RU2618253C2 - Method of obtaining water-redispersible polymer powders - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of obtaining water-redispersible polymer powders is described. It is defined as loading of reactor with at least two unsaturated monomers, one of which is hydrophilic, and the other one is hydrophobic, with polymerization initiator, after which carbon dioxide is injected into the reactor to specific pressure. The primary components are heated to a temperature that ensures transfer of carbon dioxide to supercritical state, during the polymerization the mixture is stirred to ensure its homogeneity. Monomers are taken in amount, providing production of polymer powder with molecular weight of not more than 100,000. The glass transition temperature is in range between 0 and +40°C, and the average calculated equivalent mass of the hydrophobic part of polymer powder is 1.3-1.5 times greater than theoretical equivalent mass of the hydrophobic part of the polymer, which enables to achieve solubility of polymer powder. A water-redispersible polymer powder has been also described. It is obtained by polymerizing a mixture of unsaturated monomers of at least one hydrophobic and at least one hydrophilic monomer in the presence of polymerization initiator and supercritical carbon dioxide.

EFFECT: method of obtaining water-redispersible polymer powders with homogeneous structure of polymer particles has been developed with simplification of technology.

57 cl, 6 dwg, 4 tbl, 30 ex

Description

FIELD OF THE INVENTION

The invention relates to the field of production of polymeric materials, namely, to the production of water-redispersible polymers that have a wide range of applications - from the creation of paints and varnishes based on them to dry building mixtures, in particular, can be used as water repellents for sand, clay, paper, textile, for protective coatings, etc.

State of the art

The present invention is a method for the synthesis of one of the most popular types of polymeric materials — redispersible polymers — based on the use of supercritical carbon dioxide, which is a supercritical fluid, as a solvent.

Redispersible polymers are polymer powders that, when dispersed in water, can quickly form stable aqueous dispersions that can subsequently form a thin polymer film on the surface. A neutral inorganic solvent (water) used in the preparation of dispersions based on redispersible polymers allows the production of environmentally friendly materials.

Redispersible polymers have a number of undoubted advantages in comparison with classical organic and aqueous solutions / dispersions of polymers: non-toxicity, fire and explosion safety; the stability of the composition due to the absence of sedimentation processes and chemical reactions during long-term storage; cheap packaging, warehousing and transportation; storage and transportation of redispersible polymers are possible even in extremely difficult climatic conditions (from -40 to + 40 ° C) without changing the characteristics of the redispersible polymer.

Known traditional methods for the synthesis of redispersible polymer binders (powders) using an organic solvent or water, followed by drying and grinding, which is accompanied by a large amount of waste.

In particular, from RU 2411266, DE 102006007282, RU 2417234, RU 2339592, RU 98118234, RU 2368583, RU 2456252, RU 2288240, RU 2371450, there are known methods for producing redispersible polymers that are reduced to the polymerization of monomers in water or organic solvents. The polymers are then isolated from aqueous or organic dispersions. Various methods are known from RU 2371450 for isolating a redispersible polymer from dispersions, such as, for example, fluid-bed drying, thin-layer drying (roller drying), freeze-drying, polymer freeze drying or spray drying. There is also known a method of producing a redispersible polymer powder by precipitation from a dispersion with further drying and grinding [RU 2210576].

Obtaining redispersible polymers in the described manner causes a large amount of production waste - organic solvents and water, which must subsequently be disposed of. It should be noted that the known methods for the isolation of redispersible polymer powders from dispersions are multistage, energy-intensive and require special hardware design.

One of the promising ways to solve these problems is the synthesis of redispersible polymers in supercritical media (using supercritical fluids) that can act as a solvent in this process, which should greatly simplify the process of their preparation, since it is possible to avoid the main environmental problem - a huge amount of solvents that have to remove from the finished product.

Supercritical fluids are substances that can, at a certain temperature and pressure, transition to a state that is average between a liquid and a gas, has a higher diffusion coefficient and lower interfacial tension than ordinary liquids, which allows it to be effectively used as a solvent in the synthesis of polymers. 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).

It is known from the prior art that supercritical fluid carbon dioxide (critical temperature and pressure parameters T _k = 31.1 ° C, P _k = 72.8 atm), which is a gas under normal conditions, is used in the synthesis of polymer powders. Under supercritical conditions, carbon dioxide is in a state whose parameters are intermediate between its properties in the liquid and gas phases. Under operating conditions, such a fluid has good solubility, is relatively safe and inexpensive.

Closest to the claimed invention is a method for producing a redispersible polymer (powder) in liquid and supercritical carbon dioxide [US 5688870], which includes two stages, where in the first stage from one group of monomers get a hydrophobic polymer (core), on the second from another group of monomers - hydrophilic shell for him in order to give the product the ability to redisperse. In this case, at the first stage, the first monomer or mixture of monomers, initiator, surfactant, liquid or supercritical CO _{2 is} loaded into the reactor and the polymerization process is started with the formation of polymer cores insoluble in water; with the subsequent introduction (at the second stage) into the reactor of the second monomer together with the initiator, as well as liquid or supercritical CO ₂ with the formation of a water-soluble or water-dispersible polymer shell on a water-insoluble polymer core, thereby forming a polymer with a core structure shell ”. In this case, the first monomer can be selected from the group consisting of styrene monomers, olefins, acrylic monomers, vinyl ester monomers, vinyl chloride, fluoroolefins, maleic anhydride and mixtures thereof. The surfactant may be selected from the group consisting of: reactive and inert fluorinated polyhydrocarbons, reactive and inert oligo- and polysiloxanes, polypropylene oxide and mixtures thereof. Said second monomer is selected from the group consisting of acrylic acid, methacrylic acid, acrylamide, N-vinylformamide, N, N-dimethylacrylamide, N-vinylpyrrolidone, aziridine and diacrylamide to form a crosslinked hydrophilic shell. The initiator, which is added with the first monomer, is selected from the group consisting of: peroxides, azo compounds, peroxide esters, peroxide dicarbonates and redox initiators. In one embodiment, the polymer core shell is recovered from the reactor as an aqueous solution by purging the reactor and then collected as a dry powder.

The disadvantage of this synthesis method is the need to obtain a redispersible polymer using a two-stage technology, which complicates and increases the synthesis process in time due to the need to complete the synthesis at the completion of the first stage (formation of the hydrophobic polymer core) with the conversion of CO ₂ from the supercritical to the gaseous state and its further removal from the reaction zone with the aim of introducing into the autoclave in the second stage a second portion of monomers for the synthesis of a hydrophilic shell, and reintroducing into the reaction OSUD CO ₂ with its transfer to the supercritical state for further polymerization. In addition, in the known method there is no possibility of carrying out the synthesis process using monomers in the gas phase. It is known that monomers such as ethylene are extremely important starting materials for the synthesis of redispersible copolymers with the required high physical and mechanical properties, while the known analogue does not provide for the possibility of introducing ethylene in the gas state during the synthesis of the polymer redispersible powder. In addition, the presence of such hydrophobic compounds as oligofluorocarbon and oligosiloxane surfactants in the composition affects the redispersibility of the final product. In addition, the soluble hydrophilic shell, which determines the redispersibility in water of the final polymer, when formed from the last coating, leads to its partial washability and, thus, causes its defectiveness during operation. And the presence of a hydrophobic core does not allow this part of the redispersible polymer to swell in water, which is an indispensable condition for obtaining a coating with high performance properties. The hydrophobic core does not allow the use of this polymer not only as a binder, but also as an additional water-retaining additive, which is extremely important when producing thin coatings based on redispersible paints due to the fact that water evaporates extremely quickly from a thin coating layer and does not allow cement to crystallize completely. on the basis of which such paints are made. The introduction of a large amount of water-retaining additives for these purposes, the role of which is water-soluble polymers, can lead to a washable coating. Thus, it is preferable to play the role of a water-retaining additive by a dispersible monomer. Another disadvantage of this synthesis method is the extremely limited composition of the starting monomers, which significantly limits the achievement of the desired characteristics of the final product, since the main task of using a redispersible polymer is not only to obtain a stable aqueous dispersion, but also to achieve the required coating characteristics and / or performance properties modified inorganic binders and dry building mixtures.

Disclosure of invention

The objective of the invention is to develop a method for producing water-redispersible polymer powders with a homogeneous structure of polymer particles while simplifying the technology.

