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    Home > Coatings News > Paints and Coatings Market > Coating knowledge: urea formaldehyde resin composition

    Coating knowledge: urea formaldehyde resin composition

    • Last Update: 2020-04-03
    • Source: Internet
    • Author: User
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    The key points are as follows: (1) the urea formaldehyde resin used as molding powder requires the use of condensation polymer with a shallow degree of reaction At this time, the resin viscosity is small, which is convenient for impregnating the filler, and can ensure the proper fluidity after a long production cycle and drying In industry, the condensation of urea and formaldehyde at low temperature (a mixture of Dihydroxymethyl urea) is often used Generally, the ratio of urea to formaldehyde is 1:1.5 (mol ratio), which is completely dissolved at pH = 8 (and temperature) 30-35 ℃, then 0.3% - 0.54% oxalic acid and 0.33% - MDAS are added Paint knowledge | precautions for wall paint color selection Recommended introduction: when painting the wall, the owner sometimes has difficulty in choosing what color of the wall paint to paint In fact, there is no ugly color in the wall paint, only the disharmonious color matching The use of wall color contains the knowledge of health Too strong color will stimulate people's perception, make people have a sense of fidgety, affect people's mental health Grasp the basic principles of wall color and paint a colorful space 1、 Wall paint color selection notice 1 Light color is generally used for the top surface Light colors make people feel light, dark colors make people feel heavy Usually, the treatment of rooms is from top to bottom, from shallow to deep For example, the ceiling and walls of rooms are white and Home of coatings news: (1) the urea formaldehyde resin used as compression molding powder requires the use of a condensation polymer with a shallow degree of reaction At this time, the resin viscosity is small, which is convenient for impregnation of fillers, and can ensure proper fluidity after a long production cycle and drying In industry, the condensation of urea and formaldehyde at low temperature (a mixture of Dihydroxymethyl urea) is mostly used Generally, the ratio of urea to formaldehyde is 1:1.5 (mol ratio) After the urea is completely dissolved at pH = 8 (and temperature) 30-35 ℃, 0.3% - 0.54% oxalic acid and 0.33% - 0.88% oxalate are added, and then exothermic reaction occurs The temperature rises, and the temperature is kept at 55-60 ℃, and pH = 5.5-6.5 is strictly controlled After 60-75min, the required urea formaldehyde resin is obtained Due to the low degree of polycondensation, in fact, it is just over the addition reaction stage, and the main polycondensation reaction is in the curing process (2) The curing agent used in the powder is required to have a certain latency, commonly used oxalic acid, phthalic acid, benzoic acid, monochloroacetic acid, etc (3) The most commonly used filler is pulp, followed by wood powder or inorganic filler (asbestos, glass fiber, mica, etc.) The pulp used is pure cellulose, which is made from wood, treated with sulfite, dissolves the non cellulose impurities in the wood, and then bleached The amount of filler is 25% - 32% of the total amount of materials If the amount of filler is too small, the fluidity of molding powder is large and the strength of products is low; otherwise, if the amount of filler is too much, the fluidity of molding powder is reduced, the surface of products is not smooth and the water resistance is reduced (4) Colorant colorant can give plastics bright colors When choosing colorant, it should be noted that the colorant used has strong coloring ability, can disperse evenly in plastics, does not change color under processing temperature and long-term sunlight, and does not separate from products The usual colorant is pigment, less dye is used, the dosage is 0.01% - 0.2% of the material quantity (5) Lubricant can improve the fluidity of the material when pressing the finished product, and can be separated from the product, forming an isolation film between the product and the mold, so that the product is not easy to stick to the mold The commonly used lubricants are metal salts of stearic acid (such as metal salts of zinc, calcium, aluminum, magnesium, etc.), esters of organic acids (such as cyclohexyl stearate, glycerin stearate, etc.) The addition amount is 0.1% - 1.5% of the material amount, which will pollute the appearance of the products and reduce the luster if it is too much, and it is difficult to demould the products if it is too little (6) Although the catalyst added in the powder is a latent catalyst, a small amount of acid will be released during the storage at room temperature, which will affect the quality of the powder Therefore, some basic substances are usually added to absorb the released acid, and the commonly used alkali is six methylene four amine or ammonium carbonate (7) Plasticizers are generally used in special occasions instead of plasticizers in compression molding powder, in order to improve the fluidity of materials and reduce the shrinkage during curing Available plasticizers are urea and thiourea Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,
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