KR20140123286A - Synthetic method of poly(vinyl acetate) using atom transfer radical polymerization and the product thereof - Google Patents

Abstract

The present invention provides a method for synthesizing polyvinyl acetate using atom transfer radical polymerization (ATRP) and a product thereof, the method comprising the steps of mixing vinyl acetate monomers and a reaction initiator under supercritical carbon dioxide over a reaction catalyst (first step); churning and polymerizing the mixture at temperature of 50 to 75°C and at pressure of 3000 to 8000 psi (second step); and obtaining polyvinyl acetate from the churned and polymerized reactant (third step). Therefore polyvinyl acetate can be synthesized via atom transfer radical polymerization under supercritical carbon dioxide. Polyvinyl acetate with a high polydispersity index and various molecular weights can be manufactured if the polyvinyl acetate is synthesized by inputting the initiator and the reaction catalyst under supercritical carbon dioxide.

Description

Methods for synthesizing polyvinyl acetate using atom transfer radical polymerization (ATRP) and polyvinyl acetate obtained according to the above synthesis method (Synthetic method of poly (vinyl acetate) using atom transfer radical polymerization and synthesis thereof)

The present invention relates to a method for synthesizing polyvinyl acetate using atom transfer radical polymerization (ATRP) and a preparation thereof, and more particularly, to a method for synthesizing polyvinyl acetate using atom transfer radical polymerization (ATRP) A method for synthesizing polyvinyl acetate having an appropriate molecular weight and a polyvinyl acetate obtained according to the above synthetic method.

In general, polyvinyl acetate (PVAc), which is a polymer of vinylacetate type, is used to saponify polyvinyl alcohol (poly (vinyl alcohol) (PVA)). Since polyvinyl alcohol has excellent strength and has the highest crystalline elastic modulus together with polyethylene, the fibers formed from the polyvinyl alcohol have high tensile strength, tensile elastic modulus and abrasion resistance, so that they have remarkably excellent alkali resistance, oxygen resistance Permeability and adhesiveness, it is used in many fields including industrial materials, high-modulus organic fibers for replacing asbestos, and substitutes for reinforcing concrete for concrete. The vinyl alcohol used as a monomer in the production of polyvinyl alcohol is usually prepared by saponification of a vinyl ester-based polymer such as vinyl acetate. Vinyl acetate is the most commonly used because of its low cost and easy saponification. However, because of the branching reaction caused by the rapid chain transfer reaction due to high polymerization heat, high molecular weight polyvinyl acetate with excellent molecular linearity and radioactivity There is a problem that it is difficult to obtain. In response to this, the synthesis of vinyl acetate proceeded in the direction of using living radical polymerization.

Atom transfer radical polymerization (ATRP) has been widely used for vinyl acetate synthesis because it can accurately control the molecular weight of various kinds of monomers. However, in this case, it has been pointed out that the molecular weight of the monomer is relatively wide, Catalysts were used to improve the problems. When living polymerization is carried out using alkyl iodides as a substituent and 2,2'-azobis (isobutyronitrile) (AIBN) as a substituent, a narrow molecular weight distribution Was able to synthesize polyvinyl acetate.

On the other hand, in the radical polymerization, suspension polymerization or emulsion polymerization is usually carried out, but supercritical carbon dioxide is attracting attention as a new solvent. Since supercritical carbon dioxide reaches a critical point (31.1 ° C, 73.8 bar) and has similar gas-like diffusion characteristics, supercritical carbon dioxide is remarkable in terms of reaction kinetics and has a density similar to that of a liquid. The density of the supercritical carbon dioxide associated with the solvent power can be controlled by changing only the temperature or pressure conditions. From this, supercritical carbon dioxide is preferred as a solvent in chemical reactions, especially in polymerization because it can dissolve various types of monomers. In addition, a simple pressure drop allows a process of separation of the carbon dioxide solvent from the polymer product, thus saving a significant amount of energy. Because carbon dioxide is a gas present in the environment, it is easily recycled after use. It has flame retardant and non - toxic properties, is not only inexpensive, but also easily manufactured in high purity and selected as a solvent.