The technical result consists in reducing the number of stages for producing a powder while improving the operational characteristics of the resulting polymers (polymer powders) and coatings formed from them. The powder is obtained in one stage - the polymerization of the starting components, which is carried out in the presence of supercritical carbon dioxide, while the components are loaded into the reactor with a balance of the hydrophilic and hydrophobic parts in the structure of the final product, which allows combining the high redispersibility of the polymer in water and the water resistance of based on it coating. The introduction of additional functional additives in a redispersible polymer powder makes it possible to obtain products with a wide range of performance characteristics.

In the claimed technological process, in comparison with the traditional method (polymerization in water or in an organic solvent), there is no stage of drying the redispersible polymer ("forced" removal of water or an organic solvent from the reaction zone), grinding, wastewater and organic solvents, while using The claimed carbon dioxide technology is cyclical in nature. Thus, the inventive method allows to obtain polymer powders without residues of an organic solvent, the quality of which corresponds to powders obtained by the traditional method of synthesis.

The problem is solved in that the method of producing water-dispersible polymer powders involves loading at least two unsaturated monomers into the reactor, one of which has an affinity for water (hydrophilic), and the second does not have an affinity for water (hydrophobic) (monomers “Having an affinity for water” and “having no affinity for water” subsequently form the hydrophobic and hydrophilic parts of the polymer) as well as the polymerization initiator, after which carbon dioxide is injected into the reactor to a certain pressure and heated transition components to a temperature that ensures the transition of carbon dioxide to a supercritical state, during the polymerization, the mixture is stirred to ensure its homogeneity, while the monomers are taken in an amount that provides a polymer powder with a molecular weight of not more than 100,000, the glass transition temperature is in the range from -50 to + 50 ° (preferably from 0 to + 40 ° C), and the average calculated equivalent mass of the hydrophobic part of the polymer powder (EMG) is 1.3-1.5 times the pain e theoretical equivalent weight of the hydrophobic portion of the polymer, causes achieving solubility of the polymer powder.

The transition of carbon dioxide to a supercritical state for the synthesis of redispersible polymers can be provided by a process in which it is pumped in a reactor to a pressure of 80-500 atm and heated to a temperature of 60-100 ° C. As a reactor, it is recommended to use an autoclave for synthesis at a pressure of over 70 atm.

To obtain a polymer with a molecular weight of not more than 100,000, the initiator is loaded into the reactor in an amount of 0.1-5% by weight of the monomers. In one embodiment, to control the molecular weight during polymerization and to produce a polymer with a molecular weight of not more than 100,000, an additional chain growth regulator is used, which is loaded into the reactor in an amount of not more than 5% by weight of monomers. The polymerization is initiated using initiators commonly used in emulsion polymerization or combinations of redox initiators. As the polymerization initiator, any known polymerization initiators, such as 2,2'-azoisobutyronitrile (AIBN), and / or benzoyl peroxide, or combinations thereof with reducing agents, can be used. Examples of use as a chain growth regulator are n-dodecyl mercaptan and / or tert-dodecyl mercaptan and / or mercaptopropionic acid and / or mercaptopropionic acid methyl ester, sodium hydroxymethanesulfinate and ascorbic acid as reducing agents, while reducing agents are charged into the reactor the amount of up to 5% by weight of the loaded monomers.

In one embodiment of the invention, an additional reinforcing polymer may be charged to the reactor, using butanolized diphenylol propane formaldehyde oligomer (BDFO) with a molecular weight of Mn = 500-850, a content of methylol groups of 10-20%, butoxyl groups of 10-25%, which can be synthesized according to the procedure presented in the materials of patents RU 2264416 or RU 2318835, introduced in an amount up to 30% by weight of a redispersible polymer powder, while after receiving a redispersible polymer powder in urotropin is added as a crosslinking agent in an amount of from 2 to 5% of the amount of butanolized diphenylol propane formaldehyde oligomer (BDFO) used.

As examples of the use of monomers having an affinity for water, carboxylic acids and / or nitriles of carboxylic acids and / or amides can serve.

As examples of the use of monomers that do not have an affinity for water, esters of carboxylic acids and / or olefins and dienes and / or glycidyl acrylates and / or vinyl aromatic compounds and / or vinyl halides can be used.

Acrylic and / or methacrylic acids are suitable as carboxylic acids, acrylonitrile as carboxylic nitriles, N-vinylformamide as amides, and / or N, N-dimethylacrylamide and / or N-vinylpyrrolidone, and / or diacrylamide, while using carboxylic acids, zinc oxide-based compositions, for example, Zimplex 15 brand of Munzing Chemie GMBH (Germany), are additionally added to the obtained polymer powder as a cross-linking agent, in an amount of 2-5% by weight of loaded acids.

Suitable vinyl esters of carboxylic acids are vinyl esters of carboxylic acids with 1-15 carbon atoms, and / or esters of acrylic and methacrylic acids with branched or unbranched alcohols with 1-15 carbon atoms. As vinyl esters of carboxylic acids with 1-15 carbon atoms, vinyl acetate, and / or vinyl laurate, and / or vinyl pivalate, and / or vinyl esters of α-branched monocarboxylic acids with 9-13 carbon atoms can be used, for example, VeoVa9® products , VeoVa10®, or VeoVa11® (trade name of the product is Resolution Europe BV, Hoogvliet, Netherlands). Among these, vinyl acetate is most preferred. As acrylic and methacrylic acid esters with branched or unbranched alcohols with 1-15 carbon atoms, methyl acrylate and / or methyl methacrylate and / or ethyl acrylate, ethyl methacrylate and / or propyl acrylate and / or n-butyl acrylate and / or butyl methacrylate and / or norbornyl acrylate. As olefins and dienes, ethylene and / or propylene and / or 1,3-butadiene and / or decene can be used. As glycidyl acrylates, glycidyl acrylate and / or glycidyl methacrylate can be used, and amines are additionally added to the obtained polymer powder as a crosslinking agent in an amount of 2-5% by weight of the loaded glycidyl acrylate. Styrene and / or divinyl benzene are used as vinyl aromatic compounds. As vinyl halides, vinyl chloride and / or vinyl fluoride are used.

The regulation of the properties of the final product can be accomplished through the use of functional additives, which can be used as a protective colloid, and / or color and / or luminous additives, and / or corrosion inhibitor, and / or anti-corrosion agent, and / or biocidal additive, and / or a dispersant, which is loaded into the reactor together with the monomers, or added to the polymer powder obtained after polymerization.

In particular, to further stabilize the aqueous dispersion based on the synthesized redispersible polymers, protective colloids are loaded into the reaction system together with monomers, which can be partially saponified with polyvinyl alcohol with a degree of hydrolysis from 80 to 98 mol. %, and / or cellulose, and / or their carboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivatives, and / or starch, while the protective colloid is used in an amount up to 50% by weight of the loaded monomers. It is optimal to use polyvinyl alcohol modified with acetoacetic groups as a protective colloid with a saponification degree of 92-95% and an average degree of polymerization of 350-450.

The composition of the starting components may also contain other functional additives, for example, color and / or luminous additives, which are used as pigments (for example, inorganic pigment iron blue, organic pigment brand "scarlet red", obtained on the basis of diazotized 3-nitro-4 -aminotoluene and β-naphthol), and / or fluorescent pigments (for example, grades VQ, in particular VQ-D-24, which are an organic dye based on ethylamine, methoxycarbonyl and dimethyl chloride in an amino resin), and / or waterproof phosphor s (for example, BG 300M, the chemical composition of which is Sr ₄ Al ₁₄ O ₂₅ : Eu, Dy, as well as GSS-SA, GSS-LA, the chemical composition of which is based on ZnS, etc.), which are added in an amount up to 10% of mass of loaded monomers.

As a corrosion inhibitor, a zinc-containing complex salt can be used, for example, SER-AD-FA-179 (Servo, Germany); and / or sodium nitrite and / or sodium benzoate, while the corrosion inhibitor is administered in an amount up to 2% by weight of the loaded monomers.

Examples of the use of an anticorrosive agent are calcium and magnesium oxyaminophosphate complex, for example, Pigmentan EA brand of Pigmentan Ltd (Israel), while the anticorrosive agent is added in an amount of up to 5% by weight of the loaded monomers.

As a biocidal additive, compositions of the brand Metatin K 520 f can be used. Acima, Switzerland (based on isothiazoline and halogenated alkanol derivatives); and / or Tiuram D brand (GOST 740-76) (based on tetramethylthiuram disulfide); and / or Skein brand 8 (F. Rohm and Haas) (based on 2-n-octyl-4 isothiazoline), while the biocidal additive is introduced in an amount up to 5% by weight of the loaded monomers.

