Technological scheme for obtaining complex polyesters. Technical methods for carrying out polycondensation
Polycondensation in melt and solution
POLYETHYLENE TEREPHTHALATE.. 2
Polyester acrylates. 7
Polycarbonate production. nine
POLYESTERS
Heterochain polyesters include high molecular weight compounds4 containing essential ester bonds in the main chain. In general, the structure of linear polyesters of dicarboxylic acids and diols can be represented by the formula [-OCRCOOR "O-)", where R is the residue of the dicarboxylic acid, and R" is the residue of the diol.
Synthetic polyesters were first obtained over 100 years ago. In 1833, Gay-Lussac and Peluza synthesized polyester by heating lactic acid. Unsaturated polyesters of maleic and fumaric acids with ethylene glycol were obtained in 1.894 by Forlender. In 1901, Smith synthesized polyesters from phthalic anhydride and glycerol.
Intensive research in the field of polyesters began after 1925, when, as a result of the work of Carothers, Madsorov, Kinley and other scientists, polyesters of various structures were obtained and the possibility of their practical use was shown. The beginning of the industrial production of glyphthalic, and then other alkyd polymers, dates back to the same time. In 1941, Winfield and Dixon synthesized polyethylene terephthalate, the production of which is now steadily increasing. In the last decade, the industrial production of polycarbonates - polyesters of dihydric phenols and carbonic acid, as well as new heat-resistant polyesters of dihydric phenols and aromatic dicarboxylic acids, called polyarylates, has been mastered.
Of the aliphatic polyesters, unsaturated polyesters, synthesized from glycols and unsaturated dicarboxylic acids, have become widespread in recent years.
ALKYD POLYMERS
Alkyd polymers are polycondensation products of polybasic acids with polyhydric alcohols. Glyphthalic polymers have the greatest technical application,
obtained by polycondensation of phthalic anhydride with glycerin:
Such modified polyesters are able to polymerize when heated in air, giving durable films.
In practice, drying oils such as linseed are used to obtain alkyd oligomers and polymers. To do this, a preliminary reaction of glycerolysis is carried out by heating glycerol with oils, and the resulting monoglycerides are used for polycondensation with phthalic anhydride.
Pentaerythritol is also used as an alcohol component for the synthesis of alkyd polymers. pentaerythritol containing
Polycondensation is usually carried out at an equimolar ratio of phthalic anhydride (3 mol) and glycerol (2 mol) at 150-180°C. At the first stage, the formation of acidic esters containing acidic and hydroxyl groups occurs, which can be further esterified, first to obtain polymers of a linear structure, and then (at higher temperatures) to transform them into polymers of a three-dimensional structure. The second stage proceeds much more slowly than the first. Isolation of water begins after the completion of the reaction by about 50%, when all the anhydride groups of phthalic anhydride are practically used up. The further process is the esterification of carboxyl groups with alcohol. Due to the greater reactivity of the α-hydroxyl groups of glycerol, α-substituted mono- and diesters are formed first of all, then the p-hydroxyl groups of glycerol react. At 75-80% conversion, the glyptal polymer (molecular weight 700-1100) gelatinizes. Premature gelatinization can be avoided by introducing a monobasic acid, a monohydric alcohol, or other additives into the reaction mixture. When using unsaturated fatty acids (for example, oleic, linoleic) as modifying additives, polyesters are obtained containing double bonds in side branches:
the molecule has equivalent primary alcohol groups, reacts with dibasic acids more vigorously than glycerol, so gelatinization in this case occurs at an earlier stage of the reaction. Polypentaerythritol phthalates are modified to prevent gelatinization. The higher functionality of pentaerythritol compared to glycerol makes it possible to use oils in much larger quantities for the modification of alkyd polymers, to replace drying oils with semi-drying and even non-drying ones, which makes coatings based on such polymers much more elastic.
The drying rate of modified alkyd polymers is a function of their unsaturated acid content. To speed up drying, desiccants are added to them.
In recent years, research in the field of synthesis of alkyd resins has been carried out in the following areas: 1) replacement of glycerol and pentaerythritol with other polyhydric alcohols (for example, trimethylolpropane, trimethylolethane); 2) partial replacement of phthalic anhydride with other acids (for example, trimellitic anhydride, isophthalic, fumaric, maleic acids); 3) the use of various oils, fatty acids and products of their processing for the modification of alkyd polymers (for example, methyl esters of fatty acids of linseed, soybean, dehydrated castor, tung oils, dimeric acids, etc.).
As a result of these works, alkyd polymers of various chemical structures were obtained. Coatings of alkyd polymers based on trimethylolpropane modified with tall oil fatty acids in terms of heat resistance, hardness, toughness, resistance to 5% alkali and boiling water, gloss retention compare favorably with coatings from corresponding alkyd resins based on trimethylolethane and glycerin .
The use of isophthalic acid phthalic anhydride instead of phthalic anhydride for the synthesis of alkyd oligomers and polymers makes it possible to obtain "air-drying varnishes based on these polymers with a shorter drying time, greater impact strength, abrasion resistance and hardness. Alkyd polymers synthesized from terephthalic and isophthalic acids are characterized by greater heat resistance than the corresponding polymers of orthophthalic acid.The properties of alkyd polymers are significantly improved when phthalic anhydride is replaced in them by hexahydrophthalic anhydride.Films made of such polymers are characterized by increased physical and mechanical properties, and the oligomers and polymers themselves have a lower viscosity, lighter color, lower acid number , less tendency to gelatinize, better compatibility with driers Alkyd resin coatings based on trimellitic anhydride have higher hardness and faster
is white crystals or shiny needles, melting at 131 ° C, soluble in alcohol and hardly soluble in water. Phthalic anhydride is obtained in 70-80% yield by the oxidation of naphthalene with atmospheric oxygen in the presence of vanadium oxides as a catalyst.
