に添加するものが使用でき、一種または二種以上を任意の割合で併用してもよい。なかでもタルク、クレー、シリカ、炭酸マグネシウム、炭酸カルシウム、カーボンブラック、弁柄、酸化亜鉛、酸化チタンが好ましい。外層皮膜中の無機充填材の添加量は任意であるが、好ましくは３０〜９９．９重量％、更に好ましくは５０〜９５重量％である。添加量が多すぎると外層皮膜の力学的強度が低下する場合があり、一方添加量が少なすぎると成膜中に肥料粒同志が接着して皮膜形成が困難となる場合がある。又いずれの無機充填材も皮膜の連続性を阻害せず、且つ粉体同志が凝集を起こさない平均粒子径、例えば外層膜厚の１／２以下の平均粒子径が好ましい。
【００４１】
被覆方法は、通常は溶液中に分散させて使用するが、乾燥風とともにそのまま内層被覆肥料粒に付着させても構わない。また、皮膜中での分散状態は、目的に応じて適宜選択される。通常は、皮膜の均一性を重視して均一に分散させることが好ましいが、例えば、被覆性をより改良したり、皮膜強度を制御するために、皮膜の外殻または内殻に分散させるなどの濃度勾配があってもよい。
【００４２】
外層皮膜を形成後に、被覆粒状肥料粒同志が接着する場合などは、外層皮膜表面に無機充填材を展着させることが好ましい。さらに外層皮膜の撥水性により該被覆肥料が浮上する場合は、外層皮膜中に、上述したような界面活性剤を添加すると、浮上防止効果があるので好ましい。
【００４３】
さらには、内層被覆肥料の皮膜（内層皮膜）と同様に、本発明の目的を損なわない範囲で、外層皮膜中にも先述のような光分解性資材、酸化促進物質、光分解促進物質および昇華性物質等を添加してもよく、これらの一種または二種以上を任意の割合で併用してもよい。また内層皮膜及び／または外層皮膜中に他の肥料成分、農薬、植物生理活性物などの農業資材、または植物の生長促進物質などを添加してもよく、それらの資材の皮膜中の分散状態も任意である。また、溶出制御性、分解性、保存安定性、および皮膜の力学的強度を考慮して、外層皮膜の更に外側に皮膜を設けた３層以上の被覆構造でもよい。
【００４４】
本発明の被覆粒状肥料においては、上述した各項の好ましい範囲を組み合わせることで、皮膜の力学的強度に優れ、保存中に皮膜の変質により溶出制御性を変化させることなく、長期間にわたり土壌中での溶出制御性が良好で、且つ最終的に皮膜が土壌内外の施肥条件下で分解し、環境への負荷が軽減されるので好ましい。具体的には、分岐鎖含有量が１０重量％以下、重量平均分子量３００〜１００００、好ましくは分岐鎖含有量が０．００１〜５重量％、重量平均分子量６００〜１０００の直鎖状炭化水素の皮膜中に、無機充填材を０．１〜７０重量％及び／又は界面活性剤を０．０１〜２０重量％含有する被覆粒状肥料である。中でも更にこの肥料を、ポリイソプレンを主成分とし無機充填材を３０〜９９．９重量％、好ましくは５０〜９５重量％含有する外層皮膜で被覆することにより、耐衝撃性が向上するので好ましい。
【００４５】
本発明の被覆粒状肥料において核となる肥料成分粒子としては、従来公知の任意のものを使用できる。例えば、尿素、硫安、塩安、硝安、石灰窒素、燐安、過燐酸石灰、重過石、重焼燐、塩加、硫加等の単肥の他に、Ｎ、Ｐ2Ｏ5、Ｋ2Ｏ等の２成分以上からなる化成肥料、およびこれらを２種以上複合したバルクブレンド肥料が挙げられる。中でも溶出制御の観点から、肥料成分が高く肥効が最も顕著に現れる尿素が特に好ましい。
また、肥料自体に溶出制御性のあるイソブチリデンジウレアなどの化合物型緩効性肥料を用いるとさらに多様な溶出制御性が得られるので好ましい。肥料成分粒子の粒子径は任意であるが、通常０．５〜１５ｍｍ、好ましくは１〜５ｍｍである。肥料成分粒子の形状も任意であるが、真球性が高い程、被覆均一性が高くなるので好ましい。
【００４６】
本発明の被覆粒状肥料の製造方法及び装置は、従来公知の任意の被覆肥料製造技術を採用することができる。例えば、装置自体の運動に付随して粒状物質を攪拌する回転ドラム式、回転パン式、回転落下式や、気流で粒状物質を攪拌する流動式等の各型の被覆装置を用いた方法が挙げられる。中でも被覆中の粒状肥料を気流を主として攪拌し、肥料粒子に対する衝撃が小さい噴流層、流動層を用いる方法が好ましい。粒状肥料表面への被覆材の適用は、一般的に被覆材またはその皮膜溶液を噴霧することによって行い、噴霧には一流体もしくは二流体スプレーノズルを用いる。中でも噴霧粒子径が細かく、より均一に成膜できる二流体スプレーノズルが好ましい。また被覆均一性をより高くするために、スプレー位置を適宜変更できる装置が好ましい。
【００４７】
皮膜の被覆方法としては、溶剤を使用する方法（以下「溶剤法」と言うことがある。）及び溶剤を使用しない方法（以下「無溶剤法」と言うことがある。）を適用できる。溶剤法では用いる被覆材を溶剤に溶解または分散して肥料表面に噴霧後、瞬時に溶剤を乾燥させる方法で、被覆均一性が高くなるので好ましい。溶剤法で使用される溶剤種は任意のものを使用でき、被覆材を溶解または分散させるものであればよい。具体的には、クロロホルム、ジクロロメタン、トリクロロエチレン、テトラクロロエチレン等に代表される塩素化炭化水素系溶剤、ヘキサン、オクタン、トルエン、キシレン、ベンゼン、エチルシクロヘキサン等に代表される炭化水素系溶剤が好ましい。また、生分解樹脂および水溶性樹脂を使用する場合は、水、エチルアルコール、イソプロピルアルコール、エチレングリコール、アセトン、メチルイソブチルケトン、アセトニトリル、ジオキサン、ジメチルホルムアミド、酢酸エチル、テトラヒドロフラン、ジメチルスルホキサイド等に代表される極性溶剤を用いればよい。
【００４８】
一方、無溶剤法は被覆材の溶融物または溶融分散物を肥料表面に噴霧して被覆する方法、さらには被覆後、表面を加熱溶融させて被覆均一性を高める方法で、安全性、経済性、環境負荷低減の面で好ましい。
【００４９】
これら溶剤の除去および被覆材の乾燥は熱乾燥風下で実施されるが、そのガス種としては、空気のほかに窒素、炭酸ガスなどの不活性ガスも安全面から使用できる。内層皮膜の被覆においては、各製造条件の好適な範囲を選択することで、均一な皮膜を形成し、かつ溶出制御性に優れた被覆肥料を提供することができる。以下、溶剤法における製造条件について説明する。
【００５０】
溶解液または分散液の全重量に対する被覆材の重量（以下「固形物濃度」と言うことがある。）を大きくすると、溶剤の使用量が低減し、被覆時間が短くなるので生産性の面からも好ましい。しかしながら、溶液粘度が高く、成膜中にスプレーノズル部で被覆材が閉塞し成膜が困難となる場合は、使用するスプレーノズルおよび噴霧圧力に応じて、適当な噴霧状態が得られる粘度になるように適宜調整される。これらの観点から、固形物濃度は通常０．１〜３０重量％、好ましくは０．５〜２５重量％、さらに好ましくは１〜２０重量％である。
【００５１】
また、溶解または分散液の肥料粒子へのスプレー速度は、被覆均一性、生産性、および溶剤種により適宜選択される。一般に、スプレー速度を大きくすると溶剤の乾燥が不充分となり、肥料粒同志が融着し易く成膜が困難となり、また噴霧時間が短くなる結果、皮膜の均一性が低下する。一方、小さくすると噴霧液のミスト径が小さくなるため、肥料粒子に展着する前に被覆材が乾燥し、肥料表面での展着性が悪化する結果、皮膜の均一性が低下する。さらに、被覆効率が低下し生産性の面からも好ましくない。これらの観点から、粒状肥料１ｋｇに対し、１分間あたりの溶解または分散液（固形物濃度が５重量％の場合）のスプレー速度は、通常２５〜３００ｇ／分・ｋｇ、好ましくは８０〜２５０ｇ／分・ｋｇの範囲である。
【００５２】
さらに、被覆時の肥料粒子の表面温度（以下、「品温」という）および熱乾燥風量は、特に限定されない。肥料粒子が融着することなく均一に混合され、安定した転動または噴流状態を維持し、かつ溶剤の除去および被覆材の乾燥が良好である範囲であれば良い。しかしながら、品温については影響を受け易く、一般に、高すぎると成膜中に皮膜材が軟化または溶融する結果、肥料粒同志が融着し成膜性が悪化する。一方、低すぎると乾燥が不充分となり成膜不良となる。これらの観点から、例えば、テトラクロロエチレンを使用する場合の品温は、通常４０〜１３０℃、好ましくは５０〜１１０℃、さらに好ましくは６０〜９０℃である。
【００５３】
先述の無機充填材や界面活性剤は、本発明の被覆粒状肥料の被覆方法において、直鎖状炭化水素を含む皮膜溶液中に、無機充填材及び／又は界面活性剤を溶解または分散させて使用する方法が一般的である。但し、乾燥風と共にそのまま肥料粒に展着または付着させてもよい。また、皮膜中での分散状態は目的に応じて適宜選択されるが、通常は皮膜の均一性を重視して均一に分散させることが好ましい。例えば、無機充填材は皮膜強度を制御するため、界面活性剤においては被覆肥料粒の浮上防止を抑制するために、皮膜の外殻に分散させるなどの濃度勾配があってもよい。
【００５４】
外層皮膜の製造においては、装置内での噴流、流動、攪拌などの衝撃により、内層皮膜が剥離または欠損しないように、できるだけ短時間で被覆できるような条件を設定することが好ましい。またこのことは生産性の面からも好ましい。具体的には、固形物濃度およびスプレー速度は、成膜中に肥料粒同志が接着しない範囲でできる限り大きくすることが好ましく、被覆均一性が多少損なわれても問題は少ない。
【００５５】
品温については使用する材料により適宜選択されるが、例えば、ポリイソプレンを主成分とする生分解性樹脂を使用する場合には、通常４０〜９０℃、好ましくは５０〜８０℃である。また、内層被覆肥料を一旦装置から取り出して再度被覆装置内で外層を被覆しても良いが、内層を被覆後そのまま外層を被覆する方が工業的に有利である。
【００５６】
また、本発明の被覆粒状肥料の用途は特に限定されるものではなく、作物の養分要求特性に合わせて適宜選択される。例えば、シグモイド型の溶出パターンを示す被覆窒素肥料は、生育中期に窒素の追肥が必要な水稲の栽培で好適に使用される。さらに、溶出制御期間が１年以上の被覆肥料は、樹木などの生育期間が長期にわたる永年植物に好適に使用される。
【００５７】
【実施例】
以下に実施例を示し、本発明をさらに具体的に説明するが、本発明はその要旨を超えない限り以下の実施例に限定されるものではない。
炭化水素の分岐鎖含有量は尿素付加法により求めた。また被覆率の測定は、被覆粒状肥料１０ｇを秤取り、小型粉砕器で粉砕した後、水を加えて尿素を溶解させ、皮膜のみを濾過回収し、この皮膜を乾燥したのち、秤量することで、次式から被覆率を算出した。
被覆率（％）＝（皮膜重量［ｇ］／（１０−皮膜重量）［ｇ］）×１００
なお、本発明でいう内層皮膜の被覆率は、被覆される尿素等肥料の重量に対する被覆率をいい、外層皮膜の被覆率は、被覆される内層被覆肥料の重量に対する被覆率をいう。また、被覆後の皮膜全体の被覆率は、使用した尿素等肥料の重量に対する被覆率をいう。
