Polyacrylates are polymers and copolymers of acrylic and methacrylic acid and their derivatives.
Copolymers of acrylic monomers with various unsaturated compounds are used as film-forming agents.
Monomers:
acrylic acid
methacrylic acid
and their derivatives of the general formula
Including esters, amides, nitriles, for example:
methyl methacrylate
butyl methacrylate
acrylamide
acrylonitrile
Esters of methacrylic (acrylic) acid are also used, the alkyl substituent R¢ of which contains functional groups (hydroxyl, epoxy): monoacrylic ethers of glycols, glycidyl esters of acrylic acids, for example:
hydroxyethyl acrylate
glycidyl methacrylate
Of other types of monomers, styrene is most often used in the synthesis of polyacrylates:
and vinyl-n-butyl ether:
Schematically, a polyacrylic copolymer can be represented by the following formula:
Units of acrylic acid derivatives in the copolymer provide elasticity to the film, and this effect increases with increasing length of the alkyl radical.
Methacrylic acid derivatives give the copolymer hardness and rigidity. As the length of R increases from C1 to C14 and its branching, the alkyl acrylate is converted into a plasticizing comonomer.
Non-acrylic components also change the properties of the film former over a wide range. Thus, styrene gives it rigidity, vinyl butyl ether - elasticity. By selecting components and adjusting their ratio, it is possible to obtain copolymers that satisfy various requirements.
Polyacrylates used as film-forming agents are usually divided into two groups - thermoplastic and thermosetting.
Thermoplastic polyacrylates are products of copolymerization of monomers that do not contain other functional groups except for double bonds. These are copolymers of methyl methacrylate with methyl and butyl acrylate, butyl methacrylate, etc. The formation of coatings based on thermoplastic polyacrylates is not accompanied by chemical transformations and proceeds quickly when room temperature, but received varnish coatings at elevated temperatures they soften.
Thermosetting polyacrylates are produced by copolymerization of two or more comonomers, at least one of which, in addition to the double bond, has some kind of functional group. Curing of such materials occurs as a result of chemical transformations in which this functional group participates, for example, with the introduction of hardeners.
Based on the type of functional groups, thermosetting polyacrylates are divided into:
- with N-methylol groups;
- with epoxy groups;
- with hydroxyl groups;
- with carboxyl groups.
Polyacrylates with N-methylol groups are obtained by using acrylic or methacrylamide as a comonomer. This is how, for example, copolymers of these amides are obtained with butyl methacrylate, acrylonitrile, styrene, etc.
Upon subsequent treatment of copolymers with formaldehyde, N-methylol derivatives of amides are formed. To increase the stability of these copolymers, some of them are esterified with n-butyl alcohol. Schematically, the formation of polyacrylates with N-methylol groups and their esterified derivatives can be represented as follows:
Here M is a comonomer.
Methylated copolymers of acrylic and methacrylamide at 160-170°C can be cured by conventional condensation reactions of N-methylol derivatives or their esters. To cure these polymers, hardeners can also be used - phenol-, urea-, melamine-formaldehyde and epoxy oligomers, polyisocyanates and hexamethoxymethylmelamine.
The mass fraction of amide units in the copolymer should not exceed 30%, otherwise the fragility of the coatings sharply increases.
Polyacrylates with epoxy groups are obtained by polymerization of a mixture of monomers, one of which contains an epoxy group (glycidyl acrylate, glycidyl methacrylate). These copolymers are cured by all common epoxy oligomer hardeners. But their use is limited by the scarcity of glycidyl ethers.
The composition of hydroxyl-containing polyacrylates includes hydroxyethyl or hydroxypropyl methacrylates. They are cured with polyisocyanates, as well as melamine and urea-formaldehyde oligomers.
Carboxyl-containing copolymers are obtained by introducing into the acrylic copolymer composition from 3 to 25% monobasic unsaturated carboxylic acids, for example acrylic or methacrylic. Dibasic unsaturated acids or their anhydrides (for example, maleic) are also used. Copolymers containing up to 5% unsaturated acids are sometimes used as thermoplastics. A small amount of polar carboxyl groups gives coatings based on them increased adhesion.
