RU2534550C1 - Method of production of urea-formaldehyde oligomer - Google Patents

Abstract

FIELD: woodworking industry.

SUBSTANCE: method of production of urea-formaldehyde oligomer comprises loading of formalin, its neutralisation to pH 7.0-7.5 with modifier-catalyst based on salt of polyfunctional acid, adding of urea, after dissolution of urea, if necessary, reduction of pH to 6.8-7.2 with ammonium chloride, followed by heating to 90-92°C and keeping for 30 minutes. Further, reduction of pH of the mixture is carried out with a solution of ammonium chloride to 4.2-4.5 and kept at 90-92°C with stirring for 30 min, cooled to 60-65°C, adjusted to pH 6.7-7.0, the catalyst modifier is added while stirring based on salt of polyfunctional acid, urea is added, and kept at 60-65°C while stirring for 30 minutes to obtain an oligomer, it is neutralised with modifier-catalyst based on salt of polyfunctional acid to pH 8.0-8.5. The catalyst-modifier based on salt of polyfunctional acid is used as modifier obtained by mixing caustic soda or potassium hydroxide, lactic acid or tartaric acid and water with the ratio of ingredients in parts by weight: caustic soda or potassium hydroxide 13-15, lactic or tartaric acid 16-19, water 68-69.

EFFECT: reduction of toxicity with improved physical and mechanical properties of plates obtained with the use of urea-formaldehyde oligomer according to the invention.

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Description

The invention relates to the woodworking industry and can be used in the manufacture of urea-formaldehyde oligomer used in the manufacture of chipboards. A known method of manufacturing a urea-formaldehyde oligomer, in which the starting products are analyzed for the content of basic substances, neutralized, and then loaded into a container for the manufacture of the reaction solution, from where the reaction mixture by gravity through the dispenser enters the reactor. After filling the reactor with the reaction mixture, the reflux condenser is turned on and steam is supplied to the reactor jacket. The reaction mixture is heated to 55-60 ° C, after which the steam supply is stopped, and the mixture is heated to 80-85 ° C due to the heat generated during the reaction. At this temperature, the reaction is carried out for the necessary time at a given pH of the medium to the desired viscosity of the solution. Then the reaction mixture is cooled to 65-70 ° C, neutralized, the reflux condenser is transferred to a direct line and the vacuum pump is turned on. Vacuum drying is carried out at a residual pressure in the apparatus of 0.04 MPa. During this period, it is necessary to ensure that there is no transfer of the oligomer solution through the condenser to the condensate receiver. The drying process is monitored by the amount of condensate formed, the pH of the medium and the refractive index and terminated when the oligomer condensation reaches 60-70%. The solution is cooled to 25-30 ° C, stabilized with ammonia water in the apparatus and poured through a filter into a collection of finished products (See. Azarov V.I., Tsvetkov V.E. Technology of binders and polymeric materials: Textbook for universities. - M. : Lesn. Prom-ty, 1985.- 216 s; p. 61-62).

The closest technological solution is a method of manufacturing a urea-formaldehyde oligomer, including loading formalin, neutralizing it to a working concentration of hydrogen ions, loading urea, ammonium chloride, heating the reaction mixture, holding (See V.E. Tsvetkov and others. Polymers in the production of wood materials : practical work. Moscow, GOU VPO MGUL, 2007. - 55 p.: p. 16).

The disadvantages of the known solutions is the insufficient reduction in the toxicity of the oligomer and the particle board obtained using this oligomer.

The problem solved by the claimed invention is to reduce toxicity, while improving the physico-mechanical properties of the plates.

The solution to this problem is provided by the fact that in the method of manufacturing urea-formaldehyde oligomers, including loading formalin, neutralizing it to pH 7.0-7.5 with a modifier-catalyst based on a polyfunctional acid salt, introducing urea, after dissolving urea, if necessary, lower the pH to 6, 8-7.2 with ammonium chloride, followed by heating to 90-92C ° and holding for 30 minutes, followed by lowering the pH of the mixture with a solution of ammonium chloride to 4.2-4.5 and holding at 90-92C ° with stirring for 30 min, cool dilution to 60-65C °, adjusting the pH to 6.7-7.0, adding a modifying catalyst based on a polyfunctional acid salt with stirring, introducing urea and holding at 60-65C ° with stirring for 30 minutes to obtain an oligomer and its neutralization with a modifier-catalyst based on a salt of polyfunctional acid to a pH of 8.0-8.5, according to the invention, as a modifier-catalyst based on a salt of polyfunctional acid, obtained by mixing caustic soda or potassium, lactic or tartaric acid and water, etc. ratio of the components:

Caustic Soda or Potassium 13-15 Lactic or tartaric acid 16-19 Water 68-69

The technical essence of the claimed invention lies in the fact that in the synthesis of urea-formaldehyde oligomers, alkali, in particular NaOH, is used to neutralize formalin. Pretreatment of formalin with a modifier catalyst based on salts of polyfunctional acids reduces the amount of free formaldehyde in urea-formaldehyde oligomers, and hence the toxicity of particle boards based on them.

