RU2287356C1 - Method of production of filter material - Google Patents

Abstract

FIELD: production of filter materials on base of three-dimensional globular polymers; water filtration systems.

SUBSTANCE: proposed method includes poly-condensation of carbamide and aldehyde in presence of acid and forming of resin at cooling and holding till complete hardening; furfural is used as aldehyde; poly-condensation is carried out at heating till dynamic viscosity of solution gets equal to 40-50 mPs; cooling is performed at rate making it possible to obtain material at average diameter of pores of 1-4 mcm.

EFFECT: enhanced efficiency; possibility of producing pure material.

12 cl, 4 tbl, 4 ex

Description

The invention relates to a technology for the manufacture of filter materials based on polymers of a spatially globular structure (hereinafter ASG polymers) and can be used in water filtration systems.

The PGS polymer is a highly permeable article that is not melting and insoluble in ordinary solvents, the structure of which is formed by interconnected microglobules that form a regular spatial structure. The average pore size can be 0.1-10 microns. A large unfolded surface (up to 100-150 m ² / g), a narrow range of pore size distribution (usually 10%) give these materials good mechanical and technological properties and allow their use as filter baffles.

The structure and properties of the most famous PGS polymers are disclosed, in particular, in the Encyclopedia of Polymers, M .: Soviet Encyclopedia, 1972, p. 652-658.

The prior art method for producing filter material in the form of an ASG polymer based on urea-formaldehyde resin [1], which is the closest to the claimed solution and selected by the applicant as a prototype. The known method includes the following steps:

- polycondensation of urea and formaldehyde without heating;

- molding the resulting resin with cooling and holding until the polymer has cured in a sealed form for 10-50 minutes at 15-25 ° C;

- the use for the implementation of the method of an aqueous solution of urea with a concentration of 250-600 g / l, formaldehyde and an acid catalyst with their mass ratio equal to 1: (0.5-1.0) :( 0.01-0.12), respectively;

- simultaneous polycondensation and molding.

The known method is simple to implement and consists in the fact that an aqueous solution of urea, formalin, acid (catalyst) is poured into a container of the desired shape and the resulting mixture is kept under static conditions. Exothermic heating of the solution takes place, which is then cooled. In 10-50 minutes, a urea product of any given shape and various purposes is synthesized.

The method allows to obtain thick-walled tubes of a macroporous globular structure with a pore size set in the range of 0.5-10 μm, effective when used as dividing walls during filtration. However, the known technology does not meet the increased requirements for environmental safety, because based on the use of formaldehyde resin. A significant amount of toxic formaldehyde is released from the ASG of the polymer obtained in a known manner into the environment, as a result of which the field of application of products from this polymer is significantly narrowed. ASG polymers are highly effective filtering materials for the purification of mechanical and chemical impurities from aqueous and organic solutions, however, the presence of formaldehyde in the filtrate belonging to hazard class 2 substances is generally not allowed. In addition, when using a urea-formaldehyde ASG polymer as a filter material, expensive equipment is needed to remove formaldehyde from the filtrate.

It should be noted that the disposal of spent filter products from urea-formaldehyde ASG polymer due to the constant release of formaldehyde into the environment by the polymer is also a laborious process.

The objective of the invention is to provide a method that provides a more safe sanitary standards and rules in the conditions of production and operation of the filter material in the form of an ASG polymer based on urea and aldehyde, which does not require additional purification of filtrates and wastewater of a similar production from toxic substances, as well as energy-intensive recycling.

The technical result is achieved by the fact that in the method of manufacturing the filter material, including polycondensation of urea and aldehyde in the presence of acid and molding the resulting resin with cooling and holding until complete curing, furfural is used as the aldehyde, polycondensation is carried out by heating until the solution has a dynamic viscosity equal to 40-50 MP, and cooling is carried out at a speed that allows you to get a material with an average pore diameter in the range of 1-4 microns. In an embodiment of the method, polycondensation and molding are carried out in one and the same tank, which performs the function of a reactor and equipment. In an embodiment of the method, the polycondensation is carried out in the reactor when heated and when the dynamic viscosity of the solution reaches 40-50 mP, the mold is bottled and cooled under the conditions indicated above. Those. in this case, polycondensation and molding are carried out in different containers - polycondensation in the reactor, and molding in the form (equipment), which allows to obtain a product of a given shape.