As an example of the synthesis of a polyvinyl acetate polymer, Korean Patent Laid-Open Publication No. 10-2005-0021762 discloses that the content ratio of ion-exchanged water and vinyl acetate / butyl acrylate mixed monomer is 60 to 65 parts by weight and 35 to 40 parts by weight; Polyvinyl alcohol as a protective colloid and potassium persulfate as an initiator are respectively 12 to 18 parts by weight and 0.5 to 1.0 part by weight of the mixed monomer content, and the mixed monomer has a content ratio of vinyl acetate to butyl acrylate of 94 to 97 wt. And 3 to 6 parts by weight of a polyvinyl acetate / polybutyl acrylate copolymer and a method of synthesizing the copolymer emulsion.

However, the conventional method of producing polyvinyl alcohol is a method of producing polyvinyl alcohol through emulsion polymerization using water as a dispersion medium, and a method of producing polyvinyl acetate through atom transfer radical polymerization of vinyl acetate under supercritical carbon dioxide, There is still a need to develop a method for synthesizing vinyl acetate under supercritical carbon dioxide.

It is an object of the present invention to provide a method for synthesizing polyvinyl acetate using ATRP capable of controlling the molecular weight distribution, and more particularly, to a method for environmentally synthesizing polyvinyl acetate by conducting synthesis under supercritical carbon dioxide, It is an object of the present invention to provide polyvinyl acetate.

The present invention relates to a method for synthesizing polyvinyl acetate using ATRP, comprising the steps of: (1) mixing a vinyl acetate monomer and a reaction initiator with a reaction catalyst under supercritical carbon dioxide; Stirring the mixed mixture at a temperature of 50 to 75 DEG C and a pressure of 3000 to 8000 psi (second step); And a step of obtaining polyvinyl acetate from the agitated polymerized reactant (third step). The present invention also provides a method for synthesizing polyvinyl acetate using ATRP.

The reaction catalyst may be a complex represented by the following general formula (1) or (2) obtained by reacting CuBr with terpyridine (tPy).

[Chemical Formula 1]

(2)

Also, the reaction catalyst may be characterized in that 20 to 60 parts by weight of CuBr and 80 to 40 parts by weight of terpyridine are reacted at a temperature of 50 to 75 ° C and a pressure of 3000 to 8000 psi.

In the first step, 0.15 to 0.80 parts by weight of a reaction initiator and 0.3 to 3.0 parts by weight of a reaction catalyst are mixed with 100 parts by weight of the vinyl acetate monomer. If the content of the reaction initiator and the reaction catalyst is out of the above range, the yield, the molecular weight, and the polydispersity index may increase.

Wherein the second step is characterized in that the mixture is subjected to stirring polymerization at a temperature of 50 to 75 DEG C and a pressure of 3000 to 8000 psi for 2 to 80 hours. If the polymerization conditions are exceeded, a problem of decreasing the molecular weight and increasing the polydispersity index may occur.

The present invention also provides a polyvinyl acetate produced by the method of synthesizing polyvinyl acetate using the atom transfer radical polymerization (ATRP), wherein the polyvinyl acetate has a number average molecular weight of 8000 to 60000 g / mol, a polydispersity index of 1.30 2.0.

The method for synthesizing polyvinyl acetate using ATRP according to the present invention provides the following effects.

Polyvinyl acetate can be synthesized by atom transfer radical polymerization under supercritical carbon dioxide. In the case of synthesizing polyvinyl acetate by administering the initiator and the reaction catalyst under supercritical carbon dioxide, polyvinyl acetate having various polydispersities and having various molecular weights can be produced.

