Polyvinyl acetal mixed aldehyde adhesive can be prepared by using polyvinyl alcohol (PVA) and crotonaldehyde as the main raw materials, hydrochloric acid (HCl) as the catalyst and acetaldehyde as the modifier.
Put a certain amount of PVA into a three-necked flask equipped with a mechanical stirrer and a reflux condensation device, add deionized water, adjust the water bath temperature to 95°C, and keep it warm for 2 hours to fully dissolve it; when the solution cools to room temperature, Slowly add measured HCl dropwise while stirring, and mix thoroughly; heat the water bath to the specified temperature, add crotonaldehyde and acetaldehyde solutions according to the formula, and stir thoroughly; after the reaction is completed, use NaOH solution to adjust the pH value to 8 to 9, and then add Add appropriate amount of urea and stir for 20 minutes.
The results show that when the reaction temperature is (90±2)℃, the reaction time is 4 h, 8% PVA solution is 200 mL, HCl is 1mL, crotonaldehyde is 1.0~1.5mL, and acetaldehyde is 4mL, acetalization The viscosity of the product is moderate, the bonding strength is relatively maximum (4.5MPa), and the water resistance is relatively good; under the premise that other conditions remain unchanged, by changing the amount of crotonaldehyde, the final viscosity of the system can be further adjusted to meet the requirements of wood. Adhesive usage requirements.
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