The authors also found that the polycondensation of urea and furfural in the presence of iron salts in the process of manufacturing a new ASG polymer can significantly reduce the migration of furfural to the aquatic environment. This conclusion is based, in particular, on the following experimental results:

- in the synthesis of furfural-urea-PGS polymer in the case of adding iron salts, for example, iron sulfate (2+), to the reaction mass, the concentration in the reaction mass is 0.05 M, furfural migration from the material used as a filter medium of 0.6 l (s the density of the dry polymer 300 g / dm ³ ) in 1 liter of water at room temperature is - 3 mg / l per day.

- when iron salts, for example, iron sulfate (2+) are added to the reaction mass to a concentration of 0.15 M in the reaction mass, furfural migration from the filter medium material with a volume of 0.6 l (with a dry polymer density of 300 g / dm ³ ) in 1 l of water at room temperature is - 1-2 mg / l per day.

With the addition of an iron salt of less than 0.05 M, furfural migration is more than 3 mg / l per day. With the addition of an iron salt of more than 0.15 M, furfural migration does not significantly decrease compared to the achieved level.

At the same time, the authors found that the addition of an iron salt has almost no effect on the strength of the polymer and the average pore diameter in it and in the absence of an iron salt, with all other conditions unchanged, these polymer characteristics are reproduced in the range of ± 10%.

Acid, as in the known method, is a catalyst for the process. The most suitable catalysts are hydrochloric and sulfuric acids.

It should be noted that the introduction of furfural instead of formaldehyde requires a significant change in the process parameters that are not obvious to a specialist, since the formation of a spatially globular polymer structure in this case is complicated by the following processes:

1) It is possible to separate the organic and aqueous phases during the synthesis of ASO polymer, with the formation in the organic phase of a resin that does not have a highly developed system of open pores.

2) The decrease in the properties of the final product associated with the need to remove the organic solvent from the volume of the ASG polymer after it has cured.

The essence of the proposed method consists in the fact that furfural is used as the aldehyde, polycondensation of urea and furfural solutions is carried out by heating in an acidic medium until the dynamic viscosity of the polymer solution reaches 40-50 mP. The molding is carried out by cooling the specified solution in the reactor or poured into molds to room temperature at a speed that allows to obtain a material with an average pore size of 1-4 microns. Finished products have a given geometric shape, porosity of 60-75% and a compressive strength of at least 0.8 MPa.

The authors established not only the process parameters necessary for the manufacture of less toxic urea-furfural PGS polymer, but also the conditions providing high filtration ability of the new filter material. The effect of the cooling rate on the average pore size and strength is illustrated by the data in Table. one.

Tab. one Porosity,% Cooling rate: The average pore diameter, microns The limit of compressive strength, MPa 70 0.1-0.2 ° C / min four 0.9 68 0.4-0.6 ° C / min 2 1,5 65 0.7-1 ° C / min one 2

The optimal parameters of the manufacturing process of the filter material are the following parameters:

- for polycondensation - heating to T = 30-45 ° C

- mass ratio of components: furfural - 1 ... (0.8-1.2), urea 0.65 ... (0.52-0.78), organic solvent 1 ... (0.8-1 , 2), hydrochloric acid (conc.) 0.1 ... (0.08-0.12), water 2 ... (1.6-2.4), FeSO ₄ · 5H ₂ O - 0.15 ... (0.1-0.2).

The inventive method allows to obtain highly porous, having sufficient mechanical strength of the ASG polymer with a highly developed system of open pores with an average diameter in a given range of values.

