由硅酸钠制备大粒径硅溶胶颗粒研究

发布时间：2018-03-28 12:05

本文选题：大粒径硅溶胶　切入点：硅酸钠　出处：《山东大学》2017年硕士论文

【摘要】：硅溶胶[1]是无定形二氧化硅(mSiO2·nH2O)颗粒在水中均匀分散形成的一种胶态分散体。由于硅溶胶中二氧化硅颗粒表面含大量羟基,具有较强的反应活性,经过表面改性又能与有机聚合物混溶,因此被广泛用于涂料、精密铸造、耐火材料、造纸、石油化工、电子等很多行业。工业上合成的硅溶胶中纳米二氧化硅颗粒的粒径一般为10～40nm,难以满足某些特殊行业要求。如何合成大粒径(80 nm)硅溶胶,成为目前硅溶胶化学的研究热点之一。本文以硅酸钠水溶液(又称泡花碱溶液或水玻璃)为原料,探索研究了大粒径硅溶胶的制备方法,考察了聚乙二醇(PEG)对粒子形貌的影响;采用"硅酸钠直接缩聚法"和"硅酸钠直接缩聚-正硅酸四乙酯水解聚合联合法"实现了硅溶胶的粒径可控制备,并获得了均分散大粒径硅溶胶,为硅溶胶可控制备技术的研发和应用提供了参考信息。本文主要研究内容和结论如下:(1)用离子交换法以硅酸钠为原料制备出"活性硅酸",考察了影响活性硅酸缩聚快慢的条件。结果表明,在酸性条件(pH 1～3)下缩聚产物极易胶凝,添加PEG(分子量M_w=200)对胶凝无明显抑制效果;在碱性条件(pH～10)下缩聚可得分散性良好的硅溶胶(研究条件下粒径～70 nm),添加PEG可减小硅溶胶颗粒粒径(研究条件下粒径～40 nm)。(2)以氨水(NH3 ·H20)为催化剂,在乙醇(EtOH)溶剂中将正硅酸四乙酯(TEOS)水解-缩合,制备出了均一性高的硅溶胶(mSiO2·nH2O纳米颗粒)。本步骤中采用多步水解-聚合法,可调控颗粒尺寸。研究条件下制备的硅溶胶粒径为30～50 nm。(3)参照TEOS水解-缩合法,探索研究了"硅酸钠直接缩聚法"。以硅酸钠溶液为原料,在乙醇/氨水介质中直接缩聚,结果表明可制备出稳定的硅溶胶产品,呈规则球形颗粒;随硅酸钠浓度增大,所制备的硅溶胶颗粒粒径增大,即可通过改变硅酸钠溶液浓度,可调控粒径大小。该法可获得大粒径(100nm)球形颗粒,但均匀度较差,缩聚条件有待优化。另外,缩聚机理还有待研究。(4)将"硅酸钠直接缩聚法"与"正硅酸四乙酯(TEOS)水解-聚合法"相结合,探索研究了"硅酸钠直接缩聚-TEOS水解聚合联合法"制备均分散大粒径硅溶胶的可行性。结果表明,该方法可制备出尺寸均匀的大粒径(～300nm)产品,为硅溶胶的可控制备提供了新途径。该方法与硅酸钠直接缩聚法相比,可明显改善颗粒均匀度,与TEOS水解-聚合法相比,可明显降低TEOS用量(成本降低),具有实用价值。所制备硅溶胶颗粒的表面性质和应用性能还有待考察。(5)考察了 PEG对硅酸钠直接缩聚法制备硅溶胶的影响。结果表明,添加PEG可减小颗粒粒径,并具有抑制颗粒聚集的趋势。PEG分子量(M_w 4000～20000)越大,在相同条件下制备的硅溶胶颗粒越小。
[Abstract]:Silica sol [1] is a colloidal dispersion formed by the homogeneous dispersion of amorphous silica / mSiO2 / NH _ 2O particles in water. Due to the large amount of hydroxyl groups on the surface of silica particles in silica sol, the silica particles have strong reactivity. It is widely used in coatings, precision casting, refractories, paper making, petrochemical industry because of its surface modification and mixing with organic polymers. The size of nano-silica particles in industrial synthesized silica sol is generally 1040 nm, which is difficult to meet the requirements of some special industries. In this paper, the preparation method of large size silica sol was studied by using sodium silicate aqueous solution (also called sodium silicate solution or sodium silicate) as raw material, and the effect of polyethylene glycol (PEG) on the morphology of silica sol was investigated. The particle size of silica sol was controlled by "sodium silicate direct condensation" and "sodium silicate direct Polycondensation combined with tetraethyl orthosilicate hydrolysis polymerization". The main contents and conclusions of this paper are as follows: (1) the active silicic acid was prepared by ion exchange method using sodium silicate as raw material, and the effect of active silicic acid on the shrinkage of active silicic acid was investigated. The result shows that, The polycondensation product was easy to gel under acidic condition (pH 1: 3), but the addition of PEG (molecular weight MW ~ (2 +)) had no obvious inhibition effect on the gelation. The silica sol with good dispersity was obtained by condensation under alkaline condition (pH 10). The addition of PEG can reduce the particle size of silica sol (40 nm 路m ~ (2)) with ammonia water (NH _ 3H _ (20)) as catalyst. Tetraethyl orthosilicate (TEOS) nanoparticles with high homogeneity were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) in EtOH ethanol solvent. In this step, multistep hydrolysis-polymerization method was used. The particle size of the silica sol prepared under the conditions of study is 30 ~ (50) nm.f.) the direct Polycondensation method of sodium silicate was studied by referring to the TEOS hydrolysis-shrinkage method. The direct Polycondensation of sodium silicate solution was carried out in ethanol / ammonia medium. The results show that stable silica sol products can be prepared with regular spherical particles, and the size of silica sol particles increases with the increase of sodium silicate concentration, which can be changed by changing the concentration of sodium silicate solution. The particle size can be adjusted by this method. The spherical particles with large diameter of 100 nm can be obtained, but the uniformity is poor, and the Polycondensation conditions need to be optimized. The mechanism of Polycondensation is still to be studied. (4) the direct condensation of sodium silicate and the hydrolysis-polymerization of tetraethyl orthosilicate (TEOS) are combined. The feasibility of "sodium silicate direct Polycondensation-TEOS hydrolysis polymerization combined method" for the preparation of silica sol with large particle size was studied. The results showed that the product with large diameter and uniform size could be prepared by this method. It provides a new way for the controllable preparation of silica sol. Compared with direct Polycondensation of sodium silicate, this method can obviously improve the particle evenness, and compare with TEOS hydrolysis polymerization method. The effect of PEG on the preparation of silica sol by direct Polycondensation of sodium silicate was investigated. The addition of PEG can reduce the particle size and has the tendency of inhibiting particle aggregation. The larger the molecular weight of PEG is, the smaller the silica sol is prepared under the same conditions.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ427.2

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