Study On Multivariate Modification And Its UV Curing Behavior Of Allyl Resinate

Rosin is one of the most important forestry products in China. Although China is the largest producer and exporter of rosin in the world, the technologies of downstream products of rosin have not well developed, which leads to lack of international market competitiveness. Due to the cycloaliphatic and aromatic structures in rosin molecules, it is considered that rosin has advantages to improve viscosity and the brightness in the resin film. In recent years, ultraviolet(UV) curing was considered as an efficient curing technology for many high value added polymer products. However, synthesis of the high performance resin film using the UV irradiation is rarely reported. The reason is that rosin molecule lacks of sufficient active groups, which can be polymerized during the UV curing reaction. In order to solve this issue, a series of rosin based monomers with different reactive functionality were synthesized by modification of the rosin molecular structure. This solution provides a efficient method for direct introduction of rosin structure into polymer products. Besides, the properties of the UV cured polymer films from rosin-based monomers were studied. The possible mechanism were also explored for using these new functional materials during UV curing polymerization.This paper designed the molecular structure of the polymerization monomers with multiple vinyl. By coupling microwave irradiation with phase transfer catalytic technique, a series of rosin polymerization monomers with different kinds of vinyl and different active functionalities were synthesized. Based on the comparative study, the UV curing behaviors and film-forming characteristics for each monomer were researched. It provided a kind of new functional resin materials synthesis methods and created a new type of UV curing materials. The main results and conclusions of this paper are achieved as following:A series of rosin acid derivatives with multiple carboxylic acid groups were synthesized using Pinus elliottii rosin as raw material, including monocarboxylic acid rosin derivatives(resin acid, abietic acid, isopimaric acid), dicarboxylic acid rosin derivatives(acrylic modified rosin, pimaric acid, p-pimaric acid) and the tricarboxylic acid rosin derivative(the maleated pimaric acid). Resin acid(GC content 97.8 %), abietic acid(GC content 96.1 %) and isopimaric acid(GC content 92.4 %) were prepared on the basis of our previous work. Acrylic-modified rosin was synthesized by Diels-Alder reaction using resin acid and acrylic acid as raw materials. Then high purity of acrylpimaric acid(mainly consist of isomers of p-acrylpimaric acid and m-acrylpimaric acid) were prepared by adjustment of the pH value. The yield and total GC content of acrylpimaric acid was 61.2 % and 98.6 %, respectively. p-Acrylpimaric acid can be further purified by column chromatography, in the yield of 19.4 % and GC content 95.7 %, respectively. The stereo-structure of p-acrylpimaric acid was determined by two-dimensional nuclear magnetic analysis. Maleopimaric acid anhydride(MPA) was synthisized by Diels-Alder reaction using rosin and maleic anhydride as raw materials. The yield and GC content of maleopimaric acid anhydride were 57.5 % and 98.4 % under microwave irradiation, respectively. The structures of the above mentioned products were characterized by GC, MS, FT-IR, 1H NMR and 13 C NMR.The corresponding vinyl rosin monomers were prepared, including mono terminal vinyl rosin derivatives(isopimaric acid, allyl resinate, allyl abietate, allyl maleopimarate), binary terminal vinyl type rosin derivatives(allyl isopimarate, allyl acryliate-modified rosinate, allyl acrylpimarate) and the ternary terminal vinyl type rosin derivative(tri-allyl maleopimarate). In this study, a new method to synthesize allyl resinates monomer is proposed by using water as the solvent under microwave irradiation, which can significantly improve the efficiency of the reaction. Under the optimum reaction conditions, the yield of allyl resinate is 94.7 %, with the GC purity is 92.6% and other fatty acid allyl ester is 7.4 %. Allyl resinate is synthesized under the above optimum reaction conditions, and the yield and GC content of allyl resinate are 94.4 % and 89.5 %, respectively. The yield and GC content of allyl isopimarate are 92.1 % and 95.1 %, respectively. The yield and GC content of allyl acryliate-modified rosinate are 92.2 % and 78.8 %, respectively. And allyl acrylpimarate is also prepared under the optimum reaction conditions with the yield of 72.9 % and GC purity of 98.6 %. The synthesized products are characterized by GC, MS FT-IR spectroscopy, 1H NMR, 13 C NMR and elemental analysis.FT-IR spectrum was used to calculate the conversion of the monomers using area-normalization method during the UV curing reaction. Effects of different conditions on the influence of surface curing time and the relative speed of different monomers were investigated. The relative speed of all monomers increased with the decreasing of illumination distance and increasing of illumination intesity. The fastest relative speed is isopimaric acid, and the second is methyl isopimarate, the lowest is allyl isopimarate durig the curing reaction. Isopimaric acid and allyl abietate are different vinyl types of rosin and rosin derivatives. The inherent vinylic C=C double bond of isopimaric acid with a low degree of polymerization, and film curing reaction can be quickly completed. That is why the relative speed of isopimaric acid is higher than that of allyl abietate which containing an acitive terminal vinyl. The representatives with the same type of mono, binary and ternary terminal vinyl type are allyl abietate, allyl acrylpimarate, and tri-allyl maleopimarate. The order of the relative speed are as follows: tri-allyl maleopimarate > allyl acrylpimarate > allyl abietate under different illumination dosage, different illumination distance and different illumination intensity. It is shown that the mechanism of free radical polymerization reaction changed to form more crosslinking polymers with the increasing of reactive functionality rather than a linear polymer from the single functionality. At the same time, the propeties of the cured products have markedly improved along with the increasing of the polymerization monomer functionality.Thermogravimetric analysis and the glass transition temperature of UV cured product from different monomers at the same conditions were tested. The initial decomposition temperature(Tdi) and the final residual are increased with the increase of functional groups of different monomors. The Tdi of different UV cured products of UV cured product from different monomers present totally different curves. The Tdi of allyl isopimarate UV cured product is 263.9 ℃, Tdi of methyl isopimarate UV cured product increase 22.4 ℃and Tdi of allyl isopimarate UV cured product decrease 36.7 ℃. That is to say the increase of the side chain is not conducive to the thermostability of the cured products. The glass transition temperature decrease after the carboxyl of isopimaric aicd were closed. The mechanical properties of them is similar. Compared different types of functional groups, the UV cured product of inherent vinyl double bond from pimaric acid have higher Tdi and Tg than that of allyl abitate. The mechanical properties of them is similar. The Tdi and Tg of the representatives with the same types of mono, binary and ternary terminal vinyl type are allyl abietate, allyl acrylpimarate, and tri-allyl maleopimarate are increased with the increase of functionality degree. The Tdi of allyl abietate, allyl acrylpimarate, and tri-allyl maleopimarate are 218.7, 292.9 and 312.0 ℃, respectively. And the Tg of them are 22.32, 49.04 and 76.28 ℃, respectively. That is to say thermal stability of polymers with dimensional network structure is better than linear structure. And the higher crosslinking density, the better thermal stability. They all have good mechanical properties, and the pencil hardness of tri-allyl maleopimarate increased.