The presence of ASG structure was established by microscopic examination of samples of the finished polymer. Evaluation of pore sizes was carried out according to the known method of permeability [2] (based on the Kozeni-Karman equation), which consists in examining the dependence of the passing volume of water (in l / min) through a filter baffle made of a polymer obtained in accordance with the invention , from the water pressure applied at the inlet.

The new filtering material from urea-furfural PGS polymer has an average pore diameter in the range from 1 to 4 microns.

The prior art methods for producing resins by condensation of furfural with urea, in particular in the form of non-melting, resistant to dilute alkalis and acids, black-brown resins [3] or in the form of viscous bitumen-like products that cure in the presence of acid [4].

It should be noted that for the implementation of the methods disclosed in all the mentioned sources, expensive and energy-intensive equipment is required for carrying out condensation processes in the temperature range 100-160 ° C, and the resulting resins can be used exclusively as a binder, for example, in the production of pressing materials and not relate to ASG polymers. ASG polymers made according to the claimed invention can be used as a filter medium for aqueous solutions, organic solvents and gas streams.

The inventive method allows to obtain a PGS polymer with a different average pore diameter and permeability with respect to aqueous solutions, environmentally friendly, since low toxic substances are used in the process (furfural refers to environmentally hazardous substances), and features of the polymer manufacturing process with additional introduction of iron salts significantly reduce the diffusion of furfural in the filtrate.

For the implementation of the method, the following components are optimal:

Furfural ..., imp. (CAS 98-01-1, EEC 605-010-00-4)

Urea ..., GOST 2081 -92

Hydrochloric acid ..., GOST 3118-77

Ethyl alcohol ... 96%

FeSO ₄ · 5H ₂ O (Vitriol iron technical) - GOST 6981-94

The individual stages of the process are controlled by the following methods:

1. the viscosity of the solution - using a viscometer;

2. End of exposure - using a thermometer located in the inner tube of the mold;

3. end of cooling - with the help of a thermometer located in the inner tube of the mold;

4. The cooling rate is set by controlling the temperature in the production room using thermostats.

The invention is illustrated by the following examples.

Example 1

In a reactor with a volume of 1.5 l, with a stirrer and a cooling system, 420 ml of water, 240 ml of ethanol (96%), 20 ml of conc. hydrochloric acid, 120 g of urea. 200 ml of furfural is added to the resulting solution heated to 40 ° C. The solution is heated until a viscosity of 40 mP is reached and poured into cylindrical vessels made of polyethylene with a rod fixed strictly in the center. The molds are cooled with a polymer solution at a rate of 0.1-0.2 ° C / min to 20 ° C and held for 4 hours at this temperature. Then the molds, to complete the curing process of the polymer, are placed in a heating cabinet with a temperature of 60 ° C for 16 hours.

The blanks are removed from the molds and, if necessary, machined to give the desired shape.

The density of the dry polymer 291 g / DM ^{3 the} average pore size of 4 microns.

Example 2

340 ml of water, 200 ml of ethanol (96%), 18 ml of conc. Are placed in a 1 liter reactor with a stirrer and a cooling system. hydrochloric acid, 100 g of urea. 175 ml of furfural are added to the resulting solution, heated to 40 ° C. Maintain the temperature of the reaction mixture in the range of 30-40 ° C for 40 minutes until reaching a viscosity of 45 MP. The solution is poured into molds similarly to Example 1 and cooled at a rate of 0.4-0.6 ° C / min to 20 ° C, then kept for 4 hours at this temperature.

To complete the polymer curing process, place the blanks in a heating cabinet with a temperature of 60 ° C for 16 hours. Take the blanks from the molds and, if necessary, carry out the fur. processing to give the desired shape. The density of the dry polymer 309 g / DM ^{3 the} average pore size of 2 microns.

