Urea-formaldehyde resin and preparation method thereof

The invention discloses urea-formaldehyde resin. According to the invention, a step of activating formaldehyde is utilized, so that the synthetic reaction of the urea-formaldehyde resin can be finished at a low temperature, the balance constant is improved and the formaldehyde is reacted more completely. Therefore, a urea-formaldehyde resin adhesive synthesized by the urea-formaldehyde resin has low formaldehyde content, and a detection result shows that the free formaldehyde content of the synthesized urea-formaldehyde resin is less than 0.1%; under the condition that the mol ratio of the raw material formaldehyde to the urea is 1.0-1.1, the produced urea-formaldehyde resin adhesive has high cementing strength and the bonding strength of a cemented artificial plate product reaches the national standard. According to the method provided by the invention, any modifier is not added and dehydration is not carried out, so that the manufacturing process is simple and the cost is low.