Amino resin glue

The resins obtained by reacting urea and melamine with formaldehyde are all amino resins. Urea-formaldehyde resins are produced by polycondensation of urea with formaldehyde. Due to the low cost of raw materials, light color, short hot pressing time and the advantages of mildewproof and antibacterial, it is the largest in the production of plywood, particleboard, blockboard, furniture and sandwich doors. The main factors in the preparation of urea-formaldehyde resin are the molar ratio of urea to formaldehyde, the pH and concentration of the reaction solution, the reaction temperature and time. By varying these factors to control the degree of polycondensation of the resin, different properties of the resin can be produced to meet different needs. The polymer obtained by the reaction is subjected to vacuum dehydration to a solid content of 60 to 70%.

Resins made with high concentrations of formaldehyde (40-50%) are capable of achieving the desired solids without dehydration. It is also possible to add a certain amount of urea in the production of concentrated formaldehyde solution, and react under alkaline conditions and at 50-55 ° C to prepare a prepolymer of resin. When used, urea is further added as required to achieve the desired urea and The molar ratio of formaldehyde is then heated and stirred to form a high concentration of formaldehyde solution.

The prepolymer is stable in storage, easy to transport, and can eliminate the dehydration process. The urea-formaldehyde resin glue is used for the pre-pressing process of the plywood, and a small amount of polyvinyl alcohol may be added during the reaction of the urea-formaldehyde resin to improve the initial tack property, and a larger amount of the extender such as flour may be added to the general urea-formaldehyde resin. Urea-formaldehyde resin can accelerate curing under acidic conditions, so a certain amount of hardener such as ammonium chloride or ammonium sulfate is added during use. Urea-formaldehyde resin contains a certain amount of unreacted free formaldehyde, and some are released during the pressurization process, causing environmental pollution, which can be prevented by adding a part of melamine and improving the polycondensation process conditions. The melamine formaldehyde resin or the modified resin is widely used for decorative paper impregnation, and the melamine decorative board is prepared or directly affixed to the wooden substrate, and the wear resistance, heat resistance, hardness and gloss are excellent.