【００５８】
（１）被覆肥料の製造
（実施例１）
フィッシャー・トロプシュワックス（日本精蝋社製、ＦＴ１００。分岐鎖含有量：０重量％、重量平均分子量６７４、以下「ＦＴワックス」と言うことがある）３０ｇをテトラクロロエチレン２７０ｇに溶解させ、この溶液（固形物濃度１０重量％、液温度９０℃）３００ｇを、粒径２．８〜３．４ｍｍ（または粒径２〜４ｍｍ）の尿素粒３００ｇに流動層式コーティング装置を使用し、スプレー速度８１．５ｇ／分・ｋｇ、品温７０℃で噴霧被覆し、皮膜の平均膜厚６０μｍ、被覆率８．５％（対尿素粒重量）の被覆粒状肥料３２５．５ｇを得た。ここで得られた被覆粒状肥料の皮膜を内層皮膜▲１▼とする。上記の流動層式コーティング装置においては、槽内に充填した粒状肥料を装置下部より導入される熱乾燥風および装置底部に設置される攪拌翼で流動させながら、これに被覆材料を溶解または分散した噴霧液を噴霧後、さらに熱乾燥風にて溶剤を除去し、被覆材を乾燥することにより実施した。
【００５９】
（実施例２）
ＦＴワックス３０ｇと共に、ポリオキシエチレンノニルフェニルエーテル（東邦化学工業社製、非イオン系界面活性剤Ｎ２０４。ＨＬＢ８．９）０．６ｇを使用した以外は、実施例１と同様の方法により皮膜の平均膜厚６０μｍ、被覆率８．５％の被覆粒状肥料３２５．５ｇを得た。ここで得られた被覆粒状肥料の皮膜を内層皮膜▲２▼とする。
【００６０】
（実施例３）
実施例２で得られた被覆粒状肥料に、続いてポリイソプレンゴム（日本ゼオン社製、ＮＩＰＯＬ ＩＲ２２００）１．５ｇとタルク（松村産業社製、ハイフィラー＃５０００ＰＪ、平均粒径１．８μｍ）１３．５ｇをテトラクロロエチレン１３５ｇと混合して得られた溶液（固形物濃度１０重量％、９０℃）１５０ｇを、スプレー速度１９０ｇ／分・Ｋｇ、被覆粒状肥料の温度７０℃で噴霧被覆し、内層皮膜を含めた皮膜全体の被覆率１３．５％（対尿素粒重量）の被覆粒状肥料３４０．５ｇを得た。ここで得られた被覆粒状肥料の外層皮膜を外層皮膜▲３▼とする。
【００６１】
（実施例４）
ＦＴワックス１８ｇおよびポリオキシエチレンノニルフェニルエーテル（東邦化学工業社製、非イオン系界面活性剤Ｎ２０２、ＨＬＢ５．７）０．１５ｇをテトラクロロエチレン２７１ｇに溶解させた後、この溶液にタルク１２ｇを混合させ得られた溶液を用い、実施例１と同様の方法により得られた被覆粒状肥料（ここで得られた被覆粒状肥料の皮膜を内層皮膜▲４▼とする）に続いて、ポリイソプレンゴム１５ｇとホワイトカーボン（日本シリカ工業製、ニップシールＳＳ−１０、平均粒子径２．７μｍ）１５ｇをテトラクロロエチレン１２２０ｇと混合して得られた溶液（固形物濃度２．４重量％、９０℃）１２５０ｇを実施例３と同様の方法により、内層皮膜を含めた皮膜全体の被覆率１８．４％（対尿素粒重量）の被覆粒状肥料３５５．２ｇを得た。ここで得られた被覆粒状肥料の外層皮膜を外層皮膜▲５▼とする。
【００６２】
（実施例５）
ポリイソプレンゴム２２．５ｇとホワイトカーボン２２．５ｇをテトラクロロエチレン１８３０ｇと混合して得られた溶液（固形物濃度２．４重量％、９０℃）を使用した以外は、実施例４と同様の方法により、内層皮膜を含めた皮膜全体の被覆率２３．０％（対尿素粒重量）の被覆粒状肥料３６９．０ｇを得た。ここで得られた被覆粒状肥料の外層皮膜を外層皮膜▲６▼とする。
【００６３】
（実施例６）
ＦＴワックス１８ｇをテトラクロロエチレン２７０ｇに溶解させた後、この溶液にタルク１２ｇを混合させ得られた溶液を用い、実施例１と同様の方法により得られた被覆粒状肥料（ここで得られた被覆粒状肥料の皮膜を内層皮膜▲７▼とする）に続いて、硫黄微粉末（細井化学工業製、純度９９．９％以上、２００メッシュパス）４５ｇをテトラクロロエチレン２５５ｇと混合して得られた溶液（固形物濃度１５重量％、９０℃）３００ｇを用いて実施例３と同様の方法により、内層皮膜を含めた皮膜全体の被覆率２１．４％（対尿素粒重量）の被覆粒状肥料３６４．２ｇを得た。ここで得られた被覆粒状肥料の外層皮膜を外層皮膜▲８▼とする。
【００６４】
（比較例１）
実施例１において使用したＦＴワックス３０ｇの代わりに、分岐鎖含有量２５．９重量％、重量平均分子量４０００のポリプロピレンワックス（三洋化成工業社製、ビスコール５５０Ｐ。以下「ＰＰワックス」と言うことがある）３０ｇを使用した以外は、実施例１と同様の方法により皮膜の平均膜厚６０μｍ、被覆率８．５％の被覆粒状肥料３２５．５ｇを得た。ここで得られた被覆粒状肥料の皮膜を内層皮膜▲９▼とする。
【００６５】
以上の実施例１〜６、及び比較例１で得られた各被覆肥料につき、製造処方を表１にまとめた。
【００６６】
【表１】
（２）被覆肥料中の欠陥粒子数の測定
被覆肥料１０ｇ（総粒子数約４７０個）を試験管に秤取り、インク１０ｃｃを加え、４０℃の恒温水中で１時間放置した後、被覆肥料を濾過回収する。被覆肥料に付着したインクを水洗すると皮膜の欠陥部分にインクの色が残るので、これより欠陥皮膜を有する粒子を区別する。欠陥粒子を下記の３種類に区分し、これを数えてその総数を欠陥粒子数とする。
欠陥粒子の数が多いほど、欠陥部分を通して水蒸気の透過速度が大きくなり、肥料成分の溶出量も多くなる。従って、欠陥粒子の数が少ないほど初期の溶出防止性が高く、種々の溶出パターンを調整するにあたり好ましい。
（i）被覆粒状肥料粒子の大部分は着色せず、部分的に着色箇所を有する粒子（小欠陥）
（ii）欠陥部分が大きいため肥料粒子のほぼ全体が着色した粒子（中欠陥）
（iii）既に尿素が溶出して皮膜だけになった殻の粒子（大欠陥）
【００６８】
実施例１〜６及び比較例１で製造した被覆肥料について、上記に基づき欠陥粒子数の測定を行なった。結果を表２に示した。
【００６９】
【表２】
（３）被覆肥料の溶出特性の評価
水中溶出測定法
実施例１〜６及び比較例１で製造した被覆肥料を、４０℃恒温水中に７ｇ／２００ｃｃの割合で投じ、経時的に水中の尿素態窒素を定量した。なお、４０℃の評価では、測定により得られた溶出特性の結果から２５℃の溶出特性を予測することが可能であり、２５℃の加速評価法として有効なものである。結果を図１（被覆肥料のＮ溶出率％）に示した。
【００７１】
図１に示した結果から、実施例１および２のように、分岐鎖の含有量が特定量以下の直鎖状炭化水素を皮膜材料に用いることにより、単一層の被覆のみでシグモイド型の肥料成分溶出パターンを示すことがわかる。また、実施例３〜５のように、分岐鎖の含有量が特定量以下の直鎖状炭化水素で被覆された被覆粒状肥料に、さらにポリイソプレンゴムと無機充填剤を含む外層皮膜、または実施例６のように硫黄を主成分とする外層皮膜で被覆した被覆粒状肥料は、シグモイド型の溶出パターンを損なうことなく、被覆肥料皮膜の保護効果に優れた緩効性肥料であることがわかる。
即ち、これらは長期間に亘る肥料成分の溶出制御が可能であり、従来のように数回の追肥を行うことなく、一回の施肥作業で肥料成分の溶出を作物の養分要求特性に適合させるように制御された被覆粒状肥料である。
これに対し、分岐鎖の含有量が１０重量％より多い直鎖状炭化水素で被覆された被覆粒状肥料（比較例１）は、施肥環境下での溶出制御性が不安定である。「溶出制御性が不安定」とは、皮膜の分解性が水分と温度条件のみならず、微生物活性、ｐＨ、物理的な衝撃等にも影響されることを意味する。そのため、施肥後の変化の予測が困難であり、よって分解に伴う溶出促進も予測困難であるので、土壌中での溶出を制御することができない。
【００７２】
実施例１〜３および比較例１の被覆肥料につき、耐衝撃性評価を行った。
（４）被覆肥料の耐衝撃性評価
ステンレス製の円筒容器（φ６９×Ｈ６９ｍｍ）に被覆肥料を４０ｇ（総粒子数約１８８０個）入れ、レシプロ振とう機（大洋科学工業社製、TAIYO recipro shaker SR-IIw）により、垂直方向（振幅４０mm、振とう速度５往復／秒）に３０秒間振とうさせた。振とう後の被覆肥料について、欠陥粒子数の測定および水中溶出測定を行った。結果を表３及び図２（耐衝撃試験前後のＮ溶出率％）に示す。
【００７３】
【表３】
表３の結果から、分岐鎖の含有量が特定量以下の直鎖状炭化水素を皮膜材料に用いることによって、被膜強度に優れた被覆粒状肥料となることが示された。また、さらにポリイソプレンゴムを含む外層皮膜で保護することにより、より耐衝撃性に優れた被覆粒状肥料となることが示された。さらに、図２の結果から、衝撃後の溶出速度は処理前とほぼ同等であり、シグモイド型の溶出パターンを損なうことなく被覆肥料皮膜の保護効果に優れた緩効性肥料であることが示された。
これに対し、分岐鎖の含有量が１０重量％より多い直鎖状炭化水素で被覆された被覆粒状肥料（比較例１）は、施肥環境下での溶出制御性が不安定であるだけでなく、皮膜の耐衝撃強度に劣っており、緩効性肥料として実用に耐えられないものである。
以上の結果から、本発明の被覆粒状肥料は水中、土中等の施肥環境下において、溶出制御性、つまり施肥環境下での水分と温度条件のみで溶出を予測することが可能で、作物の生育に合わせた施肥管理を可能とすることがわかる。
【００７５】
（５）被覆肥料の施肥機試験評価
実施例４〜６の被覆肥料につき、Ｎ-Ｐ-Ｋ成分が16-16-16となるように化成肥料と配合し（原単位として被覆肥料約１９．３％含有）、以下の条件により施肥機適合性を評価した。
【００７６】
【表４】
表４の結果から、分岐鎖の含有量が特定量以下の直鎖状炭化水素を含む皮膜で被覆した被覆粒状肥料に、さらにポリイソプレンゴムと無機充填剤を含む外層皮膜、および硫黄を主成分とする外層皮膜で被覆した被覆粒状肥料について、施肥機処理による皮膜の損傷の程度が小さいことが示されている。また、図３の結果から、施肥機処理後の溶出速度は処理前とほぼ同等であり、シグモイド型の溶出パターンを損なうことなく、被覆肥料皮膜の保護効果に優れた緩効性肥料であることが示された。また、施肥機処理により初期（溶出開始後３日目）のＮ溶出率がやや高くなっているが、いずれもＮ溶出率が１０％以下であることから、実場面において作物および環境に与える影響は小さく、緩効性肥料として実用可能である。
【００７８】
（６）被覆材料の生分解性評価
本発明で使用したＦＴワックスおよびポリイソプレンゴムにつき、素材の生分解性試験を行った。評価方法および分解挙動の結果を図４（素材の生分解性結果）に示す。
図４の結果から、ＦＴワックスについては、試験開始後より緩やかに生分解が認められることから、最終的に二酸化炭素と水に分解されると示唆される。また、ポリイソプレンゴムについては、生分解速度は遅いが、試験開始１５０日以降から緩やかに生分解率が向上しつつあることから、素材自体が生分解性を有することは明らかである。
すなわち、本発明の被覆粒状肥料により、施肥された環境下において肥料成分の溶出が制御され、且つ溶出終了後より被覆材である皮膜が生分解を受けるので、周辺環境への負荷を軽減できる。
