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新型有机锆化合物的制备及在光固化体系中克服氧阻聚的光聚合动力学研究
中文摘要

紫外光固化技术由于其高效、节能和低污染等的特性,近年来得到人们广泛关注,在材料生产加工行业中正逐步替代热固化工艺。但由于光固化体系在固化过程中会受分子氧的阻聚作用导致产品表面发粘,而且在固化后光引发剂的光解产物会有迁移、变色等特性,严重地限制了光固化体系在某些领域中的普及,如食品包装材料等。大量的研究集中在克服氧阻聚的各种方法和大分子光引发剂的设计,以改善这两方面的缺陷。其中有机金属化合物由于对过氧化自由基敏感而被用作克服氧阻聚的添加剂。 本文旨在利用有机锆化合物的配体置换反应,合成具有多功能的新型有机锆化合物。此反应具有操作简便和无催化剂的优点,产物保持一定的活性。研究其在光固化配方中的各项性能及光聚合动力学,探索其应用价值,具体研究内容如下: 1、采用一种已商业化的光引发剂,2-羟基-2-甲基苯丙酮(PI-1173),与四丙醇锆发生配体取代反应,来合成一种新型的多官能度光引发剂。设计反应物的不同投料比,可以得到三和四官能度产物(Zr-tril173和Zr-tetra1173)。以上几种光引发剂以一定比例加入光固化混合单体(HDDA和双酚A型二丙烯酸酯SR349的混合物)后,所得配方的涂层样品在相同条件下分别经过紫外光辐照固化,期间利用实时红外光谱(real time FTIR)表征样品的光固化双键转化率。与含有类似结构小分子光引发剂PI-1173相比,含多官能度光引发剂Zr-tri1173和Zr-tetra1173的配方具有相当高的聚合速率与最终转化率。固化后的样品经过激光共聚焦显微拉曼光谱分析,得到各自的双键转化率深度分布曲线。结果显示不同浓度光引发剂的使用可以得到表面转化率差异很大的固化样品,其中Zr-tri1173和Zr-tetra1173与PI-1173相比得到的固化膜表面转化率类似。采用溶剂萃取法处理不同转化率的固化样品,使引发体系中残留的可迁移物溶于一定量溶剂中,对该溶液样品进行紫外可见吸收光谱的定量分析。结果表明,较低转化率的固化样品中Zr-tri1173和Zr-tetra1173的可迁移产物量比PI-1173稍低,其中Zr-tetra1173比Zr-tri1173稍低;而在高转化率样品中,Zr-tri1173和Zr-tetra1173的可迁移产物量接近,但与PI-1173相比则大幅度降低。 2、两种Norrish Ⅱ型光引发剂,二苯甲酮(BP)和蒽醌(AQ)的羟基衍生物被用于取代正丙醇锆的配体正丙醇,来合成两种新型有机锆多官能度光引发剂, Zr-OBP和Zr-OAQ。分别对这两种光引发剂进行分子结构、紫外吸收性能和光引发活性上的研究。与它们相应的低分子量光引发剂BP-OH和AQ-N-OH相比, Zr-OBP和Zr-OAQ具有类似的吸收带和相对较高的吸光度。随后这些光引发剂加入到HDDA和SR349的混合物中得到光固化涂料配方。在汞氙紫外灯辐照下,利用real time FTIR表征样品的光固化双键转化率。结果表明,在相同条件下多官能度光引发剂可使固化配方达到更高的最终转化率。固化膜经过激光共聚焦显微拉曼光谱分析,得出其双键转化率的深度分布,结果表明Zr-OBP和Zr-OAQ在较低浓度下能使配方得到较高转化率,且样品的表面转化率与采用单官能度光引发剂的样品相比也有一定的提高。采用溶剂萃取法处理固化膜,得到其残留的可迁移光引发剂的溶液,再通过紫外-可见光谱测量其含量来判断多官能度光引发剂的迁移特性。结果表面多官能度的光引发剂的残留物可提取量比其单官能度类似物更低。 3、首次合成了两种含全氟基团的有机锆化合物,并考察其对光固化氧阻聚的影响。固化配方由两种常规单体(Ebercyl 270和TPGDA)和对氧敏感的光引发剂TPO组成。在配方中加入不同量的有机锆化合物并在一定条件下光固化,对紫外光固化涂层使用共聚焦显微拉曼光谱测量其转化率深度分布。其中实验采用不同的辐照光源(汞氙灯和LED灯)和不同的涂覆静置时间来对比对氧阻聚作用的影响。相同配方中采用不同固化条件可以得到涂层样品的不同表面转化率,并导致表干性质的差异。结果表明,普通有机锆化合物或全氟羟基化合物单独存在配方中并不能提高固化膜表面转化率,但全氟有机锆产物可以明显提高固化膜表面转化率。进一步的研究发现在涂覆后的静置时间和使用不同光源会使固化膜的表面转化率有很大差异。最后通过调整辐照光强,可以使含全氟有机锆产物的配方得到指触表干,同等条件下空白样则不能表干。 关键词:紫外光固化技术;多官能度光引发剂;氧阻聚;有机锆化学

