KR101547767B1 - A cadmium complex catalyst containing bispyridine ligand for polymerization of ring ester monomers, a method of preparation thereof and a method of preparation of polymer by using the same - Google Patents

Abstract

The present invention relates to a cadmium complex catalyst containing a bispyridine ligand for the production of a polymer having a cyclic ester group, in particular lactide, a process for preparing the same, and a process for producing a polymer using the same, and more particularly, A catalyst for the production of a polymer of a monomer having a cyclic ester group consisting of a cadmium complex not containing a chiral center, wherein a cadmium halide compound is bonded to a bispyridine ligand which does not contain a chiral center and a method for producing the same, And more particularly to a method for producing a polymer having a cyclic ester group, particularly a polylactide.

Description

Field of the Invention: The present invention relates to a cadmium complex catalyst containing a bispyridine ligand for producing a polymer of a monomer having a cyclic ester group, a process for preparing the same, and a process for preparing a polymer using the same < / RTI >

The present invention relates to a cadmium complex catalyst containing a bispyridine ligand for producing a polymer of a monomer having a cyclic ester group, a process for producing the same, and a process for producing a polymer using the same, and more particularly, Monomer having a cyclic ester group consisting of a cadmium complex bonded to a pyridine ligand, in particular a catalyst for the production of a polymer of lactide, a process for preparing the same, and a process for producing a polylactide having a high heterotacticity and a high conversion ratio .

Among polymers of monomers having a cyclic ester group, polylactide is excellent in impact resistance, flexibility and durability, and has excellent properties such as tensile strength, mechanical strength such as elastic modulus, surface gloss and chemical resistance, Automobiles, etc. Especially, it is widely used for packaging of food products, cosmetics containers, kitchen utensils, toys, and displays due to its excellent decomposability.

As a method for producing such a polylactide resin, there is known a method of direct polycondensation of lactic acid and a ring-opening polymerization of lactide monomer in the form of ring-loosening under an organometallic catalyst. Among them, the direct polycondensation method can produce a low-cost polymer, but it is difficult to secure a sufficient physical and mechanical properties of the polylactide resin because it is difficult to obtain a polymer having an average molecular weight of 100,000 or more. In addition, since ring-opening polymerization of lactide monomers requires lactide monomers to be produced in lactic acid, a higher unit cost is required compared with the condensation polymerization, but a resin having a relatively large molecular weight can be obtained and polymerization control is advantageously commercialized.

Korean Patent Publication No. 2012-0135889 discloses that at least two block copolymerization repeating units having a hard segment of a polylactide repeat unit bonded to both ends of a soft segment of a polyether polyol repeat unit are included, Discloses a film for packaging comprising a lactide copolymer which is linked to each other via a urethane linkage group derived from a polyisocyanate compound having an equivalent isocyanate group average per isocyanate group of more than 2 and less than 3.

Korean Patent Publication No. 2002-0028588 discloses the use of lactic acid and lactide for producing a biodegradable polymer, and it is known that the biodegradable polymer can be utilized in the medical industry.

Korean Patent Laid-Open Publication No. 2014-0038158 discloses a method for producing PLGA using lactide and glycolide, and PLGA prepared by the method. According to the above production method, the weight average molecular weight is 8000 to 15000 , A narrow molecular weight distribution ranging from 1.50 to 2.40, and the prepared PLGA is used when it is used in a drug delivery system and has an effect of constantly controlling drug release.

Korean Patent Laid-Open Publication No. 2014-0037628 discloses a polylactide resin provided through copolymerization of an epoxidized cardanol derivative, which is a biomass, with a lactide monomer, and a production method thereof. Unlike conventional crude oil-based resins, the polylactide resin is based on biomass, so it is possible to utilize recycled resources. Thus, it is excellent in various physical properties such as mechanical properties, transparency and processability, and particularly excellent in coating property, and is free from contamination or toxicity problems and can be suitably applied to food packaging.