1 is an FT-IR infrared spectroscopy graph of atom transfer radical polymerization under supercritical carbon dioxide of vinyl acetate monant and polyvinyl acetate.
2 is a ¹ H NMR spectral graph of polyvinyl acetate produced.
FIG. 3 shows the yield, number average molecular weight (Mn) and polydispersity index (Mw / Mn = PDI) according to the amount of the monomer.
FIG. 4 is a graph showing the number average molecular weight and the polydispersity index according to the amount of monomers injected under supercritical carbon dioxide.
5 is a semi-logarithmic kinetic plot of the polymerization of vinyl acetate using a reaction catalyst of CuBr / tPy under supercritical carbon dioxide.
Figure 6 is a graph showing the yield for ATRP under supercritical carbon dioxide.
FIG. 7 is a graph showing the yield of polyvinyl acetate as the amount of the initiator to be added is increased.
8 is a graph showing a linear decrease in the molecular weight of polyvinyl acetate as the amount of the initiator to be added is increased.
FIG. 9 is a graph showing the yield of polyvinyl acetate with increasing amount of the ligand to be administered.
FIG. 10 is a graph showing the number average molecular weight and polydispersity index of polyvinyl acetate with an increase in the amount of the ligand to be administered.
11 is a graph showing the yield of polyvinyl acetate according to the temperature change of the reactor in the synthesis process.
12 is a graph showing the number average molecular weight and polydispersity index of polyvinyl acetate according to the temperature change of the reactor in the synthesis process.
13 is a graph showing the yield of polyvinyl acetate according to the pressure change of the reactor in the synthesis process.
14 is a graph showing the number average molecular weight and the polydispersity index of polyvinyl acetate according to the pressure change of the reactor in the synthesis process.
15 is a graph showing the yields over time of ATRP under supercritical carbon dioxide at an amount of 150 moles of the monomer to be administered.
16 is a graph showing the polydispersity index with time when ATRP proceeds under supercritical carbon dioxide at an amount of 150 moles of the monomer to be administered.

Hereinafter, a method for synthesizing polyvinyl acetate using ATRP according to an embodiment of the present invention will be described in detail. However, it should be understood that the present invention is not limited by the following examples.

First, the vinyl acetate monomer and the reaction initiator are mixed with the reaction catalyst under supercritical carbon dioxide.

The reaction catalyst is obtained by reacting CuBr with tPy. The reaction catalyst is obtained by reacting 20 to 60 parts by weight of CuBr and 80 to 40 parts by weight of terpyridine at a temperature of 50 to 75 DEG C and a pressure of 3000 to 8000 psi.

In the mixing step, 0.15 to 0.8 parts by weight of a reaction initiator and 0.3 to 3.0 parts by weight of a reaction catalyst are mixed with 100 parts by weight of the vinyl acetate monomer. If the content of the reaction initiator and the reaction catalyst is out of the above range, problems such as reduction in yield, decrease in molecular weight, and formation of by-products may occur.

The mixing step is carried out by stirring the mixture at a temperature of 50 to 75 DEG C and a pressure of 3000 to 8000 psi for 2 to 80 hours. If the polymerization conditions are exceeded, a problem of decreasing the molecular weight and increasing the polydispersity index may occur.

As the reaction initiator, 2,2'-azobis (isobutyronitrile) or ethyl 2-bromoisobutyrate can be used.

According to the above synthesis method, polyvinyl acetate can be synthesized under supercritical carbon dioxide, and polyvinyl acetate having a molecular weight of 8000 to 60,000 and a polydispersity index of 1.3 to 2.0 can be produced in the reaction.

Hereinafter, as a specific example of the above-mentioned method, a method of synthesizing polyvinyl acetate using ATRP under supercritical carbon dioxide will be described in detail.

< Example  1> Supercritical carbon dioxide  Of vinyl acetate ATRP

First, a ligand tPy (46 mg, 0.2 mmol) and a metal catalyst CuBr (28.7 mg, 0.2 mmol) were charged into a 20 ml cell which was purged with carbon dioxide at atmospheric pressure to remove oxygen, and a reaction catalyst was prepared.

The reaction catalyst prepared by the above method was charged into a reactor and subjected to polymerization by the ATRP method.

