聚合物在缓/控释肥料中的应用研究

用一种聚合物为主要包膜原料给肥料包膜,并将包膜肥料与未包膜肥料进行对比试验。结果表明,包膜肥料达到了作物所要求的缓／控释效果,说明这种聚合物在包膜肥料中的应用是可行的。     

聚合物包膜肥料养分控释研究进展

聚合物包膜肥料的养分控释机理研究对包膜肥料的开发与应用起着重要作用,国内外研究学者在Fick扩散定理的基础上建立了包膜肥料控释理论和多种数学模型,探索了影响养分释放的因素。聚合物包膜肥料按扩散机制释放养分。养分释放速度的控制因素主要有两种不同看法,一种是养分扩散速率控制,另一种是水蒸气渗透速率控制。肥料包膜层厚度、包膜材料吸水性、温度、水蒸汽压、土壤含水量等均影响养分释放。     

聚乙烯溶液构成对控释肥料释放性能的影响

以聚乙烯为主要膜材料,采用喷雾相转化法和流化床设备制备控释肥料。系统研究聚合物溶液质量分数、低密聚乙烯(LDPE)与线性低密聚乙烯(LLDPE)配比、溶剂对制备包膜尿素释放期的影响。结果表明,包膜液质量分数从5%增加到8%,包膜尿素释放期由20 d增加到173 d,说明包膜液质量分数增加对释放期延长有显著影响;LDPE/LLDPE质量比从1增加到3,控释尿素释放期从98 d减少到32 d,说明聚乙烯分子的线性结构对释放期影响显著;质量分数控制在7%时,使用四氯乙烯、正辛烷、十氢化萘和环己烷4种溶剂处理的包膜肥养分释放期在87—108 d之间,4种不同溶剂对释放性能没有显著影响。为了制备释放期适宜的包膜肥料,包膜液质量分数宜控制为7%,不同线性聚乙烯混用能改变包膜控释肥料的控释性能,上述4种溶剂均可以用来配制包膜液。     

金正大控释肥获国家专利

山东金正大生态工程股份有限公司和山东农业大学合作开发的包膜控释肥5项核心技术获得了国家发明和实用新型专利。它们分别是:“以回收热塑性树脂为可降解膜的包膜控释肥料的生产方法”、“以喷涂尿素为底涂层的改性环氧树脂包膜控释肥料的制备方法”、“以硫为底涂层的高分子聚合物包膜控释肥料的制造方法”、“管盘式多层尿素硫磺快速熔融器”、“高压气流快速加热恒温器”等,形成了具有我国自主知识产权的包膜控释肥生产技术体系。金正大控释肥获国家专利     

包膜型缓/控释肥料研究现状及其在功能农业中的应用展望

当前,我国农业发展进入了继高产农业、绿色农业之后的第三个发展阶段——功能农业阶段,即通过科学技术手段生产出具有健康改善功能的农产品。施用缓/控释功能肥料,实现对作物的"精准给肥"是功能农业的关键科学问题之一。缓/控释肥料凭借其可显著提高肥料利用率、减轻因养分流失造成的环境污染、提高作物产量及品质等优点受到国内外研究人员的广泛关注。其中包膜型缓/控释肥料通过包膜材料的设计,可更好地实现对养分的控释。综述了国内外包膜型缓/控释肥料的研究现状,分析了包膜型缓/控释肥料在实际应用中存在的问题,并对包膜型缓/控释肥料在功能农业中的应用进行了展望。     

用聚合物乳液为包膜剂制备缓释尿素

介绍了采用聚合物乳液作为包膜剂制备包膜缓释尿素,具有工艺简洁和包膜过程绿色的特点,能够根本解决现有包膜过程中毒性有机溶剂的污染和回收问题。实验考察了聚合物乳液包膜剂平板成膜时的渗透系数,表明聚合物乳液是良好的缓释包膜剂。实验采用转鼓流化床工艺制备包膜尿素,测定了包膜尿素在水中的释放特性。通过扫描电镜检测包膜尿素和膜层的形貌特征。结果表明,采用聚合物乳液直接对尿素颗粒包膜时,在颗粒表面形成的高湿性环境容易导致尿素表面溶解,水分蒸发后形成针状尿素结晶,复合在聚合物膜层中,包膜尿素进入水中时,针状尿素快速溶出,造成膜层多孔性渗漏,降低了包膜尿素的缓释性能。在聚合物乳液包膜前,先在尿素颗粒表面包覆一层硫磺阻隔层或石蜡疏水层,能有效抑制尿素在包膜时的溶出过程。     