Also, Chunh Hsing University research team, Inorg. Chem. Commun 2013, 35, 247-251 discloses a method of polymerizing polylactic acid with a complex having a coordination number of four with a β-ketiminate ligand coordinated at the center of a Zn metal as a catalyst, and Kyungpook (S) -1-phenyl-N - [(S) -1- (pyridin-2-yl) ethyl] ethanamine as a zinc metal complex catalyst in the National University Research Team, Polyhedron , 2012, 43, Discloses a catalyst in which N atoms are coordinated to a central metal using two ligands of S - (S) -1- (6-methylpyridin-2-yl) -N - [(S) Furthermore, a method of polymerizing polylactide at various temperature conditions under the above catalyst using 3,6-dimethyl-1,4-dioxane-2,5-dione (monomer = lactide) as a monomeric lactide has been disclosed .

Under these circumstances, the present inventors have made a catalyst comprising a cadmium complex in which a cadmium halide compound is bonded to a bispyridine ligand not containing a chiral center, and then using the cadmium complex catalyst, a monomer having a cyclic ester group, Polylactide having a high heterotacticity can be produced at a high conversion ratio by polymerizing tide, and thus the present invention has been completed.

It is an object of the present invention to provide a cadmium complex catalyst containing a bispyridine ligand for the production of a monomer having a cyclic ester group with a high heterotacticity and an excellent conversion, particularly a polymer of lactide.

Another object of the present invention is to provide a process for preparing a cadmium complex catalyst containing the bispyridine ligand.

It is still another object of the present invention to provide a method for producing a polymer having a high heterotacticity and a high conversion ratio, particularly a polylactide, using a cadmium complex catalyst containing the bispyridine ligand.

In order to solve the above problems, the present invention provides a catalyst for polymerizing a monomer having a cyclic ester group, which is composed of a cadmium complex containing a bispyridine ligand represented by the following general formula (1).

[Chemical Formula 1]

Wherein R is C _{3 -10} cycloalkyl, C _{3 -10} cycloalkyl C _{1 -10} alkylene, C _{6 -20} aryl, or C _{1 -10} alkoxy C _{1 -10} alkylene, M is cadmium, X is halogen.

The catalyst of the present invention comprising a bis-pyridine ligand-free cadmium complex represented by the general formula (1) according to the present invention is characterized in that it is used as a catalyst for the polymerization reaction of monomers having an ester group, particularly lactide.

Further, the cadmium complex catalyst according to the present invention is characterized in that it is activated by using methyl lithium (MeLi, Methyllithium lithium bromide complex solution) as a cocatalyst to polymerize a monomer having an ester group in a ring-loosened form.

In the present invention, the ring-loosened polymer has two asymmetric centers due to the monomer, and it is characterized in that the polylactide polymer body has a heterotacticity of 80% or more and excellent catalytic activity despite the absence of a chiral center in the catalyst .

Preferably, the R is a C _{3 -6} cycloalkyl, C _{3 -6} cycloalkyl, C _{1 -4-alkylene,} C _6-10 aryl, or C _{1 -4} alkoxy C _{1 -4-alkylene.}

More preferably, R is -CH ₂ C ₆ H ₁₁ , -C ₆ H ₅ , -C ₆ H ₁₁ , - (CH ₂ ) ₂ OCH ₃ , or - (CH ₂ ) ₃ OCH ₃ .

Preferably, X is Cl or Br.

In the present invention, the catalyst may have a dimer structure by combining X and M of different catalysts.

In the present invention, when R is C _{1 -10} alkoxy C _{1 -10} alkylene, the oxygen atom of the alkoxy bonds to M to form a ring in which R and M form a ring.

Even more preferably, the catalyst is a catalyst comprising a cadmium complex containing a bispyridine ligand represented by the formula:

[Formula 1a]

[Chemical Formula 1b]

[Chemical Formula 1c]

≪ RTI ID = 0.0 &

[Formula 1e]

Wherein M is cadmium and X is halogen.

In the present invention, the monomer having the cyclic ester group is preferably selected from the group consisting of lactide, glycolide,? -Caprolactone, (3S) -cis-3,6-dimethyl-1,4-dioxane- Combinations thereof, but are not limited thereto.