As a dispersant, compositions of the OP-7 and / or OP-10 brand are used, which are the products of processing a mixture of mono- and dialkylphenols with ethylene oxide, while the dispersant is introduced in an amount up to 5% by weight of monomers.

An anti-caking agent is added to the obtained polymer powder, which is calcium-magnesium carbonate (dolomite), and / or talc, and / or kaolin, and / or silicates, for example, magnesium hydrosilicate with a dispersion of 10 nm to 10 μm, while anti-caking agent is introduced in an amount up to 30% by weight of the loaded monomers.

The above component composition of the reaction mass does not limit the present invention, but only shows possible embodiments of the invention to achieve the claimed polymer properties.

The problem is also solved by the fact that the inventive method receive a water-dispersible fine polymer powder, the equivalent mass of the hydrophobic part of which (EMG) is in the range of 1.3-1.5 times the theoretical equivalent mass of the hydrophobic part of the polymer, which determines the achievement of polymer solubility powder, the molecular weight is not more than 100,000 and the glass transition temperature is in the range of from -50 to + 50 ° (preferably from 0 to + 40 ° C, even more preferably from +5 to + 27 ° ).

Brief Description of the Drawings

The invention is illustrated by graphs and diagrams, where in FIG. 1. The IR spectra of redispersible acrylate-type copolymers synthesized in an aqueous medium are presented — curve (1), in supercritical carbon dioxide — curve (2); in FIG. 2 shows the viscosity curves of aqueous dispersions of polymers synthesized in supercritical carbon dioxide (1) and by traditional technology in an aqueous medium (2); in FIG. 3 shows a graph of the dynamic viscosity of various dispersions of polymers on their concentration, curve (1) characterizes the dispersion according to the prototype, curves (2), (3), (4) according to the claimed technology; in FIG. 4 shows graphs of the distribution of the dispersion particles obtained based on the synthesized in supercritical CO ₂ redispersible polymer radially, where the curve (1) - polymer synthesized with the addition of 5 wt% of n-dodecyl mercaptan, curve (2) - polymer synthesized with the addition of 3 wt % n-dodecyl mercaptan, curve (3) -autocorrelation function; in FIG. 5 is a diagram of an experimental setup for synthesis, where the positions are: 1 — cuvette, 2 — pressure generator (compressor), 3 — manometer, 4 — CO ₂ cylinder; in FIG. 6 shows an example of realization of the high pressure cell of the experimental setup for the synthesis of polymers in supercritical _CO2. The positions in the drawing indicate: 5 - heater, 6 - magnetic stirrer, 7 - temperature sensor, 8 - gasket, 9 - brass ring, 10 - input for supplying CO ₂ , 11 - output for CO ₂ , 12 - modifier, 13 - polymer . In the manufacture of polymer powder on an industrial scale, an industrial autoclave can be used as a reactor.

The implementation of the invention

The claimed invention can be implemented as follows.

To carry out the polymerization process, the initial components are loaded into the reactor — monomers having an affinity for water, and monomers having no affinity for water, subsequently forming hydrophilic and hydrophobic parts of the polymer, respectively, as well as a polymerization initiator, if necessary, additionally load a regulator (limiter) chain growth, initiator reducing agents, functional additives, which can be used as color or luminous additives (for example, pigment, fluorescent pigment, phosphor), inhibitors corrosion agent, anticorrosive agent, dispersant, reinforcing polymer, protective colloid, after which carbon dioxide is pumped into the reactor to the required pressure (80-500 atm) and the starting components are heated to a temperature (60-100 ° С), ensuring the transition of carbon dioxide to supercritical state. During the polymerization, the mixture is further mixed to ensure its homogeneity and a more complete reaction.

At the end of the synthesis, the pressure and temperature in the reactor are released, after which carbon dioxide passes into a gaseous state and is independently removed from the system, and the polymer remains in the reactor in the form of a fine powder. In addition, when removing gaseous CO ₂ from the reaction zone at the end of the synthesis, one more technological problem is solved - the finished product is easily and quickly cleaned of monomer residues carried away from the reactor by gaseous CO ₂ , and if necessary, the process of deeper purification of the product from monomers with using supercritical CO ₂ can be conducted repeatedly, which again injected into the reactor heated carbon dioxide to convert it into a supercritical state, followed by removal of CO ₂ in the gaseous state to p stvorennymi monomer residues therein. Thus, this process flow diagram for producing a redispersible polymer allows the drying and grinding operations of the resulting product to be excluded from the process.

As the starting monomers (hydrophilic and hydrophobic), polymerization initiator, initiator reducing agents, chain growth regulator, and functional additives, it is proposed to use the compounds shown in Table 1.

The inventive technology is not obvious, solves a whole range of interrelated tasks. Namely, the chemical nature of redispersible polymers must combine absolutely opposite properties - hydrophilicity and hydrophobicity, in order to be able to both provide a stable water-dispersion system when the polymer powder is dispersed in water and resist washability after coating formation. This combination of the opposite properties of the redispersible polymer can be achieved by balancing the hydrophilic and hydrophobic parts of the structure of this material, which is manifested in the production of a polymer powder with a molecular weight of not more than 100,000, a glass transition temperature in the range from -50 to + 50 °, and an average calculated equivalent mass of the hydrophobic part of the polymer powder 1.3-1.5 times greater than the theoretical equivalent mass of the hydrophobic part of the polymer, which determines the solubility of the polymer powder .

It is known that lyophilic dispersions are obtained on the basis of polymers having a high affinity for water due to the presence of polar groups in the polymer. If the polymer contains a sufficient amount of nonionic polar groups (—OH, —NH ₂ , —O—) or ionogenic groups (—COOH, —COONH ₄ , —COONa), then such polymers are usually soluble in water. The degree of influence of the above groups on the affinity for water is different. A semi-quantitative measure of the effect of polar groups on their affinity for water is the equivalent mass of the hydrophobic part of the polymer per polar group (EMG), i.e. equivalent mass at which the polymer still retains an affinity for water. The maximum EMG to achieve the solubility of the homopolymer in water is shown in table 2.

In the process of creating the inventive technology, it was also taken into account that the polymer should have redispersibility, and not solubility in water. To ensure the indicated properties and achieve redispersibility of the final product, the monomer ratio should be selected so that the average calculated EMG is 1.3–1.5 times higher than the theoretical EMG of the polymer, which determines the affinity for water. Below is an example, by analogy with which the selection of monomers can be realized with a preliminary assessment of the redispersibility of the polymer powder obtained on their basis.

In the case of the synthesis of a polymer based on butyl acrylate (M = 128), styrene (M = 104) and methacrylic acid (M = 86) with a percentage ratio of units of 61: 32: 7, respectively, the EMG of the units of the synthesized polymer is determined - for butyl acrylate, EMG = 126, for styrene EMG = 102 and methacrylic acid EMG = 84, after which the average EMG for the copolymer is found: 0.61⋅126 + 0.32⋅102 + 0.07⋅84 = 115.38. The required EMG to achieve redispersibility (for the carboxyl group) = 90–1.3 = 117. Since 115.38 <117, presumably this polymer will have a tendency to redisperse.

At the same time, it was taken into account that the redispersibility of the polymer in water decreases with increasing molecular weight. The maximum molecular weight of a redispersible polymer (Mn) should not exceed 100,000. Thus, another important factor in regulating the structural features of the obtained polymer is the production of a polymer (polymer powder) with a molecular weight that not only determines its ability to disperse in an aqueous medium, but also allowing subsequently to form a continuous polymer coating. The molecular weight can be controlled by the additional introduction of a chain growth restrictor (regulator) into the system.

In addition, additional ability to redisperse the resulting polymer in water can be imparted by introducing into the system a protective colloid, which was selected from polymers having maximum solubility in water, i.e. EMG which was maximum in table 1.

Based on the above, the polymer structure was selected, providing its optimal redispersibility in water.

In addition, when choosing monomers for the synthesis of a redispersible polymer with the aim of using it as a coating, it should be borne in mind that their hydrophilic part must contain functional groups that ensure polymer adhesion to the selected substrate. Similar functional groups should be at least 15% of the total number of groups.