Coatings based on acrylic copolymers are optically transparent, with high gloss, chemical resistance, and aging resistance. Coatings based on thermoplastic polyacrylates have high weather and light resistance. They are colorless, sand and polish well, and retain their shine for a long time.
Thermosetting polyacrylates form films with high mechanical strength, which persists under conditions elevated temperatures, high water, atmospheric, petrol and chemical resistance, high adhesion to metals, as well as good decorative properties.
Coatings based on polyacrylates with methylol groups are characterized by particularly high adhesion to various metals and primers, very high mechanical strength and high water resistance. Polyacrylates with epoxy groups have exceptional anti-corrosion properties.
Various paints and varnishes are produced based on polyacrylates:
- solutions in organic solvents (varnishes);
- non-aqueous dispersions;
- aqueous dispersions;
- water-soluble systems;
- powder materials.
Both thermoplastic and thermosetting polyacrylates are used as film-forming agents in the manufacture of varnishes. Solvents: esters, ketones, aromatic hydrocarbons. Polyacrylates for varnishes are obtained by polymerizing monomers in suspension or in a solvent. The solutions are directly used in the form of varnishes.
Varnishes based on polyacrylates are used in the automotive industry, for painting rolled metal, aluminum building structures, as well as household appliances ( washing machines, refrigerators).
Non-aqueous dispersions polyacrylates with a particle size of 0.1-30 μm can, for example, be obtained by copolymerizing acrylic monomers with a stabilizer in volatile organic solvents that do not dissolve the copolymers (aliphatic hydrocarbons). Acrylic monomers with substituents that have a high affinity for the liquid acting as the reaction medium, for example lauryl methacrylate, are used as stabilizers.
Main Application aqueous dispersions acrylates – automotive industry. They are also used to produce high-quality coatings with good adhesion to various substrates - fabric, paper, wood, concrete, brick, etc. In addition, they are used in construction paints (due to low permeability into the substrate and high thixotropy).
Aqueous dispersions(latexes) are produced by emulsion polymerization in the presence of water-soluble initiators and surfactants (emulsifiers). Based on them, emulsion paints are produced to protect products made of ferrous and non-ferrous metals and for exterior and interior decoration premises.
Water-soluble polyacrylates
synthesized by copolymerization of several monomers, at least two of which have different polar reactive groups, ensuring the solubility of the polymer in water and its curing on the substrate.
They are received by:
- copolymerization of acrylic monomers in water-miscible organic solvents;
- emulsion copolymerization followed by transferring the latex into an aqueous solution by neutralizing the carboxyl groups of the copolymer with amines.
Water-soluble polyacrylates are used to produce paint and varnish materials applied by electrophoresis. The resulting films have better adhesion to the substrate than polyacrylate coatings applied by other methods.
For getting powder materials use only thermosetting polyacrylates with carboxyl, hydroxyl and epoxy groups. In powder materials, copolymers are used in combination with hardeners. Polyacrylate powder materials are applied by electrostatic spraying and used for painting car bodies, household electrical appliances, etc.
In Fig. 57 shows a diagram of the production of acrylic copolymer by the emulsion method.
In reactor 6, equipped with a steam-water jacket, an aqueous phase is prepared, consisting of water heated to 50°C and an emulsifier, and with vigorous stirring, a mixture of monomers purified from the inhibitor and a pre-prepared solution of a water-soluble initiator (for example, ammonium persulfate) are loaded. Copolymerization is carried out in a stream of nitrogen at 75-80°C. Upon completion of the synthesis, the copolymer emulsion, with continuous stirring, is transferred to apparatus 9, which contains a 10% sodium chloride solution heated to 60-70°C; in this case, the copolymer emulsion is destroyed. Then the reaction mixture, pre-cooled to 30°C, is fed to a horizontal washing centrifuge 10 with a screw discharge of sediment, in which the polymer is squeezed out from the aqueous phase and washed with water. Drying of the pressed and washed polymer is carried out in a “fluidized bed” dryer 12, after which the finished copolymer is sent through the receiving hopper 13 for packaging.