In an embodiment of the present invention, a polymeric polymerization method in which the cyclic ester group-containing monomer is ring-opened using lactide (3,6-dimethyl-1,4-dioxane-2,5-dione, Lactide) Polylactide is generated. This polylactide has five types of heterotacticity since there are two chiral centers, and this heterotacticity affects the properties of the polylactide.

Heterotacticity when the asymmetric center of polylactide is present affects the specific properties of the polymer itself, and catalysts with asymmetric centers do not have the desired activity and heterotacticity. However, the catalyst of the present invention is excellent in activity of the polymer as well as the heterotacticity, even though the asymmetric center does not exist.

That is, in the case of producing a polylactide as a polymer using lactide, which is a monomer having an ester group in the form of a ring-loosened form, the present invention uses a catalyst of the present invention and an initiator called methyllithium to form a ring of a monomer having a cyclic ester group It is possible to provide a high molecular weight and high heterotacticity corresponding to the asymmetric center even when the catalyst has no asymmetric center and at the same time to provide a high yield at a low cost.

In other words, although the catalyst of the present invention does not have an asymmetric center, the resulting polylactide may have five kinds of tacticity: sis, isi, sii, iis, iii. At this time, in the ring opening reaction by the achiral catalyst, polylactide having a high heterotacticity, that is, a polylactide having a high ratio of sis and isi in ¹ H NMR can be polymerized.

Therefore, when the polylactide is produced by the catalyst of the present invention, a large molecular weight can be obtained at a low cost and a conversion of resin can be made to reach 100%. There is no monomer remaining and there is a difference in toxicity compared to the other lactide of the prior art.

The present invention also provides a catalyst composition for polymerizing monomers having a cyclic ester group containing an alkyl lithium compound as a cocatalyst and a catalyst of the above formula (1).

Preferably, the alkyllithium compound may be methyllithium (MeLi, methyllithium), but is not limited thereto. The methyllithium may be commercially available. Specifically, in one embodiment of the present invention, MeLi (methyllithium lithium bromide complex solution) obtained from Tosoh was used.

The present invention also provides a catalyst for polymerizing monomers having a cyclic ester group, which comprises reacting an N, N-bipyridine amine derivative represented by the following formula (2) and a cadmium halide compound represented by the following formula And a manufacturing method thereof.

(2)

(3)

MX ₂ E _n

Wherein R is C _{3 -10} cycloalkyl, C _{3 -10} cycloalkyl C _{1 -10} alkylene, C _{6 -20} aryl, or C _{1 -10} alkoxy C _{1 -10} alkylene, M is cadmium, X is a halogen, E is a Lewis base which can be coordinated to cadmium, and n is an integer of 0 to 4.

Preferably, the R is a C _{3 -6} cycloalkyl, C _{3 -6} cycloalkyl, C _{1 -4-alkylene,} C _6-10 aryl, or C _{1 -4} alkoxy C _{1 -4-alkylene.}

More preferably, R is -CH ₂ C ₆ H ₁₁ , -C ₆ H ₅ , -C ₆ H ₁₁ , - (CH ₂ ) ₂ OCH ₃ , or - (CH ₂ ) ₃ OCH ₃ .

Even more preferably, the N, N-bispyridine amine derivative represented by Formula 2 is an N, N-bipyridine amine derivative represented by Formula 2 below:

(2a)

(2b)

[Chemical Formula 2c]

(2d)

[Formula 2e]

Preferably, X is Cl or Br.

Preferably, the cadmium halide compound represented by Formula 3 is cadmium bromide.

In the present invention, the reaction temperature for the reaction of the N, N-bipyridine amine derivative represented by the formula (2) for preparing the catalyst and the halogenated cadmium compound represented by the formula (3) may be room temperature, preferably 15 to 30 ° C, The reaction time can be from 12 to 48 hours.

In the present invention, a catalyst having good stability in the air can be obtained at a low cost and a high yield through the production of the catalyst.