Depending on the chemical structure of the starting monomers, the polymers are divided into thermoplastic and thermosetting. The inventive method was synthesized as thermoplastic redispersible polymers, i.e. copolymerization products of monomers that do not contain other functional groups other than a double bond, and thermosetting products obtained by copolymerization of two or more comonomers, at least one of which, in addition to a double bond, has any functional group. In particular, thermosetting polymers containing carboxyl and epoxy groups were synthesized.

The formation of coatings based on thermoplastic polymers is not accompanied by chemical transformations and proceeds rapidly at room temperature. The curing of thermosetting polymers is accompanied by chemical reactions.

The choice of comonomers in the synthesis of redispersible polymers was also carried out taking into account the need for certain operational properties of the products obtained from them (including coatings). The presence of units of derivatives of acrylic acid (derivatives of carboxylic acids) in the copolymer gives the coatings elasticity, derivatives of methacrylic acid, on the contrary, give them rigidity. The presence of small alkyl substituents causes an increase in the rigidity of the final products. As the alkyl substituent increases, the polymers become more elastic, since the alkyl substituents act as an internal plasticizer, and due to the large alkyl substituents, the interchain interaction in the polymer decreases. The same principles also determine the choice of monomers from a number of esters of carboxylic acids with 1-15 carbon atoms. The use of olefins, dienes and vinyl halides as monomers promotes the production of copolymers with high deformation-strength properties. The choice of vinyl aromatic compounds as comonomers promotes the production of polymers with high hardness. The choice of acrylonitrile is due to its strong polarity, which contributes to an increase in the affinity for water of the final copolymer. The introduction of acrylonitrile in the copolymers helps to increase adhesion and increase the resistance of the final products to solvents and fats. The choice of olefins and vinyl halides included in the synthesized copolymer was determined by the need to increase the hydrophobic part in order to achieve the necessary operational properties of the polymer, increase the elasticity of the product and increase resistance to solvents and fats. The combination of solid and elastic fragments in the polymer structure allows to obtain a product with great resistance to physical and mechanical loads.

Thus, the choice of comonomers also contributes to the production of a redispersible polymer with high performance properties. The balance of alternating hydrophilic and hydrophobic units in the polymer makes it possible to obtain a redispersible polymer with a homogeneous structure, having an affinity for water and, thereby, ensuring the formation of a stable aqueous dispersion, and, due to its hydrophobic part, which leads to the formation of indelible coating with high performance properties.

Also, when choosing the composition and content of monomers to obtain a redispersible polymer, it was taken into account that the glass transition temperature Tc should usually be in the range from -50 to + 50 ° C, preferably from -30 to + 40 ° C, even more preferably from 0 to + 40 ° C. The glass transition temperature Tg of _the polymers can be determined by known methods, e.g., by differential scanning calorimetry (DSC). Approximate values of the glass transition temperature can also be preliminarily calculated using the Fox equation. In accordance with the methodology of Fox (Fox TG, Bull. Am. Physics Soc. 1.3, 1956, p. 123), the glass transition temperature can be calculated by the following formula:

1 / T _c = x ₁ / T _c1 + x ₂ / T _c2 + ... + X _n / T _cn ,

where x _n denotes the mass fraction (wt.% / 100) of monomer n, and T _cn denotes the glass transition temperature expressed in degrees Kelvin of the homopolymer of monomer n. Glass transition temperatures for homopolymers are provided in the Polymer Handbook, 2nd ed., J. Wiley & Sons, New York, 1975.

The addition of functional additives to the composition (system), which can be carried out both at the stage of loading the starting components into the reactor and at the end of the synthesis of the redispersible polymer, was determined by the need to achieve certain characteristics of the final product. The introduction of functional additives simultaneously with the loading of monomers did not significantly affect the process of synthesis of redispersible acrylic copolymers in supercritical carbon dioxide, but subsequently made it possible to significantly improve the redispersibility of the obtained product and facilitated the preparation of a stable aqueous dispersion with the desired performance characteristics.

Thus, the dispersant made it possible to improve the dispersibility of the polymer in water, and the protective colloid led to an improvement in the stability of the aqueous dispersion. Of the protective colloids commonly used in the preparation of redispersible polymers, it is optimal to use polyvinyl alcohol modified with acetoacetic groups with a saponification degree of 92-98% and an average degree of polymerization of 350-450.

Phosphors, pigments and fluorescent pigments are added to the polymer when it is necessary to achieve certain color characteristics or the luminescence of the coating. Corrosion inhibitors and anticorrosion agents can be added to the system during the subsequent formation of coatings for metal. Biocidal additives are determined by the need to protect coatings from biological damage.

The reinforcing butanolyzed diphenylol propane formaldehyde oligomer made it possible to obtain coatings for critical purposes with a high crosslinking frequency and enhanced physicomechanical characteristics of the coatings.

The introduction of cross-linking agents into the polymer powder at the end of the synthesis makes it possible to obtain chemically curable coatings with increased resistance to aggressive agents and high deformation-strength characteristics.

Anti-caking agents are incorporated into polymer powders to confer resistance to caking.

Below are examples of the preparation of a redispersible polymer according to the claimed technology (Examples 1-26) and according to the traditional method — the production of redispersible acrylic copolymers by emulsion polymerization in an aqueous medium, followed by the isolation of the polymer by spraying (Example 27), a comparative analysis of the characteristics of the obtained polymer powders, as well as an example of obtaining from a redispersible polymer of a paint and varnish material (Examples 28, 29). The results of the comparative analysis are also presented in FIG. 1-4.

Examples of the invention

The inventive method were obtained redispersible materials based on various monomers (see Examples 1-26). The best result in terms of technical and operational properties was shown by materials that were synthesized using carboxylic acids and their esters (high chemical resistance to various aggressive media, resistance to ultraviolet radiation, good mechanical properties, low water adsorption, and low carbon dioxide permeability )

The setup diagram for the synthesis of polymers (Figs. 5 and 6) consisted of a manual plunger pressure generator 2 (working volume 90 ml) to obtain a pressure of 50-400 atm. The valve system provided the supply of CO ₂ to the reaction cuvettes 1. The pressure generator and cuvettes were equipped with manometers 3 for operational pressure control and a gas inlet / outlet system. To establish and maintain the required constant temperature, a thermostat was used. Temperature control was carried out with an accuracy of ± 0.2 ° С. Cuvette 1 is designed to conduct experiments at pressures up to 1000 atm and temperatures up to 300 ° C. A magnetic stirrer was placed inside the working cell 1. For the synthesis of redispersible polymers, monomers and initiator were loaded into a stainless steel cuvette. The filling volume of the cell was 1/3. After sealing and purging with compressed CO ₂ gas, the cuvette was placed in a heating element. After some time, necessary to establish the desired temperature in the cuvette, the required pressure was set using a hand press so that a supercritical state was achieved for CO ₂ in the system. Upon completion of the polymer synthesis in supercritical carbon dioxide, the heating of the cuvette was turned off and the pressure in the system was slowly released. To obtain aqueous dispersions, redispersible polymers were dispersed in water by conventional mechanical mixing at room temperature to obtain a stable 30% dispersion.

Also, based on redispersible polymers synthesized both in water and in supercritical carbon dioxide, redispersible paints were obtained, which are pigmented powder coatings based on an inorganic binder and redispersible polymer powder with the addition of various additives (table 3).

The curing of thin polymer coatings based on aqueous polymer dispersions was carried out at room temperature.

Example 1

At the same time, vinyl acetate - 11.08 g, VeoVa10 ^® - 5.27 g, butyl acrylate - 0.88 g, acrylonitrile - 0.3 g, 2.2'-azoisobutyronitrile - 0.17 g, was loaded into the autoclave into the autoclave using a compressor carbon dioxide was supplied until a pressure of 400 atm was established (pressure parameters were monitored using a manometer) and the temperature was raised to 65 ° C. The stirrer was turned on and polymerization was carried out at the indicated temperature. Upon reaching the required molecular weight, the heating of the autoclave was turned off and the pressure in the reactor was reduced, transferring to the gaseous state carbon dioxide, which was removed from the reaction zone independently through the capture system.