" Glycerin HOCH2CHONCH2OH- syrupy colorless
liquid, sweet tasting, miscible in every way
with water and alcohol, insoluble in ether and chloroform; tons of bales
f 290 C, m.p. -17.9 °С, density 1.2604 g/cm3, refractive index
Lenia 1,474. In the technique, glycerin is obtained by saponification of fats and
Also made from propylene. "
; Pentaerythritol C (CH2OH) 4 - crystalline substance, hour-
^ partially soluble in water, with so pl. 263.5 °C, density 1.397 g/cm3.
| Pentaerythritol is obtained by condensation of acetic and formic
Zaldehydes in aqueous solution in the presence of alkali.
Production of alkyd polymers
In industry, unmodified glyphthalic resins are obtained by the condensation of glycerol with phthalic anhydride 7 (2 mol: 3 mol). The reaction is carried out in reactors made
dry compared to alkyd polymer coatings based on phthalic anhydride or isophthalic acid.
The choice of a method for carrying out polycondensation is determined by the physicochemical properties of the initial substances and the resulting polymers, technological requirements, tasks that are set during the process, etc.
By temperature polycondensation methods are divided into high temperature(not lower than 200С) and low temperature(0-50С), according to the state of aggregation of the reaction system or phase state- for polycondensation in mass(melt), solid phase, solution, emulsions(suspensions), two-phase system(interfacial polycondensation - for example, at the interface of the organic phase with dichloride and water with diamine, a polyamide film is obtained).
Polycondensation in the melt and solid phase occurs at high temperatures; emulsion polycondensation and interfacial polycondensation - at low temperatures; polycondensation in solution - at high and low temperatures.
Low temperature polycondensation is predominantly nonequilibrium, high temperature - mainly equilibrium.
Melt polycondensation, the method of conducting polycondensation (usually equilibrium) in the absence of a solvent or diluent; the resulting polymer is in a molten state. The starting materials (and sometimes the catalyst) are heated at a temperature 10-20°C higher than the melting (softening) temperature of the resulting polymer (usually at 200-400°C). To avoid the oxidation of monomers and thermal-oxidative degradation of the polymer, the process is first carried out in an atmosphere of an inert gas (often dried), and finished in a vacuum to more completely remove low-molecular reaction products and shift the equilibrium towards the formation of a high-molecular polymer.
Advantages of the method: the possibility of using low-reactive monomers, the comparative simplicity of the technological scheme, the high yield and degree of purity of the resulting polymer, the possibility of forming fibers and films from the resulting polymer melt.
Flaws: the need to use thermally stable monomers and the process at high temperatures, the duration of the process, the use of catalysts.
Due to the high viscosity of the melts of most polymers, the rate at the final stages of the process is determined not so much by the activity of the reacting groups as by diffusion factors(mobility of macromolecules).
Melt polycondensation is practically the only industrial method for the synthesis of aliphatic polyamides and polyesters (for example, polyamide-6,6 and polyethylene terephthalate). It is carried out on a periodic and continuous scheme. In the first case, the process is carried out in an autoclave, squeezing the finished polymer out of it with nitrogen through a heated valve. The continuous process is carried out in U- and L-shaped, as well as tubular reactors, equipped with a screw mixer at the polymer outlet, which ensures effective mixing of the melt and its extrusion through a spinneret in the form of a monofilament, tow or film. The tubular apparatus does not need a stirrer, since the process takes place in a thin layer.
In laboratory practice by the method of polycondensation in the melt synthesize polyamides, polyesters, polyheteroarylenes, block and random copolymers.
Solution polycondensation- a method of carrying out polycondensation, in which the monomers and the resulting polymer are in solution in one phase. Various variants of the method are possible when the monomer and (or) polymer are partially soluble in the reaction medium. To obtain polymers of high MW, the monomers and the polymer must, as a rule, be completely dissolved in the reaction medium, which is achieved by using a mixture of two or more solvents or by increasing the reaction temperature. Usually the process is carried out at 25-250°C. The resulting polymer can form thermodynamically unstable (metastable) solutions or lyotropic liquid crystal systems. After the polymer has precipitated from such a solution, it cannot be re-dissolved in this solvent. In the precipitated crystalline polymer, which does not swell in the reaction solution, the growth of macromolecules stops; in an amorphous polymer capable of swelling continues. Precipitation of the polymer from the reaction solution can lead to its crystallization.
Advantages of the method: the possibility of carrying out the process at relatively low temperatures; the ability of the solvent to act as a catalyst; good heat transfer; the possibility of direct use of the resulting polymer solutions for the manufacture of films and fibers.
A distinctive feature is the influence of the nature of the solvent on the pier. mass and structure of the resulting polymer. Examples are known when a solvent (pyridine, tertiary amines, N,N-dimethylacetamide, N-methylpyrrolidone, etc.) binds the acid formed in the reaction, for example. at polyesterification or polyamidation(so-called acceptor catalytic polycondensation). The solvent and impurities contained in it, for example, H 2 O, can cause side reactions leading to the blocking of functional groups. A special place among them is occupied by cyclization, the intensity of which increases with decreasing concentration of the reaction solution.
