RU2150478C1 - Method of preparing carbamido-formaldehyde filler - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: described is method of preparing carbamidoformaldehyde polymer which includes finely dispersed particles of cross-linked carbamidoformaldehyde polymer which are used as white synthetic fillers for polymers, paper and paint materials. Carbamide is reacted with carbamidoformaldehyde concentrate containing 54-60 wt.% of formaldehyde, 20-24 wt.% of carbamide and up to 100 wt.% of aqueous phase balance comprising branched oligomer in the presence of phosphoric acid. Reaction is carried out at elevated temperature. The resulting suspension is then neutralized with mixture of chalk and stillage residue resulting from distillation of monoethanol amine spent during purification of gas being converted from carbon dioxide in ammonia production. After separation of deposit, filtrate is recycled into process for partial substitution of water. Chalk to stillage reside weight ratio is 5:1-1:5, industrial of natural chalk is used, and desalted water is used for producing aqueous medium. EFFECT: increased yield of the desired product, reduced oil absorption and lower price of the product. 4 cl, 12 ex, 3 tbl

Description

 The invention relates to methods for producing fine particles of crosslinked urea-formaldehyde polymers, which are used as synthetic white fillers for polymers, paper, paints and varnishes.

 Known methods for producing urea-formaldehyde polymers by reacting urea and formaldehyde in an aqueous medium in the presence of alkaline and acidic components to obtain polymers in dry or dissolved form [A. F. Nikolaev. Technology of plastics. M., "Chemistry", 1997, p. 148-154].

 However, urea-formaldehyde polymers obtained by known methods do not find application as white polymer fillers, but are widely used as binders in press powders, for impregnation and gluing of heat-insulating, electrical insulating and other materials.

 A known method of producing a urea-formaldehyde polymer by reacting formalin and urea in an alkaline medium, then acidifying the main solution of the prepolymer and forming finely dispersed polymer particles in the form of spherical beads in the presence of colloid-forming material. The urea-formaldehyde polymer is used as a filler, in particular for paints and varnishes [US Patent N 3850868, 1971, MKI C 08 G 37/08].

 The disadvantages of the method are the low yield of the product (not more than 66%), pollution of wastewater with industrial waste.

 The closest in technical essence and the achieved effect is a method of producing a filler for paper pulp by reacting urea with a formaldehyde-containing reagent in an aqueous medium, in the presence of sulfuric acid at elevated temperature, neutralizing the resulting suspension and filtering the precipitate. As the formaldehyde-containing reagent, bottoms of methanol rectification from the tar resin from the production of urea-formaldehyde resin are used [A. with. USSR N 1010171, MKI 4 D 21 H 3/52, D 21 D 3/00, BI N 13, 1983 - prototype].

 The disadvantages of the prototype are the low yield of the target product in relation to the spent raw materials, low output per unit of the reaction volume, loss of reagents and their pollution of wastewater, neutralization of the suspension with pure reagents makes the process more expensive. The resulting filler has a high oil absorption, which limits its use.

 The basis of the invention is the task of improving the method of producing a urea-formaldehyde filler by reacting urea with a formaldehyde-containing component in an aqueous medium in the presence of phosphoric acid at elevated temperature, neutralizing the suspension with a mixture of chalk with a bottom residue of distillation of monoethanolamine, spent on purification of the converted gas from carbon dioxide in the production of ammonia sediment and return of the aqueous filtrate to prepare the initial reaction m ssy, which provides higher yield of the finished product in general, and the reaction volume unit, reducing oil absorption of the filler, with the exception of wastewater and reagent losses and waste disposal.

 The problem is solved by the interaction of urea with a formaldehyde-containing component in an aqueous medium in the presence of an acid catalyst at an elevated temperature, neutralizing the resulting suspension and filtering the precipitate according to the method, as a formaldehyde-containing component, a urea-formaldehyde concentrate containing 54-60 wt.% Formaldehyde, 20-24 wt. % urea and the rest up to 100 wt.% the aqueous phase, including the branched oligomer, as an acid catalyst - phosphoric acid, neutralization The suspension obtained is carried out with a mixture of chalk and distillation residue of monoethanolamine, which was spent during the purification of the convertible gas from carbon dioxide in the production of ammonia, and the aqueous filtrate is returned to the process to partially replace water after separation of the precipitate, the chalk used is technical or natural, and neutralization is carried out a mixture of chalk and distillation residue of monoethanolamine distillation at a mass ratio of 5: 1-1: 5, desalted water is used to create an aqueous medium.

 The use in the proposed method as a formaldehyde-containing component of a urea-formaldehyde concentrate with a high content of branched oligomers and formaldehyde in combination with a selected catalyst and neutralizing reagents at a certain ratio allows increasing the filler yield with respect to the initial carbamide and formaldehyde, and from a unit of the reaction volume due to the formation of white dispersed phosphates from neutralizing agents, as well as the performance of technological equipment education. The presence of branched oligomers in CPC causes the formation of a three-dimensional structure and reduces the oil absorption of the product, the latter expands the scope of application of the filler. The totality of the proposed reagents does not lead to the accumulation of pollution in the aquatic environment, and this allows you to repeatedly return the spent aqueous medium, after separation of the fine particles, to prepare the initial reaction mass, excluding wastewater and loss of reagents with them.

