RU2594215C1 - Method of producing water-re-dispersible polymer powder - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to method for production of re-dispersible polymers, which can be used as waterproofing agents for sand, clay, paper, textile, for producing protective coatings, dry construction mixtures and other purposes. Method involves obtaining polymerisation of re-dispersible polymer powder of butyl acrylate, styrene and glycidyl methacrylate in autoclave in medium of supercritical carbon dioxide at temperature of 60-65 °C and pressure of 370-440 atm. Initiator of polymerisation process is 2.2′-azoisobutyronitrile. To increase re-dispersing polymer powder used is modified acetacetic groups polyvinyl alcohol with extent of saponification from 90 to 99.8 mol. %, average polymerisation degree from 50 up to 2000 and etherification degree acetacetic acid from 0.01 to 10 mol. %.

EFFECT: invention enables to obtain re-dispersible polymers using simple process scheme with preservation of their high operational characteristics.

1 cl, 3 ex

Description

The invention relates to the field of production of polymeric materials, and in particular to a method for the production of water redispersible polymers that can be used as water repellents for sand, clay, paper, textiles, for obtaining protective coatings, dry building mixes and other purposes. Redispersible polymers are polymer powders capable of forming stable aqueous dispersions when combined with water.

Known methods for producing redispersible polymers [RU 2411266, C08L 29/04, 02/10/2011, RU 2417234, C08F 8/00, 04/27/2011, RU 98118234, C08F 2/20, 09/12/1997], which reduce to the polymerization of monomers in water or organic solvents. The polymers are then isolated from aqueous or organic dispersions.

From [RU 2371450, C08F 210/00, 10.27.2009], various methods are known for isolating a redispersible polymer from dispersions, such as, for example, drying in a fluidized bed, drying in a thin layer (drying in a roller dryer), freeze-drying, and freeze-drying or spray drying. Of these, spray drying is preferred.

From [RU 2210576, C08J 3/12, 08/20/2003] a method is known for producing a redispersible polymer powder by precipitation from a dispersion, followed by drying and grinding.

The production of redispersible polymers by the described methods causes a large amount of production waste - organic solvents and water - which must subsequently be disposed of. It should be noted that the main method for separating redispersible polymer powders from dispersions is energy-intensive and requires special hardware design.

The closest in technical essence and the achieved result is a method of producing redispersible polymers in an aqueous dispersion followed by spray drying to isolate the polymer [RU 2411266, C08L 29/04, 02/10/2011], which is selected as the prototype.

According to this method, a dispersion medium is prepared in a stainless steel reaction vessel equipped with a stirrer and reflux condenser, that is, water and polyvinyl alcohol modified with acetoacetic groups are loaded with a saponification degree from 90 to 99.8 mol. %, an average degree of polymerization from about 50 to 2000 and a degree of esterification with acetoacetic acid of 0.01 to 10 mol. % Then, the resulting mixture is heated to 85 ° C to dissolve polyvinyl alcohol in water. Then, at a constant temperature of 80 ° C, a mixture of previously prepared butyl acrylate, styrene and glycidyl methacrylate monomers with a weight ratio of 54.5 / 44.5 / 1 is introduced into the reaction vessel. To initiate polymerization, ammonium persulfate is introduced into the reaction vessel for 1 hour. Then, the remaining amount of the monomer mixture is added dropwise to the reaction vessel over 4 hours to maintain the polymerization, with additional addition of ammonium persulfate as the polymerization initiator. Upon completion of the addition of the monomer mixture, the reaction mixture was kept at the same temperature for 1 hour and a 20% aqueous solution of partially saponified polyvinyl alcohol with an average degree of polymerization of 600 and a saponification degree of 88 mol was added to improve redispersibility. % Then the resulting mixture is thoroughly mixed and get an aqueous emulsion of synthetic resin with a solids concentration of 46%. Next, the specified emulsion is dried by spraying in a stream of warm air acting as a heat source at 150 ° C using a nozzle-type spray dryer, and a redispersible polymer powder is obtained.

The disadvantage of this method of obtaining redispersible polymers is the need for their further separation from the aqueous dispersion using high-temperature spray drying.

The objective of the invention is to reduce the amount of waste, simplifying the technology for producing and reducing the number of apparatuses for the production of redispersible polymers while maintaining their characteristics.