Example 2

Redispersible powder was obtained analogously to example 1, with the only difference that an additional 0.88 g of vinyl laurate was additionally charged into the autoclave, VeoVa9 ^{® was} used instead of VeoVa10 ^® , and 10.5 g of vinyl acetate was additionally charged. 1.75 was added to the autoclave before polymerization g as a protective colloid polyvinyl alcohol with a degree of hydrolysis of 88 mol. % Carbon dioxide was introduced into the autoclave until a pressure of 80 atm was established. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 3

Redispersible powder was obtained analogously to example 1 with the only difference that instead of VeoVa10 ^® , VeoVa11 ^{® was used} , butyl acrylate was charged 1.72 g, and vinyl acetate was used in an amount of 10.5 g. Carbon dioxide was introduced into the autoclave until a pressure of 120 atm was established.

Example 4

Redispersible powder was obtained analogously to example 1 with the only difference being that 1.72 g of butyl acrylate, 1.72 g of vinyl laurate and 8.74 g of vinyl acetate were used.

Example 5

Redispersible powder was obtained analogously to example 1 with the only difference that vinyl pivalate was used instead of vinyl laurate. Additionally, 0.17 g of n-dodecyl mercaptan was added.

Example 6

Redispersible powder was obtained analogously to example 1 with the only difference that methyl acrylate was used instead of butyl acrylate, and benzoyl peroxide instead of 2,2'-azoisobutyronitrile. An additional 0.17 g of sodium hydroxymethanesulfinate was added.

Example 7

Redispersible powder was obtained analogously to example 1 with the only difference that methyl methacrylate was used instead of butyl acrylate. Additionally, 2 g of starch (Avedex 36 LAC14) and 0.17 g of mercaptopropionic acid were charged into the autoclave before polymerization. Then, carbon dioxide was introduced into the autoclave until a pressure of 80 atm was established. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 8

Redispersible powder was obtained analogously to example 1 with the only difference that ethyl methacrylate was used instead of butyl acrylate. Additionally, 0.17 g of mercaptopropionic acid and 0.17 g of ascorbic acid were added. Carbon dioxide was fed into the autoclave until a pressure of 440 atm was established.

Example 9

Redispersible powder was obtained analogously to example 1 with the only difference that propyl acrylate was used instead of butyl acrylate. Additionally, 1 g of hydroxyethyl cellulose (Tylose H20) was charged into the autoclave before polymerization. Carbon dioxide was introduced into the autoclave until a pressure of 500 atm was established and the temperature was raised to 60 ° C. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 10

Redispersible powder was obtained analogously to example 1 with the only difference that butyl methacrylate was used instead of butyl acrylate.

Example 11

Redispersible powder was obtained analogously to example 1 with the only difference that norbornyl acrylate was used instead of butyl acrylate. Additionally, 0.17 g of tert-dodecyl mercaptan was added. Carbon dioxide was introduced into the autoclave until a pressure of 300 atm was established and the temperature was raised to 100 ° C. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 12

Redispersible powder was obtained analogously to example 1 with the only difference that before the start of polymerization under a pressure of 30 bar ethylene was fed into the autoclave (its calculated amount in the autoclave was 0.88 g), and vinyl acetate was used in an amount of 10.5 g. Then, after termination feeding ethylene into the autoclave was fed carbon dioxide until a pressure of 400 atm was established and the temperature was raised to 65 ° C. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 13

Redispersible powder was obtained analogously to example 12 with the only difference that propylene was used instead of ethylene.

Example 14

Redispersible powder was obtained analogously to example 12 with the only difference that 1,3-butadiene was used instead of ethylene.

Example 15

Redispersible powder was obtained analogously to example 1 with the only difference that an additional 0.88 g of decene was additionally loaded into the autoclave, vinyl acetate was used in an amount of 10.5 g.

Example 16

Redispersible powder was obtained analogously to example 1 with the only difference that butyl acrylate was not used.

Example 17

9.2 g of vinyl acetate and 0.05 g of 2,2'-azoisobutyronitrile were charged into the autoclave, then ethylene was fed into the autoclave at a pressure of 30 bar (its calculated amount in the autoclave was 0.8 g). Then, after the ethylene supply ceased, carbon dioxide was fed into the autoclave until a pressure of 400 atm was established and the temperature was raised to 65 ° C.

Example 18

0.05 g of 2,2'-azoisobutyronitrile was charged into the autoclave and ethylene and vinyl chloride were fed to their ethylene: vinyl chloride ratio of 2 g: 8 g, respectively. Then, carbon dioxide was introduced into the autoclave until a pressure of 400 atm was established, and the temperature was raised to 65 ° C. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 19

9.2 g of vinyl acetate and 0.05 g of 2,2'-azoisobutyronitrile were charged into the autoclave, then ethylene and vinyl chloride were fed into the autoclave (their calculated amount in the autoclave was 0.15 g and 0.65 g, respectively). Then, carbon dioxide was introduced into the autoclave until a pressure of 400 atm was established, and the temperature was raised to 65 ° C. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 20

9.38 g of vinyl acetate, 5.27 g of VeoVa10 ^® , 0.88 g of butyl acrylate, 2.00 g of styrene, 0.17 g of 2,2'-azoisobutyronitrile were loaded into the autoclave. Then, carbon dioxide was introduced into the autoclave until a pressure of 400 atm was established, and the temperature was raised to 65 ° C. The stirrer was turned on and polymerization was carried out at the indicated temperature.

Example 21

Redispersible powder was obtained analogously to example 1 with the only difference that vinyl acetate was not loaded into the reactor, butyl acrylate was loaded in an amount of 5.27 g and 3.2 g of N-vinylformamide were additionally loaded into the reactor.

Example 22

Redispersible powder was obtained analogously to example 1 with the only difference that vinyl acetate was not loaded into the reactor, butyl acrylate was loaded in an amount of 4.37 g and 2.7 g of N-vinylpyrrolidone were additionally loaded into the reactor.

Example 23

Redispersible powder was obtained analogously to example 1 with the only difference that vinyl acetate was not loaded into the reactor, butyl acrylate was loaded in an amount of 5.00 g and 3.1 g of N, N-dimethyl acrylamide were additionally loaded into the reactor.

Example 24

Redispersible powder was obtained analogously to example 1 with the only difference that vinyl acetate was not charged into the reactor, butyl acrylate was loaded in an amount of 2.25 g, acrylonitrile was charged 1 g and 0.88 g of glycidyl methacrylate was additionally charged into the reactor.

Example 25

Redispersible powder was obtained analogously to example 1 with the only difference that 1.55 g of glycidyl acrylate and 0.88 g of methacrylonitrile were additionally charged into the reactor.

Example 26

Redispersible powder was obtained analogously to example 1 with the only difference that an additional 7 g of diphenylol propane formaldehyde oligomer with a molecular weight of Mn = 650, a content of methylol groups of 10%, butoxyl groups of 20%, synthesized according to the procedure described in patent materials RU 2318835, isolated from the solvent in a vacuum oven and ground to a powder state.

Example 27

Redispersible powder was obtained analogously to example 1 with the only difference being that instead of VeoVa10®, VeoVa11® was used, butyl acrylate was charged 1.24 g. Additionally, 1.77 g and 0.09 g of “Zimplex 15” were introduced into acrylic acid, and 2.2 The α-azoisobutyronitrile was used in an amount of 0.02 g. The synthesis was carried out at a temperature of 100 ° C.

Example 28

Redispersible powder was obtained analogously to example 1 with the only difference that vinyl acetate was loaded in an amount of 11.38 g, VeoVa10® was used in an amount of 1.95 g, and acrylonitrile was introduced in an amount of 2.32 g.

Example 29

Redispersible powder was obtained analogously to example 12 with the only difference that acrylonitrile was not administered, and VeoVa10® was administered in an amount of 4.74 g. Additionally, methacrylic acid was added in an amount of 0.53 g and Zimplex 15 in an amount of 0.01 g. Temperature raised to 100 ° C.

Example 30

Redispersible powder was obtained analogously to example 1 with the only difference that vinyl acetate was loaded in an amount of 9.45 g, acrylonitrile was introduced in an amount of 0.35 g. Methacrylic acid in an amount of 1.58 g and Zimplex 15 in an amount of 0.05 were additionally introduced. d. The temperature was raised to 80 ° C.

Example 31 (analogue is a traditional method of synthesis in the aquatic environment)

The reactor was charged with water, monomers, and an initiator listed in Example 1 to obtain a 30% aqueous dispersion. The stirrer was turned on and the temperature was raised to 65 ° C. At the indicated temperature, polymerization was carried out. Upon reaching the required molecular weight, the heating of the reactor was turned off. The polymer was filtered off and then dried using the hot spray drying method.

The glass transition temperature of all redispersible polymers obtained according to examples 1-31, lay in the range 0- + 40 ° C.

