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I: Basic formula (weight/kg)
Liquid formic acid (content of not less than 85%): appropriate amount Liquid caustic soda (concentration of 36%): appropriate amount of industrial urea (nitrogen content of not less than 46%): 100 Formaldehyde: 256 Formaldehyde adsorbent: dosage of 15-20% of free formaldehyde.

Second, the production

1、Put the measured formaldehyde into the reaction kettle.
2, under constant stirring, add the caustic soda solution into the formaldehyde, adjust the pH value to 7.8, and begin to slowly warm up to 25-30 ℃.
3、Under constant stirring, add 50% of the total dosage of urea (crushed into powder) into the reaction kettle, and raise the temperature to 60℃ within 30 minutes (about 10℃ every 10 minutes).
4, when the reactor temperature reaches 60 ℃, the second addition of 25% of urea, the same should be constantly stirring, and control the speed of warming as before, control in 30 minutes to make the temperature rise to 90 ℃.
5、Finally add the remaining part of the urea, holding at 90 ℃ for 30 minutes.
6, after the constant temperature, that is, with liquid caustic soda (concentration of 36%) to adjust the pH value to 4.5, after the adjustment of acid should pay attention to its natural exothermic reaction, such as the case of rapid cooling, so as not to affect the quality of the rubber.
7, adjust the acid within 10-20 minutes, with room temperature water to check whether the rubber reaches the reaction end point, to reach the end point of the reaction of the rubber drop into the water will be a white mist. If the reaction endpoint has been reached, immediately reduce the temperature to 75 ℃, then use caustic soda to adjust the pH value of 7.8, and constant temperature into the glue. This constant temperature stage is also the dehydration stage, dehydration time according to the requirements of the concentration of glue.
8, into the material immediately after the glue cooled to 35-40 ℃, and add formaldehyde adsorbent, and then put into the glue barrel, not applicable for the time being, should be sealed lid, placed in a cool room for storage.

Usage

1、Modulation of urea-formaldehyde resin glue
Before using the best in the glue to add ammonium chloride, its role is to make the glue solidification speed up, but pay attention to the amount of appropriate, add less curing time is too long, not conducive to the construction operation; add more glue will be brittle, the quality of the joint is not good. According to experience, to 100 grams of urea-formaldehyde resin, in the temperature below 10 ℃, generally should add 2.5-3 grams of ammonium chloride, and in the temperature of 30 ℃, as long as the addition of 1 calendar is enough. In gluing wood panels, sometimes in the glue also add 5-10% of soybean meal or flour (powder can not be granular, to pass 100 mesh sieve), the purpose is to increase the viscosity, to prevent excessive glue infiltration into the wood, so that the glue increases the coarse viscosity.
2, the use of methods and precautions
The moisture content of the wood to be glued should not be more than 12%, the gluing surface should be flat, and the pressing surface should be clean. The glue should be applied evenly, and after the glue is applied on the surface, the gluing surface should be clamped with a jig until the glue is cured before it is unloaded. Adopt the hot pressing method to heat up to 60℃, the glue can solidify in about 5 hours. Cold pressing method generally takes more than 10 hours at room temperature for the glue to solidify.