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Method for preparing modified urea-formaldehyde resin

A urea-formaldehyde resin and modification technology, which is applied in the field of preparation of modified urea-formaldehyde resin, can solve the problems of low free formaldehyde content, high free formaldehyde content, and failure to meet environmental protection requirements, and achieve the goal of reducing formaldehyde emission and free formaldehyde content Effect

Inactive Publication Date: 2009-12-23
INST OF WOOD INDUDTRY CHINESE ACAD OF FORESTRY
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Problems solved by technology

[0006] The purpose of the present invention is to overcome the shortcoming that the free formaldehyde content of the melamine modified urea-formaldehyde resin prepared by the existing preparation method is relatively high and cannot meet the requirements of environmental protection, and provide a method that can prepare the resin with a low free formaldehyde content and can meet the requirements of environmental protection. Method for modifying urea-formaldehyde resin required by environmental protection

Method used

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  • Method for preparing modified urea-formaldehyde resin

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preparation example Construction

[0014] According to a preferred embodiment of the present invention, the preparation method of the modified urea-formaldehyde resin provided by the present invention includes the following steps: adjust a part of the formaldehyde solution to pH 8-9, and heat it to 40-70°C, then add urea, and the addition is completed Then raise the temperature to 80-95°C, and stir the reaction at this temperature for 10-30 minutes, then adjust the temperature to no more than 85°C, adjust the pH value to 4-6, and continue to stir the reaction until the obtained product is mixed with water The resistance is 1.0-2.5 times; then lower the temperature to 40-60°C, adjust the pH to 8-9, add another part of formaldehyde or its solution, and add the first batch of urea-formaldehyde resin to modify the temperature and pH value. neutralizing agent, adjust the reaction temperature to 75-90°C, pH value to 9.0-9.5, stir the reaction until the water miscibility of the product is 1.0-2.5 times, then lower the ...

Embodiment 1

[0018] This example is used to illustrate the preparation method of the modified urea-formaldehyde resin provided by the present invention.

[0019] 416.67 grams of concentration is 36% formalin (formaldehyde is 5 moles) to join in the 1000 milliliters of four-neck flasks with stirrer, condenser and thermometer, with concentration is the sodium hydroxide aqueous solution of 20% by weight. The formalin was adjusted to pH 8.2 and heated to 50°C, then 151.67 g of urea was added with stirring, the temperature was raised to 90°C and stirred at this temperature for 15 minutes. Then the reaction temperature is reduced to 85°C, and the pH value of the reaction system is adjusted to 5.0 with a concentration of 10% by weight aqueous formic acid, and the stirring reaction is continued until the water miscibility of the product obtained in the flask is 2.5 times, and then cooled to 60°C. The sodium hydroxide solution that is 20% by weight is that the pH value of reaction system is adjuste...

Embodiment 2

[0024] This example is used to illustrate the preparation method of the modified urea-formaldehyde resin provided by the present invention.

[0025] 416.67 grams of concentration is 36% formalin (formaldehyde is 5 moles) to join in the 1000 milliliters of four-neck flasks with stirrer, condenser and thermometer, with concentration is the sodium hydroxide aqueous solution of 20% by weight. The formalin was adjusted to pH 8.2 and heated to 50°C, then 151.67 g of urea was added with stirring, the temperature was raised to 90°C and stirred at this temperature for 15 minutes. Then the reaction temperature is reduced to 85°C, and the pH value of the reaction system is adjusted to 5.0 with a concentration of 10% by weight aqueous formic acid, and the stirring reaction is continued until the water miscibility of the product obtained in the flask is 1.0 times, and then cooled to 60°C. Adding 104.69 grams of formalin with a concentration of 36% after the pH value of the reaction system ...

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Abstract

A method for preparing a modified urea-formaldehyde resin, the method comprises mixing and contacting the product of the contact reaction between formaldehyde and urea and a urea-formaldehyde resin modifier, wherein the urea-formaldehyde resin modifier is added at least twice. The free formaldehyde content of the urea-formaldehyde resin prepared by the preparation method of the modified urea-formaldehyde resin provided by the invention is very low, so that the formaldehyde release amount of wood-based panel products can be greatly reduced when used in the wood manufacturing process. For example, the free formaldehyde content of the modified urea-formaldehyde resin prepared by the method provided by the invention can be reduced to no more than 0.20%, so that the plywood prepared by using the modified urea-formaldehyde resin can reach the E1 (≤1.5 mg / liter) regulation in the national standard . In addition, the modified urea-formaldehyde resin prepared by the method provided by the invention can not only be in liquid form, but also in powder form, and can be used under wet and outdoor conditions.

Description

technical field [0001] The invention relates to a preparation method of modified urea-formaldehyde resin. Background technique [0002] Urea-formaldehyde resins, especially melamine-modified urea-formaldehyde resins (MUF), are widely used in the wood manufacturing industry for bonding wood or as adhesives in the production of wood-based materials, such as for particleboard, plywood and various fiberboards. in production. Urea-formaldehyde resin is the reaction product of urea and formaldehyde. Because the water resistance and intensity of this urea-formaldehyde resin are relatively poor, therefore generally use urea-formaldehyde resin modifier to modify the urea-formaldehyde resin of gained, to obtain modified urea-formaldehyde resin such as commonly used melamine-modified urea-formaldehyde resin (MUF), The water resistance and strength of this urea-formaldehyde resin are significantly higher than that of unmodified conventional urea-formaldehyde resin. The urea-formaldeh...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08L61/24
Inventor 秦特夫李改云
Owner INST OF WOOD INDUDTRY CHINESE ACAD OF FORESTRY
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