All obtained polymers were tested for redispersibility, which was determined by the following method: aqueous dispersions of polymer powder with its content equal to 30 wt. %, prepared by re-dispersing it in water when exposed to high shear forces. Next, the redispersibility of diluted reconstituted dispersions was determined, for which 100 ml of such a dispersion was placed in a graduated tube and the height of the settled solid layer was determined. The height of the settled solid layer in millimeters was measured after 24 hours of settling of the dispersion. Values exceeding 7 mm indicate unsatisfactory redispersibility of the powder.

The redispersibility of all dispersions obtained from polymer powders according to examples 1-27 after 24 hours had a height of the settled layer of solid substance less than 7 mm, which indicates their good redispersibility.

The synthesis products obtained by both methods were investigated using the IR spectroscopy method. According to IR spectrometry, it was found that the redispersible copolymer of the polymerization type (according to Example 1) synthesized according to the claimed technology in supercritical carbon dioxide had the same characteristics as the polymer synthesized according to the traditional method (according to Example 27 with the release of the final product from the solvent by spraying ), as evidenced by the identity of their IR spectra (Fig. 1). Based on the identity of the absorption bands of both spectra at 3400 cm ^-1 (ν (С-О)), 3150 cm ^-1 (νa (СН2)), 2950 cm ^-1 (νa (СН3)), 2580 cm ^-1 (ν ( OH)), 1650-1750 cm ^-1 (ν (С = O)), 1450 cm ^-1 (δ (СН2)), 1300 cm ^-1 (νa (С-С-О), ν (С-О) ), 1150 cm ^-1 (νs (С-С), δ (СН)), a conclusion was made about a similar chemical structure of both polymers. IR spectra of the obtained polymers were recorded on an IR-380 brand Nicolet (USA) IR Fourier spectrometer with a resolution of 2 cm ^-1 in the region from 400 to 4000 cm ^-1 at room temperature in the mode of transmission from tablets in KBr.

Thus, it has been proved that the synthesis of a redispersible polymer of the polymerization type under supercritical carbon dioxide is an alternative to the traditional method of synthesis in an aqueous or organic medium and allows one to obtain redispersible polymers with the required set of characteristics.

One of the important operational characteristics of redispersible polymers is the viscosity value of their dispersions. As you know, the high viscosity of the dispersions prevents their successful use as paints and varnishes.

Redispersible polymers obtained in an aqueous medium and under conditions of supercritical carbon dioxide (Examples 27 and 1, respectively) were dispersed in water and formed water dispersions stable during the day, which had similar structural parameters, as evidenced by the viscosity curves of aqueous dispersions of both polymers (Fig. . 2). The dependence of the viscosity of the aqueous dispersion of the redispersible polymer on shear stress was determined on a Reotest-2 rotational viscometer (Fig. 2). Operating temperature 25 ° C. The principle of operation of the rotational viscometer "Reotest-2" is based on measuring the angle of delay (α) of the inner cylinder during the deformation of a material located in the gap between two coaxially located cylinders at specified test conditions - temperature and rotor speed. As can be seen from FIG. 2, the logarithm of the lowest Newtonian viscosity for aqueous dispersions of both redispersible polymers is in the range of 0.55-0.70. The value of the logarithm of the shear rate corresponding to the complete destruction of the structures is not large in all cases and is approximately 2.2–2.5. Thus, the experimental data indicate a low degree of structure formation in aqueous dispersions of redispersible polymers and their ability to redisperse when small shear forces are applied.

To assess the dynamic viscosity of polymer solutions at different values of its concentration, we used an A&D SV-10 sinusoidal vibro viscometer (Japan). Operating temperature 25 ° C. The results of a study of the dynamic viscosity dependence of various polymer dispersions are shown in FIG. 3.

The figure shows that the dispersion based on the oligomers synthesized by the claimed technology (curves 2, 3, 4 - examples No. 1, 3, 12, respectively) have low viscosity values compared to the dispersion of the oligomer synthesized according to the prototype (curve 1). As can be seen from FIG. 3, the viscosity of the dispersion obtained on the basis of a redispersible polymer synthesized according to the prototype increased significantly when the polymer concentration was above 7%, which made its further use difficult.

Thus, redispersible polymers synthesized by the present method allow to obtain dispersions with a concentration of at least 15%, which suggests their successful use as paints and varnishes.

After obtaining an aqueous dispersion based on a redispersible polymer, the size of the formed dispersion particles and the effect on it of the amount of chain growth inhibitor introduced during polymer synthesis were studied. The particle size of the aqueous dispersion was investigated by dynamic light scattering. The test result is shown in FIG. 4. It can be seen from the above dependence that an increase in the number of chain growth restrictor introduced during the synthesis of a redispersible polymer leads to a decrease in the size of macromolecules, which is indirectly characterized by the particle size of the aqueous dispersion obtained on the basis of the redispersible polymer.

Another important characteristic of aqueous polymer dispersions is resistance to mechanical stress. This indicator is not only a characteristic of the colloidal state of the system, but it is an important technological indicator that makes it possible to use this dispersion as a paint and varnish material. The resistance of the polymer dispersion to mechanical stress was determined on a Maron device by the amount obtained at the end of the coagulum exposure [Reichsfeld V.O., Erkova L.N., Ruban V.L. Workshop on synthetic rubbers, L. Chemistry, 1967, 228 pp .; Colloidal Chemistry of Synthetic Latexes: A Training Manual. / R.E. Neumann, O.G. Kiseleva, A.K. Egorov, T.M. Vasilieva. - Voronezh: Publishing House of the Voronezh State University, 1984. - 196 p. ]. The amount of coagulum formed after 15 minutes of machining was determined, expressed as% of the amount of polymer in the analyzed volume of the aqueous dispersion. The rotor speed is 3000 rpm, the gap between the coaxial cylinders is 0.05 mm. The measurement results are shown in table 4. From the data in table 4 it is seen that the amount of coagulum of aqueous dispersions obtained by the proposed method is more than 2-3 times less than that of the aqueous dispersion obtained by the prototype.

An important technological indicator of the dispersion of polymers used in the paint industry is the wettability of the dispersion of the substrate. The good wettability of the substrate determines the ease of spreading of the dispersion over the surface and the formation of a quality defect-free coating. Wettability is characterized by a wetting angle. The technique for determining the contact angle is as follows: a drop of polymer dispersion of 1-10 mm ³ is applied to the surface with a microsyringe, and the equilibrium contact angle Θ is determined using a horizontal optical microscope with a goniometric attachment. The absolute error in determining the wetting angle is not more than 0.5 °. The measurement results are shown in table 4. From the data in table 4 it is seen that the contact angle of water dispersions obtained by the proposed method has a smaller value than the aqueous dispersion obtained by the prototype, which indicates better wettability and spreadability of the proposed polymer dispersions Compared to the prototype. This indicator is especially important when obtaining thin polymer coatings based on synthesized polymers (including those based on redispersible paints).

Example 28. Obtaining a redispersible paint material based on a polymer powder.

The components listed below (in parts by weight) were loaded into a ball mill and ground to a fineness of 65 microns:

Portland cement one hundred potassium silicate 10.0 CaCl ₂ 5,0 redispersible polymer 8.0 TiO ₂ 15.0 sodium polyphosphate 0.1 zeolite 5,0 mica 3.0 calcium stearate 2.0 defoamer BYK 024 0.05 ethyl cellulose 1,0 hydroxyethyl cellulose 1,0 ethylene glycol 1,0

The powder formed after grinding in a ball mill was the required form of water redispersible paint.

The ready-to-use paint material was obtained by adding water to the powder in the ratio powder: water 1: 1.1 (by weight) and thoroughly mixing first for at least 60 s and then after a fifteen-minute break for another 5 minutes.

The material was applied (with a brush, roller, paint sprayer) to metal, glass, wooden, concrete and plaster substrates. After curing, the coatings obtained were evaluated by their appearance, adhesion, and washability.

Based on liquid paints and varnishes obtained according to example 28 (using redispersible polymers synthesized in an aqueous medium and supercritical carbon dioxide (according to Examples 27 and 1, respectively)), coatings were formed and their operational properties were studied. It has been established that coatings are not washable and have high adhesion, impact strength, elasticity and chemical resistance. In particular, the coatings obtained were characterized by the following properties: adhesion - 1 point (maximum), chemical resistance in acidic and alkaline media - chemically resistant, elasticity - 1 mm, resistance to direct impact - 100 cm.