In laboratory practice by the method of polymerization in solution synthesize various carbo- and heterochain polymers, incl. organoelemental (polyacetylenes, polyamides, polyesters and polyethers, polysulfones, polyheteroarylenes, polysiloxanes, etc.).
Technology and instrumentation depend on the type of polycondensation. With equilibrium (reversible) polycondensation in solution, the process is carried out at 100–250°C and solvents are used that dissolve the resulting polymers well, and low molecular weight reaction products poorly. The boiling point of such solvents should be higher than that of low molecular weight reaction products. Sometimes solvents are used that form an azeotropic mixture with a low molecular weight reaction product, the boiling point of which is lower than that of the solvent ( azeotropic polycondensation). In industry, this process is rarely used. The first stage in the production of a number of polyesters, for example, polyethylene terephthalate, is a kind of equilibrium polycondensation in solution, when one of the monomers (in this example, ethylene glycol), taken in excess, serves as a solvent.
Non-equilibrium (irreversible) polycondensation in solution is subdivided into low- and high-temperature - process temperatures below 100°C and above 100°C, respectively (more often up to 200°C). A variation of low-temperature polycondensation in solution is emulsion polycondensation, when the polymer is formed in the organic phase of a water-organic heterogeneous system. The liberated HNa1 is neutralized in the aqueous phase with alkali metal carbonates or hydroxides. In industry, non-equilibrium solution polycondensation is used in the production of polyamides, polycarbonates, polyarylates, polyheteroarylenes and others and carried out on a periodic basis.
Polycondensation in the solid phase (solid state polycondensation), a method of carrying out polycondensation, when the monomers or oligomers are in a crystalline or glassy state and a solid polymer is formed. A kind of solid-state polycondensation is possible, when during its course the starting materials melt or soften. In many ways (conditions, regularities of the process), solid-state polycondensation is similar to polycondensation in a melt. The solid-state polycondensation of aliphatic (-amino acids), which is characterized by the presence of autocatalysis due to the increase in the monomer-polymer interface during the reaction, on which the monomer molecules are more mobile than in the crystal, has been studied in detail.
The method is used to obtain polyheteroarylenes from highly reactive monomers. Carrying out the process under pressure in a mold, they combine the synthesis of the polymer and the molding of the product. In this way, in particular, monolithic products are obtained from polyimides, poly(aroylen- bis-benzimidazoles).
An important variety of solid-state polycondensation is the second stage in the process of formation of many polyheteroarylenes, carried out in films or fibers formed from pre-obtained intermediate high molecular weight polymers (prepolymers). This is a thermal process of intramolecular polycyclization carried out in an inert gas flow or vacuum at temperatures usually below the glass transition temperature of the intermediate polymer (for example, polyamic acid) or above it, but below the glass transition temperature or softening temperature of the final polyheteroarylene. In some cases (for example, during the transformation of polyhydrazides into poly-1,3,4-oxadiazoles), kinetic inhibition of the process is observed due to an increase in the glass transition temperature during cyclization; then resort to a stepwise increase in temperature. Sometimes polycyclization is accompanied by solid-state polycondensation at the terminal functional groups of macromolecules, leading to an increase in the molecular weight of the polymer.
PC: 1 – in the melt; 2 - in solution; 3 - in emulsion; 4 - in suspension; 5 - interphase.
Methods 2 - 4 have already been considered in the study of the polymerization reaction. Therefore, we will focus on the remaining 2.
PC in the melt. If the starting materials and the polymer are stable at the melting temperature, then the reaction is carried out in the melt in an inert gas atmosphere at reduced pressure, and finished in a vacuum (to remove by-products).
Interfacial PC. This reaction is carried out between 2 immiscible solutions of monomers or (more rarely) monomers in the liquid and gas state. In this case, the polymer is formed at the interface between the media (from where it is continuously removed), and by-products are dissolved in one of the phases. That's why interfacial PC - irreversible(and removal of by-products is not required) and makes it possible to obtain linear polymers with high MM (up to 500,000).
9. The PC reaction is often carried out in the presence of catalysts that speed up the process and balance the reaction.
Lecture No. 14 - Production of polymeric dielectric material
(on the example of polyethylene)
Let us consider a simplified scheme of the technological cycle for the production of high-pressure polyethylene (LDPE).
raw material initiator ______________________
↓ ↓ ↓
→→→→→→→→ →
1 2 3 4 2 5 6 7 8 9
_________________
polyethylene ← ←← ← additives
14 12 11
1 – ethylene shop. The ethylene gas plant is located close to the reactor for the synthesis of PE by the reaction polymerization in a gaseous monomer medium. This technical polymerization method provides a chemically pure polymer suitable for the production of dielectrics. The reaction is carried out at elevated pressure in order to increase the yield of the polymer.
Ethylene gas, through collector - 2, enters low pressure mixer - 3 where it mixes with initiator at low pressure. (Polymerization reaction of high pressure ethylene initiated by oxygen or peroxides).
Then, compressor of the 1st stage - 4, compresses the mixture, after which it through mixer - 5 and 2nd stage compressor - 6 goes to reactor - 8, which is separated from the compressor stages flame arrester - 7.
