Comparative analysis of the qualitative characteristics of formaldehyde and acetaldehyde resins based on styrene-modified oil shale alkylresorcinols

Abstract Reducing the amount of volatile compounds in alkylresorcinol-aldehyde resins, reducing the impact of their components on the environment, and improving their performance can be achieved by replacing formaldehyde with acetaldehyde and by preliminary aralkylation of the resorcinol components of the raw material. To prove this, a comparative analysis of the properties of resins synthesized based on oil shale alkylresorcinols pre-treated with styrene, formaldehyde, or acetaldehyde was carried out. The effects of the molar ratio of feedstock/aldehyde and the amount of catalyst on the yield and characteristics of the resins were considered. Both individual alkylresorcinols (R, 5-MR, 2.5-DMR) and industrial fractions (REZOL, HONEYOL) were used as the raw materials. The following indicators were used to compare the obtained resins: softening point, ash content, coke number, moisture content, volatile substances, and solubility in organic solvents. The thermal properties of the resins were studied by TG/DTG/DTA in inert and oxidative atmosphere. Qualitative and quantitative analyses of resins and distillates for the content of unreacted resorcinol, individual alkylresorcinols, and styrene were carried out using iodometry, thin-layer chromatography (TLC), and gas chromatography (GC). It has been shown that the use of acetaldehyde makes it possible to obtain resins with the stated characteristics. The formaldehyde (SF) and acetaldehyde (SAc) resins obtained consist of oligomers with different chain lengths. Synthesized SAc resins are solids with a softening point of 51 °C–103 °C. Resins are soluble in acetone, EtOH, acetonitrile, and THF, and insoluble in benzene. SAc resins contain 3–4 times less unreacted original resorcinol components compared to SF resins. The conversion of styrene in the synthesis of Rez₁₀₀SF resins was 42 wt%, Rez₁₀₀SAc and Hon₁₀₀SAc are 98 and 97 wt%, respectively. A comparative analysis of resins synthesized using acetaldehyde instead of formaldehyde helped identify both the advantages and disadvantages of the proposed synthesis variation.