Thus, the advantages of the proposed method for producing polymer powders using supercritical carbon dioxide as a solvent are obvious: it has a high dissolving power and is inert with respect to most monomers; has a high diffusion coefficient (~ 100 times higher than that of a liquid) and low viscosity (~ 10-100 times lower than the viscosity of liquids); it is easily and without residue removed from the reaction zone at the end of the synthesis and it can be used cyclically; non-toxic, fire, explosion and environmentally friendly; cheap. In addition, there is no problem of breaking and transferring the chain to the solvent in the polymerization processes. Owing to the high diffusion rate, supercritical carbon dioxide also makes it possible to easily carry out additional purification of the reaction product from monomer and initiator residues — it is enough to rinse the resulting polymer with fresh fluid.

The advantages of the proposed technology for the synthesis of redispersible polymers in supercritical carbon dioxide are also the simplification of the technological process for the synthesis of redispersible polymers by reducing the number of process steps (compared with traditionally used synthesis technologies in an aqueous or organic solvent, there is no stage for polymer isolation from the solvent), reduction in the amount of equipment, and the absence the need to isolate the final product is a redispersible polymer Since the end of the synthesis, the solvent is removed independently from the reaction zone during transfer of the supercritical CO ₂ in a normal state; obtaining the final product directly in powder form, the dispersion value of which can be controlled by synthesis conditions (temperature and pressure), for example, the rate of removal of gaseous CO ₂ from the autoclave at the end of synthesis (the faster CO ₂ is removed, the finer the powder); lack of liquid waste; the possibility of using carbon dioxide cyclically, because carbon dioxide is one of the most frequent by-products of many technological processes in various industries, its use for the production of redispersible polymers solves the problem of utilization of carbon dioxide of the mentioned industries.

The absence of wastewater requiring polymerization during the polymerization process, the reduced amount of equipment needed to obtain the polymer, and the simplification of the process, ultimately lead to a significant reduction in the cost of the resulting product while maintaining its high performance. When redispersed in water, these polymer powders form a stable dispersion. The test results indicate that the inventive method for producing redispersible polymers in supercritical carbon dioxide allows to obtain materials identical in properties to redispersible polymers synthesized by traditional technology in aqueous dispersion.

It should be noted that the developed synthesis method allows not only to facilitate the process of obtaining redispersible polymer powders, but also allows to obtain redispersible oligomers with a wide range of predetermined operational characteristics, due to the wide range of applications of water-redispersible oligomers. The redispersible polymers obtained in supercritical carbon dioxide can be used both in the preparation of aqueous dispersions in order to obtain thin protective polymer films and inorganic binders for paint, construction and household applications.

Thus, the proposed method for the synthesis of redispersible polymers in a medium of supercritical carbon dioxide is extremely promising and environmentally friendly.

Claims (57)