 With the introduction of the bottom residue of the distillation of spent monoethanolamine to neutralize the suspension, production waste is disposed of and the need for commercial reagents is eliminated.

 The proposed method is implemented in this way.

In a reactor equipped with a stirrer and a jacket for heating and cooling, 80 l of demineralized water and 46.2 kg of urea are loaded. The resulting solution was heated to 80 ^° C. by supplying hot water to the jacket of the reactor, acidified to pH 2.0-2.15 by the addition of phosphoric acid, and a separately prepared solution of 38.5 kg of CPA in 40 L of demineralized water was quickly added. The reaction mixture is kept under these conditions for 0.5-1 hour until the residual formaldehyde content in the aqueous phase is not more than 75 mg / L. Then the suspension is cooled to 30-35 ^o C and neutralized by feeding a mixture of chalk with a distillation residue of spent MEA to a pH of 6.5-7.0. The solid white insoluble product is separated by filtration, dried (if necessary) and analyzed for compliance with TU U 3.01 013-93 "Polymer filler". The filtrate of the aqueous phase is collected in a separate container. Characteristics of raw materials:
- KFK TU U 6-05761614.005-96 "Urea-formaldehyde concentrate." The urea-formaldehyde concentrate is obtained by the catalytic oxidation of methyl alcohol, followed by absorption of formaldehyde with an aqueous urea solution, and is a colorless, transparent viscous liquid with a pungent irritating odor. Urea-formaldehyde concentrate contains components in the following ratio, wt.%:
Urea - 20-24
Formaldehyde - 54-60
The aqueous phase, including a branched oligomer - Rest
- urea according to GOST 2081-92;
- phosphoric acid according to GOST 6552-80;
- technical chalk according to GOST 17498-72 (calcium carbonates with magnesium 95-99%);
- distillation residue of spent monoethanolamine (KODO MEA), wt.%:
IEA - 20-30
Amine type resin - 30-40
Potassium carbonate - 10-20
Water - Else
Table 1 shows the characteristics of raw materials, in table 2 - finished products, in table 3 - the results from the use of methods.

Example 1. In a reactor equipped with a stirrer and a jacket for heating and cooling, load 80 l of demineralized water and 46.2 kg of urea. The resulting solution is heated to 80 ^o C by supplying hot water to the jacket of the reactor, acidified to pH 2.0-2.15 by the addition of phosphoric acid, and a separately prepared solution of 38.5 kg of CPA containing 60% formaldehyde and 24% urea in 40 l is quickly added. demineralized water. The reaction mixture is kept under these conditions for 0.5-1 hours to a residual formaldehyde content in the aqueous phase of not more than 75 mg / L. The suspension is neutralized by feeding a mixture of technical chalk with KODO MEA at a ratio of 5: 1 to a pH of 6.5-7.0.

The output is, kg:
Urea-formaldehyde filler (CFN paste) with a humidity of 45% - 150
The filtrate of the aqueous phase (FVF) - 70
The composition of the filtrate of the aqueous phase (FVF), g / l:
Residual urea - 22.3
Soluble products containing methylol groups, in terms of formaldehyde - 1.53
Dense residue - 90.4
IEA - Absence
The total cost of the filler decreased by 23%. The results are shown in tables 1-3.

 The resulting KFN paste is used in the production of water-dispersion paint brand VD-VA (GOST 28196-89) instead of titanium white in the amount of 50% of the prescription amount of titanium white. The quality of the paint meets the requirements of GOST 28196-89, the weather resistance of the coating increased by 2 times.

 The dried urea-formaldehyde filler (CFN) is introduced into polystyrene paint (TU U 05761614.004-96) instead of titanium dioxide in the amount of 50% of the prescription requirement. The quality of the paint corresponds to TU U 05761614.004-96, the weather resistance is 3 times higher.

 Example 2. Analogously to example 1. CPK with a formaldehyde content of 58% and urea 22%. As the aqueous phase load 70 kg of FVF according to example 1 and 50 l of demineralized water. The resulting suspension is neutralized with a mixture of chalk with KODO MEA in a mass ratio of 1: 1. The results are given in tables 1-3. The resulting KFN paste is used in the manufacture of water-dispersion paint, and dried urea-formaldehyde filler is used for polystyrene paint. The results are similar to example 1.

 Example 3. Analogously to example 1. CPK with a formaldehyde content of 54% and urea 20%. As the aqueous phase, 65 kg of FVF according to example 2 and 55 l of demineralized water. The resulting suspension is neutralized with a mixture of natural chalk with KODO MEA in a mass ratio of 1: 5. The results are given in tables 1-3. The resulting KFN paste is used in the manufacture of water-dispersion paint, and dried urea-formaldehyde filler is used for polystyrene paint. The results are similar to example 1.