The present invention also provides a process for producing a polymer comprising the step of polymerizing a monomer having a cyclic ester group in the presence of the catalyst of the formula (1).

In the present invention, the monomer having the cyclic ester group is preferably selected from the group consisting of lactide, glycolide,? -Caprolactone, (3S) -cis-3,6-dimethyl-1,4-dioxane- Combinations thereof, but are not limited thereto.

In the present invention, the monomer having the cyclic ester group may be in particular lactide.

In the present invention, an alkyllithium compound can be used as a cocatalyst together with the catalyst.

In the present invention, the polymerization temperature in the production of the polymer may preferably be -60 캜 to -40 캜, more preferably -55 캜 to -45 캜, and most preferably -50 캜, 48 hours.

In one embodiment of the present invention, a catalyst comprising a cadmium complex having a cadmium halide compound bonded to a bispyridine ligand not containing a chiral center represented by Formula 1 is used as a monomer having a hexacyclic ester group, that is, a lactide Can be used as a catalyst in the polymerization reaction. In this case, the cadmium complex catalyst can be polymerized with a monomer having an ester group by a polymerization method in which the cadmium complex catalyst is activated by a methyllithium (MeLi, methyllithium lithium bromide complex solution) Respectively. In addition, it was confirmed that two asymmetric centers were formed in the ring-loosened polylactide due to the monomer, and the polylactide polymer exhibited a heterotacticity of 90% or more in spite of the absence of a chiral center in the catalyst, And that it is differentiated by showing different properties from lactide.

In particular, in one embodiment of the present invention, polylactide (PLA) having a conversion of 70 to 100% can be prepared by using the catalyst represented by the above formula (1), and thus the activity of the catalyst is excellent. Further, since there is almost no residual monomer, the toxicity of the monomer and the residual amount of the metal of the catalyst are insignificant.

The cadmium metal complex catalyst according to the present invention is stable in the air and is easy to use as a catalyst in the polymerization. Examples of the prepared polymer include polylactide (PLA, polylactic acid) in the form of a ring- Especially lactide. The polylactide is polymerized in the form of a polymer having two chiral centers in one molecule. The polylactide is differentiated by exhibiting heterotacticity of 0.9 or more and exhibiting properties different from those of other polylactides.

Hereinafter, the present invention will be described in more detail with reference to Examples. These embodiments are only for describing the present invention more specifically, and the scope of the present invention is not limited by these examples.

A. Bispyridine amine Ligand  Synthesis and its substituents Synthetic ligand  Produce

Example  One

N, N-di (2- Picoll ) Cyclohexylmethylamine (L _A ) Ligand  One

The N, N-di (2-picolyl) cyclohexylmethylamine ligand was prepared by a known method (Dalton Trans (2009) 4795-4805).

Specifically, N, N-di (2-picolyl) cyclohexylmethylamine was prepared as follows.

First, the de-suspended in 10 ㎖ acetone (2 blood kolil) amine (0.70 g, 3.52 mmol) and _{K 2 CO 3 (0.97 g,} 7.03 mol) to the addition of a small amount of KI crystals, acetone 20 ㎖ in Bromo Methyl cyclohexane (0.62 g, 3.52 mol) was added dropwise over 30 minutes. To the mixture was heated at reflux for 24 hours and then removing the acetone in vacuo, and the residue was dissolved in CHCl ₃ (100 mL). The the solution was washed twice with water (100 mL) and then, after the organic phase was dried over MgSO _4, filtered, the solvent was removed in vacuo. Column chromatography of the residue _{[CHCl 3 / MeOH (98:} 2), SiO 2] to yield the title ligand present in the first fraction as a brown oil. Yield: 0.6 g, (58%).

Example  2

N, N- Bis (Pyridine- 2-methylethyl methyl ) Benzene amine (L _B ) Ligand  2

N, N-bis (pyridin-2ylmethyl) benzenamine ligand was prepared by a known method (Polyhedron 19 (2000) 1333-1338).

Specifically, N, N-bis (pyridin-2-ylmethylimethyl) benzeneamine was prepared as follows.

