Preparation process of polyamide adhesives

Preparation of Dimeric Linoleic Acid: Linoleic acid, clay, lithium carbonate, and water were added to a reactor and stirred at a pressure of 0.8–1.2 MPa. The temperature was raised to 230°C and reacted for 5 hours. The mixture was then cooled to 100°C, and 1.92 g of phosphoric acid aqueous solution was added. The pressure was then reduced to 0.3–0.5 MPa, and the temperature was raised to 150°C for 1 hour. Finally, the temperature was lowered to 100°C, and the mixture was filtered while hot to remove the catalyst. Unpolymerized unsaturated fatty acids were then evaporated under high vacuum (6.7–10.7 Pa) at 220–225°C to obtain high-purity dimerized linoleic acid.

Preparation of Polyamide Hot Melt Adhesive: Under nitrogen protection, a mixture of ethylenediamine and hexamethylenediamine was slowly added dropwise while stirring and heating the mixture to 130°C. At this point, the temperature is controlled at 140–150℃. After the addition is complete, the temperature is raised to 205–220℃ and the reaction continues until the water content of the product approaches the theoretical value. Then, the pressure is reduced, and the reaction is continued for another hour at 1.3–2.7 kPa and 220–230℃. Finally, a sample is taken to determine the amine value. If it meets the index (around 10), the product can be cooled and discharged. The softening point of the hot melt adhesive varies depending on the amount of dilinoleic acid, sebacic acid, ethylenediamine, and hexamethylenediamine used.