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Environmental Friendly Urea formaldehyde resin adhesive
1： Basic formula (weight / kg)
Liquid formic acid (content not less than 85%): appropriate amount of liquid caustic soda (concentration 36%): appropriate amount of industrial urea (nitrogen content not less than 46%): 100 formaldehyde: 256 formaldehyde adsorbent: the dosage is 15-20% of free formaldehyde.
1. Put the measured formaldehyde into the reactor.
2. Under continuous stirring, add caustic soda to formaldehyde, adjust the pH value to 7.8, and start to slowly raise the temperature to 25-30 ℃.
3. Under continuous stirring, 50% of the total amount of urea (crushed into powder) is added into the reactor, and the temperature is raised to 60 ℃ within 30 minutes (about 10 ℃ every 10 minutes).
4. When the temperature in the reactor reaches 60 ℃ and 25% of urea is added for the second time, it is also necessary to keep stirring and control the heating rate as before, and control the temperature to 90 ℃ within 30 minutes.
5. Finally, the remaining part of urea was added and kept at 90 ℃ for 30 minutes.
6. After constant temperature, adjust the pH value to 4.5 with liquid caustic soda (concentration of 36%). Pay attention to its natural exothermic reaction after adjusting acid. If this happens, it is necessary to reduce the temperature rapidly to avoid affecting the quality of rubber compound.
7. Within 10-20 minutes after acid adjustment, use normal temperature water to check whether the rubber compound reaches the reaction end point, and the glue solution that reaches the reaction end point drops into the water and becomes white mist. If the end point of the reaction has been reached, the temperature should be immediately lowered to about 75 ℃, then the pH value should be adjusted to 7.8 with caustic soda, and the gelation can be formed at constant temperature. This constant temperature stage is also the dehydration stage, and the dehydration time depends on the requirement of the glue concentration.
8. Immediately cool the rubber to 35-40 ℃ and add formaldehyde adsorbent, and then put it into the plastic barrel. If it is not suitable for the time being, it should be sealed and stored in a cool room.
1. Preparation of urea formaldehyde resin adhesive
Before use, it is better to add ammonium chloride to the rubber compound, its function is to speed up the setting speed of the compound, but attention should be paid to the proper dosage. If the curing time is too long, it is unfavorable to the construction operation; if the glue is added too much, it will be brittle and the bonding quality will be poor. According to experience, in the case of 100 g urea formaldehyde resin, 2.5-3 g of ammonium chloride should be added when the temperature is below 10 ℃, and only one calendar is added at 30 ℃. When gluing wood, sometimes 5-10% soybean powder or flour is added into the glue (the powder can not be granular, and it should pass through 100 mesh sieve) in order to increase the viscosity and prevent excessive glue from penetrating into the wood, so as to increase the coarse viscosity of the glue liquid.
2. Usage and precautions
The moisture content of the wood to be glued shall not exceed 12%. The bonding surface shall be flat and the contact surface shall be clean. The glue should be applied evenly. After the glue is coated on the surface of the material, clamp the bonding surface with a clamp until the glue liquid solidifies. The rubber can solidify after heated to 60 ℃ by hot pressing method for about 5 hours. Cold pressing usually takes more than 10 hours to solidify.
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