The monomer vinyl acetate (99%) was purchased from Aldrich and purified by vacuum distillation under calcium hydride by removing the reaction inhibitor from the alumina column.

The initiator, EBiB (30 μL, 0.2 mmol) and the monomer vinyl acetate (11.2 ml, 120 mmol) were introduced into two different glass tubes and purged with nitrogen to remove oxygen and introduced into the reactor.

Synthesis was carried out in a 20 ml reactor equipped with a sapphire window to observe the reactants. Pressure was controlled using an ISCO injection pump while carbon dioxide (99.999%) was introduced.

The final pressure of the reactor was maintained at 4500 psi, and the temperature of the reactor was maintained at 65 ° C using a constant temperature water bath.

After 24 hours, the reactor was cooled and the vent of the reactor was operated to lower the pressure of the reactor. The reaction was carried out at 1000 rpm using a magnetic stirrer in the synthesis step.

 To purify the Cu catalyst that may be present in the reaction, tetrahydrofuran (THF) was added to the reactor to dissolve and the Cu was recovered by filtration through a neutral alumina column purification.

In order to collect the polymer synthesized from the purified reaction product, a hexane solution was added to precipitate rapidly, and then the precipitate was dried to prepare pure polyvinyl acetate.

< Example  2> The yield according to the amount of monomer input, Number average molecular weight , Polydispersity index  Measure

In order to find optimal conditions for the synthesis of polyvinyl acetate under supercritical carbon dioxide, the amounts of EBiB, CuBr, and tPy added were 1 mol and 150, 300, 600, and 1200 mol of the corresponding vinyl acetate monomers were added, respectively. The synthesis proceeded for a period of time. The reactor was fixed at 4500 psi, 65 ° C. After the reaction, yield, number average molecular weight and polydispersity index were measured according to the number of moles of monomers charged.

< Example  3> yield, Number average molecular weight , Polydispersity index  Measure

1 mole of EBiB, CuBr, tPy was added and 600 moles of the corresponding vinyl acetate monomer was charged and the reaction time was changed while the other conditions were fixed. The yield was obtained at 3, 6, 12, 24, 48 and 72 hours, , And the polydispersity index was measured.

< Example  4> The yield according to the amount of the initiator, Number average molecular weight , Polydispersity index  Measure

600 moles of the corresponding vinyl acetate monomer was charged with 1 mol of CuBr and tPy added, and the amount of EBiB initiator added was 0.5 to 2 mol, and the yield, number average molecular weight, and polydispersity index were measured.

< Example  5> Ligand  Yield, Number average molecular weight , Polydispersity index  Measure

1 mole of EBiB and CuBr were added, 600 moles of vinyl acetate monomer was added, and synthesis was carried out at 4500 psi and 65 ° C. The amount of the ligand was adjusted to 0.5 to 2 mol, and the yield, number average molecular weight, and polydispersity index were measured.

< Example  6> The yield, Number average molecular weight , Polydispersity index  Measure

600 moles of vinyl acetate monomer and 1 mole of EBiB, CuBr and tPy were charged and reacted at a pressure of 4500 psi while changing the temperature inside the reactor from 55 ° C to 70 ° C. The yield, number average molecular weight, polydispersity The index was measured. Synthesis was carried out for 24 hours.

< Example  7> The yield according to the change of reactor pressure, Number average molecular weight , Polydispersity index  Measure

600 mol of vinyl acetate monomer, 1 mol of EBiB, CuBr, and tPy were added to react, and the synthesis was carried out at 65 ° C. The pressure inside the reactor was varied from 3500 to 5500 psi, and the yield, number average molecular weight, and polydispersity index were measured. Synthesis was carried out for 24 hours.

