Preparation method of phenol modified urea resin

Abstract

The invention provides a preparation method of phenol modified urea resin. The preparation method comprises the following steps of: (a), mixing phenol, formaldehyde and an alkali catalyst for reacting to obtain reaction products, wherein the reaction products include a phenol-alcohol mixture and formaldehyde; and (b), mixing the reaction products obtained in the step (a) with urea, an alcohol compound and an weak acid compound for reacting to obtain the phenol modified urea resin. The preparation method of the phenol modified urea resin provided by the invention can be used for enabling the phenol and the formaldehyde to react in the presence of the alkali catalyst, enabling the reaction products to react with the urea and the alcohol compound under an weak acid condition, so that the alcohol compound and excessive formaldehyde react to generate alcohol formaldehyde in the reaction process; moreover, the alcohol compound further can be cross-linked with the urea resin to form macromolecules, so that the content of the free formaldehyde is lowered and the storage period is prolonged. Moreover, the phenol modified urea resin obtained by the preparation method disclosed by the invention is foamed and cured to obtain a foaming body with a higher percentage of close area.

Description

technical field [0001] The invention relates to the technical field of polymers, in particular to a preparation method of phenol-modified urea-formaldehyde resin. Background technique [0002] Urea-formaldehyde resin is a thermosetting resin synthesized from urea and formaldehyde as the main raw materials. It is a kind of amino resin and one of the oldest synthetic resins. Due to its low cost, light color, no pollution to wood, high hardness, and bond strength High, oil resistance, mildew resistance, good insulation and temperature resistance, etc., are widely used in wood processing, plywood and other industries. It accounts for more than 80% of the total in wood adhesives and occupies a very important position. However, urea-formaldehyde resin also has serious disadvantages, such as water resistance, aging resistance, poor mechanical strength, and high formaldehyde content. [0003] In the prior art, in order to overcome the shortcomings of urea-formaldehyde resins, phen...

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Problems solved by technology

[0004] The inventors have found that the phenol-modified urea-formaldehyde resin obtained by the synthesis process disclosed in the prior art has higher reactivity at the para-position of phenol than at the ortho-position, and the para-position of phenol is more likely to undergo an addition reaction with formaldehyde to generate p-hydroxymethylphenol; After generating p-hydroxymethylphenol, the activity of the ortho-position of the phenolic hydroxyl group will decrease significantly, and it will be more difficult to add reaction with formaldehyde, resulting in less formaldehyde consumption, and the content of free formaldehyde in the obtained phenol-modified urea-formaldehyde resin is relatively low. High; and due to the residual formaldehyde oxidation of the solution in the storage process and the reduction of methylol to acidic substances, the acidity of the adhesive increases, the polycondensation reaction accelerates, and the aging of the adhesive is caused. The storage period is too short; the phenol modification disclosed in the prior art The closed cell rate of the foam obtained by foaming urea-formaldehyde resin after curing is very low, and the open cells are serious

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