Rice. 57. Technological diagram of the process for producing polyacrylate using the emulsion method:
1, 2, 7 – weight measuring instruments; 3 – volumetric measuring cup; 4, 8 – capacitors; 5 – liquid meter; 6, 9 – reactors; 10 – washing centrifuge; 11 – auger;
12 – “fluidized bed” dryer; 13 – receiving hopper
The scheme for the production of acrylic copolymer in a solvent is shown in Fig. 58.
The synthesis of the copolymer according to this scheme is carried out in reactor 10, equipped with a jacket for heating with water vapor. A solvent is loaded into it (via a liquid meter 6) and a pre-prepared mixture of monomers containing required amount organosoluble initiator. A mixture of monomers with the addition of an initiator is prepared in apparatus 7, into which all the necessary components are supplied from weight measuring cups 1 and 2 and volumetric measuring cup 3. Copolymerization is carried out at 60-90°C (depending on the type of initial monomers and initiator) in a flow of inert gas. The resulting copolymer solution (varnish) is poured into an intermediate container 11, from where it is first sent for purification by filtration and then for packaging.
Rice. 58. Technological diagram of the process for the production of polyacrylate in a solvent:
1, 2, 5 – weight measuring instruments; 3 - volumetric measuring cup; 4, 8- capacitors; 6 - liquid meter; 7 – mixer; 9 - centrifugal pump; 10 - reactor; 11-intermediate capacity; 12, 14 – gear pumps; 13 - disc filter
Polymers of acrylic and methacrylic acid derivatives, or so-called polyacrylates, are a large and diverse class of polymerization polymers widely used in technology.
The significant asymmetry of the molecules of acrylic and methacrylic esters determines their greater tendency to polymerize.
Polymerization has a chain radical nature and occurs under the influence of light, heat, peroxides and other factors that initiate the growth of free radicals. Pure thermal polymerization is very slow and this method is rarely used. Typically, polymerization is carried out in the presence of initiators—benzoyl peroxide and water-dissolved peroxides. Three main methods of initiated polymerization of esters are used: block, water-emulsion and in solvents.
It is advisable to use the block polymerization method for the production of polymethyl methacrylate, which is produced in the form of transparent and colorless plates and blocks (organic glass). Polymethyl methacrylate in the form of a block polymer is obtained by thoroughly mixing the initiator - benzoyl peroxide - with the monomer and then pouring the mixture into glass forms. The main difficulty of the block polymerization process is the difficulty of adjusting the temperature inside the block. Due to the exothermic nature of polymerization and the low thermal conductivity of the polymer (0.17 W/m-°C), overheating inside the block is inevitable due to an increase in the reaction rate and, consequently, a sharp increase in temperature. This leads to evaporation of the monomer and the formation of blisters if the outer layers of the block are already sufficiently viscous and prevent the release of gases from it. To a certain extent, swelling can be avoided by changing the concentration of the initiator and the polymerization temperature. The thicker the resulting block, the lower the initiator concentration, the slower the temperature rise and the lower the polymerization temperature. It must be borne in mind that local overheating, which is completely impossible to avoid, inevitably leads to internal stresses in the block due to different degrees of polymerization in its internal and external layers.
Production process organic glass includes preparation of molds and their pouring, preliminary and final polymerization and release of molds. The molds are usually made of polished mirror silicate glass, which must be thoroughly washed under conditions that prevent the ingress of dust. To make the mold, take two glass sheets. Gaskets made of flexible elastic material are placed on the edges of one of them, equal in height to the thickness of the block being manufactured. These spacers are covered with a second sheet of glass, after which the edges are covered with strong and thin paper, leaving a hole for pouring monomer. At the same time, prepare the mixture by thoroughly mixing the monomer, initiator and plasticizer. Mixing can be done in a nickel boiler equipped with a propeller or anchor mixer, hermetically sealed with a spherical lid, which has a hatch and fittings for loading monomer, initiator and other components. Mixing is carried out at normal temperature for 30-60 minutes, after which the mixture flows through the bottom drain fitting into the weighing measuring cups, and from the measuring cups through a funnel into the molds. Polymerization is carried out by sequentially passing the filled molds through a series of chambers with approximately the following regime: in the first chamber at 45--55°C they are kept for 4--6 hours, in the second at 60--66°C for 8--10 hours and in the third at 85--125°C - 8 hours. At the end of polymerization, the forms are immersed in water, after which the blocks can be easily separated from the silicate glasses. The finished sheets are sent for trimming and polishing. The sheets should be transparent, without bubbles or swelling. Dimensions (with tolerances) and physical and mechanical properties must correspond technical specifications. Polymethyl methacrylate glasses are made in various thicknesses - from 0.5 to 50 mm and sometimes more.