英文摘要

UV-curing technology has been widely concerned in recent years due to its advantages of high efficiency, energy saving and low pollution. It is gradually replacing the thermal curing process in the material production and processing industry. But the process of UV-curing could be suffered from oxygen inhibition, which leads to tackness of the product surface. And photolysis products in the UV-cured system may undergo migration, discoloration and other undesirable process, which severely limits the popularization of UV-curing technique in industial applications, such as food packaging materials. A large number of studies have focused on the methods of overcoming the oxygen inhibition during the photopolymerization and the design of macromolecular photoinitiators to solve these two defects. Organometallic compounds are used as additives to overcome the oxygen inhibition because they are sensitive to peroxide radicals during the photopolymerization. In this paper, a new type of organozirconium compounds with multi-functions was prepared by the ligand substitution of organic zirconium compounds. The synthesis method has the advantages of simple operation and catalyst-free, and the products maintain a certain activity to peroxides. The properties of organozirconiums are studied and as well as the UV-curing formulations. The specific research contents are as follows: 1.A commercial photoinitiator, 2-hydroxy-2-methylpropiophenone (PI-1173), was employed to synthesize a novel multifunctional photoinitiator (MPI) via ligand substitution of zirconium propoxide in the absence of any catalyst. With different feed ratios of the reactant, trifunctional and tetrafunctional zirconium-based photoinitiators were prepared. The photoinitiation properties of the MPIs were evaluated by real-time FTIR of the UV-curing formulations, which shows that the photoinitiation ability of MPIs were comparable to PI-1173. Three different levels of final conversion were achieved with varied concentrations of MPIs. The residual-free PIs in UV-cured samples were also measured by extraction of chloromethane. The results show that Zr-tri 1173 and Zr-tetra 1173 had slightly lower amounts of migrating products than PI-1173 in UV-cured samples with lower conversion, and Zr-tetra1173 was slightly lower than Zr-tri1173. In the samples with high conversion, the ones with Zr-tri1173 and Zr-tetra1173 have similar amount of migrating products, but it is greatly reduced compared with PI-1173. The multifunctional structures of MPIs are more immobilized in the cross-linked networks than the parent molecule. 2.Two hydroxyl derivatives of benzophenone and anthraquinone were chosen as the ligands of zirconium complexes in the substitution of zirconium propoxide to obtain zirconium-based multifunctional photoinitiators (MPIs), Zr-OBP and Zr-OAQ. The MPIs were characterized in terms of molecular structures, UV-vis absorption properties and photoinitiation reactive ability. The absorption bands of the MPIs are similar to their low-molecular-weight counterpart with higher absorbance. These photoinitiators were used for the UV-curing of a formulation with bisphenol A diacrylate (SR349) and hexanedioldiacrylate (HDDA). The kinetics of photopolymerization of the formulations was monitored by real-time FTIR spectroscopy, under the irradiation of a mercury-xenon lamp. The results show that under the same conditions, multifunctional photoinitiators can achieve a higher final conversion rate of the formulation. Organozirconium complexes are known to tap the potential of overcoming the oxygen inhibition, thus the depth conversion profiles of the UV-cured films were followed by confocal Raman microscopy. Furthermore, the migration of residual photoinitiator was investigated via solvent extraction from the UV-cured films, the solution of which being measured by UV-vis spectroscopy. 3.Organozirconiums had been studied as the peroxyl radical scavenger in UV-curing systems, which had varied performance in overcoming the oxygen inhibition. Herein we modified the complex of zirconium with organic fluorides in order to increase its efficiency of peroxyl radical scavenging. A formulation consists of two conventional monomers (Ebercyl 270 and TPGDA) and an oxygen-sensitive photoinitiator TPO was employed in this study. With different content added in the formulation, the UV-cured coatings had different depth conversion profiles, which were measured by confocal Raman microscopy. Moreover, the standing time for the enrichment of fluorinated organozirconium products to the surface of the coatings and two irradiation sources (Hg-Xe lamp and UV-LED lamp) were adopted to emphasize their properties against the oxygen inhibition. Finally, by adjusting the irradiation intensity, it is shown that fluorinated organozirconiums can lead to tack-free coatings, while the UV-cured films from neat formulation remain tacky. Keywords: UV-curing kinetics, multifunctional photoinitiators, oxygen inhibition, organozirconium chemistry

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