High solids content emulsions. III. Synthesis of concentrated latices by classic emulsion polymerization

Two different methods of producing bi‐ and trimodal latices of a mixture of methyl methacrylate, butyl acrylate, and small amounts of acrylic acid were tested. It is shown that a combination of concentrating blends of seed particles by semibatch reaction, followed by a nucleation of small particles plus a second semibatch phase allowed us to obtain stable latices with solids contents over 65% and viscosities of below 2500 mPa s^?1 with little coagulum formation. The key parameter in determining latex stability, coagulum formation, and viscosity appears to be the the particle size distribution, and especially its modification attributed to secondary nucleation. Because it is not possible to eliminate water‐soluble monomers from the polymerization recipe, secondary (homogeneous) nucleation must be minimized by careful addition of the free‐radical initiator and choice of monomer feed flow rates. The nucleation of the third population in the trimodal latices is best accomplished with a mixed surfactant system because renucleation by anionic surfactant alone leads to detrimental changes in the particle size distribution (PSD) resulting from excessive flocculation of particles. In addition, it was found that the viscosity of the final products was not sensitive to small changes in the ionic strength of the latex, although neutralization to a pH of 6 effectively doubles the final latex viscosity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1916–1934, 2002; DOI 10.1002/app.10513     

原位聚合法研制纳米胶囊相变材料

采用超声波工艺及细乳液原位聚合方法,研制了以聚苯乙烯为囊壁、正十八烷为囊芯的纳米胶囊相变材料;系统探讨了聚合反应各因素如引发剂、链转移剂、表面活性剂以及正十八烷/苯乙烯比等对乳胶粒子的形态、胶囊材料热性能的影响,对所研制的胶囊相变材料进行激光衍射粒度分析、透射电镜及差示扫描量热等表征.实验结果表明,在引发剂AIBN 0.5%(油相质量百分比,下同);链转移荆DD在T0.4%;复合乳化剂(SDS/OP10)总量2%,配比1:1及正十八烷/苯乙烯比=1:1条件下,胶囊呈球形均匀分布,聚苯乙烯囊壁能将正十八烷囊芯很好包裹住,其胶囊Z均直径124nm,相变焓可达124.4kJ·kg-1.     

Continuous emulsion polymerization of vinyl acetate. II Operation in a single Couette–Taylor vortex flow reactor using sodium lauryl sulfate as emulsifier

Continuous emulsion polymerizations of vinyl acetate were conducted at 50°C in a single continuous Couette–Taylor vortex flow reactor (CCTVFR) using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator. The polymerization can be carried out very smoothly and stably, but the steady‐state monomer conversion attained in a CCTVFR is not as high as that in a plug flow reactor (PFR), but only slightly higher than that in a continuous stirred tank reactor (CSTR), even if the Taylor number is adjusted to an optimum value. Also, the effects of operating variables, such as the emulsifier, initiator, and monomer concentrations in the feed and the mean residence time on the kinetic behaviors were almost the same as those observed in a CSTR. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2755–2762, 2002     

非离子型聚氨酯预聚体可聚合乳化剂的合成及性能

采用甲苯二异氰酸酯 (TDI) ,聚乙二醇 10 0 0 (PEG -10 0 0 ) ,丙烯酸为原料 ,通过分子设计合成了带有双键的非离子型可聚合乳化剂。并对其CMC值、流变行为及乳化力进行了表征。结果显示 :此乳化剂的CMC值在 6.0 %左右、浊点为 (54± 1)℃、HLB值为 16.1可以取代OP -10的乳化能力 ;该乳化剂可以与丙烯酸酯类单体进行乳液共聚 ,得到性能优异的共聚乳液     

OP-1O丙烯酸酯的合成及其乳化特性的研究

本文对OP－10丙烯酸酯非离子反应性乳化剂的合成方法进行了研究，并对合成乳化剂的各种乳化剂性能进行了测试。经过测试和聚合实验表明，在本实验条件下，OP－10与丙烯酸可以有效地进行酯化反应，合成的OP－10丙烯酸酯有较好的聚合与乳化特性。     

金属闪光外墙乳胶漆的研制及性能研究

以丙烯酸酯及有机硅单体为原料合成了核-壳型硅丙乳液,用自制分散剂将闪光铝粉分散成水性闪光铝粉浆,并成功分散于硅丙乳液中,加入进口助剂,配制成水性金属闪光外墙乳胶漆.讨论了基料的玻璃化温度、单体的加入方式、引发剂、乳化剂、反应温度、聚合工艺和pH等对乳胶漆性能的影响.     

聚醋酸乙烯乳液缩醛化的改性研究

本文介绍了为提高聚醋酸乙烯乳液稳定性、耐水性和防冻性而进行缩醛化改性的原理，并确定了最佳工艺条件即甲醛与聚乙烯醇的配比为０．４５～０．５０。     

新型技术用于乳状液膜法脱酚的进一步研究

本文对模拟的含酚废水,采用新型技术对乳状液膜法脱酚进行了进一步的探讨。对所采用的制乳设备———撞击流-旋转填料床对制乳率、提取设备———旋转填料床对脱酚率、破乳设备———无机微孔膜法破乳的重要参数(如透过压方式、膜孔径等对膜通量和破乳率的影响)进行了研究。并且讨论了破乳后的油相回用情况。实验结果表明:撞击流-旋转填料床的制乳效率可达99.90 %以上,脱酚率可达99%左右,且瞬间完成;膜孔径越小,破乳率越高,膜通量越小;外压内抽方式的破乳效果优于单外压方式的破乳效果。对于粒径为5～2 5 μm乳液,用膜孔径为2 .0 μm的SiC微孔膜,在外压为6 0kPa、内负压为30kPa的外压内抽破乳方式下破乳,破乳率可达96 .4 % ,膜通量可达90 0L·(m2 ·h) -1。     

纸塑复合用丙烯酸酯乳液胶粘剂的制备

采用半连续法制备了一种纸塑复合用丙烯酸酯乳液胶粘剂,讨论了乳化剂的用量、松香乳液的用量、交联剂的用量等因素对胶粘剂性能的影响。结果表明,当乳化剂的用量为4.5%、松香乳液用量为10%,胶粘剂的性能较好;另外,加入一定量的交联剂,可显著提高该胶粘剂的耐水性。     

Oxidative flavour deterioration of fish oil enriched milk

The oxidative deterioration of milk emulsions supplemented with 1.5 wt‐% fish oil was investigated by sensory evaluation and by determining the peroxide value and volatile oxidation products after cold storage. Two types of milk emulsions were produced, one with a highly unsaturated tuna oil (38 wt‐% of n‐3 fatty acids) and one with cod liver oil (26 wt‐% of n‐3 fatty acids). The effect of added calcium disodium ethylenediaminetetraacetate (EDTA) on oxidation was also investigated. Emulsions based on cod liver oil with a slightly elevated peroxide value (1.5 meq/kg) oxidised significantly faster than the tuna oil emulsions, having a lower initial peroxide value (0.1 meq/kg). In the tuna oil emulsions the fishy off‐flavour could not be detected throughout the storage period. Addition of 5—50 ppm EDTA significantly reduced the development of volatile oxidation products in the cod liver oil emulsions, indicating that metal chelation with EDTA could inhibit the decomposition of lipid hydroperoxides in these emulsions. This study showed that an oxidatively stable milk emulsion containing highly polyunsaturated tuna fish oil could be prepared without significant fishy off‐flavour development upon storage, provided that the initial peroxide value was sufficiently low.