Example 3

In a 1 L reactor, with a stirrer and cooling system, 320 ml of water, 180 ml of ethanol (96%), 20 ml of conc. hydrochloric acid and 120 g of urea and 14 g of FeSO ₄ · 5H ₂ O. 175 ml of furfural is added to the resulting solution, heated to 40 ° C. Maintain the temperature of the reaction mixture in the range of 35-45 ° C for 40 minutes until a viscosity of 50 mP is reached. The polymer solution is bottled in the forms analogous to Example 1. The polymer solution is cooled at a rate of 0.7-1 ° C / min to 20 ° C and kept for 4 hours at this temperature. To complete the polymer curing process, place the blanks in a heating cabinet with a temperature of 60 ° C for 16 hours.

The blanks are removed from the molds and, if necessary, machined to give the desired shape. The density of the dry polymer 337 g / DM ^{3 the} average pore size of 1 μm.

Example 4

320 ml of water, 180 ml of ethanol (96%), 20 ml of concentrated hydrochloric acid and 120 g of urea and 40 g of FeSO ₄ · 5H ₂ O are placed in a 1 liter cylinder with a stirrer and a cooling system. To the resulting solution, heated to 40 ° C poured 175 ml of furfural. Maintain the temperature of the reaction mixture in the range of 35-45 ° C for 40 minutes until a viscosity of 50 mP is reached. Remove the mixing device. Cool the cylinder with the polymer solution at a rate of 0.7-1 ° C / min. to 20 ° C and incubated for 4 hours at this temperature. Then, to complete the curing process of the polymer, the filled cylinder is kept in a temperature cabinet with a temperature of 60 ° C for 16 hours. The billet is removed from the cylinder and machined to give it the desired shape. The density of the dry polymer 337 g / DM ^{3 the} average pore size of 1 μm.

Filter materials manufactured in accordance with Examples 1-4 in the form of hollow cylinders with a height of 150 mm, a diameter of 75 mm and a volume of 550 ml were tested with a positive result.

During the filtration process, water (tap water of the centralized drinking water supply system, water temperature corresponds to the temperature in the water supply network) enters the cylinder (average pore diameter is 1-4 μm), seeps through the pores and enters the container to collect the filtrate.

Model solutions corresponded to the requirements of GOST R 51871 2002 "Water-purifying devices. General requirements for efficiency and methods for its determination."

Water was passed through 10 l at intervals of 1 hour. Every 50 L of effluent was subjected to chemical analysis. The test results in dynamics are presented in Table 2.

Tab. 2 Water passed through the filter cartridge, l pH Turbidity Free chlorine, mg / l PMO ^* , mg O ₂ / l [Fe ^{+2, +3} ], mg / l Source water 6.7 0.9 0.4 3.0 0.5 twenty 6.1 0 0 2.0 0.05 150 6.1 0 0 2,5 0.05 500 6.15 0 0 3.0 0.05 1000 6.6 0 0.01 3.0 0.05 1500 6.6 0.1 0,07 3.0 0.1 2000 6.6 0.3 0.15 3.0 0.3 Note: the filtrate transmission rate is 1.5 l / min.

The results of water purification by a filter cartridge from a material taken as a prototype are presented in Table. 3. The tests were carried out under the same conditions as the inventive filter material.

Tab. 3 Water passed through the filter cartridge, l pH [Fe ^{+2, +3} ], mg / l Free chlorine, mg / l PMO ^* , mg O ₂ / l Turbidity Unit / L Source water 6.7 0.5 0.4 3.0 0.9 twenty 7.0 0.09 0.1 10 0 150 7.3 0.12 0.1 9 0 500 7.1 0.15 0.08 9 0 1000 7.4 0.20 0.11 7 0 1500 7.0 0.13 0.14 6 0.1 2000 7.1 0.18 0.12 6 0.3 Note: the filtrate transmission rate is 1.5 l / min.

Water analysis was carried out in accordance with the following requirements:

Tab. four No. Defined parameter MPC SanPiN 2.1.4.1074-01 DKM, GN.2.3.3.972-00 Test methods one Total iron, mg / l 0.3 MU 08-47 / 104 2 Turbidity, EMF 2.6 GOST 3351-74 3 Permanganate oxidizability (PMO), mg O ₂ / l 5.0 PNDF 14.2: 4.154-99 four Chlorine, mg / L free 0.3 GOST 18190-72 5 pH 6-9 GOST 2874-82 The transmission rate of water is 1.5 l / min.