First, an aqueous solution (7 ml) of NaOH (1.46 g, 36.6 mmol) was added to an aqueous solution (3 ml) of 2- (chloromethyl) pyridine hydrochloride (6.00 g, 36.6 mmol) and neutralized. Aniline (1.70 g, 18.3 mmol) was added to the vigorously stirred solution over 2 h at 0 <0> C, followed by methylene chloride (5 mL). Over 7 days, the pH was kept below 9 by the addition of small portions of aqueous NaOH (1.46 g, 36.6 mmol) (7 mL). The reaction was stirred for an additional 7 days. The pH was adjusted to 8 by the addition of NaOH or HCl and the phases were separated. The separated aqueous phase was extracted with CH ₂ Cl ₂ (3 × 30 ml) and the combined organic extracts were washed with water (10 ml), dried over anhydrous sodium sulfate and evaporated to dryness. The crude product was purified on a Soxhlet apparatus using petrol (bp 60-80 占 폚) to obtain the title ligand. 2.4 g, 47.6% pale yellow crystals.

Example  3

N, N-di (2- Picoll ) Cyclohexylamine (L _C ) Ligand  3

The N, N-di (2-picolyl) cyclohexylamine [N, N-di (2-picolyl) cyclohexylamine] ligand was prepared by a known method (Polyhedron 63 (2013) 139-146).

Specifically, N, N-di (2-picolyl) cyclohexylamine was prepared as follows.

First, an aqueous solution (15.0 mL) of cyclohexylamine (1.98 g, 0.020 mol) was added to an aqueous solution (15.0 mL) of 2-picolyl chloride hydrochloride (6.58 g, 0.040 mol) and NaOH pellet (3.20 g, 0.080 mol) Was added. After stirring at room temperature for 5 days, the product was extracted with dichloromethane. The reaction solution was dried over MgSO4 and the filtrate solvent was removed under reduced pressure to obtain the title ligand (4.61 g, 82.0%) as a brown powder.

Example  4

2- Methoxy -N, N- Bis (Pyridin-2- Yl methyl ) Ethanamine (L _D ) Ligand  4

The 2-methoxy-N, N-bis (pyridin-2-ylmethyl) ethanamine ligand was prepared by a known method (Inorg. Chim. Acta, 357 (2004) 2694-2702).

Specifically, 2-methoxy-N, N-bis (pyridin-2-ylmethyl) ethanamine was prepared as follows.

2-methoxyethyl) -N- (pyridin-2-ylmethyl) amine (916 mg, 5.52 mmol), 2-picolylchloride hydrochloride (903 mg, 5.51 mmol) and K ₂ CO ₃ &lt; / RTI &gt; (1.53 g, 11.1 mmol) was refluxed for 9 hours. The mixture was cooled and filtered. The acetonitrile was removed from the filtrate and the residue was taken up in water (30 mL) and chloroform (20 mL) and the mixture was made alkaline with approximately 10% sodium hydroxide solution to pH 8. After separating the layers, the aqueous layer was extracted with chloroform (6 x 30 ml). The combined organic layers were dried over anhydrous sodium sulfate. After removal of the solvent, the title ligand was obtained as an orange red oil. Yield: 1.11 g (78%).

Example  5

3- Methoxy -N, N- Bis (pyridin-2-ylmethyl) propane -1-amine ( L _E ) Ligand  5

The 3-methoxy-N, N-bis (pyridin-2-ylmethyl) propan-1-amine ligand is a known (Inorg. Chim. Acta, 357 (2004) 2694-2702).

Specifically, 3-methoxy-N, N-bis (pyridin-2-ylmethyl) propane-1-amine was prepared as follows.

To a solution of N- (3-methoxypropyl) -N- (pyridin-2-ylmethyl) amine (454 mg, 2.52 mmol), 2-picolylchloride hydrochloride (416 mg, 2.53 mmol) in acetonitrile A mixture of K ₂ CO ₃ (704 mg, 5.10 mmol) was refluxed overnight and the solvent was removed by means of a diffuser evaporator. The residue was taken up in water (15 mL) and dichloromethane (10 mL) and the mixture was made alkaline with ammonia to approximately pH 9. After separating the layers, the aqueous layer was extracted with dichloromethane (5 x 30 ml). The combined organic layers were dried over anhydrous sodium sulfate. After removal of the solvent, the title ligand was obtained as an orange red oil. Yield: 602 mg (88%).