The reaction takes place at a temperature (200 - 300)˚С and pressure (1.5 - 3) thousand atmospheres. The residence time of the reaction mixture in the reactor no more than 30 sec. This achieves 15% ethylene conversion. unreacted ethylene is separated from the polymer in high separators - 9 and low - 10 pressure, after which, through return ethylene purification units – 13 and collectors - 2 served, respectively, in mixers high – 5 and low - 3 pressure. The PE obtained in the reactor is mixed with additives and granulated in 11 and then through dust collector - 12 goes to packaging - 14. Operations 11 – 14 are called confectioning.
LDPE production dangerously for a number of reasons: the presence of high-pressure equipment, the possibility of an explosion and ignition of ethylene in the event of a leak in the process line; narcotic and toxic effects of ethylene and initiators on humans. the maximum allowable concentration of ethylene in the air is 50 mg/m 3 .
Lecture 16 Transformation of polymers
The electrophysical properties of polymers are influenced not only by the chemical structure of molecules and their flexibility, but also by many other factors, among which the structure of the material is of particular importance. For example, if we talk about mechanical strength, fibrils are stronger than spherulites. Large diameter spherulites are more brittle than small ones. Therefore, a thoughtful choice of crystallization conditions is necessary. But this is a simplified view of the problem, because The morphology of a polymer dielectric depends not only on the supramolecular structure of the polymer. It is influenced by the processing method, modification methods (i.e. intentional impact on the polymer in order to change the properties of the material), temperature, and much more, which can be called the term "polymer transformation" under the influence of external factors during manufacture, storage and use.
This transformation is a spontaneous, often undesirable (destruction, cross-linking) or purposeful (cross-linking, molecular rearrangement, plasticization) change in the composition, structure, and, as a result, the electrophysical, chemical, and mechanical properties of polymers.
Reactions of chemical transformations of polymers can be conditionally divided into 2 main groups:
1 . not affecting the polymer backbone– cross-linking, interaction of functional groups, etc.;
2. Occurring with a change in the polymer backbone –
a. intramolecular rearrangements, block copolymerization, etc.;
b. rupture of the main polymer chain with the formation of macrofragments (destruction) or gradual cleavage of individual links (depolymerization).
In addition, it is worth considering separately the mutual dissolution of solid and liquid dielectrics, which is extremely important in relation to impregnated polymer insulation.
In practice, spontaneously developing chemical reactions can occur simultaneously:
______ _________ _______________ ____________ _______
___ _______________ __ |____________ ______ |_____________ ______
___________ _______ ___________ |______ ___ ______ |_______________
destruction crosslinking destruction and crosslinking
As a result, spatial and branched structures are formed, which significantly reduces elasticity, increases brittleness, reduces solubility, and also affects the electrical and mechanical properties of polymers.
The invention relates to a method for producing polyester by the method of polycondensation of polyfunctional organic compounds of natural origin with adipic or sebacic acid and to the disposal of waste from the wood chemical industry. The resulting polymer can be used as a binder in the production of fibreboard or chipboard. The technical task is to simplify the technology for producing polyester, to reduce the melting point of the resulting polymer and to maintain the strength of composite materials based on this polyester. SUBSTANCE: proposed is a method for producing polyester by polycondensation between suberic acids (SA), adipic (AA), or sebacic (SebK) acid and a diamine selected from p-phenylenediamine (p-PD), o-phenylenediamine (o-PD) and hexamethylenediamine (HMDA) at mass ratio of SK: (AA or SebK): (p-PD, or o-PD, or HMDA) = 10: (2-4): (3.1-6.2), and the process is carried out at a temperature of 150-220 °C for 1.5-2.5 hours. 1 z.p. f-ly, 2 tab.
The invention relates to the field of polymer chemistry and waste disposal of the wood chemical industry, and in particular to a method for producing polyester by polycondensation of polyfunctional organic compounds of natural origin with adipic or sebacic acid. The resulting polymer can be used as a binder in the production of fibreboard or chipboard.
Suberic acids are a mixture of aliphatic C 18 -C 32 mono- and dicarboxylic saturated and unsaturated hydroxy and epoxy acids. The presence of all these functional groups makes it possible to use them as monomers in the preparation of high-molecular compounds by the polycondensation method.
| Table 1 Composition of suberic acids |
|
| Acid | % by mass |
| Octadecan-9-ene-1,18-dioic | 2,1-3,9 |
| Octadecan-1,18-dioic | 0,5-1,5 |
| 18-Hydroxyoctadec-9-ene | 6,0-17,1 |
| 9,16- and 10,16-Dihydroxyhexadecanoic | 2,3-6,2 |
| 9,10-Epoxy-18-hydroxyoctadecanoic | 29,2-43,2 |
| 20-Hydroxyeicosanoic | 2,3-4,4 |
| 9,10,18 - Trihydroxyoctadecanoic | 6,3-11,4 |
| Docosan-1,22-dioic | 3,6-7,4 |
| 22-Hydroxydocosanoic | 11,7-17,4 |
| Other | 9,5-14,7 |
Table 1 shows the acids with the highest content in birch bark (Kislitsyn A.N. Extractive substances of birch bark: isolation, composition, properties, application. Chemistry of wood. - 1994. - No. 3. - C.11).
In the prior art, studies are known in the field of obtaining polymers based on suberic acids, namely: varnish resins obtained by the condensation of betulino-suberic mixtures with phthalic anhydride (Povarnin I.G. Alcohol furniture varnishes of domestic wood chemical raw materials. - M., 1949, p. .78-80).