 Example 4 (control). Analogously to example 1. As the aqueous phase load 62 kg of FVF according to example 3 and 58 l of demineralized water. The resulting suspension is neutralized KODO MEA (tables 1-3).

 Example 5 (control). Analogously to example 1. As the aqueous phase load 62 kg of FVF and 58 l of demineralized water (according to example 4). The resulting suspension is neutralized with chalk, foaming is observed, the duration of the neutralization process is increased by 2 times. The results are in tables 1-3.

 Example 6 (control). Analogously to example 1. As formaldehyde-containing reagent using commercial formaldehyde, in which 37% formaldehyde. The results are shown in tables 1-3.

 Example 7 (control). Analogously to example 1. Sulfuric acid was used as a catalyst. The results are given in tables 1-3. The resulting product clumped, its rigidity increased, which worsened the quality of the filler.

 Example 8 (control). Analogously to example 1. The neutralization of the resulting suspension are sodium hydroxide. Sludge filtration is deteriorating. The results are given in tables 1-3.

 Example 9. Analogously to example 1. CPK with a formaldehyde content of 58% and urea 22%. As the aqueous phase, 70 kg of FVF and 50 L of demineralized water are charged in accordance with Example 2. The resulting suspension is neutralized with a mixture of chalk with KODO MEA in a weight ratio of 1: 6. The results are given in tables 1-3.

 Example 10. Analogously to example 9. The resulting suspension is neutralized with a mixture of chalk with KODO MEA in a mass ratio of 5: 0.8. The product is highly compacted and prone to clumping. The results are given in tables 1-3.

 Example 11. Analogously to example 1. CPK with a formaldehyde content of 58% and urea 22%. As the aqueous phase, 70 kg of PF and 50 L of demineralized water are charged as in Example 2. The resulting suspension is neutralized with a mixture of chalk with KODO MEA in a weight ratio of 0.8: 5. The results are given in tables 1-3.

 Example 12. analogously to example 11. The resulting suspension is neutralized with a mixture of chalk with KODO MEA in a mass ratio of 6: 1.0. The product is heavily rammed, prone to clumping (tab. 1-3).

 Examples 4-8 (control) and 9-12 confirm that outside the proposed method, the achieved effect is lost. An exception to the chalk formulation (Example 4) increases the toxicity of the product because an MEA residue appears in the aqueous phase. With the exclusion of the bottom residue from the formulation (Example 5), the process of neutralizing the reaction mixture worsens, its duration doubles. The replacement of formaldehyde-containing reagent with commercial formaldehyde (example 6) reduces the yield of the product. Replacement of the catalyst (example 7) affects the quality of the filler. The use of alkali to neutralize the suspension (example 8) affects the filtering process of the precipitate. It is impractical to introduce, to neutralize, beyond the stated ratio, the CODE MEA (examples 9, 10) and chalk (examples 11, 12), because there is an overspending of raw materials (examples 10, 12) or an excess of KODO MEA (examples 9, 11) that did not react at the stage of neutralization, returns to the reaction volume again, and this will require the cost of adjusting the ratio between the catalyst and neutralizing agents in subsequent cycles.

 The data (see tables 1-3) show that in the proposed method (examples 1-3) compared with the prototype, an increase in the yield of the target product is achieved by 13% and 18% per unit reaction volume, the oil absorption of the product is reduced by 41.7 % and the total cost of 23%, which allows you to use the product as a filler for polystyrene and water-dispersion paints. Wastewater emissions are eliminated, losses associated with effluents are eliminated. Recycled ammonia production waste - KODO MEA.

Claims (4)

 1. A method of producing a urea-formaldehyde filler by reacting a urea with a formaldehyde-containing component in an aqueous medium in the presence of an acid catalyst at elevated temperature, neutralizing the resulting suspension and filtering the precipitate, characterized in that a urea-formaldehyde concentrate containing 54-60 wt.% Formaldehyde is used as a formaldehyde-containing component 20 to 24 wt.% Urea and the rest up to 100 wt. % of the aqueous phase, including the branched oligomer, phosphoric acid as the acid catalyst, neutralization of the resulting suspension is carried out with a mixture of chalk and distillation residue of monoethanolamine, spent on purification of the convertible gas from carbon dioxide in the production of ammonia, and the aqueous filtrate is returned to the process for separation of the precipitate partial replacement of water.  2. The method according to p. 1, characterized in that the chalk is technical or natural.  3. The method according to claim 1, characterized in that the neutralization is carried out with a mixture of chalk and distillation residue of monoethanolamine distillation at a mass ratio of 5: 1 to 1: 5.  4. The method according to claim 1, characterized in that desalted water is used to create an aqueous medium.

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