【００８０】
以上の結果から、本発明の被覆粒状肥料が力学的強度に優れた皮膜を有し、且つ皮膜の変質・破損等により溶出制御性が変化することなく、長期間にわたり施肥環境下における溶出制御性が良好であり、最終的にコーティング材の皮膜が土壌内外で分解することにより、環境への負荷を軽減したものであることは明らかである。これに対し、分岐鎖の含有量が１０重量％より多い鎖状炭化水素で被覆された被覆粒状肥料は、施肥環境下での溶出制御性が不安定であるだけでなく、皮膜の耐衝撃強度も劣っており、緩効性肥料として実用に耐えられないものである。
【００８１】
【発明の効果】
本発明の被覆粒状肥料によって、施肥された環境下において肥料成分の溶出が制御され、且つ被覆材である皮膜が生分解するので周辺環境への負荷を軽減した被覆粒状肥料を提供することが出来る。
本発明の被覆粒状肥料はその皮膜の力学的強度が優れ、他の肥料との配合時や輸送中および機械施肥時などにおいて、皮膜の一部が剥離または欠損等の損傷を受けず、かつ溶出制御性に影響を与えない。
【図面の簡単な説明】
【図１】 被覆肥料のＮ溶出率％（４０℃水中）
【図２】 耐衝撃性試験前後のＮ溶出率％（４０℃水中）
【図３】 施肥機処理前後のＮ溶出率％（４０℃水中）
【図４】 素材の生分解性結果[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coated granular fertilizer, and more particularly, to a coated granular fertilizer in which elution of fertilizer components is controlled in a fertilized environment and a burden on the surrounding environment is reduced by biodegrading a coating film as a coating material.
[0002]
[Prior art]
Fertilizer according to the growth stage is necessary for cultivation of agricultural crops, and in order to match the required time, fertilizer has been applied several times before harvesting crops such as raw fertilizer and topdressing. In recent years, with the modernization of agriculture and the decline in the agricultural population, there has been a demand for the development of fertilizers that require less time and less fertilization, and the elution of fertilizer components is adapted to the nutrient requirements of crops. Various fertilizers have been developed to control.
[0003]
For example, in order to physically control the elution of fertilizer components fertilized in soil, studies have been widely conducted to coat the surface of granular fertilizer with a polymer resin film, some of which have been put into practical use. For example, there are various elution types such as a linear elution type in which the elution curve of fertilizer components is a straight line and a sigmoid elution type in which the elution curve of the fertilizer component is a straight line. It became possible to manage the fertilization according to the growth of the rice (SHO54-3104, SHO60-3040, SHO60-37074, etc.).
[0004]
However, in recent years, such polyolefin resins are non-degradable, so that the shell of the shell accumulates in the field where the coated granular fertilizer is introduced, and further, this shell flows out of the field and as a result accumulates in the ecosystem. There is concern about the load. Therefore, a technique has been proposed in which a biodegradable material is added to a polyolefin resin to cause the film to collapse.
For example, there are a method of adding a sugar polymer and a derivative thereof as biodegradable materials (JP-A-6-87684, JP-A-11-322479), a method of adding an aliphatic polyester (JP-A-9-263476), and the like. However, these do not promote the decomposition of the polyolefin resin that occupies most of the covering material, and have the disadvantage that the elution controllability in soil becomes unstable with the increase of biodegradable materials.
[0005]
A technique using a covering material having decomposability so that the coating material itself can be decomposed by some action has been studied, but each has a problem and has not been solved.
For example, a technique in which a photodegradable resin is the main component of the film has been proposed, and an ethylene / carbon monoxide copolymer is used as the photodegradable resin (Japanese Patent Publication No. 23-25516), and a vinyl ketone copolymer is used ( JP-B-7-506) and those using an olefin / carbon monoxide / olefinically unsaturated compound copolymer (JP-A-6-56568). Since these are decomposed only under conditions where the coated granular fertilizer is exposed to sunlight, etc., it is not possible to avoid accumulation of the film shell in the field and outflow outside the field area, and the film changes in quality during storage, There is a problem that elution controllability changes.
[0006]
In addition, a technique in which a biodegradable resin is the main component of the film has been proposed. As the biodegradable resin, modified natural rubber (Japanese Patent Laid-Open No. 59-92989) and various aliphatic polyesters (Japanese Patent Publication No. 23-2517, JP-B-7-505, JP-A-4-89384, JP-A-5-85873, JP-A-7-33577, JP-A-7-61884, JP-A-7-315976, JP-A-8-157290, JP-A-9-24977, JP-A-9-24977. 10-7484) are known, but because these resins have high moisture permeability, it is impossible to create a sigmoid-type elution type having an elution stagnation period, and the rate of biodegradation in soil is large, and elution controllability is achieved. Has the disadvantage of being unstable.
