brief history
1789 chemical analysis records that turpentine is treated with sulfuric acid to produce resin. 1909, the United States published a patent that turpentine can react with sulfuric acid to produce a resin similar to Indian rubber. 1937 American gulf oil refining company obtained the patent of aluminum trichloride as terpene polymerization catalyst. 1938 American commercial β -pinene resin came out. Terpene resin was successfully synthesized from α -pinene in 1965. China began to produce terpene resin from turpentine in 1960s.
kind
Due to different raw materials, the names are different, such as α -pinene resin, β -pinene resin, dipentene resin and so on. Terpenes can be polymerized with olefins, phenols, acids, anhydrides, etc. To produce terpene polymers such as terpene phenol resins.
Polymerization mechanism
① Terpene polymerization: cationic catalytic solution polymerization is used in industry. The catalyst is Lewis acid, such as AlBr3, AlCl3, ZrCl4, BF3, BF3(C2H5)2O, SnCl4, BiCl3, SbCl3, ZnCl2, etc. , represented by AlCl3. α-pinene, β-pinene and dipentene are polymerized in solvent under the action of Lewis acid. Polymerization goes through chain initiation, chain growth and chain termination. Due to the existence of exocyclic or terminal methylene, β -pinene and dipentene are easier to polymerize than α -pinene Therefore, in the polymerization of α-pinene, composite catalysts are often used to improve the yield and quality of products. Composite catalysts include aluminum trichloride-aluminum tribromide, aluminum trichloride-trialkyl silicon chloride, aluminum trichloride-alkyl silicon dichloride, aluminum trichloride-triethylamine, aluminum trichloride-triethyl germanium tetrachloride and so on. ② Polymerization of β-pinene: With β-pinene as raw material and anhydrous AlCl3 as catalyst, anhydrous AlCl3 is derived into composite protonic acid under the action of cocatalyst (such as adding trace water).
When the exocyclic methylene of ALC L3+H2O-→H+[ALC L3 oh]-≡H+G-β- pinene monomer collides with the proton, the chain initiation is completed. Before the carbocation rearrangement reacts with another monomer, the chain growth step begins, and according to this reaction process, the chain polymer is finally formed. ③ Polymerization of dipentene: the chain grows through terminal methylene. The initiation step of dipentene polymerization is similar to that of β -pinene polymerization. ④ Polymerization of α-pinene: α-pinene can easily produce the same initiating carbonium ion as β-pinene, but the chain growth is difficult due to the space effect. Therefore, cocatalyst is used to stabilize the carbocation in the growing chain and prolong its residence time so that it can collide with another α -pinene monomer and polymerize. During terpene polymerization, different solvents, catalyst ratio, polymerization temperature and polymerization time are selected according to different raw materials to obtain the best polymerization conditions. After polymerization, the catalyst was hydrolyzed by heating water under stirring to destroy the catalyst, and the residue was removed by filtration, then washed with hot water, and left to stand and separate layers to remove the lower water phase. After washing the organic phase with hot water to neutrality, the solvent was recovered under atmospheric distillation, and unpolymerized monomers and low molecular weight substances were removed under reduced pressure distillation to obtain the resin product.
The manufacturing process of terpene resin is shown in the figure.
Nature and use
Terpene resin can be a viscous liquid until it becomes a brittle solid. Pale yellow, nontoxic and tasteless, insoluble in water, methanol, ethanol, acetone and ethyl acetate. Soluble in nonpolar solvents and vegetable oils. It has excellent moisture resistance, steam permeability resistance, flexibility and adhesion. Strong adhesion, high cohesion, good heat resistance, light resistance, dilute acid resistance, alkali resistance and aging resistance. In the application of adhesives, different kinds and specifications of terpene resins have different adhesive properties, so they have different uses. Terpene resin is used as tackifier in adhesives. (1)β- pinene resin has light color, good color retention and excellent adhesion, and can be used as adhesive for natural rubber and polyisoprene, solvent-based pressure-sensitive adhesive tape, label making, and can end sealing. ② Dipentene resin has good thermal stability, oxidation resistance and thermal adhesion. Used to produce hot melt adhesives and coatings. ③ α -pinene resin has good color stability. The systems used for hot-melt pressure-sensitive adhesives and solvent-based adhesives are excellent adhesives of styrene-butadiene rubber (SBR) and styrene-butadiene-styrene (SBS). ④ Terpene phenol resin is an excellent adhesive for styrene-butadiene rubber, natural rubber, isoprene rubber, neoprene rubber and ethylene-vinyl acetate polymer. Terpene phenol resin can increase the ductility and flexibility of products when making hot melt adhesives and coatings.
The mass number average molecular weight of 4 1 1364 is one of the important quality indexes. The number average molecular weight of commercial terpene resin is shown in the table.
Terpene resins are divided into three categories according to softening point: high softening point terpene resins with softening point of 100 ~ 135℃; Medium and low softening point terpene resin with softening point of 55 ~ 85℃; Liquid and semi-solid terpene resins, softening point 10 ~ 25℃. Color, acid value, saponification value, iodine value or bromine value and toluene insoluble matter are all important indicators of product quality. The quality index of α -pinene resin in China is basically the same as that in other countries.