B. Preparation of Catalyst

Example  6

[L _A Cd (m- Br ) Br ] ₂ Manufacturing

A solution of the ligand [L _A ] (148 mg, 0.500 mmol) in 50 mL of ethanol and a solution of CdBr ₂ .4H ₂ O (172 mg, 0.500 mmol) in 20 mL of ethanol were mixed and reacted at 25 ° C for 24 hours. The reaction solvent was removed by vacuum drying and then washed three times with 30 ml of cold ethanol and then washed three times with 30 ml of hexane to obtain a white solid compound. The yield was 0.250 g (88.1%).

Analysis calculated for C ₃₈ H ₅₀ Br ₄ Cd ₂ N ₆ : C, 40.2% H, 4.44% N, 7.40%. Found: C, 41.0% H, 4.56% N, 7.57%.

IR (solid neat; cm ^-1 ): 3145 (w), 2920 (w), 2851 (w), 1601 (m), 1559 (m), 1444 (s), 1048 957 (m), 841 (s), 762 (s), 712 (s), 641 (s).

Example  7

[ L _B CdBr ₂ ]

A solution of the ligand [L _B ] (140 mg, 0.500 mmol) in 50 mL of ethanol and a solution of CdBr ₂ .4H ₂ O (172 mg, 0.500 mmol) in 20 mL of ethanol were mixed and reacted at 25 ° C for 24 hours. The reaction solvent was removed by vacuum drying and then washed three times with 30 ml of cold ethanol and then washed three times with 30 ml of hexane to obtain a white solid compound. The yield of the obtained compound was 0.240 g (88.3%).

Analysis calculated for C ₁₈ H ₁₇ BrCdN ₃ : C, 36.8% H, 3.37% N, 7.80%. Found: C, 38.6% H, 3.16% N, 7.84%.

IR (solid neat; cm ^-1 ): 3112 (w), 3040 (w), 2897 (w), 2657 (w), 1773 (m), 1667 (m), 1524 1087 (m), 898 (m), 833 (m), 758 (s), 674 (s).

Example  8

[ L _C CdBr ₂ ]

A solution of the ligand [L _C ] (141 mg, 0.500 mmol) in 25 mL of ethanol and a solution of CdBr ₂ .4H ₂ O (172 mg, 0.500 mmol) dissolved in 25 ml of ethanol were mixed and reacted at 25 ° C for 24 hours. The reaction solvent was removed by vacuum drying and then washed three times with 30 ml of cold ethanol and then washed twice with 30 ml of hexane to obtain a white solid compound. The yield of the obtained compound was 0.270 g (97.5%).

Analysis calculated for C ₁₈ H ₂₃ Br ₂ CdN ₃ : C, 39.1% H, 4.19% N, 7.59%. Found: C, 39.5% H, 4.16% N, 7.55%.

IR (solid neat; cm ^-1 ): 3144 (w), 3088 (w), 3023 (w), 2911 (w), 2844 (w), 1765 (s), 1693 1478 (s), 1425 (s), 1370 (s), 1299 (s), 1155 (s), 1093 (s), 1016 (s), 947 764 (s), 646 (s).

[ L _C CdBr ₂ ]

Example  9

[ L _D CdBr ₂ ]

A solution of the ligand [L _D ] (260 mg, 1.00 mmol) in 25 mL of ethanol and a solution of CdBr ₂ .4H ₂ O (0.34 g, 2.54 mmol) dissolved in 25 ml of ethanol were mixed and reacted at 25 ° C for 24 hours. The reaction solvent was removed by vacuum drying and then washed three times with 30 ml of cold ethanol and then washed twice with 30 ml of hexane to obtain a white solid compound. The yield of the obtained compound was (0.940 g, 70.7%).