The invention is illustrated by the following examples.

Example 1

By mixing 10 parts by weight of caustic soda, 21 parts by weight of citric acid and 69 parts by weight of water, we obtain a modifying catalyst based on a salt of polyfunctional acid.

Then 135 parts by weight of formalin are loaded into the reaction flask, the formalin pH is measured using a pH meter, the pH is adjusted using a polyfunctional acid salt-based modifier-catalyst to a value of 7.0-7.5, 50 parts by weight of urea are introduced (main load) . Turn on the stirrer and heat the water bath. After complete dissolution of the urea at a temperature of 40-50 ° C, check the pH, the value of which should be in the range of 6.8-7.2. If necessary, lower the pH, ammonium chloride is added dropwise. Continue heating to 90 ÷ 92 ° C and incubated for 30 minutes. Before the end of the first stage of synthesis, the pH of the reaction solution is checked (in the range of 6.5-7.0). The second stage is carried out in an acidic environment. For this, the pH of the mixture is reduced with a solution of ammonium chloride to 4.2-4.5 and maintained at 90-92 ° C, stirring for 30 minutes. Cool the system to 60-65 °, adjusting the pH to 6.7-7.0 by adding dropwise a catalyst modifier based on a salt of polyfunctional acid, without stopping mixing. 27 mass parts of urea are introduced. The reaction system is maintained at 60-65 ° and a working stirrer for 30 minutes. The resulting oligomer is concentrated by evaporation in a fume hood in a porcelain cup and with thorough stirring to a refractive index of 1.460-1.467, determined using a refractometer. The concentrated oligomer is cooled to 25-30 ° C, neutralized with a modifying catalyst based on a salt of polyfunctional acid to a pH of 8.0-8.5. The finished oligomer is poured into a storage tank. Comparative properties of urea-formaldehyde oligomers are shown in table 1.

Example 2

By mixing 15 parts by weight of caustic soda, 16 parts by weight of lactic acid and 69 parts by weight of water, we obtain a modifying catalyst based on a polyfunctional acid salt.

Then 135 parts by weight of formalin are loaded into the reaction flask, the pH of formalin is measured using a pH meter, the pH is adjusted with a modifier-catalyst based on a polyfunctional acid salt to a value of 7.0-7.5, 50 parts by weight of urea are introduced (main load) . Turn on the stirrer and heat the water bath. After complete dissolution of the urea at a temperature of 40-50 ° C, check the pH, the value of which should be in the range of 6.8-7.2. If necessary, lower the pH, ammonium chloride is added dropwise. Continue heating to 90 ÷ 92 ° C and incubated for 30 minutes. Before the end of the first synthesis step, the pH of the reaction solution is checked (in the range of 6.5-7.0). The second stage is carried out in an acidic environment. For this, the pH of the mixture is reduced with a solution of ammonium chloride to 4.2-4.5 and maintained at 90-92 ° C, stirring for 30 minutes. Cool the system to 60-65 ° C, adjusting the pH to 6.7-7.0 by adding dropwise a catalyst modifier based on a polyfunctional acid salt, without stopping mixing. 27 mass parts of urea are introduced. The reaction system is maintained at 60-65 ° and a working stirrer for 30 minutes. The resulting oligomer is concentrated by evaporation in a fume hood in a porcelain cup and with thorough stirring to a refractive index of 1.460-1.467, determined using a refractometer. The concentrated oligomer is cooled to 25-30 ° C, neutralized with a modifying catalyst based on a salt of polyfunctional acid to a pH of 8.0-8.5. The finished oligomer is poured into a storage tank.

Comparative properties of urea-formaldehyde oligomers are shown in table 1.

Example 3

By mixing 13 parts by weight of caustic potassium, 19 parts by weight of tartaric acid and 68 parts by weight of water, we obtain a modifying catalyst based on a polyfunctional acid salt.