The optimal process parameters presented in the description do not exclude the introduction of changes while maintaining the essence of the invention.

Information sources

1. SU 1162822, C 08 G 12/12 - prototype.

2. Mulder M. Introduction to membrane technology. M., 1999.

3. Patent of England No. 293871, 1929.

4. Moshinska N.K. "Chemical. Industry", 1963, 1.

Claims (12)

1. A method of manufacturing a filter material, including polycondensation of urea and aldehyde solutions in the presence of acid and molding the resulting resin with cooling and holding until the polymer has completely cured, characterized in that furfural is used as an aldehyde, polycondensation is carried out by heating until the solution reaches a dynamic viscosity of 40 -50 MP, and cooling is carried out at a speed that provides a material with an average pore diameter in the range of 1-4 microns. 2. The method according to claim 1, characterized in that the polycondensation is carried out in the presence of iron salts. 3. The method according to claim 1 or 2, characterized in that the polycondensation is carried out by heating in the temperature range of 20-40 ° C. 4. The method according to claim 2, characterized in that iron sulfate is used as an iron salt in an amount of 0.05-0.15 M. 5. The method according to claim 1 or 2, characterized in that the polycondensation and molding is carried out in different containers. 6. The method according to claim 1 or 2, characterized in that the polycondensation and molding is carried out in one tank. 7. The method according to claim 1, characterized in that in order to obtain an average pore diameter of 1 μm, cooling is performed at a rate of 0.1-0.3 ° C / min with a mass ratio of components in the reaction mixture in the range of: furfural - 0.8 -1.2: urea 0.52-0.78: organic solvent 0.8-1.2: hydrochloric acid (conc.) - 0.08-0.12: water 1.6-2.4. 8. The method according to claim 2, characterized in that in order to obtain an average pore diameter of 1 μm, cooling is performed at a rate of 0.1-0.3 ° C / min with a mass ratio of components in the reaction mixture in the range of: furfural - 0.8 -1.2: urea 0.52-0.78: organic solvent 0.8-1.2; hydrochloric acid (conc.) - 0.08-0.12: water 1.6-2.4: FeSO ₄ · 5H ₂ O 0.1-0.2. 9. The method according to claim 1, characterized in that in order to obtain an average pore diameter of 2 μm, cooling is performed at a rate of 0.3-0.5 ° C / min with a mass ratio of components in the reaction mixture in the range of: furfural - 0.8- 1.2: urea 0.52-0.78: organic solvent 0.8-1.2, hydrochloric acid (conc.) 0.08-0.12: water 1.6-2.4. 10. The method according to claim 2, characterized in that in order to obtain an average pore diameter of 2 μm, cooling is performed at a rate of 0.3-0.5 ° C / min with a mass ratio of components in the reaction mixture in the range of: furfural - 0.8- 1.2: urea 0.52-0.78: organic solvent 0.8-1.2: hydrochloric acid (conc.) - 0.08-0.12: water 1.6-2.4: FeSO ₄ 5H ₂ O — 0.1-0.2. 11. The method according to claim 1, characterized in that in order to obtain an average pore diameter of 4 μm, cooling is performed at a rate of 1-0.5 ° C / min with a mass ratio of components in the reaction mixture in the range of: furfural - 0.8-1, 2: urea 0.52-0.78: organic solvent 0.8-1.2: hydrochloric acid (conc.) - 0.08-0.12: water 1.6-2.4. 12. The method according to claim 2, characterized in that in order to obtain an average pore diameter of 4 μm, cooling is performed at a rate of 1-0.5 ° C / min with a mass ratio of components in the reaction mixture in the range of: furfural - 0.8-1, 2: urea 0.52-0.78: organic solvent 0.8-1.2: hydrochloric acid (conc.) - 0.08-0.12: water 1.6-2.4: FeSO ₄ · 5H ₂ O is 0.1-0.2.