[0007]
On the other hand, for the purpose of imparting biodegradability to the coating material and maintaining elution control over a long period of time, a technology in which low molecular weight polyethylene, petroleum wax, paraffin wax and the like are the main components of the coating has been proposed. (Japanese Patent Publication Nos. 49-3339, 9-263476, 10-231190, 10-291880, 11-71192, 11-1126389, etc.). However, the film material has a low melting point, the fertilizer particles are fused together during film formation, making film formation difficult, and the film has poor mechanical strength, that is, impact resistance and wear resistance. As a result, the film is easily damaged by a physical impact. As a result, the elution controllability becomes unstable, and the originally expected elution control cannot be performed.
[0008]
In order to make up for the above-mentioned drawbacks, techniques for coating the outer layer with a film having a polymer substance are disclosed (Japanese Patent Laid-Open Nos. 7-33576, 7-215789, 8-1515186, 9-30883). , JP-A-9-214090, JP-A-10-231191, etc.) improve the handling properties after coating the outer layer, but cannot essentially improve the defects at the time of coating the inner layer. If an attempt is made to provide an elution control function in both coating layers, there is a problem that the elution control becomes complicated.
[0009]
[Problems to be solved by the invention]
The object of the present invention is to have a film with excellent mechanical strength, and the elution controllability in a fertilized environment is good over a long period of time without changing the elution controllability due to alteration or breakage of the film. In particular, a coated granular fertilizer that reduces the burden on the environment by disintegrating the coating film of the coating material inside and outside the soil is provided.
[0010]
[Means for Solving the Invention]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a linear hydrocarbon having a specific molecular weight with a branched chain content of a specific amount or less as a coating material in the coated granular fertilizer. A coating that solves the above-mentioned problems that granular fertilizer becomes a slow-acting fertilizer having a sigmoid-type elution curve that could not be realized with a conventional single coating layer, and has excellent coating strength and can also provide coating degradability. It was found that it became a granular fertilizer and reached the present invention.
[0011]
That is, the present invention relates to a coated granular fertilizer formed by coating with a film containing a linear hydrocarbon having a branched chain content of 10% by weight or less and a weight average molecular weight of 300 or more. Further, a coated granular fertilizer characterized by being coated with an outer layer film containing a biodegradable resin Exist.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The linear hydrocarbon in the present invention is a linear (linear) compound having a branched chain content of 10% by weight or less and a weight average molecular weight of 300 or more. Thus, by specifying the branched chain content and the weight average molecular weight at the same time, the crystallinity, the melting point, and the material strength are increased, and the water vapor permeability is also decreased, which is preferable as a coating material for the coated granular fertilizer. From this point of view, the content of the branched chain of the linear hydrocarbon in the present invention is preferably as small as possible, and in particular, a linear hydrocarbon containing no branched chain is ideal.
[0013]
The branched chain in the present invention refers to a carbon chain (side chain) branched from the longest carbon chain (main chain) in the chain hydrocarbon, and includes a side chain further branched from this branched chain. Including. Moreover, the content rate of a branched chain shows the weight ratio (%) of the branched chain part with respect to the total weight of the chain hydrocarbon which comprises the membrane | film | coat of a covering granular fertilizer. Therefore, the branched chain content in the present invention is defined as measured by the urea addition method.
[0014]
The value of the branched chain content of the linear hydrocarbon may be 10% by weight or less, preferably 5% by weight or less, and the smaller the branched chain content, the better. However, chain hydrocarbons with extremely low branch chain content are difficult to obtain industrially, and even if they are ideally completely straight chain, it is difficult to expect any more special effects. The chain content is selected from the range of 0.001 to 5% by weight, preferably 0.001 to 1% by weight.
[0015]
The branched chain structure in the straight-chain hydrocarbon is arbitrary, specifically, an alkyl group such as a methyl group, an ethyl group, or an n-butyl group; an alkenyl group such as a vinyl group, an allyl group, or a 1-propenyl group; Examples thereof include alkynyl groups such as ethynyl group and propargyl group; aryl groups such as phenyl group, tolyl group and naphthyl group. Among them, those having an alkyl group, an alkenyl group and the like are preferable, and those having an alkyl group are particularly preferable. The position of the branched chain bonded to each carbon is not particularly limited. The chain hydrocarbon may be a single type or a mixture of two or more types.
[0016]
The hydrocarbon in the present invention refers to a compound having a linear structure in which carbon atoms constituting the main chain are linearly arranged. The carbon bonds in the straight-chain hydrocarbon may have a single bond, a double bond, other modes, or a plurality of these types. Among them, a saturated compound in which all carbon bonds are single bonds is preferable because of excellent crystallinity and hydrophobicity. For example, high molecular weight polyethylene such as high density polyethylene and linear low density polyethylene; synthetic wax such as Fischer-Tropsch wax and polyethylene wax; petroleum wax represented by paraffin wax, microcrystalline wax, and petrolatum. Of these, synthetic waxes having particularly few branched chains, excellent film formability and good decomposability, and Fischer-Tropsch wax are particularly preferable.
[0017]
The weight average molecular weight of the linear hydrocarbon in the present invention is a specific range of 300 or more, and is usually 300 to 10000, preferably 500 to 5000, and more preferably 600 to 1000. Moreover, as melting | fusing point measured by DSC (differential scanning calorimeter) method, it is 44-110 degreeC, Preferably it is 50-100 degreeC. If the weight average molecular weight is too small, the melting point will be low, and the fertilizer grains will fuse together during film formation, which may cause problems with the coating moldability, and the biodegradation rate in the soil will be too fast, resulting in poor elution control. It becomes stable. On the other hand, if the weight average molecular weight is too large, the initial elution suppression of the fertilizer component is excellent, but the decomposability and disintegration of the film may be reduced.
[0018]
Further, the linear hydrocarbon in the present invention may have a certain molecular weight distribution, but this distribution is preferably as small as possible. Specifically, it is preferable that the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), that is, Mw / Mn is 1.01 to 3.00. In addition, the average molecular weight of the chain hydrocarbon in this invention means what was measured by the high temperature GC (gas chromatography) -FID (hydrogen flame ionization detector) method.
[0019]
The film thickness of the film can be appropriately selected according to desired elution controllability, film strength, biodegradability and the like. A thin film is economically advantageous, but the strength of the film is weak, and peeling and defects are likely to occur. A thick film is excellent in film strength, initial elution prevention property and elution controllability over a long period, but is economically disadvantageous. For the above reasons, it is generally 30 to 210 μm, preferably 45 to 175 μm, and most preferably 50 to 140 μm as a slow-acting fertilizer for paddy rice.
[0020]
The coating rate of the coated granular fertilizer of the present invention (weight% of the film with respect to the weight of the fertilizer component particles to be coated) is usually in the range of 6 to 25% by weight, preferably 7 to 20% by weight. It is obtained by calculation by measuring the film thickness of the coated granular fertilizer, the fertilizer particle diameter and its specific gravity.
[0021]
The coating in the coated granular fertilizer of the present invention contains a linear hydrocarbon having a branched chain content of 10% by weight or less and a weight average molecular weight of 300 or more. The film may be entirely composed of the linear hydrocarbon, but various substances can be blended in the film within a range not impairing the effect. For example, using high molecular compounds, resins, inorganic substances, salts and other additives to change the properties of the film to control the elution of fertilizer components and to increase or decrease the biodegradability and moisture permeability of the film be able to. The mechanical strength can also be changed.
[0022]
As the polymer compound, a compound having a molecular weight of 10,000 or more and a main chain mainly composed of a covalent bond can be used. In addition, oligomers having a molecular weight of 1000 to 10,000 can be used as long as the object of the present invention is not impaired. For example, polyethylene, polypropylene, ethylene / propylene copolymer, polybutene, butene / ethylene copolymer, butene / propylene copolymer, olefin copolymer such as polystyrene, ethylene / vinyl acetate copolymer, whose main chain is made of carbon. Polymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / carbon monoxide copolymer Copolymers, butadiene copolymers, isoprene polymers, chloroprene polymers, diene polymers such as butadiene / styrene copolymers and styrene / isoprene copolymers, and synthetic polymers such as polyvinyl chloride can be used. On the other hand, natural polymers can be used as long as they promote the degradability and disintegration of the film. Although these are high molecular compounds, in the present invention, they are grasped as biodegradable resins and will be described later in detail. These organic polymers are preferable because they are easily compatible with the linear hydrocarbon of the present invention and have good film formability and coating uniformity.
[0023]
In addition to organic polymer compounds, inorganic polymer compounds composed of silicon, sulfur, phosphorus, and the like can also be used. Moreover, these polymer compounds may be used alone or in combination of two or more at any ratio within a range not impairing the object of the present invention. The addition amount of these polymer compounds in the film is usually 0.1 to 50% by weight, preferably 0.5 to 40% by weight, particularly preferably 1 to 30% by weight, based on the weight of the film.
[0024]
In the present invention, an inorganic filler may be contained in the linear hydrocarbon film described above. It is preferable to include an inorganic filler in the film because it is possible to adjust the elution control of the coated granular fertilizer and reduce the temperature dependency. Examples of the inorganic filler include talc, clay, mica, montmorillonite, bentonite, activated clay, sepiolite, imogolite, sericite, glass fiber, glass beads, glass flake, silica-based balun, silica, diatomaceous earth, alumina, zinc oxide, Titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, ferrites, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dosonite, hydrotalcite, calcium sulfate , Barium sulfate, gypsum fiber, calcium silicate, aluminum nitride, boron nitride, silicon nitride, carbon black, graphite, carbon fiber, carbon balun, charcoal powder, various metal powders, metal foil, petal, aluminum borate Silicon carbide, zinc borate, aluminum borate, graphite, litharge, and sulfur and the like.
