Method for synthesizing urea-formaldehyde resin
A synthesis method and urea-formaldehyde resin technology are applied in the field of urea-formaldehyde resin synthesis, and can solve the problems of prolonged resin curing time, difficult end-point control, and complicated urea-formaldehyde resin production process.
Inactive Publication Date: 2011-09-21
钱彤
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Problems solved by technology
[0008] There are various ways to reduce the content of free formaldehyde in urea-formaldehyde resin, the most effective method is to reduce the molar ratio of formaldehyde to urea, but reducing the amount of formaldehyde will lead to complex production process of urea-formaldehyde resin, difficult end point control, Disadvantages such as prolonged resin curing time and reduced resin bond strength and storage stability
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[0031] In order to describe in detail the technical content, the achieved purpose and the effect of the present invention, the following detailed description will be given in conjunction with the embodiments.
[0032] Raw materials and reagents:
[0033] Excellent melamine products;
[0034] Polyvinyl alcohol 2099;
[0035] Urea: industrial level;
[0036] Formaldehyde: Industrial grade (37% by mass aqueous solution);
[0037] Sodium hydroxide, formic acid and ammonium chloride are all chemically pure;
[0038] Hydrochloric acid: analytically pure.
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The invention discloses a method for synthesizing urea-formaldehyde resin. The method can reduce the content of free formaldehyde, and produce the urea-formaldehyde resin with high performance. In the method, the total molar ratio of formaldehyde to urea is 1.19, which contributes to reducing the free formaldehyde content of the urea-formaldehyde resin; the formaldehyde is added once; the urea isadded for four times, wherein the dosages of the urea added in the first two times have to contribute to generating dimethylol urea, so that an addition reaction of the formaldehyde is more thorough to reduce the free formaldehyde content in the reaction to the maximum; the pH value in the reaction process is changed to meet the requirements on the pH values in different stages of the reaction process; and the appreciate reaction temperature, appreciate reaction time and appreciate urea adding time are selected.
Description
Technical field [0001] The invention relates to a method for synthesizing urea-formaldehyde resin. Background technique [0002] Urea-formaldehyde resin is the main adhesive in the wood industry at home and abroad. It is widely used due to its high bonding strength, fast curing, good operability, low production cost, and abundant raw materials. However, the free formaldehyde contained in urea-formaldehyde resin is toxic, and the lower the content of free formaldehyde in the resin, the less toxicity. [0003] The production of urea-formaldehyde resin has a history of more than 60 years, but due to the complex reaction between urea and formaldehyde, a unified conclusion has not been reached on the formation mechanism of urea-formaldehyde resin. Most scholars believe that the synthesis reaction of urea-formaldehyde resin includes two stages of addition reaction and polycondensation reaction. First, formaldehyde and urea are added in a neutral or weakly alkaline medium to form a rela...
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IPC IPC(8): C08G12/38
Inventor 聂英
Owner 钱彤
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