Method for synthesizing urea-formaldehyde resin
A synthesis method and technology of urea-formaldehyde resin, which is applied in the field of synthesis of urea-formaldehyde resin, can solve problems such as difficulty in controlling the end point, prolonging the curing time of the resin, reducing the bonding strength and storage stability of the resin, etc.
Inactive Publication Date: 2011-03-23
钱彤
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[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, achieved objectives and effects of the present invention, the following will be described in detail in combination with the embodiments.
[0032] Raw materials and reagents:
[0033] Excellent products of melamine;
[0034] Polyvinyl alcohol 2099;
[0035] Urea: industrial grade;
[0036] Formaldehyde: industrial grade (37% aqueous solution by mass percentage);
[0037] Sodium hydroxide, formic acid and ammonium chloride are 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 is added 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 synthesis method of 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 because of its advantages such as high bonding strength, fast curing, good operability, low production cost, and abundant and easy-to-obtain 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 toxic it is. [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: addition reaction and polycondensation reaction. First, formaldehyde and urea are added in a ne...
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IPC IPC(8): C08G12/38
Inventor 聂英
Owner 钱彤
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