 < Experimental Example  1> ATRP  Analysis of synthesis conditions

¹ H NMR spectrum was obtained with a 300 MHz NMR spectrometer (Bruker, DPX-300) using CDCl ₃ as a solvent. Infrared spectra were measured in the range of 650-3500 cm ^-1 , and products of Excalibur Series FTS 3000 were used. The molecular weight and the polydispersity index were measured by gel permeation chromatography (GPC) equipped with an isocratic pump and a refractive index. Molecular weight and molecular weight distribution were measured by flowing a THF eluent at a flow rate of 1 ml min ^-1 to a Styragel column for Waters polymer characterization maintained at 308 K and corrected based on polystyrene.

<Result 1> Synthesis result

As a result of ATRP under supercritical carbon dioxide and EBB as initiator, polymerization was carried out at 65 ° C at 4500 psi, and CuBr and tPy were added to produce a reaction catalyst complexed with CuBr / tPy. The overall reaction scheme of the polymerization process is as follows.

[Reaction Scheme 1]

On the other hand, the synthesized reaction catalyst has the following structural formulas (1) and (2).

[Chemical Formula 1]

(2)

The most important reaction process in the ATRP reaction is the reversible homolysis of the carbon-halogen bond by the catalyst. It has also been found that employing a combination of various metals and ligands results in that the activity and inactivity rate constants of the catalyst system can be adjusted depending on the choice of monomers.

Experiments on various kinds of metals such as Mo, Ru, Fe, Rh, Ni, Pd, and Cu have been carried out in ATRP to form a complex with nitrogen, phosphorus and cyclopentadienyl ligand. Have found the most effective for ATRP of monomers with a wide range of materials and broad molecular weight distributions. Nitrogen-based ligands have been selected in this experiment because they have been used to form complexes with various transition metals in ATRP.

tPy and CuBr form a complex because they can have a coordination sphere similar to an aliphatic triamine complex around Cu and also have a geometric structure associated with the same number of ligands.

Therefore, the polymerization mechanism as shown in Fig. 1 could be predicted. Figure 1 is a FT-IR infrared spectroscopy graph of ATRP under supercritical carbon dioxide of vinyl acetate monant and polyvinyl acetate.

In CuBr, the center of Cu is surrounded by triamine and one atom. Hageonde predict the complex was neutralized compared to the tetrahedral complexes charged with a two-bipyridine (bipyridine) molecules, radicals ^(R.) And CuBr _2, The bishalide complex was reversibly formed between the alkyl halide (RX) and CuBr in the ATRP process. The equilibrium also migrated strongly toward CuBr due to the control of the reaction requiring low radical concentration.

On the other hand, FIG. 2 is a ¹ H NMR spectral graph of polyvinyl acetate produced. Observing the ¹ H NMR spectrum of the prepared polyvinyl acetate, the peaks at 4.76, 1.74 and 1.92 ppm were found to be due to the methyl group (-CH ₃ -) of the acetate group and the methine (methine) of the polyvinyl acetate main chain -CH-)) and methylene (methylene (-CH ₂ -. was a)) also has a strong peak of f, d and e will appear in the vinyl acetate repeating units is a small peak in the a, b, c are found in the initiator EBiB .

2, the characteristic absorption peaks of 1760 (V _{c = 0} ), 1140 (V _{c = o = c} ), 1648 (V _{c = c} ) and 3094 (V _{c = c} ) will be. In ^{1-homopolymer} (homopolymer) When compared to the absorption peak of the monomer is still gajina the characteristic absorption peak of the monomer, 1620 to 1680 cm It was confirmed that the absorption peak of the C = C bond disappeared and it was confirmed that the homopolymer was produced.

<Result 2> Effect according to the amount of monomer

Determination of monolith dosage in ATRP is an important task. The monomers supplied to make the controlled synthesis process systematically increase or decrease to determine the conditions of the ideal synthesis process. Under the supercritical carbon dioxide, ATRP proceeded to four different mole numbers in order to define the effect of the synthesis process on the amount of monomers. The amount of the initiator, CuBr, and tPy was changed to 1 mol, the amount of the vinyl monomer to be added was changed to 150, 300, 600, and 1200 mol, respectively, and the polymerization was continued for 24 hours. The amount of initiator, catalyst and ligand was fixed constant in all experiments.