Analysis calculated for C ₁₅ H ₁₉ Br ₂ CdN ₃ O: C, 34.0% H, 3.62% N, 7.94%. Found: C, 34.4% H, 3.68% N, 8.02%.

IR (solid neat; cm ^-1 ): 3123 (w), 3002 (w), 2802 (w), 1695 (m), 1598 (m), 1544 (w), 1439 1144 (m), 1097 (s), 1019 (s), 835 (m), 772 (s), 643 (m).

Example  10

[L _E Cd (m- Br ) Br ] ₂ Manufacturing

A solution of the ligand [L _E ] (130 mg, 0.500 mmol) in 25 mL of ethanol and a solution of CdBr ₂ .4H ₂ O (172 mg, 0.500 mmol) dissolved in 25 ml of ethanol were mixed and reacted at 25 ° C for 24 hours. The reaction solvent was removed by vacuum drying and then washed three times with 30 ml of cold ethanol and then washed twice with 30 ml of hexane to obtain a white solid compound. The yield of the obtained compound was (0.240 g, 88.3%).

Analysis calculated for C ₃₂ H ₄₂ Br ₄ Cd ₂ N ₆ O ₂ : C, 35.4% H, 3.89% N, 7.73%. Found: C, 34.8% H, 3.85% N, 7.74%.

IR (solid neat; cm ^-1 ): 3146 (w), 2977 (w), 2808 (w), 1694 (m), 1602 (w), 1524 1089 (m), 837 (w), 771 (s), 640 (s).

C. Polymer Production

Example  11

MeLi (1 mmole, 0.5 ml) was added to a solution of the catalyst [L _C CdBr ₂ ] (277 mg, 0.5 mmole) prepared in Example 8 in tetrahydrofuran (5 ml) under an argon atmosphere, Respectively.

Similarly, lactide (0.9 g) was dissolved in methylene chloride (5 ml) under an argon atmosphere, and the activated catalyst (1 ml) prepared above was then introduced and stirred at -50 ° C for 24 hours. After 24 hours, distilled water (2 ml) was added to the obtained reaction product to terminate the reaction, and the polymer was precipitated with nuclear decane (10 ml).

After separating the polymer under reduced pressure, methanol (50 ml) was added three times to wash and the final polymer was separated. This was dried under reduced pressure to obtain 1.77 g of a polymer. It was confirmed by NMR that conversion yield was 100%. The obtained PLA had Mw = 27.1 (g / mol) x 10 ³ , Mn = 20.0 (g / mol) x 10 ³ , and Pr = 0.87.

Example  12

The reaction was carried out under the same conditions as in Example 11 except that the catalyst [L _D CdBr ₂ ] prepared in Example 9 was used.

2.07 g of a polymer was obtained and it was confirmed that conversion yield was 100% by using NMR. PLA obtained was Mw = 47.6 (g / mol) x10 3, Mn = 35.2 (g / mol) was x10 ^3, Pr = 0.87.

Example  13

The reaction was carried out under the same conditions as in Example 11 except that the catalyst [L _E Cd (m-Br) Br] ₂ prepared in Example 10 was used.

2.24 g of a polymer was obtained and it was confirmed that conversion yield was obtained up to 100% using NMR. The obtained PLA had Mw = 65.3 (g / mol) x 10 ³ , Mn = 46.9 (g / mol) x 10 ³ , and Pr = 0.90.