A significant disadvantage of this method is that it requires a lot of time and energy (the duration of the condensation process is 16 hours at a temperature of 170°C), which in turn makes this method of obtaining a polymer economically unprofitable. An additional disadvantage of these polymers is that such resins exhibit poor adhesive properties after cold drying and are very brittle after hot drying.
Polyurethanes obtained on the basis of suberin acids are also known (Cordeiro N., Belgacem M.N., Candini A., Pascoal Neto C., Urethanes and polyurethanes from suberin: 1.Kinetic study// Industrial Crops and Products, Vol.6, Iss.2 - 1997. - P.163-167).
The disadvantage of such polymers is that they are highly elastic and their processing is possible only through solutions, which sharply reduces their scope as binders.
Also known are resins prepared on the basis of suberic acids esterified with betulin (Povarnin I.G. Alcohol furniture varnishes from domestic wood-chemical raw materials. M., All-Union cooperative publishing house, 1949, p. 71-73). Such resins dissolve well in a number of organic solvents, such as turpentine, benzene, alcohol benzene, acetates, ethyl methyl ketone, and have good adhesion to glass and metal. However, a significant disadvantage of these resins is poor adhesion to wood, which excludes the possibility of their use in the production of fiberboard and chipboard.
The closest analogue to the claimed invention is a method for producing polyester by polycondensation of betulin with dicarboxylic acid in an inert medium (nitrogen) with constant stirring in the temperature range of 256-260°C and a process duration of 22-24 hours (RF patent No. 2167892, IPC C 08 G 63/197, published in Bulletin No. 15, May 27, 2001; Orlova T.V., Nemilov V.E., Tsarev G.I., Voitova N.V. Method for producing polyester). The melting temperature of these polyesters is 200-230°C. Wood fiber composites based on these polyesters have a tensile strength of 65-77 MPa.
The disadvantage of this method of obtaining a binder is that it is quite energy intensive, since the temperature of the condensation process is 256-260°C and the duration, respectively, 22-24 hours.
The technical result of the present invention is to simplify the technology for producing polyester by reducing the temperature of polycondensation and reducing the duration of the process while reducing the melting temperature of the resulting polymer, as well as while maintaining the strength of composite materials based on this polyester.
This goal is achieved by the fact that in the claimed method of obtaining polyester, which consists in the polycondensation of polyfunctional organic compounds of natural origin with adipic acid or sebacic acid at elevated temperature in an inert medium (nitrogen), the polycondensation process is carried out between: suberic acids (SA), adipic acid (AA ), n-phenylenediamine (n-PD), sebacic acid (SebK), o-phenylenediamine (o-PD), hexamethylenediamine (HDA) at a mass ratio of SC: AA or SebK: n-PD, or o-PD, or GDA - 10:(2÷4):(3.1÷6.2), and the process is carried out at a temperature of 150-220°C and the duration of the process is 1.5-2.5 hours.
The essential differences of the claimed invention is the use of dicarboxylic acid and diamine in a certain ratio with suberic acids, which are adipic acid or sebacic acid and n-phenylenediamine, or o-phenylenediamine, or hexamethylenediamine. The choice of adipic acid and sebacic acid is due to the fact that they are able to condense into a linear macromolecule and thereby prevent the formation of a spatial network during the polycondensation of suberic acids, and n-phenylenediamine, o-phenylenediamine, and hexamethylenediamine were chosen to control the melting temperature and rigidity of the polymer chain.
According to the claimed technical solution, the polycondensation of monomers occurs due to the interaction of reactive groups of suberic acids, such as carboxyl, hydroxyl and epoxy groups with each other and with amino groups of n-phenylenediamine (o-phenylenediamine or hexamethylenediamine) and carboxyl groups of adipic acid (sebacic acid), these interactions can be represented by the following reactions.
From the reactions presented above, it is clearly seen that ether bonds (reaction 2), ester bonds (reaction 1), amide bonds (reaction 4), and amine bonds (reaction 5) are formed in the structure of the resulting polymer.
In this way, new polyesteramides, copolymers of suberic acids, adipic acid (or sebacic acid) and p-phenylenediamine (or o-phenylenediamine, or hexamethylenediamine), are obtained, having a branched structure and a degree of conversion up to 0.99.
The inventive method is implemented as follows.
Example 1. Suberic acids, adipic acid and n-phenylenediamine are loaded into the reactor in the ratio of SC:AA:PPD equal to 10:2:3.1, nitrogen is supplied, after which the reactor is heated to 150°C, and the polycondensation reaction is carried out for 1.5 hours with stirring, after the end of the process, the resulting polymer is unloaded.
Table 2 shows the parameters and indicators of the process and characteristics of the finished product.
The advantage of the invention compared with the prototype is that the process of polycondensation of suberic acids with bifunctional substances such as adipic, sebacic acids, n-phenylenediamine, o-phenylenediamine and hexamethylenediamine is carried out at a lower temperature (up to 220°C) and duration process 1.5-2.5 hours, which greatly simplifies the technology of the polymer synthesis process. An additional advantage is that the melting temperature of the obtained polyesteramides is lower than that of the prototype, and is 133-149°C.