[0025]
Among them, those having a small influence on the elution controllability of the coated granular fertilizer, for example, talc, clay, mica, silica, calcium carbonate, etc., are preferable even when the addition amount is increased for the purpose of improving the film strength. The addition amount of the inorganic filler in the film is usually 0.1 to 70% by weight, preferably 5 to 65% by weight, particularly preferably 10 to 60% by weight, based on the weight of the film. If the amount of the inorganic filler added is too large, the film strength may decrease and the elution controllability may decrease. On the other hand, if the amount added is too small, a sufficient effect cannot be obtained. The inorganic filler preferably has an average particle size that does not inhibit the continuity of the linear hydrocarbon film and does not cause aggregation of the inorganic fillers. An average particle size is preferred. Specifically, those having a thickness of 200 μm or less, preferably about 5 to 100 μm are used. Further, these inorganic fillers may be used alone or in combination of two or more at any ratio within a range not impairing the object of the present invention.
[0026]
Moreover, you may contain surfactant in a chain | strand-shaped hydrocarbon membrane | film | coat for the purpose of elution control adjustment of the coated granular fertilizer of this invention similarly to the above-mentioned inorganic filler. As the surfactant, any one of cationic, anionic, nonionic, and amphoteric surfactants, a mixture thereof, and the like can be used. Among these, nonionic surfactants that are easy to adjust the elution control and have excellent storage stability of the coated granular fertilizer are preferable. Nonionic surfactants include, for example, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene polystyryl phenyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene glycol, polyethylene glycol Glycol ether, polyethylene glycol fatty acid ester, alkylol amide, sorbitan fatty acid ester, sucrose fatty acid ester and the like. Among these, polyoxyethylene alkylphenyl ether and polyoxyethylene alkyl ether are particularly preferable because elution can be controlled with a small amount of addition.
[0027]
The HLB of the surfactant is arbitrary, but usually 3-20. The addition amount of the surfactant in the film is usually 0.01 to 20% by weight, preferably 0.05 to 15% by weight, and more preferably 0.1 to 10% by weight with respect to the film weight. If the addition amount of the surfactant is too large, the hydrophilicity of the film may be increased and the elution controllability may be lowered. On the other hand, if the addition amount is too small, a sufficient effect for adjusting the elution control cannot be obtained.
[0028]
In the present invention, a biodegradable resin may be contained in the linear hydrocarbon film described above. These can be used alone or in combination of two or more.
Any biodegradable resin may be used as long as it is decomposed into a low molecular weight compound by microorganisms in nature. For example, copolyester composed of 3-hydroxybutyrate and 3-hydroxyvalerate, microbial production resin represented by bacterial cellulose, polyamino acid, polyglutamic acid, polylysine, cellulose, starch, chitin / chitosan, alginic acid, gluten , Collagen, curdlan, pullulan, dextran, gelatin, lignin, xanthan gum, natural rubber, proteins, polysaccharides, natural compounds such as nucleic acids, and diols such as ethylene glycol, propylene glycol, butanediol, hexanediol, dipropylene glycol An aliphatic polyester obtained by dehydration condensation with one kind selected from succinic acid, terephthalic acid, isophthalic acid, adipic acid, sebacic acid and the like, poly ε-caprolac Emissions, polylactic acid, chemically synthetic resin typified by polyglycolic acid, and the like. These may use together 1 type, or 2 or more types in arbitrary ratios. As the biodegradable resin, for example, aliphatic polyester, aliphatic polyester introduced with aromatic or cyclic ether, sugar polymer and derivatives thereof, protein and derivatives thereof are preferable.
The addition amount of the biodegradable resin in the film is usually 0.1 to 50% by weight, preferably 0.5 to 20% by weight, particularly preferably 1 to 10% by weight, based on the film weight.
[0029]
In the present invention, the coating of the coated granular fertilizer is “biodegradable” means that the polymer material in the coating is reduced to a low molecular weight by microorganisms in the soil and finally decomposed into water and carbon dioxide. Indicates the mechanism. Furthermore, it is deteriorated by exposure to sunlight including ultraviolet rays, and is a chemical mechanism that is oxidized by oxygen in the air under conditions of appropriate temperature and humidity, to a film during soil cultivation and disintegration in farmland soil It includes physical mechanisms such as physical impact of soil, compressive expansion of soil due to changes in temperature and humidity, and film collapse due to penetration of plant roots into the film. For example, if the film strength is reduced to such an extent that the particle shape cannot be maintained by such chemical and physical mechanisms, and the film has collapsed to such a degree that it can be minimized, it remains in the particle state in the soil. Since it does not remain and is prevented from flowing out of the system due to levitation or the like, there is virtually no concern about environmental impact. Here, since the micro-sized film becomes easier for microorganisms to propagate in these films, degradation by a biological mechanism is promoted and finally disappears.
[0030]
Moreover, you may contain a photodegradable material in the membrane | film | coat of the covering granular fertilizer of this invention. As the photodegradable material, for example, photosensitive functional groups such as carbon monoxide and olefin copolymers, diene polymers, vinyl ketone copolymers, 1,2-polybutadiene, polyisobutylene oxide and the like are introduced. Resins are preferred. These can be used alone or in combination of two or more. The addition amount may be appropriately determined in consideration of elution controllability, degradability, and storage stability of the coated granular fertilizer of the present invention, but is usually 0.1 to 50% by weight, preferably 0, based on the film weight. 0.5 to 30% by weight, particularly preferably 1 to 20% by weight.
[0031]
Moreover, you may contain an oxidation promotion substance, a photodegradation promotion substance, a sublimation substance etc. in the film | membrane of the coated granular fertilizer of this invention. Thereby, the oxidative decomposition and photolysis of the film can be promoted. On the other hand, together with these, a light stabilizer or an antioxidant may be added in consideration of storage stability. Since these have effects opposite to each other, it is important to use them appropriately according to the use and purpose of the product.
[0032]
As the oxidation promoting substance / photodegradation promoting substance, for example, unsaturated fatty acids having a carbon unsaturated bond, unsaturated fatty acid esters, fats and oils, transition metals, transition metal compounds, transition metal complexes, aromatic ketones and the like are preferable. The addition amount is appropriately determined in consideration of elution controllability, decomposability, and storage stability, but is usually 0.001 to 10% by weight, preferably 0.005 to 5% by weight, particularly with respect to the film weight. Preferably it is 0.01 to 1 weight%.
[0033]
As the sublimable substance, for example, naphthalene, camphor, sulfur and the like are preferable. The addition amount is appropriately determined in consideration of elution controllability, degradability, and storage stability, but is usually 0.01 to 30% by weight, preferably 0.05 to 20% by weight, particularly with respect to the film weight. Preferably it is 0.1 to 10 weight%.
Examples of light stabilizers and antioxidants include aromatic amines and phenols, such as Irganox 1010 manufactured by Ciba Specialty Chemicals, salicylate, benzophenone, benzotriazole, nickel, cyanoacrylate, and oxalic acid anilide. And hindered amines such as LS622LD manufactured by Ciba Specialty Chemicals. The addition amount is appropriately determined in consideration of elution controllability and storage stability. It is usually 0.001 to 10% by weight, preferably about 0.01 to 1% by weight, based on the film weight.
[0034]
In the above, various blends used as an auxiliary component constituting a film together with a linear hydrocarbon having a branched chain content of 10% by weight or less and a weight average molecular weight of 300 or more have been described. As a method for adding these blends, the polymer resin (solution) containing the linear hydrocarbon described above is uniformly dispersed / dissolved using a compatibilizer or a dispersant as necessary, or a fine powder It may be dispersed in the form of a film solution. As the compatibilizing agent, water, alcohol, hydrocarbon, halogenated hydrocarbon or the like is used, which will be described later in detail.
[0035]
In the present invention, on the coated granular fertilizer coated with the above-mentioned specific linear hydrocarbon (hereinafter sometimes referred to as “inner layer coated fertilizer”), from the viewpoint of improving impact resistance, a coating ( Hereinafter, it may be referred to as “outer layer coating”). As the outer layer film, those having a protective effect as a coated fertilizer within a range not impairing the effects of the present invention are preferable, and those that decompose and disappear under fertilization conditions are more preferable. The film thickness of the outer layer film is preferably as thin as possible as long as it has a protective effect, and is usually 3 to 200 μm, preferably 5 to 150 μm, and more preferably 10 to 80 μm. The coverage is usually in the range of 0.5 to 20% by weight, preferably 1 to 15% by weight, more preferably 3 to 10% by weight, based on the weight of the coated inner layer fertilizer.
[0036]
As such an outer layer film, the biodegradable resin described above can be used, and a water-soluble resin, a linear hydrocarbon, or the like can be used. The main constituents of the outer layer film are these resins, but other auxiliary compounds can be used in the same manner as in the case of the inner layer film.
[0037]
As the water-soluble resin, a resin that is soluble in water (including acidic water and alkaline water) and is not toxic to various plants is used. The water-soluble resin includes those having biodegradability described above. Specifically, for example, natural polymer resins represented by starch, agar, sodium alginate, gum arabic, tragacanth gum, troolo oy, konjac, glue, casein, gelatin, egg white, pullulan, dextran, soluble starch, carboxyl starch, Semi-synthetic polymer resins such as dialdehyde starch, cationic starch, polyether, polymalic acid, British gum, dextrin, viscose, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, polyethylene glycol, polypropylene glycol , Polyacrylamide, polyacrylic acid, polyvinylamine, poly N-vinyl pyrrolidone, water-soluble alkyd, polyvinyl ether, polyethylene oxide Id, maleic anhydride, polymaleic acid copolymer, polyethyleneimine, polyvinyl sulfonic acid, polyvinyl ammonium, polystyrene sulfonic acid, polymethacrylic acid, polyamine, polyimine, polybetaine, and so on, and polyphosphate soda Inorganic polymer type resin represented by water glass and the like.