The results of the polymerization reaction with the cadmium complex catalyst according to the present invention are summarized in Table 1 below.

catalyst Temperature (℃) Conversion Rate (%) Mn (g / mol) x 10 ³ Mw (g / mol) x 10 ³ PDI Pr [L _C CdBr ₂ ] -50 100 20.0 27.1 1.35 0.87 [L _D CdBr ₂ ] -50 100 35.2 47.6 1.35 0.87 [L _E Cd (m-Br) Br] ₂ -50 100 46.9 65.3 1.39 0.82

Claims (17)

A catalyst for polymerizing a monomer having a cyclic ester group, which is composed of a cadmium complex containing a bispyridine ligand represented by the following formula
[Chemical Formula 1]

Wherein R is C _{3 -10} cycloalkyl, C _{3 -10} cycloalkyl C _{1 -10} alkylene, C _{6 -20} aryl, or C _{1 -10} alkoxy C _{1 -10} alkylene, M is cadmium, X is halogen.
2. The method of claim 1, wherein R is C _{3 -6} cycloalkyl, C _{3 -6} cycloalkyl, C _{1 -4-alkylene,} C _6-10 aryl, or C _{1 -4} alkoxy C _{1 -4} alkylene, catalyst .
2. The method of claim 1, wherein R is _{-CH 2 C 6 H 11, -C} 6 H 5, -C 6 H 11, - (CH 2) 2 OCH 3, or - (CH _{2) 3} OCH ₃ of the catalyst .
2. The catalyst of claim 1, wherein X is Cl or Br.
The catalyst according to claim 1, wherein the catalyst has a dimer structure by combining X and M of different catalysts.
The catalyst according to claim 1, wherein when R is C _{1 - 10} alkoxy C _{1 - 10} alkylene, the oxygen atom of the alkoxy bonds to M to form a ring of R and M.
The catalyst according to claim 1, wherein the catalyst comprises a cadmium complex containing a bispyridine ligand represented by any one of the following formulas (1a) to (1e):
[Formula 1a]

[Chemical Formula 1b]

[Chemical Formula 1c]

&Lt; RTI ID = 0.0 &

[Formula 1e]

Wherein M is cadmium and X is halogen.
The method according to claim 1, wherein the monomer having a cyclic ester group is selected from the group consisting of lactide, glycolide,? -Caprolactone, (3S) -cis-3,6-dimethyl-1,4-dioxane- Or a combination thereof.
9. A catalyst composition for polymerizing a monomer having a cyclic ester group comprising an alkyl lithium compound as a cocatalyst and a catalyst according to any one of claims 1 to 8.
A method for polymerizing a monomer having a cyclic ester group according to any one of claims 1 to 8, which comprises reacting an N, N-bipyridine amine derivative represented by the following formula (2) with a halogenated cadmium compound represented by the following formula Method of preparing catalyst:
(2)

(3)
MX ₂ E _n
Wherein R is C _{3 -10} cycloalkyl, C _{3 -10} cycloalkyl C _{1 -10} alkylene, C _{6 -20} aryl, or C _{1 -10} alkoxy C _{1 -10} alkylene, M is cadmium, X is a halogen, E is a Lewis base which can be coordinated to cadmium, and n is an integer of 0 to 4.
11. The method of claim 10, wherein R is C _{3 -6} cycloalkyl, C _{3 -6} cycloalkyl, C _{1 -4-alkylene,} C _{6 -10} aryl, or C _{1 -4} alkoxy C _{1 -4} alkylene, catalyst &Lt; / RTI &gt;
11. The method of claim 10, wherein R is _{-CH 2 C 6 H 11, -C} 6 H 5, -C 6 H 11, - (CH 2) 2 OCH 3, or - (CH _{2) 3} OCH ₃ of the catalyst &Lt; / RTI &gt;
11. The method of claim 10, wherein the N, N-bispyridine amine derivative represented by Formula 2 is an N, N-bipyridine amine derivative represented by Formula (2a)
(2a)

(2b)

[Chemical Formula 2c]

(2d)

[Formula 2e]

11. The method of claim 10, wherein X is Cl or Br.
9. A process for the preparation of a polymer comprising the step of polymerizing a monomer having a cyclic ester group in the presence of a catalyst according to any one of claims 1 to 8.
16. The method according to claim 15, wherein the monomer having the cyclic ester group is selected from the group consisting of lactide, glycolide,? -Caprolactone, (3S) -cis-3,6-dimethyl-1,4-dioxane- Or a combination thereof.
16. The process for producing a polymer according to claim 15, wherein an alkyl lithium compound is used as a cocatalyst together with the catalyst.