1. A method of producing water-redispersible polymer powders, characterized in that at least two unsaturated monomers are loaded into the reactor, one of which is hydrophilic and the second hydrophobic, as well as a polymerization initiator, after which carbon dioxide is injected into the reactor to a certain pressure and carry out the heating of the starting components to a temperature that ensures the transition of carbon dioxide to a supercritical state; during the polymerization, the mixture is mixed to ensure its homogeneity, while the monomer they are taken in an amount that ensures the production of a polymer powder, the molecular weight of which is not more than 100,000, the glass transition temperature is in the range from 0 to + 40 ° C, and the average calculated equivalent mass of the hydrophobic part of the polymer powder is 1.3-1.5 times the theoretical equivalent mass of the hydrophobic part of the polymer, which determines the solubility of the polymer powder. 2. The method according to p. 1, characterized in that carbon dioxide is pumped to a pressure of up to 80-500 atm, the heating of the starting components is carried out to a temperature of 60-100 ° C. 3. The method according to p. 1, characterized in that to obtain a polymer with a molecular weight of not more than 100,000, the initiator is loaded into the reactor in an amount of 0, 1-5 wt. % by weight of monomers. 4. The method according to p. 1, characterized in that in order to obtain a polymer with a molecular weight of not more than 100,000, an additional chain growth regulator in an amount of not more than 5 wt. % by weight of monomers. 5. The method according to claim 4, characterized in that n-dodecyl mercaptan and / or tert-dodecyl mercaptan and / or mercaptopropionic acid and / or mercaptopropionic acid methyl ester are used as a chain growth regulator. 6. The method according to p. 1, characterized in that the initiator of polymerization using 2,2'-azoisobutyronitrile and / or benzoyl peroxide, or combinations thereof with reducing agents. 7. The method according to p. 6, characterized in that as the reducing agents use sodium hydroxymethanesulfinate and ascorbic acid, while reducing agents are loaded into the reactor in an amount of up to 5 wt. % by weight of loaded monomers. 8. The method according to p. 1, characterized in that in addition to the reactor load reinforcing polymer, which is used as a butanolized diphenylol propane formaldehyde oligomer with a molecular weight of Mn = 500-850, which is introduced in an amount of up to 30 wt. % by weight of a redispersible polymer powder, while after receiving a redispersible polymer powder, urotropin is added as a crosslinking agent. 9. The method according to p. 1, characterized in that carboxylic acids and / or nitriles of carboxylic acids and / or amides are used as hydrophilic monomers. 10. The method according to p. 1, characterized in that the hydrophobic monomers are esters of carboxylic acids and / or olefins and dienes and / or glycidyl acrylates and / or vinyl aromatic compounds and / or vinyl halides. 11. The method according to p. 9, characterized in that acrylic and / or methacrylic acids are used as carboxylic acids. 12. The method according to p. 9, characterized in that as the nitriles of carboxylic acids use acrylonitrile. 13. The method according to p. 9, characterized in that as amides use N-vinylformamide, and / or N, N-dimethylacrylamide, and / or N-vinylpyrrolidone, and / or diacrylamide. 14. The method according to p. 9, characterized in that when using carboxylic acids, zinc oxide compositions, for example, Zimplex 15 by Munzing Chemie GMBH in an amount of 2-5, are additionally added to the obtained polymer powder as a crosslinking agent wt. % by weight of loaded acids. 15. The method according to p. 10, characterized in that the esters of carboxylic acids use vinyl esters of carboxylic acids with 1-15 carbon atoms, and / or esters of acrylic and methacrylic acids with branched or unbranched alcohols with 1-15 carbon atoms. 16. The method according to p. 15, characterized in that the vinyl esters of carboxylic acids with 1-15 carbon atoms use vinyl acetate, and / or vinyl laurate, and / or vinyl pivalate, and / or vinyl esters of α-branched monocarboxylic acids with 9 -15 carbon atoms. 17. The method according to p. 15, characterized in that the esters of acrylic and methacrylic acids with branched or unbranched alcohols with 1-15 carbon atoms use methyl acrylate and / or methyl methacrylate and / or ethyl acrylate, ethyl methacrylate, and / or propyl acrylate, and / or n-butyl acrylate and / or butyl methacrylate and / or norbornyl acrylate. 18. The method according to p. 10, characterized in that ethylene and / or propylene and / or 1,3-butadiene and / or decen are used as olefins and dienes. 19. The method according to p. 10, characterized in that glycidyl acrylate and / or glycidyl methacrylate are used as glycidyl acrylates. 20. The method according to p. 10, characterized in that when using glycidyl acrylates, amines are additionally introduced into the obtained polymer powder as a crosslinking agent in an amount of 2-5 wt. % by weight of loaded glycidyl acrylate. 21. The method according to p. 10, characterized in that styrene and / or divinylbenzene are used as vinyl aromatic compounds. 22. The method according to p. 10, characterized in that as the vinyl halides use vinyl chloride and / or vinyl fluoride. 23. The method according to p. 1, characterized in that in addition to the reactor load functional additives, which use a protective colloid, and / or color and / or luminous additives, and / or corrosion inhibitor, and / or anti-corrosion agent, and / or a biocidal additive and / or dispersant. 24. The method according to p. 23, characterized in that as a protective colloid using partially saponified polyvinyl alcohol with a degree of hydrolysis of from 80 to 98 mol. %, and / or cellulose, and / or their carboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivatives, and / or starch, while the protective colloid is used in an amount of up to 50 wt. % by weight of loaded monomers. 25. The method according to p. 23, characterized in that as color and / or luminous additives using pigments, and / or fluorescent pigments, and / or waterproof phosphors, which are introduced in an amount of up to 10 wt. % by weight of loaded monomers. 26. The method according to p. 23, characterized in that as a corrosion inhibitor use a zinc-containing complex salt, for example, brand SER-AD-FA-179 company "Servo"; and / or sodium nitrite and / or sodium benzoate, while the corrosion inhibitor is administered in an amount of up to 2 wt. % by weight of loaded monomers. 27. The method according to p. 23, characterized in that as an anticorrosive agent using an oxyaminophosphate complex of calcium and magnesium, for example, brand "Pigmentan EA" company "Pigmentan Ltd", while the anti-corrosion agent is administered in an amount of up to 5 wt. % by weight of loaded monomers. 28. The method according to p. 23, characterized in that as a biocidal additive using compositions based on isothiazoline and halogenated derivatives of alkanol, for example, brand Metatin K 520 company "Acima"; and / or based on tetramethylthiuram disulfide, for example, brand Tiuram D; and / or based on 2-n-octyl-4 isothiazoline, for example, the brand Skane 8 company "Rohm and Haas", while the biocidal additive is administered in an amount up to 5 wt. % by weight of loaded monomers. 29. The method according to p. 23, characterized in that as a dispersant use compositions of the brand OP-7 and / or OP-10, which are the products of processing a mixture of mono- and dialkylphenols with ethylene oxide, while the dispersant is introduced in an amount of up to 5 wt. % by weight of monomers. 30. The method according to claim 1, characterized in that an anti-caking agent is added to the obtained polymer powder, which is calcium magnesium carbonate and / or talc and / or kaolin and / or silicates, for example magnesium hydrosilicate, anti-caking agent is administered in an amount up to 30 wt. % by weight of loaded monomers. 31. A water-redispersible polymer powder obtained by polymerizing a mixture of unsaturated monomers of at least one hydrophobic and at least one hydrophilic, in the presence of a polymerization initiator and supercritical carbon dioxide, characterized in that it is a finely divided powder, the estimated equivalent mass of the hydrophobic part of which is 1.3-1.5 times larger than the theoretical equivalent mass of the hydrophobic part of the polymer, which determines the solubility of the poly ernogo powder, the molecular weight is less than 100,000 and a glass transition temperature is in the range of from -0 to + 40 ° C. 32. The polymer powder according to p. 31, characterized in that the amount of polymerization initiator in the mixture is from 0.1% to 5 wt. % by weight of monomers. 33. The polymer powder according to p. 31, characterized in that the mixture further comprises a chain growth regulator in an amount of not more than 5 wt. % by weight of monomers. 34. The polymer powder according to claim 33, characterized in that n-dodecyl mercaptan and / or tert-dodecyl mercaptan and / or mercaptopropionic acid and / or mercaptopropionic acid methyl ester are used as a chain growth regulator. 35. The polymer powder according to p. 31, characterized in that 2,2'-azoisobutyronitrile and / or benzoyl peroxide or combinations thereof with reducing agents are used as the polymerization initiator. 36. The polymer powder according to p. 31, characterized in that as reducing agents are used sodium hydroxymethanesulfinate and / or ascorbic acid in an amount of up to 5 wt. % by weight of monomers. 37. The polymer powder according to p. 31, characterized in that it further comprises a butanolized diphenylol propane formaldehyde oligomer with a molecular weight of Mn = 500-850 in an amount of up to 30 wt. % by weight of redispersible polymer powder, as well as urotropin as a crosslinking agent. 38. The polymer powder according to p. 31, characterized in that the hydrophilic monomers used are carboxylic acids and / or nitriles of carboxylic acids and / or amides. 39. The polymer powder according to p. 31, characterized in that the esters of carboxylic acids and / or olefins and dienes and / or glycidyl acrylates and / or vinyl aromatic compounds and / or vinyl halides are used as hydrophobic monomers. 40. The polymer powder according to p. 38, characterized in that acrylic and / or methacrylic acids are used as carboxylic acids, the polymer powder additionally containing a crosslinking agent, which is based on zinc oxide compositions, for example, Zimplex 15 "Firm" Munzing Chemie GMBH "in an amount of 2-5 wt. % by weight of loaded acids. 41. The polymer powder according to claim 38, characterized in that acrylonitrile is used as nitriles of carboxylic acids. 42. The polymer powder according to claim 38, characterized in that N-vinylformamide and / or N, N-dimethylacrylamide and / or N-vinylpyrrolidone and / or diacrylamide are used as amides. 43. The polymer powder according to claim 39, characterized in that the esters of carboxylic acids used are vinyl esters of carboxylic acids with 1-15 carbon atoms and / or esters of acrylic and methacrylic acids with branched or unbranched alcohols with 1-15 carbon atoms. 44. The polymer powder according to claim 43, characterized in that vinyl acetate, / or vinyl laurate, and / or vinyl pivalate, and / or vinyl esters of α-branched monocarboxylic acids are used as vinyl esters of carboxylic acids with 1-15 carbon atoms 9-15 carbon atoms. 45. The polymer powder according to claim 43, characterized in that methyl acrylate and / or methyl methacrylate and / or ethyl methacrylate and / or propyl acrylate are used as esters of acrylic and methacrylic acids with branched or unbranched alcohols with 1-15 carbon atoms and / or n-butyl acrylate and / or butyl methacrylate and / or norbornyl acrylate. 46. The polymer powder according to claim 39, characterized in that ethylene and / or propylene and / or 1,3-butadiene and / or decene are used as olefins and dienes. 47. The polymer powder according to claim 39, characterized in that glycidyl acrylate and / or glycidyl methacrylate are used as glycidyl acrylates, the polymer powder additionally containing a crosslinking agent, for which amines are used in an amount of 2-5 wt. % by weight of glycidyl acrylate. 48. The polymer powder according to claim 39, characterized in that styrene and / or divinylbenzene are used as vinyl aromatic compounds. 49. The polymer powder according to claim 39, characterized in that vinyl chloride and / or vinyl fluoride are used as vinyl halides. 50. The polymer powder according to p. 31, characterized in that it further comprises functional additives, which are used as a protective colloid, and / or color and / or luminous additives, and / or anti-caking agent, and / or corrosion inhibitor, and / or an anti-corrosion agent and / or biocidal additive and / or dispersant. 51. The polymer powder according to claim 50, characterized in that partially saponified polyvinyl alcohol with a degree of hydrolysis of from 80 to 95 mol% is used as a protective colloid. %, and / or cellulose, and / or their carboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivatives, and / or starch, while the protective colloid is contained in an amount of up to 50 wt. % by weight of monomers. 52. The polymer powder according to claim 50, characterized in that pigments, and / or fluorescent pigments, and / or waterproof phosphors in an amount of up to 10 wt.% Are used as color and / or luminous additives. % by weight of monomers. 53. The polymer powder according to claim 50, characterized in that the calcium carbonate magnesium and / or talc and / or kaolin and / or silicates, for example magnesium hydrosilicate, with a particle size of 10 nm to 10 are used as an anti-caking agent microns, while the anti-caking agent is contained in an amount up to 30 wt. % by weight of monomers. 54. The polymer powder according to claim 50, characterized in that a zinc-containing complex salt, for example, SER-AD-FA-179 from Servo, is used as a corrosion inhibitor; and / or sodium nitrite and / or sodium benzoate, while the corrosion inhibitor is contained in an amount up to 2 wt. % by weight of monomers. 55. The polymer powder according to p. 50, characterized in that the anticorrosive agent used is an oxyaminophosphate complex of calcium and magnesium, for example, the brand "Pigmentan EA" of the company "Pigmentan Ltd", while the anticorrosive agent is contained in an amount of up to 5 wt. % by weight of monomers. 56. The polymer powder according to claim 50, characterized in that, as a biocidal additive, Acima Metatin K 520 formulations based on isothiazoline and halogenated alkanol derivatives are used; and / or Tiuram D brand based on tetramethylthiuram disulfide; and / or Skein brand 8 of the company "Rohm and Haas" based on 2-n-octyl-4 isothiazoline, while the biocidal additive is contained in an amount of up to 5 wt. % by weight of monomers. 57. The polymer powder according to p. 50, characterized in that the dispersant used is the composition of the brand OP-7 and / or OP-10, which are the products of processing a mixture of mono- and dialkylphenols with ethylene oxide, while the dispersant is contained in an amount of up to 5 wt. . % by weight of monomers.

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