FIG. 3 shows the yield, number average molecular weight and polydispersity index according to the amount of monomer input. A somewhat irrelevant yield was obtained relative to the amount of monomer introduced during the 24 hour ATRP polymerization and an important feature is that there is no notable increase in yield after 30% yield is achieved. Homogeneous polymerization under supercritical carbon dioxide of a typical vinyl monomer can be carried out when the concentration of the monomer is sufficiently high. This is because the monomer acts as a cosolvent. However, the growth rates of methyl methacrylate (MMA) and butyl acrylate were decreased under supercritical carbon dioxide, like other acrylates and methacrylates. This is because the concentration of the monomer is reduced near the radical chain end.

FIG. 4 is a graph showing the number average molecular weight and the polydispersity index according to the amount of monomers injected under supercritical carbon dioxide. The molecular weight and polydispersity index increased with increasing the proportion of monomers charged. The increase in the monomer feed rate was due to the increase in molecular weight, which is due to the reduction in the number of radicals in the polymerization process. The number average molecular weight (Mn) increased from 10,000 to 46,400 g / mol as the mole number of charged monomers increased from 150 to 1200 mol. This increase in molecular weight is due to the decrease in the number of radicals formed due to the greater amount of monomer as the initiator decreases.

In addition, when the amount of monomer was increased, the polymerization process was not controlled, and the polydispersity was high and irregular. This is probably due to the fact that very large amounts of monomers are not able to control the polymerization process even though other conditions are fixed. Therefore, it was proved that the effective molar ratio of the monomer to be charged was 600: 1: 1: 1, respectively, in terms of the amount of the monomers to be charged: monomer: EBiB: CuBr: 0.38 parts by weight of a reaction initiator and 0.73 parts by weight of a reaction catalyst.

<Result 3> Effect according to reaction time

To observe the reaction rate of the polymerization of vinyl acetate monomers under supercritical carbon dioxide, six reactions were carried out under the same conditions and the reactions were carried out for 3, 6, 12, 24, 48 and 72 hours, respectively. The catalyst was removed and then precipitated in hexane solution and analyzed by GPC to determine the molecular weight of the polyvinyl acetate. 5 is a semi-logarithmic kinetic plot of the polymerization of vinyl acetate using a reaction catalyst of CuBr / tPy under supercritical carbon dioxide.

The reaction rate decreases after showing the increase rate in the early stage. The concentration of the resulting radicals was approximately constant until the conversion rate reached 30%. However, the polymerization rate decreased sharply after 24 hours, indicating that it is in the terminal stage.

Figure 6 is a graph showing the yield for ATRP under supercritical carbon dioxide. The charged molar ratio was 600: 1: 1: 1 for the monomer: EBiB: CuBr: tPy, respectively, and the polymerization was carried out at 4500 psi at 65 ° C. The dotted line indicates the number average molecular weight as a value close to a straight line. The conversion rate after the elapse of time was about 22% and showed a low molecular weight distribution, and the polymerization process showed a conversion of 34% over almost 72 hours. As shown in FIG. 6, the linear relationship between the number average molecular weight and the yield indicates that the polymerization process has progressed under control. Also, the polydispersity index was considerably high considering the process of controlling the polymerization process, and it was confirmed that the polydispersity index was significantly higher than that of the conventional bulk polymerization of polyvinyl acetate.

After 72 hours, the polydispersity index increases from 1.67 to 1.94, indicating that the control of the polymerization process is impossible. From this, it can be seen that the control of the polymerization process depends on the solubility and dispersibility of the polymer. This appears to be due to the low deactivation rate constants (k _deact ) of the reaction catalyst used in the polymerization of vinyl acetate, possibly as a result of frequent chain transfer reactions. In order to obtain a successful catalyst system in living radical polymerization, the catalyst must have a high equilibrium constant ( K _eq ) as well as a high inactivation rate constant. This is because the growing polymer radical must be converted to a dormant state before the transfer reaction (termination reaction) occurs.