Then 135 parts by weight of formalin are loaded into the reaction flask, the pH of formalin is measured using a pH meter, the pH is adjusted with a modifier-catalyst based on a polyfunctional acid salt to a value of 7.0-7.5, 50 parts by weight of urea are introduced (main load) . Turn on the stirrer and heat the water bath. After complete dissolution of the urea at a temperature of 40-50 ° C, check the pH, the value of which should be in the range of 6.8-7.2. If necessary, lower the pH, ammonium chloride is added dropwise. Continue heating to 90 ÷ 92 ° C and incubated for 30 minutes. Before the end of the first synthesis step, the pH of the reaction solution is checked (in the range of 6.5-7.0). The second stage is carried out in an acidic environment. For this, the pH of the mixture is reduced with a solution of ammonium chloride to 4.2-4.5 and maintained at 90-92 ° C, stirring for 30 minutes. Cool the system to 60-65 ° C, adjusting the pH to 6.7-7.0 by adding dropwise a catalyst modifier based on a polyfunctional acid salt, without stopping mixing. 27 mass parts of urea are introduced. The reaction system is maintained at 60-65 ° and a working stirrer for 30 minutes. The resulting oligomer is concentrated by evaporation in a fume hood in a porcelain cup and with thorough stirring to a refractive index of 1.460-1.467, determined using a refractometer. The concentrated oligomer is cooled to 25-30 ° C, neutralized with a modifying catalyst based on a salt of polyfunctional acid to a pH of 8.0-8.5. The finished oligomer is poured into a storage tank.

Comparative properties of urea-formaldehyde oligomers are shown in table 1.

Example 4

By mixing 14 parts by weight of caustic potassium, 16 parts by weight of citric acid and 70 parts by weight of water, we obtain a modifying catalyst based on a salt of polyfunctional acid.

Then 135 parts by weight of formalin are loaded into the reaction flask, the pH of formalin is measured using a pH meter, the pH is adjusted with a modifier-catalyst based on a polyfunctional acid salt to a value of 7.0-7.5, 50 parts by weight of urea are introduced (main load) . Turn on the stirrer and heat the water bath. After complete dissolution of the urea at a temperature of 40-50 ° C, check the pH, the value of which should be in the range of 6.8-7.2. If necessary, lower the pH, ammonium chloride is added dropwise. Continue heating to 90 ÷ 92 ° C and incubated for 30 minutes. Before the end of the first synthesis step, the pH of the reaction solution is checked (in the range of 6.5-7.0). The second stage is carried out in an acidic environment. For this, the pH of the mixture is reduced with a solution of ammonium chloride to 4.2-4.5 and maintained at 90-92 ° C, stirring for 30 minutes. Cool the system to 60-65 ° C, adjusting the pH to 6.7-7.0 by adding dropwise a catalyst modifier based on a polyfunctional acid salt, without stopping mixing. 27 mass parts of urea are introduced. The reaction system is maintained at 60-65 ° and a working stirrer for 30 minutes. The resulting oligomer is concentrated by evaporation in a fume hood in a porcelain cup and with thorough stirring to a refractive index of 1.460-1.467, determined using a refractometer. The concentrated oligomer is cooled to 25-30 ° C, neutralized with a modifying catalyst based on a salt of polyfunctional acid to a pH of 8.0-8.5. The finished oligomer is poured into a storage tank.

Comparative properties of urea-formaldehyde oligomers are shown in table 1.

Thus, the invention allows to obtain low toxic urea-formaldehyde oligomers.

Table 1 Comparative properties of urea-formaldehyde oligomers Properties of Oligomers Example 1 Example 2 Example 3 Example 4 The closest analogue The solids content at 105 ° C,% 66 68 65 67 66 ± 2 Hydrogen indicator, units pH 7.4 7.3 7.7 7.5 7.3 Conditional viscosity according to B3-4 at 20 ° С 89 91 90 93 95 The content of free formaldehyde,% 0.12 0.15 0.11 0.12 0.30 Gelatinization time at 100 °, sec 45 46 44 49 53

Claims (1)

A method of manufacturing a urea-formaldehyde oligomer, comprising loading formalin, neutralizing it to pH 7.0-7.5 with a modifier-catalyst based on a polyfunctional acid salt, introducing urea, after dissolving the urea, if necessary, lower the pH to 6.8-7.2 with ammonium chloride with followed by heating to 90-92 ° C and holding for 30 minutes, followed by lowering the pH of the mixture with a solution of ammonium chloride to 4.2-4.5 and holding at 90-92 ° C with stirring for 30 minutes, cooling to 60- 65 ° C, adjusting the pH to 6.7-7.0, adding with stirring the introduction of a modifier catalyst based on a polyfunctional acid salt, the introduction of urea and aging at 60-65 ° C with stirring for 30 minutes to obtain an oligomer and its neutralization by a modifier-catalyst based on a polyfunctional acid salt to a pH of 8.0-8.5, characterized in that as a modifier-catalyst based on a salt of polyfunctional acid using a modifier obtained by mixing caustic soda or potassium, lactic or tartaric acid and water, with a ratio of components, parts by weight:
Caustic Soda or Potassium 13-15 Lactic or tartaric acid 16-19 Water 68-69