These may use together 1 type, or 2 or more types in arbitrary ratios.
[0038]
As a method for forming the outer layer film, that is, a method for coating the inner layer-coated fertilizer, it is usually used by dissolving or dispersing in the solvent together with the above-mentioned linear hydrocarbon, but it may be melted. Also, it can be used as a colloidal dispersion dispersed in an appropriate solvent in the form of fine powder, or an emulsion to which an emulsifier is added.
[0039]
Among the biodegradable resins and water-soluble resins described above, polyisoprene has a protective effect as an outer layer coating, has good coverage and degradability, is inexpensive, and has little influence on the elution controllability of the inner layer coating fertilizer. What has a main component is preferable.
Here, the biodegradable resin mainly composed of polyisoprene may be a polymer whose structure is a chain of isoprene or isoprene derivatives. Formic acid is added to latex contained in rubber tree (Hevea brasiliencis). Obtained by solidification and drying, or obtained by a polymerization reaction using a Ziegler-Natta catalyst or an alkyllithium catalyst, and has a weight average molecular weight of 1 × 10 Five ~ 5x10 6 A degree is preferred. In addition, several types of polyisoprene having an isomer structure can be obtained from the polymerization reaction. Among them, those containing 60% by weight or more of cis-1,4-polyisoprene are preferable because of their high decomposability. Further, vulcanized rubber obtained by adding sulfur to a cis-1,4-polyisoprene solution after heating, chlorinated rubber and hydrochloric acid rubber obtained through chlorine and hydrogen chloride, as well as sulfuric acid and p-toluenesulfonyl chloride Alternatively, polyisoprene derivatives typified by cyclized rubber obtained through heavy metal chlorides can also be used as long as the object of the present invention is not impaired.
[0040]
In the present invention, it is preferable to add an inorganic filler in the outer layer film for the purpose of improving the coatability of the outer layer film, improving the film strength, and reducing the amount of expensive resin used. As an inorganic filler, what is added in the membrane | film | coat of the above-mentioned inner layer coating fertilizer can be used, and 1 type or 2 types or more may be used together in arbitrary ratios. Of these, talc, clay, silica, magnesium carbonate, calcium carbonate, carbon black, petal, zinc oxide, and titanium oxide are preferable. The amount of the inorganic filler added to the outer layer film is arbitrary, but is preferably 30 to 99.9% by weight, more preferably 50 to 95% by weight. If the amount added is too large, the mechanical strength of the outer layer film may be reduced. On the other hand, if the amount added is too small, the fertilizer grains may adhere to each other during film formation, making it difficult to form the film. In addition, any of the inorganic fillers preferably has an average particle diameter that does not inhibit the continuity of the film and does not cause aggregation of the powders, for example, an average particle diameter that is 1/2 or less of the outer layer thickness.
[0041]
The coating method is usually used after being dispersed in a solution, but it may be attached to the inner layer coated fertilizer grains as it is along with the dry air. Further, the dispersion state in the film is appropriately selected according to the purpose. Usually, it is preferable to disperse the film uniformly with emphasis on the uniformity of the film. For example, in order to improve the coating property or to control the film strength, the film is dispersed in the outer shell or inner shell of the film. There may be a concentration gradient.
[0042]
When the coated granular fertilizer grains adhere after forming the outer layer film, it is preferable to spread an inorganic filler on the surface of the outer layer film. Further, when the coated fertilizer floats due to the water repellency of the outer layer film, it is preferable to add a surfactant as described above to the outer layer film because it has the effect of preventing the floating.
[0043]
Further, as in the case of the inner layer coated fertilizer film (inner layer film), the photodegradable material, oxidation promoting substance, photodegradation promoting substance and sublimation as described above are also included in the outer layer film within the range not impairing the object of the present invention. An active substance or the like may be added, and one or two or more of these may be used in an arbitrary ratio. In addition, other fertilizer components, agricultural chemicals such as agricultural chemicals and plant physiologically active substances, or plant growth promoting substances may be added to the inner layer film and / or outer layer film, and the dispersion state of these materials in the film Is optional. In consideration of elution controllability, decomposability, storage stability, and mechanical strength of the film, a coating structure of three or more layers in which a film is provided on the outer side of the outer layer film may be used.
[0044]
In the coated granular fertilizer of the present invention, by combining the preferable ranges of the above-mentioned items, the mechanical strength of the film is excellent, and the soil can be kept in the soil over a long period without changing the elution controllability due to the alteration of the film during storage. This is preferable because the elution controllability is good, and the film is finally decomposed under fertilization conditions inside and outside the soil, reducing the burden on the environment. Specifically, it is a linear hydrocarbon having a branched chain content of 10% by weight or less and a weight average molecular weight of 300 to 10000, preferably a branched chain content of 0.001 to 5% by weight and a weight average molecular weight of 600 to 1000. The coated granular fertilizer contains 0.1 to 70% by weight of an inorganic filler and / or 0.01 to 20% by weight of a surfactant in the film. Among them, it is preferable to coat this fertilizer with an outer layer film containing polyisoprene as a main component and an inorganic filler in an amount of 30 to 99.9% by weight, preferably 50 to 95% by weight, since the impact resistance is improved.
[0045]
As a fertilizer component particle used as the core in the coated granular fertilizer of the present invention, any conventionally known fertilizer can be used. For example, in addition to simple fertilizers such as urea, ammonium sulfate, ammonium sulfate, ammonium nitrate, lime nitrogen, phosphoric acid, lime superphosphate, heavy peridotite, heavy calcined phosphorus, salted salt, sulfurized salt, N, P 2 O Five , K 2 Examples thereof include a chemical fertilizer composed of two or more components such as O, and a bulk blend fertilizer obtained by combining two or more of these. Among these, from the viewpoint of elution control, urea is particularly preferable since it has a high fertilizer component and the most remarkable effect of fertilization.
In addition, it is preferable to use a compound-type slow-acting fertilizer such as isobutylidene diurea, which has elution controllability, in the fertilizer itself, because more various elution controllability can be obtained. The particle diameter of the fertilizer component particles is arbitrary, but is usually 0.5 to 15 mm, preferably 1 to 5 mm. The shape of the fertilizer component particles is arbitrary, but the higher the sphericity, the higher the coating uniformity, which is preferable.
[0046]
The coated granular fertilizer manufacturing method and apparatus of the present invention can employ any conventionally known coated fertilizer manufacturing technique. For example, there are methods using various types of coating devices such as a rotating drum type, a rotating pan type, a rotary dropping type, and a flow type that stirs a granular material with an air current, which stirs the granular material accompanying the movement of the apparatus itself. It is done. Among them, a method of using a spouted bed or a fluidized bed in which the granular fertilizer in the coating is mainly stirred in an air flow and has a small impact on the fertilizer particles is preferable. The coating material is generally applied to the surface of the granular fertilizer by spraying the coating material or a coating solution thereof, and a one-fluid or two-fluid spray nozzle is used for spraying. Among these, a two-fluid spray nozzle is preferable because it has a fine spray particle size and can form a film more uniformly. Moreover, in order to make coating | coated uniformity higher, the apparatus which can change a spray position suitably is preferable.
[0047]
As a coating method of the film, a method using a solvent (hereinafter sometimes referred to as “solvent method”) and a method not using a solvent (hereinafter sometimes referred to as “solvent-free method”) can be applied. The solvent method is preferably a method in which the coating material used is dissolved or dispersed in a solvent and sprayed on the fertilizer surface, and then the solvent is instantly dried. Any solvent can be used in the solvent method as long as it dissolves or disperses the coating material. Specifically, chlorinated hydrocarbon solvents typified by chloroform, dichloromethane, trichloroethylene, tetrachloroethylene and the like, and hydrocarbon solvents typified by hexane, octane, toluene, xylene, benzene, ethylcyclohexane and the like are preferable. When using biodegradable resins and water-soluble resins, use water, ethyl alcohol, isopropyl alcohol, ethylene glycol, acetone, methyl isobutyl ketone, acetonitrile, dioxane, dimethylformamide, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, etc. A representative polar solvent may be used.
[0048]
On the other hand, the solvent-free method is a method in which a coating material melt or dispersion is sprayed onto the fertilizer surface for coating, and after coating, the surface is heated and melted to increase the coating uniformity. From the viewpoint of reducing the environmental load.
[0049]
The removal of these solvents and the drying of the coating material are carried out under hot drying air. As the gas species, inert gases such as nitrogen and carbon dioxide can be used in addition to air. In the coating of the inner layer film, by selecting a suitable range of each production condition, it is possible to provide a coated fertilizer that forms a uniform film and is excellent in elution controllability. Hereinafter, manufacturing conditions in the solvent method will be described.
[0050]
Increasing the weight of the coating material relative to the total weight of the solution or dispersion (hereinafter sometimes referred to as “solids concentration”) reduces the amount of solvent used and shortens the coating time. Is also preferable. However, when the solution viscosity is high and the coating material becomes clogged at the spray nozzle part during film formation, which makes film formation difficult, the viscosity is such that an appropriate spray state can be obtained according to the spray nozzle used and the spray pressure. Is adjusted as appropriate. From these viewpoints, the solid concentration is usually 0.1 to 30% by weight, preferably 0.5 to 25% by weight, and more preferably 1 to 20% by weight.