The problem is achieved by the method of producing redispersible polymer powders, which consists in the fact that polyvinyl alcohol modified with acetoacetic groups with a degree of saponification from 90 to 99.8 mol. %, an average degree of polymerization from about 50 to 2000 and a degree of esterification with acetoacetic acid of 0.01 to 10 mol. %, butyl acrylate, styrene, glycidyl methacrylate, a polymerization initiator 2,2′-azoisobutyronitrile (AIBN) and a dispersion medium — supercritical carbon dioxide, and the polymerization process is carried out at a temperature of 60-65 ° C and a pressure of 370-440 atm.

This method of synthesis of redispersible polymers allows us to solve a number of important technological and environmental problems:

1) Simplification of the process of synthesis of redispersible polymers:

- reduction in the number of technological stages;

- reduction in the amount of equipment;

- no need for isolation of the end product, since at the end of the synthesis solvent is simply removed from the redispersible oligomer, due to the fact that the transfer of the supercritical CO ₂ in the normal state it will be removed from the reaction zone.

- obtaining the final product directly in powder form, the dispersion value of which can be controlled by the synthesis conditions (temperature and pressure).

2) Solving environmental problems:

- reducing the toxicity of the synthesis itself - improving the working conditions of staff;

- Utilization of carbon dioxide, which is one of the most frequent by-products of many technological processes in various industries.

Supercritical fluids are substances that are capable, at a certain temperature and pressure, of passing into a state that is intermediate between a liquid and a gas. At typical industrial temperatures and pressures, supercritical fluids can be obtained from many substances, including various hydrocarbons (in particular methane, ethane, propane, butane, pentane, hexane, ethylene and propylene), halogenated hydrocarbons and inorganic compounds (in particular ammonia , water, carbon dioxide, sulfur hexafluoride, hydrogen chloride, hydrogen sulfide, nitrous oxide and sulfur dioxide). Carbon dioxide most often used as the supercritical fluid (critical parameters: T _c = 304.1 K, P _c = 73.8 bar) under normal conditions is a gas. In the supercritical state, carbon dioxide is a compressed fluid with a high density and moderate temperature. Under operating conditions, such a fluid is relatively safe, inexpensive, and chemically inactive [Gumerov F., Yaruplin R. Supercritical fluids and GFR technologies // The Chemical Journal 10.2008 26-30 p.] At the same time, it is also possible to synthesize redispersible polymers apply other fluids, however, they can have a higher temperature T _s and a higher pressure P _s , are less accessible, expensive and may have a certain chemical activity. Known methods for carrying out chemical reactions in supercritical fluids: [PE Savage, S. Gopalan, TI Mizan, Ch.J. Martino, EE Brock. Reactions at supercritical conditions: Applications and fundamentals. AIChE Journal, 1995, 41, 1723-1778. MJ Antal, M. Carlsson, X. Xu and DGM Andeson. Mechanism and kinetics of the acid-catalyzed dehydration of 1-and 2-propanol in hot compressed liquid water, Ind. Eng. Chem. Res., 1998, 37, 3820-3829].

Supercritical fluid, by its nature, is a middle state between a liquid and a gas, has a higher diffusion coefficient and lower interfacial tension than ordinary liquids, which makes it possible to effectively use it as a solvent in the synthesis of polymers. At the end of the synthesis, the pressure in the reactor is released, carbon dioxide is independently removed from the system (flies away), and the polymer remains in the reactor in the form of a fine powder. Thus, this process flow diagram for producing a redispersible polymer allows the drying and grinding operation to be excluded from the process.

The invention is illustrated by the following examples:

Example 1 is given on the prototype.

Example 1

In a 2-liter stainless steel reaction vessel equipped with a stirrer and reflux condenser, 670 parts of water and 46 parts of polyvinyl alcohol modified with acetoacetic groups with a saponification degree of 97 mol. %, an average degree of polymerization of 200 and a degree of esterification with acetoacetic acid of 0.03 mol. % (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.). The reaction vessel is heated to 85 ° C until polyvinyl alcohol modified with acetoacetic groups is dissolved in water. Then, while maintaining the temperature of the reaction vessel at 80 ° C, 66 parts of the monomer mixture prepared previously (358 parts of butyl acrylate / 293 parts of styrene / 6.5 parts of glycidyl methacrylate = 54.5 / 44.5 / 1 (weight ratios) are added to it). ammonium persulfate for 1 hour, then, the remaining amount of the monomer mixture is added dropwise to the reaction vessel over 4 hours to maintain the polymerization, with ammonium persulfate being additionally introduced as the polymerization initiator. When adding a mixture of monomers, the reaction mixture is kept at the same temperature for 1 hour and added to improve the redispersibility of 276 parts of a 20% aqueous solution of partially saponified polyvinyl alcohol with an average degree of polymerization of 600 and a saponification degree of 88 mol% (trade name "Gohensol GL 05 "manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.).