The resulting polyesters with conversion rates of 0.80-0.99 and a melting point of 133-149°C are taken in a ratio of 20:80 with wood fiber, pressed at t - 200°C and a pressure of 6 MPa for 1 min / mm of thickness . Finished products (wood fiber boards) have a strength of 77-83 MPa, which is 1.5-2 times higher than the GOST indicator for industrially produced analogues. The strength was evaluated according to the method of GOST 11262-80.
From the experimental data shown in table 2, it can be seen that in comparison with the prototype according to the claimed method, a polyester with a melting point of 133-149 ° C was obtained, which makes it possible to use it as a binder in the technology of polymer composite materials. The materials obtained in this way have high strength properties that are not inferior to the prototype.
Table 2 shows that with an increase in the temperature of the polycondensation process (examples No. 1-3), the degree of conversion of the obtained polyester increases, and the strength of the fiberboards also increases.
With an increase in the duration of the process (examples No. 2, 4, 5) there is also an increase in the degree of transformation and the melting temperature of the obtained polyesters, while the strength of the plates lies in the range corresponding to the strength of the plates obtained according to the prototype.
Changing the ratio of components (examples No. 1, 7, 12) in the entire range of the claimed temperatures and duration of the process allows you to get a plate with a strength equal to the strength of the plates corresponding to the prototype.
| table 2 Parameters of the polycondensation process and characteristics of the resulting polymers |
||||||
| №/№ | The ratio of components, wt.% | Temperature, | Process duration, h | Degree of conversion | Melting point, °С | Plate strength, MPa |
| Suberic acids: adipic acid: n-phenylenediamine | ||||||
| 1 | 10:2:3,1 | 150 | 1,5 | 0,85 | 139 | 77 |
| 2 | 10:2:3,1 | 180 | 1,5 | 0,87 | 142 | 78 |
| 3 | 10:2:3,1 | 220 | 1,5 | 0,88 | 143 | 79 |
| 4 | 10:2:3,1 | 180 | 2 | 0,90 | 146 | 79 |
| 5 | 10:2:3,1 | 180 | 2,5 | 0,95 | 148 | 83 |
| 6 | 10:3:4,6 | 150 | 1,5 | 0,83 | 138 | 77 |
| 7 | 10:3:4,6 | 180 | 1,5 | 0,88 | 143 | 78 |
| 8 | 10:3:4,6 | 220 | 1,5 | 0,94 | 148 | 83 |
| 9 | 10:3:4,6 | 150 | 2 | 0,86 | 140 | 78 |
| 10 | 10:3:4,6 | 150 | 2,5 | 0,93 | 147 | 83 |
| 11 | 10:4:6,2 | 150 | 1,5 | 0,80 | 137 | 77 |
| 12 | 10:4:6,2 | 180 | 1,5 | 0,89 | 145 | 79 |
| 13 | 10:4:6,2 | 220 | 1,5 | 0,95 | 149 | 79 |
| 14 | 10:4:6,2 | 150 | 2 | 0,86 | 140 | 78 |
| 15 | 10:4:6,2 | 150 | 2,5 | 0,97 | 149 | 78 |
| Suberic acids: adipic acid: o-phenylenediamine | ||||||
| 16 | 10:3,8:6,0 | 200 | 2,3 | 0,98 | 146 | 78 |
| Suberic acids: sebacic acid: n-phenylenediamine | ||||||
| 17 | 10:3,4:6,1 | 215 | 2,5 | 0,98 | 146 | 77 |
| Suberic acids: sebacic acid: o-phenylenediamine | ||||||
| 18 | 10:3,1:6,1 | 210 | 2,4 | 0,99 | 144 | 78 |
| Suberic acids: adipic acid: hexamethylenediamine | ||||||
| 19 | 10:3,9:6,0 | 220 | 2,5 | 0,98 | 136 | 77 |
| Suberic acids: sebacic acid: hexamethylenediamine | ||||||
| 20 | 10:3,8:6,0 | 215 | 2,5 | 0,99 | 133 | 77 |
| Prototype (Betulin: sebacic acid) | ||||||
| 21 | 1:1,034 | 260 | 23 | 0,996 | 200 | 65-77 |
Replacing adipic acid with sebacic acid in polyester (example No. 18) also makes it possible to obtain plates with a strength that is not inferior to the prototype. Replacing n-phenylenediamine with o-phenylenediamine (example No. 17, 19) or hexamethylenediamine (example No. 20, 21) in the case of using sebacic or adipic acid also makes it possible to obtain plates with a strength corresponding to the strength of the plates according to the prototype.
It should also be noted that in all cases, the degree of conversion of polyesters according to the proposed method is lower than that of the prototype, but the strength of the resulting plates is equal to the strength of the plates according to the prototype. The melting temperature of the obtained polyesters according to the claimed method, regardless of the ratio of components and component composition, is less than that of the prototype, which makes the process of obtaining fiberboards more economical.
1. A method for producing polyester, which consists in the polycondensation of polyfunctional organic compounds of natural origin with adipic acid or sebacic acid at elevated temperature in an inert environment, characterized in that the polycondensation process is carried out between suberic acids, adipic acid or sebacic and n-phenylenediamine, or o-phenylenediamine , or hexamethylenediamine at a mass ratio of suberic acids: adipic or sebacic acid: p-phenylenediamine, or o-phenylenediamine, or hexamethylenediamine - 10: (2 ÷ 4): (3.1 ÷ 6.2) at a temperature of 150-220 ° C .