[0051]
The spray rate of the dissolved or dispersed liquid to the fertilizer particles is appropriately selected depending on the coating uniformity, productivity, and solvent type. In general, when the spray rate is increased, the drying of the solvent becomes insufficient, the fertilizer grains are easily fused, film formation becomes difficult, and the spraying time is shortened, resulting in a decrease in film uniformity. On the other hand, since the mist diameter of a spray liquid will become small if it makes small, a coating | coated material dries before spreading on a fertilizer particle | grain, and the spreading property on a fertilizer surface deteriorates, As a result, the uniformity of a film | membrane will fall. Furthermore, the coating efficiency is lowered, which is not preferable from the viewpoint of productivity. From these viewpoints, the spray rate of dissolution or dispersion per minute (when the solid concentration is 5% by weight) with respect to 1 kg of granular fertilizer is usually 25 to 300 g / min · kg, preferably 80 to 250 g / kg. The range is minutes / kg.
[0052]
Furthermore, the surface temperature of fertilizer particles at the time of coating (hereinafter referred to as “product temperature”) and the amount of hot drying air are not particularly limited. The fertilizer particles may be mixed uniformly without fusing, maintaining a stable rolling or jetting state, and removing the solvent and drying the coating material may be within a range. However, the product temperature is easily affected. In general, when the temperature is too high, the film material softens or melts during film formation, and as a result, the fertilizer grains are fused together to deteriorate the film formability. On the other hand, if it is too low, drying is insufficient and film formation is poor. From these viewpoints, for example, the product temperature in the case of using tetrachloroethylene is usually 40 to 130 ° C, preferably 50 to 110 ° C, more preferably 60 to 90 ° C.
[0053]
The aforementioned inorganic filler and surfactant are used by dissolving or dispersing the inorganic filler and / or surfactant in the coating solution containing linear hydrocarbons in the coating method of the coated granular fertilizer of the present invention. The method to do is common. However, it may be spread or adhered to the fertilizer grains as it is with the dry air. The dispersion state in the film is appropriately selected according to the purpose, but it is usually preferable to disperse the film uniformly with an emphasis on the uniformity of the film. For example, the inorganic filler may have a concentration gradient such as being dispersed in the outer shell of the coating in order to control the strength of the coating and to suppress the floating of coated fertilizer grains in the surfactant.
[0054]
In the production of the outer layer film, it is preferable to set conditions that allow the inner layer film to be coated in as short a time as possible so that the inner layer film is not peeled off or lost due to an impact such as jet, flow, or stirring in the apparatus. This is also preferable from the viewpoint of productivity. Specifically, it is preferable to increase the solid concentration and the spray speed as much as possible within the range where the fertilizer grains do not adhere during film formation, and there are few problems even if the coating uniformity is somewhat impaired.
[0055]
The product temperature is appropriately selected depending on the material to be used. For example, when a biodegradable resin containing polyisoprene as a main component is used, it is usually 40 to 90 ° C, preferably 50 to 80 ° C. Further, the inner layer-coated fertilizer may be once taken out from the apparatus and coated again in the coating apparatus, but it is industrially advantageous to coat the outer layer as it is after coating the inner layer.
[0056]
Moreover, the application of the coated granular fertilizer of the present invention is not particularly limited, and is appropriately selected according to the nutrient requirement characteristics of the crop. For example, a coated nitrogen fertilizer exhibiting a sigmoid-type elution pattern is suitably used in the cultivation of paddy rice that requires additional fertilization of nitrogen during the middle growth stage. Furthermore, the coated fertilizer having an elution control period of 1 year or more is suitably used for a permanent plant having a long growth period such as a tree.
[0057]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
The branched chain content of the hydrocarbon was determined by the urea addition method. The covering rate is measured by weighing 10 g of the coated granular fertilizer, pulverizing with a small pulverizer, dissolving water by adding water, filtering and collecting only the film, drying this film, and weighing it. The coverage was calculated from the following equation.
Coverage (%) = (film weight [g] / (10−film weight) [g]) × 100
In addition, the coating rate of the inner layer coating referred to in the present invention refers to the coating rate with respect to the weight of fertilizer such as urea to be coated, and the coating rate of the outer layer coating refers to the coating rate with respect to the weight of the inner layer coated fertilizer to be coated. Moreover, the coverage of the whole film after coating refers to the coverage with respect to the weight of the fertilizer such as urea used.
[0058]
(1) Manufacture of coated fertilizer
Example 1
30 g of Fischer-Tropsch wax (manufactured by Nippon Seiwa Co., Ltd., FT100. Branched chain content: 0 wt%, weight average molecular weight 674, hereinafter sometimes referred to as “FT wax”) was dissolved in 270 g of tetrachloroethylene, and this solution (solid Using a fluidized bed type coating device to 300 g of urea particles having a particle size of 2.8 to 3.4 mm (or particle size of 2 to 4 mm) and a spray speed of 81.5 g. Spray coating was performed at a product temperature of 70 ° C./min/kg to obtain 325.5 g of a coated granular fertilizer having an average film thickness of 60 μm and a coverage of 8.5% (vs. urea particle weight). The coated granular fertilizer film obtained here is referred to as an inner layer film (1). In the above fluidized bed type coating apparatus, the granular fertilizer filled in the tank is flown by the hot drying air introduced from the lower part of the apparatus and the stirring blade installed at the bottom of the apparatus, and the coating material is dissolved or dispersed therein. After spraying the spray solution, the solvent was removed with hot drying air, and the coating material was dried.
[0059]
(Example 2)
The average film thickness was determined in the same manner as in Example 1 except that 0.6 g of polyoxyethylene nonylphenyl ether (manufactured by Toho Chemical Industry Co., Ltd., nonionic surfactant N204, HLB 8.9) was used together with 30 g of FT wax. 325.5 g of coated granular fertilizer with a film thickness of 60 μm and a coverage of 8.5% was obtained. The coated granular fertilizer film obtained here is referred to as an inner layer film (2).
[0060]
(Example 3)
Following the coated granular fertilizer obtained in Example 2, 1.5 g of polyisoprene rubber (manufactured by Nippon Zeon Co., Ltd., NIPOL IR2200) and talc (manufactured by Matsumura Sangyo Co., Ltd., high filler # 5000PJ, average particle size 1.8 μm) 13 150 g of a solution obtained by mixing 0.5 g with 135 g of tetrachlorethylene (solid concentration 10 wt%, 90 ° C.) is spray-coated at a spray rate of 190 g / min · Kg and a temperature of the coated granular fertilizer 70 ° C. 340.5 g of coated granular fertilizer having a covering ratio of 13.5% (vs. urea particle weight) of the entire coating film was obtained. The outer layer film of the coated granular fertilizer obtained here is designated as outer layer film (3).
[0061]
Example 4
18 g of FT wax and 0.15 g of polyoxyethylene nonylphenyl ether (manufactured by Toho Chemical Industry Co., Ltd., nonionic surfactant N202, HLB 5.7) are dissolved in 271 g of tetrachloroethylene, and then 12 g of talc can be mixed with this solution. Using the obtained solution, the coated granular fertilizer obtained by the same method as in Example 1 (the coated granular fertilizer film obtained here is referred to as inner layer film (4)), followed by 15 g of polyisoprene rubber and white 1250 g of a solution (solid concentration 2.4% by weight, 90 ° C.) obtained by mixing 15 g of carbon (Nippon Silica Kogyo Co., Ltd., nip seal SS-10, average particle size of 2.7 μm) with 1220 g of tetrachloroethylene was obtained as Example 3. By the same method, the coated granular fertilizer 3 having a covering rate of 18.4% (vs. urea particle weight) of the entire coating including the inner layer coating It was obtained 5.2g. The outer layer film of the coated granular fertilizer obtained here is designated as outer layer film (5).
[0062]
(Example 5)
By the same method as in Example 4 except that a solution obtained by mixing 22.5 g of polyisoprene rubber and 22.5 g of white carbon with 1830 g of tetrachloroethylene (solids concentration 2.4 wt%, 90 ° C.) was used. Thus, 369.0 g of coated granular fertilizer having a covering ratio of 23.0% (vs. urea particle weight) of the entire film including the inner layer film was obtained. The outer layer film of the coated granular fertilizer obtained here is designated as outer layer film (6).
[0063]
(Example 6)
After dissolving 18 g of FT wax in 270 g of tetrachloroethylene, using the solution obtained by mixing 12 g of talc with this solution, the coated granular fertilizer obtained by the same method as in Example 1 (the coated granular fertilizer obtained here) The inner layer film (7) is followed by 45 g of sulfur fine powder (Hosoi Chemical Industries, purity 99.9% or more, 200 mesh pass) mixed with 255 g of tetrachloroethylene (solid matter) Using the same method as in Example 3 using 300 g of a concentration of 15 wt% and 90 ° C., 364.2 g of coated granular fertilizer having a coating rate of 21.4% (vs. urea particle weight) of the entire coating including the inner layer coating was obtained. It was. The outer layer film of the coated granular fertilizer obtained here is designated as outer layer film (8).
[0064]
(Comparative Example 1)
Instead of 30 g of FT wax used in Example 1, polypropylene wax having a branched chain content of 25.9% by weight and a weight average molecular weight of 4000 (manufactured by Sanyo Kasei Kogyo Co., Ltd., Viscol 550P. Hereinafter referred to as “PP wax”) ) A coated granular fertilizer of 325.5 g having an average film thickness of 60 μm and a coverage of 8.5% was obtained in the same manner as in Example 1 except that 30 g was used. The coated granular fertilizer film obtained here is referred to as an inner layer film (9).
[0065]
For each coated fertilizer obtained in Examples 1 to 6 and Comparative Example 1, the production recipes are summarized in Table 1.
[0066]
[Table 1]
(2) Measurement of the number of defective particles in coated fertilizer
10 g of coated fertilizer (total number of particles of about 470) is weighed in a test tube, 10 cc of ink is added, and the mixture is left in constant temperature water at 40 ° C. for 1 hour, and then the coated fertilizer is collected by filtration. When the ink adhering to the coated fertilizer is washed with water, the color of the ink remains in the defective portion of the film, and thus the particles having the defective film are distinguished. The defective particles are classified into the following three types and counted to make the total number of defective particles.