控释肥料包膜材料的研究进展

从无机材料和有机材料两个方面论述了控释肥料包膜材料的分类,介绍了国内外控释肥料包膜材料的研究进展,分析了目前各类控释肥料包膜材料的优点和不足,提出了包膜材料研究的重点问题和应用前景。     

几种缓控释肥料的养分释放特性研究

采用水浸提法对国内外6种缓控释肥料的养分释放特性进行了系统的比较研究,并探讨了土壤含水量对在水浸提试验中养分释放速率差异较大的两种肥料养分释放特性的影响。研究结果表明:通过一系列的数学变换,可以从理论上对缓控释机理不同的肥料进行新的分类;土壤含水量不但与缓控释肥料的养分释放率显著相关,还影响到普通缓溶肥料养分释放曲线拟合方程的相关系数和高分子聚合物包膜肥料的滞后期。     

包膜型缓/控释肥的研究现状及应用前景

阐述了包膜型缓/控释肥料的包膜类型、养分释放机理及其影响因素;论述了国内外包膜型缓/控释肥料的研究现状及其发展趋势;综合分析了我国包膜型缓控释肥料在生产和应用方面存在的问题及其解决办法.     

包膜型缓释/控释肥料的研究现状和发展前景

对包膜型缓释／控释肥料的一些概念、包膜材料、制备工艺及性能的影响因素等方面进行了论述，并简单分析了缓释／控释肥料发展进程和发展前景。     

Preparation and characterization of triple polymer‐coated controlled‐release urea with water‐retention property and enhanced durability

Triple polymer coated with controlled‐release water retention fertilizer (TCWF) and enhanced mechanical property was developed by coating polyethylene (first layer), poly (acrylic acid‐co‐acrylamide) superabsorbent (second layer), and poly (butyl methacrylate) (third layer) consecutively on the granule core urea in the fluidized‐bed coater. The inner layer possessed controlled‐release property, the middle layer had water absorbent characteristic, and the thin outer layer aimed to protect the fragile layer of the superabsorbent. The relationship between the thickness of coating layer and the nutrient releasing properties was established. The effects of polymerization parameters on the water absorbency of the superabsorbent were studied and optimized as well. The nutrients release behaviors of this triple‐coated urea in both water and soil were investigated and compared. The results showed that TCWF not only performed as a good controlled‐release fertilizer but also had excellent water retention capacity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Powder coating efficiency of small particles and their agglomeration in circulating fluidized bed

The coating efficiency of fluidizing small particles and their agglomeration were investigated to evaluate the possibility of powder coating by the use of a circulating fluidized bed. Glass beads, whose mean diameter was 43 Μm, and silica powder of 1 Μm were used as a core and a coating material. Polyvinyl alcohol was used as a binder and its solution was supplied together with silica powder from a spray nozzle equipped in the circulating fluidized bed. Glass beads of 43 Μm, which had been impossible to coat in a conventional fluidized bed coater, were successfully coated with silica powder in a circulating fluidized bed, and agglomeration among core particles was prevented. From this result, it was confirmed that a circulating fluidized bed performs excellently as a coater, especially for fine core particles, so a circulating fluidized bed coater has bright prospects for particle coating.     

Fine particle coating by a novel rotating fluidized bed coater

Fine particle coating has been conducted by using a novel rotating fluidized bed coater. The coater consists of a plenum chamber and a horizontal porous cylindrical air distributor, which rotates around its axis of symmetry inside the plenum chamber. Cohesive fine cornstarch (mass median diameter of 15 μm), a Geldart Group C powder, was used as core particle and an aqueous solution of hydroxypropylcellulose (HPC-L) was sprayed onto the cornstarch to generate a film coating. Fine particle coating was conducted under various coating levels (wt.% HPC-L) and the particle size distribution of the coated particles, release rate of an aqueous pigment (food blue No. 1), which had been pre-coated onto the initial cornstarch, and the degree of agglomeration were investigated. The relationship between the coating level and the physical properties of the coated particles was analyzed. The results indicated that coating of cohesive fine cornstarch with HPC-L could be achieved, producing a favorable prolonged release property with almost maintaining the individual single particle.     