Water-emulsion polymerization of acrylates is used to produce casting and pressing powders, as well as persistent water dispersions such as latex. Water and acrylic ether are taken in a ratio of 2: 1. If a hard elastic material is required, then it is rational to use the “bead” method of suspension polymerization, obtaining a granular polymer. The initiator is benzoyl peroxide, which is dissolved in the monomer (0.5 to 1%). Magnesium carbonate and polyacrylic acid are used as emulsifiers. polyvinyl alcohol and other water-soluble polymers. The size of the granules depends on the concentration of the emulsifier and the mixing speed. Water and monomer are taken in ratios of 2:1 or 3:1. The process of producing granular polymer consists of loading raw materials into a reactor, polymerization, filtration and washing of polymer granules, drying and sieving.
Distilled water and monomer are sequentially loaded from a measuring tank into a nickel reactor equipped with a steam jacket and a stirrer, then the emulsifier is added manually through a fitting. After stirring for 10-20 minutes, a plasticizer, dye and initiator, soluble in the monomer, are introduced into the reactor. By supplying steam to the reactor jacket, the temperature is raised to 70-75°C. After 40-60 minutes, due to the heat released as a result of polymerization, the temperature in the reactor rises to 80-85°C. The temperature can be controlled by supplying water or steam to the reactor jacket. The process is controlled by determining the monomer content. Polymerization lasts 2-4 hours; upon completion of polymerization, the reaction mixture is transferred to a centrifuge with a basket of of stainless steel, in which the polymer granules are easily separated and washed repeatedly with water to remove the emulsifier.
The washed powder is loaded onto aluminum baking sheets thin layer and dried in ovens with a slow rise in temperature within 40-70°C for 8-12 hours. After drying, the powder is sifted and placed in a container. Granular polymethyl methacrylate can be used to make varnishes without processing.
To obtain pressing powders, granulated polymer must be passed through rollers for 3--5 minutes at 170--190°C; During this operation, plasticizers and dyes can be added to polymethyl methacrylate. Rolled sheets are crushed in an impact cross mill and sifted through a sieve.
Lampshade Abacus
Top plate of a column capital; in architecture - the crowning part of the column, which takes on the weight of the cornice.
Abaca Avant-garde The general name for a number of movements in the art of the twentieth century. Avant-garde is the negation of traditional forms of art, the destruction of established aesthetic views, and a tendency toward expression.
Avant-garde Asian style The main features of this style are order, balance, clarity and simplicity. Interest in Feng Shui has made this style popular recently. Texture, a neutral palette and an emphasis on the concept of home as a sanctuary are all important. This style is accurately described by the phrase “less is more.”
Asian style Acanthus South herbaceous plant with large serrated leaves collected in the form of rosettes. The acanthus motif is widely used in ancient art.
Acanthus Watercolor Water-soluble paint and painting technique using the effect of transparency of the paint layer.
Colloquial name for polymers based on acrylic acid derivatives and materials made from them.
Acrylic Axonometry A method of depicting objects in a drawing using parallel projections. This image is characterized by great clarity, because illustrates a 3D model.
Axonometry Accent of composition The main part, the compositional center.
Allegory
Conventional image of an abstract concept.
Diamond edge
Decorative elements in the shape of pieces of precious stones.