The greater the number of defective particles, the greater the permeation rate of water vapor through the defective portion, and the greater the amount of fertilizer components eluted. Therefore, the smaller the number of defective particles, the higher the initial elution prevention property, which is preferable for adjusting various elution patterns.
(I) Most of the coated granular fertilizer particles are not colored, and have particles that are partially colored (small defects)
(Ii) Particles in which almost all of the fertilizer particles are colored due to the large defect (medium defect)
(Iii) Shell particles (large defects) from which urea has already been dissolved to form a film only
[0068]
About the coated fertilizer manufactured in Examples 1-6 and Comparative Example 1, the number of defective particles was measured based on the above. The results are shown in Table 2.
[0069]
[Table 2]
(3) Evaluation of dissolution characteristics of coated fertilizer
Elution measurement method in water
The coated fertilizers produced in Examples 1 to 6 and Comparative Example 1 were poured into 40 ° C. constant temperature water at a rate of 7 g / 200 cc, and urea nitrogen in the water was quantified over time. In the evaluation at 40 ° C., it is possible to predict the elution characteristic at 25 ° C. from the result of the elution characteristic obtained by the measurement, which is effective as an accelerated evaluation method at 25 ° C. The results are shown in FIG. 1 (N elution rate% of the coated fertilizer).
[0071]
From the results shown in FIG. 1, as in Examples 1 and 2, by using a linear hydrocarbon having a branched chain content of a specific amount or less as a coating material, a sigmoid fertilizer can be formed only by a single layer coating. It turns out that a component elution pattern is shown. Further, as in Examples 3 to 5, the coated granular fertilizer coated with linear hydrocarbons having a branched chain content of a specific amount or less, and an outer layer film further comprising polyisoprene rubber and an inorganic filler, or It can be seen that the coated granular fertilizer coated with an outer layer film containing sulfur as a main component as in Example 6 is a slow-acting fertilizer excellent in the protective effect of the coated fertilizer film without impairing the sigmoid type elution pattern.
That is, they can control the elution of the fertilizer components over a long period of time, and adapt the elution of the fertilizer components to the nutrient requirements of the crop in a single fertilization operation without performing additional fertilization several times as in the past. Coated granular fertilizer.
On the other hand, the coated granular fertilizer (Comparative Example 1) coated with a linear hydrocarbon having a branched chain content of more than 10% by weight has unstable elution controllability in a fertilization environment. “Unstable elution controllability” means that the degradability of the film is influenced not only by moisture and temperature conditions but also by microbial activity, pH, physical impact, and the like. For this reason, it is difficult to predict changes after fertilization, and therefore it is difficult to predict elution acceleration associated with decomposition, so that elution in soil cannot be controlled.
[0072]
The coated fertilizers of Examples 1 to 3 and Comparative Example 1 were evaluated for impact resistance.
(4) Impact resistance evaluation of coated fertilizer
Put 40g of coated fertilizer (total number of particles about 1880) in a stainless steel cylindrical container (φ69 × H69mm), and use a reciprocating shaker (TAIYO recipro shaker SR-IIw) (vertical direction: 40mm amplitude) , Shaking speed was 5 reciprocations / second) for 30 seconds. For the coated fertilizer after shaking, the number of defective particles and the elution measurement in water were measured. The results are shown in Table 3 and FIG. 2 (N elution rate% before and after the impact resistance test).
[0073]
[Table 3]
From the results in Table 3, it was shown that a coated granular fertilizer with excellent coating strength was obtained by using a linear hydrocarbon having a branched chain content of a specific amount or less as a coating material. Further, it was shown that a coated granular fertilizer having more excellent impact resistance can be obtained by further protecting with an outer layer film containing polyisoprene rubber. Furthermore, the results of FIG. 2 indicate that the dissolution rate after impact is almost the same as that before treatment, and that this is a slow-acting fertilizer excellent in the protective effect of the coated fertilizer film without impairing the sigmoid-type dissolution pattern. It was.
On the other hand, the coated granular fertilizer (Comparative Example 1) coated with a linear hydrocarbon having a branched chain content of more than 10% by weight not only has unstable elution controllability in a fertilization environment. The film is inferior in impact strength and cannot be practically used as a slow-release fertilizer.
From the above results, the coated granular fertilizer according to the present invention can be predicted for elution control under the fertilization environment such as in water and soil, that is, the elution can be predicted only by the moisture and temperature conditions in the fertilization environment. It can be seen that it is possible to manage fertilization according to the conditions.
[0075]
(5) Fertilizer application test evaluation of coated fertilizer
About the coated fertilizer of Examples 4-6, it mix | blends with a chemical fertilizer so that NPK component may be 16-16-16 (contains about 19.3% coated fertilizer as a basic unit), and fertilizes according to the following conditions Machine suitability was evaluated.
[0076]
[Table 4]
From the results of Table 4, the coated granular fertilizer coated with a coating containing a linear hydrocarbon having a branched chain content of a specific amount or less, an outer coating containing polyisoprene rubber and an inorganic filler, and sulfur as a main component The coated granular fertilizer coated with the outer layer film is shown to have a small degree of film damage by the fertilizer treatment. In addition, from the results of FIG. 3, the dissolution rate after the fertilizer treatment is almost the same as that before the treatment, and it is a slow-release fertilizer excellent in the protective effect of the coated fertilizer film without impairing the sigmoid-type dissolution pattern. It has been shown. In addition, the N elution rate at the initial stage (3 days after the start of elution) is slightly higher due to the fertilizer treatment, but the N elution rate is 10% or less in all cases. Is small and practical as a slow release fertilizer.
[0078]
(6) Evaluation of biodegradability of coating materials
The FT wax and polyisoprene rubber used in the present invention were subjected to biodegradability tests on the raw materials. The evaluation method and the result of the decomposition behavior are shown in FIG. 4 (result of biodegradability of the material).
From the results shown in FIG. 4, FT wax is gradually biodegraded after the start of the test, suggesting that it is finally decomposed into carbon dioxide and water. In addition, although the biodegradation rate of the polyisoprene rubber is slow, it is clear that the raw material itself has biodegradability since the biodegradation rate is gradually improving after 150 days from the start of the test.
That is, with the coated granular fertilizer of the present invention, the elution of fertilizer components is controlled in a fertilized environment, and the coating as the coating material undergoes biodegradation after the end of the elution, thereby reducing the load on the surrounding environment.
[0080]
From the above results, the coated granular fertilizer of the present invention has a film with excellent mechanical strength, and the elution controllability in a fertilized environment over a long period of time without changing the elution controllability due to alteration or breakage of the film. It is clear that the coating of the coating material is finally decomposed in and out of the soil, thereby reducing the burden on the environment. On the other hand, the coated granular fertilizer coated with chain hydrocarbons having a branched chain content of more than 10% by weight has not only unstable elution controllability in the fertilization environment, but also the impact strength of the coating. It is also inferior and cannot be practically used as a slow-release fertilizer.
[0081]
【The invention's effect】
With the coated granular fertilizer of the present invention, the elution of fertilizer components is controlled in a fertilized environment, and the coated film is biodegraded, so that it is possible to provide a coated granular fertilizer that reduces the load on the surrounding environment. .
The coated granular fertilizer of the present invention is excellent in the mechanical strength of the film, and part of the film is not damaged such as peeling or chipping when mixed with other fertilizers, during transportation, and during mechanical fertilization. Does not affect controllability.
[Brief description of the drawings]
[Fig.1] N elution rate% of coated fertilizer (in 40 ° C water)
[Figure 2] N elution rate% before and after impact resistance test (in 40 ° C water)
[Figure 3] N elution rate before and after fertilizer application (% in 40 ° C water)
[Figure 4] Results of biodegradability of materials
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001391005A JP4050052B2 (en) | 2001-01-29 | 2001-12-25 | Coated granular fertilizer |
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| JP2001020326 | 2001-01-29 | ||
| JP2001-20326 | 2001-01-29 | ||
| JP2001391005A JP4050052B2 (en) | 2001-01-29 | 2001-12-25 | Coated granular fertilizer |
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| JP2002293684A JP2002293684A (en) | 2002-10-09 |
| JP4050052B2 true JP4050052B2 (en) | 2008-02-20 |
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090101542A1 (en) * | 2005-05-20 | 2009-04-23 | Volker Klaus Null | Compositions comprising a fischer-tropsch derived white oil as carrier oil |
| JP4245584B2 (en) * | 2005-05-23 | 2009-03-25 | 多木化学株式会社 | Coated granular fertilizer |
| JP2012522722A (en) * | 2009-04-06 | 2012-09-27 | ドンブ ハンノン カンパニー リミテッド | Leaching controlled, naturally degradable coated fertilizer |
| JP5604819B2 (en) * | 2009-07-09 | 2014-10-15 | 住友化学株式会社 | Method for producing resin-coated granular fertilizer |
| CN104109598A (en) * | 2014-06-05 | 2014-10-22 | 铜陵市银树生态养殖有限责任公司 | Banana peel-containing composite coated fertilizer and preparation method thereof |
| DE102014108703A1 (en) * | 2014-06-20 | 2015-12-24 | Thyssenkrupp Ag | Urea composition and process for its preparation |
| JP6897154B2 (en) * | 2017-02-27 | 2021-06-30 | 井関農機株式会社 | Raising seedling method |
| KR102111607B1 (en) | 2018-03-28 | 2020-05-15 | 주식회사 엘지화학 | Controlled release fertilizers |
| CN115417711B (en) * | 2022-05-11 | 2024-01-26 | 龙蟒大地农业有限公司 | Organic-inorganic compound fertilizer with slow-release mineral elements wrapping active microorganisms and preparation method thereof |
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