2. The method according to claim 1, characterized in that the duration of the polycondensation process is 1.5-2.5 hours.
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The present invention relates to a food or beverage container containing a polyethylene terephthalate polymer. Described is a food or beverage container containing a polyethylene terephthalate polymer, where said polymer contains a terephthalate component and a diol component, where the terephthalate component is selected from terephthalic acid, dimethyl terephthalate, isophthalic acid, and combinations thereof, and the diol component is selected from ethylene glycol, cyclohexanedimethanol, and combinations thereof, moreover, both components - terephthalate and diol, are partially or completely obtained from at least one material based on bio-raw materials. EFFECT: obtaining a container for foodstuffs or drinks containing polyethylene terephthalate produced from renewable resources, which has the same properties as polyethylene terephthalate obtained from oil. 1 n. and 13 z.p. f-ly, 1 ill., 1 tab., 1 pr.
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The invention relates to a method for producing polyester by the method of polycondensation of polyfunctional organic compounds of natural origin with adipic or sebacic acid and to the disposal of waste from the wood chemical industry
LECTURE #6
INTRODUCTION TO THE TECHNOLOGY OF POLYMER SYNTHESIS
MATERIALS
Terms and Definitions
In the technology of obtaining polymeric materials, a set of physical and chemical phenomena is considered, from the complex of which the technological process is formed. It includes the following stages:
Supply of reacting components to the reaction zone;
Chemical reactions - polymerization or polycondensation;
Withdrawal of the obtained products from the reaction zone, etc.
The overall speed of the technological process can limit the speed of one of the three constituent elementary processes (stages), which proceeds more slowly than others. So, if chemical reactions proceed most slowly, and they limit the overall speed, then the process proceeds in the kinetic region. In this case, technologists tend to enhance precisely those factors (monomer and initiator concentrations, temperature, pressure, etc.) that especially affect the reaction rate. If the overall rate of the process is limited by the supply of reagents to the reaction zone or the removal of polymers, then this means that the process occurs in the diffusion region. They strive to increase the diffusion rate primarily by mixing (turbulization of the reacting system), increasing the temperature and concentration of the monomer and transferring the system from multiphase to single-phase, etc. If the speeds of all elements that make up the technological process are commensurate, then it is necessary to influence primarily such factors that accelerate both diffusion and reaction, i.e. increase the concentration of starting substances and temperature. For the functioning of any process, it is very important to maintain its technological regime at an optimal level. Technological mode is a set of main factors (parameters) that affect the speed of the process, the yield and quality of the polymer material. For polycondensation processes, the main parameters of the regime are temperature, pressure, reaction time, monomer and catalyst concentrations.
CLASSIFICATION OF EQUIPMENT FOR POLYMER SYNTHESIS
Equipment is called technical devices designed to create conditions that provide the required technological parameters (temperature, pressure, mixing of the reaction mass, etc.). A technological scheme is a set of devices and machines designed to produce a polymer material with a set of useful properties. The central place in the scheme is given to the reactor, since the productivity and quality of the produced polymer material depend on its type. Reactors of various shapes and designs are used in industry. Differences in the design of reactors are determined by the requirements of the technological process and the properties of the materials being processed, which are reflected in the solution of their individual components and parts (developed heating surfaces, various types of mixing devices), as well as in equipping these reactors with additional auxiliary coolers, receivers, etc.
As an example, consider a horizontal reactor - a polycapacitor for the continuous synthesis of polyethylene terephthalate. The reactor is a cylindrical horizontal vessel equipped with a heating jacket. Mixing and transportation of the reaction mass along the reactor vessel is carried out by rotating mesh inclined disks 4.
The reactor is provided with heating of the mass and a large surface of the evaporation mirror, which is necessary for the complete removal of a low molecular weight substance. To do this, the reactor is filled with a mass up to the axis of the stirrer. The process takes place in a thin layer. The mass covers the disks with a thin layer and enters the reactor steam space, where a rarefaction is created. In this case, effective removal of the low molecular weight compound, which is released during the reaction, is achieved. The mass of polymer from the disks is removed by scrapers of the body of the apparatus.
Film type reactors
The film-type reactor can be made in the form of two concentric cylinders with heat-conducting walls (Fig. 5.15). The inner cylinder is made in the form of a screw, which during rotation uniformly mixes the reaction layer and moves it along the reactor axis. By changing the rotation speed of the inner cylinder, and hence the residence time of the mass in the reactor, the characteristics of the resulting polymer vary. The reaction mixture from the reactor is fed into the evaporation chamber, which is under vacuum. Instantaneous expansion causes separation of the reaction mass into resin and reaction by-products. Freed from impurities, the resin is continuously taken by the screw for cooling.
column apparatus
On fig. 5.16 shows a column for the synthesis of phenol-formaldehyde resin. The column consists of sections arranged one above the other 1 . Agitators 2 all sections have a common shaft 3 , which is driven by a drive 5 . The agitator shaft passes freely from one section to another through the nozzles welded into the bottom of each section 4 . Their upper ends are raised above the level of the reaction mass. Steam spaces of all sections of the column communicate with each other and are connected by a fitting 6 with common reflux condenser. The input of reagents is carried out in the upper loading fitting 7 , and the output of the finished product occurs through the fitting 8 located at the bottom of the machine. Each column section is provided with a jacket 9 . The condensation process proceeds in each section stepwise and the composition of the reaction mixture varies from section to section.