A recess or niche in a wall. An alcove originally designated a sleeping area, a bed enclosed by a curtain. IN modern interior alcoves are small side rooms into which light does not penetrate directly from the outside, but only from other rooms through glass doors or windows.
Alcove Empire Late classicism style (1st third of the 19th century). Characterized by massive lapidary, emphatically monumental forms; rich (often exotic) decor; reliance on the artistic heritage of imperial Rome, the use of military-imperial symbols. The style developed during the reign of Napoleon I Bonaparte.
Empire Amphora Ancient Greek vase with a narrow neck.
Painting with colored clay on ceramics.
Engobe Entablature Beam floor span, supported by columns, and consisting of an architrave, frieze and cornice. An entablature is an integral part of an architectural order.
Entablature Antiquity History and culture Ancient Greece And Ancient Rome, as well as countries and peoples.
Flooring, a shelf under the ceiling for storing various things, separated from the room by doors. The word is also used to refer to the top of a cabinet. The mezzanine is also called the upper part high room, divided into two mezzanines.
Mezzanine Anthropometry One of the branches of anthropology that studies the dimensional characteristics of the structure, basic movements and postures of the human body. Anthropometry establishes average values for people of different gender, age, ethnicity and geographical region. Anthropometric data is used in design to ensure the proportionality of objects to humans, and as a result - ease of use and comfort.
Entourage
Environment, environment. That which accompanies the visual center, the main element. To some extent, the surroundings can be compared to the scenery in which the main action takes place.
A series of interconnecting rooms, doorways which are on the same axis. Characteristic of Baroque and Classicism.
Enfilade Applique A technique of decorative and applied art that creates an ornament or any image by superimposing pieces of another material onto the main background.
A flat or thin stucco ornament with a complex, usually symmetrical, pattern stylizing plant shoots (sometimes in combination with geometric shapes, inscriptions, images of people and animals). Borrowed by European art of the Middle Ages from the ornamental compositions of Islamic art.
Arabesque Arch A type of architectural structure, an arched covering of an opening - the space between two supports - columns, pylons.
Arch of Arcatur. Arcature frieze. Row decorative arches on the facade of the building or on the walls inside.
Arcatura. Arcature frieze. Flying buttresses In Gothic basilicas there are arched bridges that transfer the thrust forces of the arches of the central vault to the buttresses; form the exoskeleton supporting structures.
Flying buttresses Harlequin Furniture with a secret, appearance which does not correspond to the function.
Harlequin Reinforcing Window Profile Steel reinforcing element located inside the PVC profile.
1920-1940 Direction, geometric style in architecture and home furniture, popular in the 20s and 30s of the 20th century. Characteristic emphatically geometric, rounded, “flowing” facades, wooden furniture with chrome handles and other details, glass countertops. Art Deco uses solid maple, ash, rosewood, and madronya wood. Deco style has many sources: cubist drawings, American Indian art, modern automotive and aviation design.
Art Deco Art Nouveau A style developed in France and Europe in the late 19th century, with decorative flowing lines. Nature is a source of inspiration, which is why the style is characterized by themes of flowers, leaves, birds and insects. Natural motifs are often fairy-tale and asymmetrical. This style is also characterized by images of women with long straight hair and long dresses.
Art Nouveau Archaic Ancient, characteristic of antiquity; in Greek art - the period until the middle of the 5th century. BC e.
Archaic
Smells of antiquity, outdated.
Architectonics
Structural patterns inherent in the design of a building, sculpture.
Architectural division
A general designation for columns, pilasters, cornices, profiles, arches, arcades, balusters, risalits, etc., adopted in architectural structures, which can be found in old furniture products.
Architectural
A type of construction characteristic of the art of construction.
A load-bearing column in the form of a powerful male figure on furniture or buildings.
Atlas Atrius. Atrium. The central part of the ancient Roman and ancient Italian dwelling (domus), which was an internal light courtyard, from where there were exits to all other rooms. IN modern architecture atrium is a central, usually multi-light, distribution space public building, insolated through a skylight or an opening in the ceiling.
Atrius. Atrium. Atticus The wall above the cornice crowning the structure. The attic is often decorated with reliefs or inscriptions.