The resulting mixture was thoroughly mixed. Thus, an aqueous emulsion of synthetic resin with a solids concentration of 46% is obtained. Next, the specified emulsion is dried by spraying in a stream of warm air acting as a heat source at 150 ° C using a nozzle-type spray dryer. Thus, a redispersible polymer powder is obtained.

Example 2

458 masses are simultaneously charged into the autoclave. including modified acetoacetic groups of polyvinyl alcohol with a degree of saponification of 90 mol. %, an average degree of polymerization of 50 and a degree of esterification with acetoacetic acid of 0.01 mol%. (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.), 358 mass. including butyl acrylate, 293 mass. including styrene, 6.5 mass. including glycidyl methacrylate (weight ratios of the main monomers 54.5 / 44.5 / 1, respectively) and 1 mass. including the polymerization initiator - 2,2′-azoisobutyronitrile (AIBN). Carbon dioxide is fed into the autoclave at room temperature until a pressure of 150 atm is established. Next, the autoclave is heated to a temperature of 60 ° C, while the pressure in the autoclave increases to 370 atm. The polymerization of monomers is carried out under the conditions of: pressure 370 atm and temperature 60 ° C. At the end of the synthesis, the pressure and temperature in the reactor are reduced to room conditions and a polymer powder is obtained. Then the powder of the obtained polymer to improve redispersibility is mixed with 55.2 mass. including PVA with an average degree of polymerization equal to 600, and a degree of saponification of 88 mol. % (trade name "Gohensol GL 05" manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.).

As a result of the described operations, a redispersible polymer powder is obtained.

Example 3

458 masses are simultaneously charged into the autoclave. including modified polyvinyl alcohol with acetoacetic groups with a saponification degree of 99.8%, an average degree of polymerization of 2000, and a degree of esterification with acetoacetic acid of 10 mol%. (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.), 358 mass. including butyl acrylate, 293 mass. including styrene, 6.5 mass. including glycidyl methacrylate (weight ratios of the main monomers 54.5 / 44.5 / 1, respectively) and 5 mass. including the polymerization initiator - 2,2′-azoisobutyronitrile (AIBN). Carbon dioxide is fed into the autoclave at room temperature until a pressure of 150 atm is established. Next, the autoclave is heated to a temperature of 65 ° C, while the pressure in the autoclave increases to 440 atm. The polymerization of monomers is carried out under conditions: pressure of 440 atm and a temperature of 65 ° C. At the end of the synthesis, the pressure and temperature in the reactor are reduced to room conditions and a polymer powder is obtained. Then, the powder of the obtained polymer to improve redispersibility is mixed with 55.2 wt., Parts of PVA with an average degree of polymerization of 600, and a degree of saponification of 88 mol. % (trade name "Gohensol GL 05" manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.).

As a result of the described operations, a redispersible polymer powder is obtained.

In all cases (examples 1, 2, and 3), the redispersible polymers were a white fine powder with a glass transition temperature of + 1 ° C and good redispersibility in water (the height of the settled layer was 100 ml of a 50% aqueous dispersion of not more than 5 mm).

As can be seen from the above examples, the technical and economic efficiency of the invented method for producing a redispersible polymer is that there is no wastewater, the amount of equipment needed to obtain is reduced, the process is simplified, which ultimately leads to a significant reduction in the cost of the resulting product while maintaining it high operational characteristics. When redispersed in water, said polymer powder forms a stable dispersion. The coating obtained from the specified dispersion has good adhesion (1 point), as well as high resistance to water and humidity.

Claims (1)

A method of obtaining a redispersible polymer powder, which consists in the fact that a polyvinyl alcohol modified with acetoacetic groups with a degree of saponification from 90 to 99.8 mol. %, the average degree of polymerization from 50 to 2000 and the degree of esterification with acetoacetic acid from 0.01 to 10 mol. %, butyl acrylate, styrene, glycidyl methacrylate, a polymerization initiator and a dispersion medium, polymerization is carried out at elevated temperature, characterized in that an autoclave is used as a reaction vessel, 2,2′-azoisobutyronitrile (AIBN) is used as a polymerization initiator, and as dispersion media use supercritical carbon dioxide, and the polymerization process is carried out at a temperature of 60-65 ° C and a pressure of 370-440 atm.