The carbon nine petroleum resin is a thermoplastic resin obtained by polymerizing a carbon dioxide fraction as a by-product of a cracking ethylene plant, polymerizing it in the presence of a catalyst, or copolymerizing it with an aldehyde, an aromatic hydrocarbon or a terpene compound. It has a molecular mass of generally less than 2,000 and a softening point of less than 150 ° C. It is a thermoplastic viscous liquid or solid. Because of its low softening point and relatively small molecular weight, it is generally not used as a material alone. Since the structure of carbon nine petroleum resin does not contain a polar group, it has good water resistance, acid and alkali resistance, weather resistance and light aging resistance, has good solubility in an organic solvent, and has good compatibility with other resins. It also has brittleness, tackiness, cohesiveness and plasticity. It is mainly used in coatings, rubber auxiliaries, paper additives, inks and adhesives.
The raw material of petroleum resin cracking carbon nine fraction is a complex mixture of more than 150 aromatic hydrocarbon components boiling in the range of 240 ° C, no fixed composition, and very dispersed, difficult to separate. From a synthetic point of view, it can be divided into two categories. One type of active component that can be polymerized, such as: styrene and vinyl toluene, dicyclopentadiene, etc.; another type of inactive components, such as alkylbenzenes and fused aromatic hydrocarbons, which act as a solvent during polymerization. The effect of the reaction is distilled off. The carbon nine feedstock typically contains about 50% of a polymerizable monomer.
Common methods for synthesizing petroleum resins include thermal polymerization, catalytic polymerization, and free radical polymerization. Among the many physicochemical properties of petroleum resins, the most important are softening point and hue. It is required to have a softening point of 50 to 140 ° C, a hue of less than l3, and a pale yellow to dark brown color. The polymerization mode of the carbon nine fraction has a great influence on the hue and softening point of the carbon nine petroleum resin.
1, thermal polymerization
The thermal polymerization of petroleum resin generally heats the carbon nine fraction in a reaction vessel to about 260 ° C. First, a Diels-Alder addition intermediate is formed from molecules of two polymerizers, and then reacts with another polymerizable component. , generating two free radicals and then initiating the polymerization. The thermal polymerization method has the advantages of simple process and high yield, but high reaction temperature, high energy consumption, easy coking, deep color of the produced resin, low product grade, industrial only used to produce dark resin, and its products are mainly used as Rubber reinforcing agent, additive for concrete.
2. Catalytic polymerization
The catalytic polymerization of petroleum resin is a cationic polyaddition reaction, mainly in which a carbon nine monomer forms a carbon cation active center under the action of a catalyst, and initiates chain polymerization to synthesize a petroleum resin. The active center is greatly affected by the degree of dissociation of the ion pair, and the different active centers of the reaction medium and solvent are also different. Catalytic polymerization is the earliest and most widely used in the synthesis of petroleum resins. Most of the petroleum resin synthesis processes mentioned in the literature use catalytic polymerization.
The free radical polymerization is due to the presence of a large number of unsaturated bonds (orphaned electrons) in the carbon nine-component molecule, which forms a radical under the action of an initiator and initiates chain polymerization. After the product is synthesized, a solid polymerization inhibitor is added to terminate the reaction. The initiators commonly used in the free radical polymerization of petroleum resins are peroxides and sodium fatty acids or mixtures thereof. The amount and ratio of initiators have a great influence on the quality of the product. The fundamental difference between cationic polymerization and free radical polymerization is that the properties of the end of the growing chain are different, that is, the active centers are different. Its main performance is as follows:
(a) cationically grown growth chain charged; (b) cationically polymerized growth chain and counterion. From the above, it can be seen that the carbon nine fraction has a complex composition and a high boiling point, which is difficult to accurately separate and is rich in unsaturated olefins. The carbon nine fraction is suitable for the production of petroleum resin raw materials.