国外生产缓释肥料一般分为两大类:第一类是尿素与醛类等物质反应生成的缓释肥料;第二类是涂层肥料,采用硫磺、聚合物(聚氯乙烯、聚乙烯、聚丙烯、酚醛树脂、聚氨酯等)以及油类、石蜡等。国外生产这种肥料所使用的涂层材料一般占缓释肥料产品总重的10%～20%;每吨产品氮含量为36%～37%之间,价格高,如美国涂硫尿素每吨氮的成本约提高31%,故只能用于草坪、花卉等高价作物,不能用于大田生产。本技术克服了上述问题,生产出低成本能用于大田的涂层肥料。其方案是研制出含有动物胶的低成本涂层材料,采用机械喷射涂层技术和手工涂层技术,生产出涂层肥料,涂层材料用量只占涂层肥料产品总重的0.3%～0.8%;每吨产品氮含量>46%,与尿素的氮含量相近,涂层尿素每吨氮的成本仅提高5.68%,只有涂硫尿素的五分之一,显示出明显的优势。涂层材料配方(份):动物胶0.5～2.5(为动物皮胶、骨胶、混合胶等);增溶剂10～25(为无机盐类,最好为无机氨类,如尿素、硫酸铵、硝酸铵等);有机酸0.5～1.5;无机酸10～30;微量元素无机盐30～50(为铁、锌、锰、钼、铜、镁、钒等元素的无机盐);非金属元素40～60(为硼、硫、氢、氧等元素化合物);表面活性剂0.5～1.5(为阳离子表面活性剂)。生产工艺:含有动物胶、增溶剂、有机酸、无机酸、微量元素无机盐、非金属元素和表面活性剂等原料,按上述比例投料,在不同的时间加入铁、锌、锰、钼、铜、镁、钒 Slow release fertilizer abroad is generally divided into two categories: the first category is urea and aldehydes and other substances generated slow-release fertilizer; the second category is coated fertilizer, the use of sulfur, polymers (polyvinyl chloride, polyethylene, Polypropylene, phenolic resin, polyurethane, etc.) and oils, waxes and the like. Foreign production of such fertilizers used coating materials generally account for 10% to 20% of the total weight of slow release fertilizer products; per ton of product nitrogen content of 36% to 37%, the price is high, such as the United States painted sulfur urea per ton Nitrogen costs increased by about 31%, it can only be used for lawn, flowers and other high-priced crops, can not be used for field production. The technology overcomes the above problems and produces coated fertilizers that can be used in fields at a low cost. The solution is to develop a low-cost coating material containing animal glue, using mechanical spray coating technology and hand-coating technology to produce coated fertilizers, the amount of coating material only accounts for 0.3% ~ 0.8 of the total weight of coated fertilizer products %; Nitrogen content per ton of product> 46%, similar to the nitrogen content of urea. The cost per ton of nitrogen of coated urea is only increased by 5.68%. Only one-fifth of sulfur-coated urea shows obvious advantages. Coating material formula (parts): animal glue 0.5 to 2.5 (for animal skin glue, bone glue, mixed glue, etc.); Solubilizer 10 to 25 (inorganic salts, preferably inorganic ammonia such as urea, ammonium sulfate, Ammonium nitrate and the like), organic acids 0.5 to 1.5, inorganic acids 10 to 30, trace inorganic salts 30 to 50 (inorganic salts of iron, zinc, manganese, molybdenum, copper, magnesium and vanadium) ~ 60 (boron, sulfur, hydrogen, oxygen and other compounds); Surfactants 0.5 to 1.5 (cationic surfactant). Production process: containing animal glue, solubilizer, organic acid, inorganic acid, trace inorganic salts, non-metallic elements and surfactants and other raw materials, according to the above ratio feed, at different times by adding iron, zinc, manganese, molybdenum, copper , Magnesium, vanadium