TECHNICAL METHODS FOR CARRYING OUT POLYCONDENSATION
The polycondensation reaction is as widely used in the industrial synthesis of polymers as polymerization. Just as varied are the ways in which it can be carried out. Thus, polycondensation is carried out in the solid phase, in the melt, in solution, in emulsion, at the phase boundary, in matrices. To obtain high molecular weight products, it is necessary to maintain an equimolar ratio of reactants, prevent side reactions of functional groups, thermal degradation of the polymer, and in the case of equilibrium processes, it is possible to more completely remove low molecular weight substances from the reaction sphere.
In the field of polycondensation, the search for new efficient catalysts is an important task. In this regard, the use of enzymatic catalysis can open up interesting prospects. The problems of stereospecific polycondensation await their solution.
Melt polycondensation
This reaction method is used when one of the monomers is a solid and does not decompose upon melting. The temperatures at which melt polycondensation is carried out are usually quite high, and therefore the reaction must be carried out in an inert atmosphere of nitrogen or CO 2 to avoid possible oxidation, decarboxylation, degradation, and other side reactions. In some cases, the reaction is carried out under reduced pressure to facilitate the removal of low molecular weight substances. Removal of the by-product is significantly more difficult in the final stages of the process, since this significantly increases the viscosity of the reaction system. Under the reaction conditions, the resulting polymer is in the melt and is discharged from the reactor hot before it solidifies, otherwise its removal will be very difficult. In most cases, the hot melt is fed directly from the reactor to the apparatus for the subsequent processing of the polymer by extrusion, injection molding, etc. Polycondensation in the melt in the industry produces polyamide-6,6 and polyethylene terephthalate.
Melt polycondensation has a number of technological advantages. First of all, it is a high concentration of monomers, which ensures a fairly high performance of the equipment. A very significant advantage of the method is the absence of "extra" components, such as a solvent. Therefore, the production of polymers by this method becomes a low-waste production, in which there is no waste water. This applies to the case where the polycondensation catalyst is not removed from the polymer. Otherwise, waste water may appear. One of the most significant technological disadvantages of melt polycondensation is the high energy intensity of the process (high consumption of thermal energy for polymer production). This is due to the rather high temperatures of the process (about 200°C) and its considerable duration. Also, a disadvantage of melt polycondensation is the difficulty in obtaining polymers with high molecular weights. This is due to the fact that the viscosities of polymer melts are very high and their mixing requires a significant amount of energy. When the process is carried out in a continuous scheme, difficulties arise due to the fact that during the process the reaction mass passes through a number of apparatuses with different parameters. Quite complicated is the transition of the reaction mass from one apparatus to another. Thus, an analysis of the advantages and disadvantages of the melt polycondensation method makes it possible to determine its most appropriate use in industry. At the final stage, a high vacuum is created in the reactor, which makes it possible to achieve the most complete removal of low molecular weight compounds released in the reaction. Melt polycondensation is the main industrial method for linear polycondensation.
SOLUTION POLYCONDENSATION
During polycondensation in a solution, in addition to the initial monomers and a catalyst, a solvent is present. The reaction can be carried out at low temperatures, at which heat and mass transfer is easier to carry out than in melt polycondensation. The presence of a solvent in the system reduces the molecular weight of the resulting polymer and also reduces the reaction rate.
Conducting polycondensation in solution provides a more uniform distribution of heat in the reaction mixture compared to the reaction in the melt, lowering the viscosity of the medium, and hence increasing the diffusion rate of the reagents and intensive removal of low molecular weight reaction products. The molecular weight of polymers increases if the polymer is highly soluble in a suitable solvent. In some cases, the reaction in solution is carried out in the presence of catalysts. This makes it possible to lower the reaction temperature and prevent numerous side processes. This method is suitable for obtaining heat-resistant polymers that cannot be synthesized by melt condensation due to their high melting points.
This method creates good conditions for the removal of heat of reaction due to the dilution of the monomers, which, in turn, avoids the occurrence of some side processes developed at elevated temperatures. In some cases, the polymer solution obtained by this method can be used to obtain films, coatings, and varnishes.
In most cases, conventional chemical equipment can be used for solution polycondensation, so the reaction of monomers in solution can compete with melt polycondensation both in terms of the cost of the entire process and in terms of equipment costs.
The isolation of the polymer from the reaction syrup requires a number of operations, which makes the process more cumbersome. This is the filtration of the polymer powder, its washing, drying, etc., as well as the operation of regenerating the solvent and preparing it for reuse. It is on the successful implementation of this operation that the profitability of the industrial process of polycondensation in solution depends.
The disadvantages of the process also include the low productivity of the equipment, due to the use of monomers in relatively low concentrations, which leads to a decrease in the molecular weight of the polymers.
At solution polycondensation there is no need to obtain a polymer melt. However, slower reaction rates, a high probability of the formation of cyclic products, and the difficulty of removing low molecular weight reaction products limit the application of this method.
Reversible solution polycondensation is rarely used in industry. On the contrary, irreversible solution polycondensation has been increasingly used in industrial processes in recent years.
Therefore, only a limited number of industrial syntheses are technologically and economically justified. For example, the production of epoxy resins in water-acetone or toluene solutions. In this case, the use of a solvent determines the completeness of the separation of by-product salts and, therefore, ensures the high quality of the resulting product. And also highly efficient continuous productions are easily organized.