可生物降解PBAT包膜尿素缓释肥料的制备与性能研究

以可生物降解PBAT为包膜材料,通过循环流化床工艺制备一系列PBAT包膜尿素缓释肥料,并对制备工艺进行了优化;通过扫描电镜观察包膜肥料表面形态特征,分析缺陷形成原因;通过水中静置法测试PBAT包膜尿素缓释肥料的缓释性能,测定缓释曲线,样品的初期释放率为20%~50%,第28天的累积释放率为70%~90%。     

Urea particle coating for controlled release by using DCPD modified sulfur

The shell of sulfur coated urea was easily cracked due to sulfur being friable. Sulfur was modified with dicyclopentadiene (DCPD) to increase its strength and abrasion resistance. SEM images showed that the micro-structure of modified sulfur was denser and more uniform than pure sulfur. The strength of modified sulfur increased with the DCPD/S ratio. Experiments of urea particle coating with sulfur and modified sulfur were carried out in a fluidized bed coater. The shell of coated urea particles with modified sulfur was more compact than that with pure sulfur. The modification retarded the sulfur phase transformation from monoclinic to orthorhombic, avoiding the crack formation in the coating shell of sulfur. The modified sulfur coated urea particles can be produced with thinner shell and higher strength, and had better controlled release properties.     

可生物降解PBS包膜尿素缓释肥料的制备与性能研究

研究可生物降解PBS包膜尿素缓释肥料的制备与性能。以可生物降解PBS为包膜材料,通过循环流化床工艺制备PBS包膜尿素缓释肥料,经过对制备工艺进行优化,确定包膜剂PBS质量分数为5%、二次流化时间为20 min、包膜率为10%的PBS包膜尿素具有良好的缓释效果,其初期释放率为10%,第28天时累积释放率为72%,基本符合缓释肥料标准。     

缓／控释BB肥是我国缓／控释肥料的发展方向

分析了树脂和硫磺包裹尿素缓释肥料发展缓慢的原因和弊端,提出以水溶性聚合物作为尿素和复混肥料的包膜、胶结和内质缓释剂,具有降解快、对作物无害、改善土壤结构、成本低等特点,将促进缓释肥料的发展。采用生产不同时间段释放养分的缓释肥,按作物不同生育期对养分的需求比例掺混在一起,生产作物专用的缓／控释BB肥料简单易行,应是我国缓／控释肥料的发展方向。     

Optimization of a Fe-Al-Ce nano-adsorbent granulation process that used spray coating in a fluidized bed for fluoride removal from drinking water

A coating granulation technology comprising the spraying of a Fe-Al-Ce nano-adsorbent suspension onto glass beads in a fluidized bed was developed. An acrylic-styrene copolymer latex was used as a binder. The granulated adsorbent was used in a packed bed for fluoride removal from drinking water. The effects of coating temperature, latex/Fe-Al-Ce ratio, and coating amount on granule compressive strength and adsorption capacity were investigated. With increased coating temperature, cross linking in the polymer in the coated layer increased, which resulted in increased granule strength but decreased adsorption capacity. With increased latex/Fe-Al-Ce ratio, more active sites were covered by the polymer, which also resulted in increased granule strength but decreased adsorption capacity. The optimal parameters for making high performance adsorbent granules were for the granules to be coated at 65 °C using a latex/Fe-Al-Ce ratio of 0.5:1 and a coating amount of 27.8%. These granules had a fluoride adsorption capacity of 2.77 mg/g (coated granules) for water with an initial fluoride concentration of 0.001 M that was treated at pH 7.     

聚氨酯包膜控释尿素制备工艺与养分释放特性研究

4,4'-二苯基甲烷二异氰酸酯(MDI)与植物油多元醇均匀喷涂在流化状态的尿素颗粒表面并发生化学反应,形成聚氨酯膜层。以侧喷流化床包膜工艺为基础,通过研究包膜量、反应温度、反应物比例等不同工艺条件下包膜尿素的养分释放性能,获得的生产聚氨酯包膜尿素的最佳工艺条件为反应温度75℃、MDI与植物油质量比1.0:1.0、反应时间20 min、催化剂用量0.40%(质量分数)、包膜比率为4.0%(质量分数),此包膜控释尿素的养分释放周期可达70 d。     

Effect of solid circulation rate on coating efficiency and agglomeration in circulating fluidized bed type coater

Circulating fluidized bed was proposed to be used as a coater, and coating experiments of glass beads with silica powder were performed in a circulating fluidized bed. Glass beads and silica powder were chosen as model particles, because their shape was almost spherical. The respective effects of gas flow rates supplied from a distributor and from an air nozzle for solid circulation, feed rate of powder suspension and particle content in the bed on coating efficiency and agglomeration are mainly discussed. Coating efficiency in circulating fluidized bed coater was correlated well with solid circulation time rather than with gas flow rates or solid circulation rate, while the agglomeration among core particles was mainly governed by solid circulation rate.