<Result 4> Initiator  Effect according to input amount

The most important role of initiators is to control the number of growing chains of polymers. Also, when the starting point is faster than the growth point, the polydispersity index becomes smaller. The various effectiveness of the initiator offers many advantages over other controlled radical polymerization. Initiators with various reactivities were used for ATRP of vinyl acetate and EBiB was found to be the best initiator in the ATRP bulk polymerization system of vinyl acetate.

FIG. 7 is a graph showing the yield of polyvinyl acetate as the amount of the initiator to be added is increased. The linear decrease in molecular weight with increasing initiator loading is shown in FIG.

 The reason for the decrease in molecular weight is that as the number of initiators increases, the number of radicals produced increases to produce lower amounts of monomers. As a result, the molecular weight was lowered and the effect of the increased amount of the initiator was insignificant with respect to the polydispersity index.

However, the significantly higher molecular weight than the bulk polymerization means that the initiation efficiency is low under supercritical carbon dioxide. All polymers showed broad molecular weight distributions and were not related to yield or molecular weight. Slow start-up rates seem to be one cause of the broad molecular weight distribution of the polymer. In general, we have found that the initiation rate should be sufficiently high when compared to the rate of obtaining a polymer with narrow molecular weight distribution through ATRP.

<Result 5> Ligand  Effect according to input amount

Ligands can serve in two different ways. Radical concentration and solubility of the metal complex, and the reaction equilibrium can be shifted by lowering or increasing the relative stability or by controlling the oxidation state of the metal complex. This can be achieved by slightly increasing the nucleophilicity of the ligand, by altering or restricting the structure of the back-bonding effect, the charge transfer interaction, and the transition metal complex. The experimental relevance of the polymerization rate with the amount of ligand appears to be due to the more or less complex effects of several auxiliary variables including accessibility to the catalyst site, proximity effect, and solubility of the ligand.

 FIG. 9 is a graph showing the yield of polyvinyl acetate according to an increase in the amount of the ligand to be administered, and FIG. 10 is a graph showing the number average molecular weight and polydispersity index of polyvinyl acetate according to an increase in the amount of the ligand to be administered.

The molecular weight and yield of polyvinyl acetate synthesized by ATRP under supercritical carbon dioxide increased as the amount of ligand input decreased. This seems to be due to two possibilities.

First, the tPy and tPy-CuBr complexes reduce the solubility of the ligand under supercritical carbon dioxide. Furthermore, the solubility of the bound catalyst is gradually reduced as monomers serving as co-solvents are consumed during the synthesis reaction. The loss of polymer chains that are not well soluble in supercritical fluids, i.e., larger molecular weight or larger ligand amounts, reduces polymerization rate. Second, the reason for the structural effect can be found. The variable linear aliphatic triamine system shows that one equivalent of ligand per Cu (I) atom is sufficient to generate saturation, which provides a well-regulated ATRP and a sufficiently soluble catalytic system .

This amount of triamine can reliably saturate the folding power around the Cu, prevent the migration of atoms, and excess ligands cause additional termination reations.

<Result 6> Effect according to temperature change

FIG. 11 is a graph showing the number average molecular weight and polydispersity index of polyvinyl acetate according to the temperature change of the reactor during the synthesis process, and FIG. 12 is a graph showing the yield of polyvinyl acetate according to the pressure change of the reactor during the synthesis. In the case of ATRP under supercritical carbon dioxide, both the density of the reactants and the rate of polymerization are affected by the temperature and pressure during the reaction. Therefore, the yield and molecular weight of polyvinyl acetate varied with the temperature of the reactor from 55 ℃ to 70 ℃. Yield was increased with increasing temperature, but molecular weight was observed to be opposite. When the synthesis was carried out at a temperature of 55 ° C., the polyvinyl acetate polymer synthesized a high molecular weight of about 38,300 g / mol in a yield of 26%. As expected, the polymerization rate increased and the yield increased to 32%. However, when the temperature was increased to 70 ° C, the molecular weight was considerably reduced to 28,200 g / mol. This is consistent with the tendency of ionic polymerization theory to account for pyrolysis.

<Result 7> Effect according to pressure change

The synthesis was carried out for 24 hours and the pressure of the reactor was changed from 3500 psi to 5500 psi. FIG. 13 is a graph showing the yield of polyvinyl acetate according to the pressure change in the reactor during the synthesis process, and FIG. 14 is a graph showing the number average molecular weight and the polydispersity index of the polyvinyl acetate according to the pressure change in the reactor during the synthesis. 13 and 14, it was found that the yield and the molecular weight were increased close to a straight line depending on the pressure. Also in Fig. 14, the polydispersity index was independent of pressure in the pressure range from 3500 to 4500 psi. At higher pressures, however, the polydispersity index decreased considerably and had a low polydispersity index of about 1.69 at 5500 psi. This seems to be due to the increased solubility of carbon dioxide as the density increases due to the high pressure of the reactor. This result shows that as the density of the continuous phase increases at high pressure, the monomer, catalyst, and ligand dissolve better than the mixture of the initial polymerization. As a result, a polymer having a high reaction rate and a high molecular weight is synthesized.

It has also been demonstrated that at higher pressures the density of carbon dioxide has a higher dissolving capacity for growing polyvinyl acetate. Therefore, prior to the initiation of precipitation, the chain became longer, and the molecular weight of the polymer chain could be simply controlled by adjusting the pressure during the reaction using this method. In addition, the synthesis at high pressure gives further increased plasticity, which means that it induces increased monomer diffusion inside the polymer phase.

The present invention is summarized as follows.

The present invention relates to a method for synthesizing polyvinyl acetate by an environmentally friendly method under supercritical carbon dioxide, and a method for producing the same. First, polyvinyl acetate is synthesized under supercritical carbon dioxide. In particular, CuBr / tPy was successfully introduced as a reaction catalyst, and the amount of monomers, initiators, catalysts, and ligands added during the synthesis process was determined. As a result, an independent high molecular weight polyvinyl acetate was produced at a yield in the synthesis reaction, and polyvinyl acetate having a high number average molecular weight was prepared.

Although the invention has been described with reference to the embodiments shown in the drawings, it is to be understood that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (6)

A method for synthesizing polyvinyl acetate using atom transfer radical polymerization (ATRP)
Mixing the vinyl acetate monomer and the reaction initiator in a reaction catalyst under supercritical carbon dioxide (first step);
Stirring the mixed mixture at a temperature of 50 to 75 DEG C and a pressure of 3000 to 8000 psi (second step); And
(ATRP), comprising the step of obtaining polyvinyl acetate from said stirred polymerized reactant (third step). The polyvinyl acetate synthesis method according to claim 1, wherein the reaction catalyst is a complex represented by the following formula (1) or (2) obtained by reacting CuBr with terpyridine :
[Chemical Formula 1]

(2)

The method according to claim 2, wherein the reaction catalyst is obtained by reacting 20 to 60 parts by weight of CuBr and 80 to 40 parts by weight of terpyridine at a temperature of 65 ° C and atmospheric pressure. The polyvinyl acetate (ATRP) Synthesis method. [2] The method of claim 1, wherein the first step comprises mixing 0.15 to 0.8 parts by weight of a reaction initiator and 0.30 to 3.0 parts by weight of a reaction catalyst with respect to 100 parts by weight of the vinyl acetate monomer, using atom transfer radical polymerization (ATRP) A method for synthesizing polyvinyl acetate. [2] The method of claim 1, wherein the second step is a step of polymerizing the mixture by stirring the mixture at a temperature of 50 to 75 [deg.] C and a pressure of 3000 to 8000 psi for 2 to 80 hours, Acetate. A polyvinyl acetate produced by the synthesis method according to any one of claims 1 to 5.

Images