JP3972100B2 - Method for producing polyester using aluminum metal compound catalyst - Google Patents

Description

  The present invention relates to a novel ring-opening polymerization catalyst for producing a polyester and a method for producing a polyester using the catalyst.

  So far, many methods for producing polyesters from lactones using a ring-opening polymerization catalyst are known, but these use a compound that is unstable under heating conditions of 100 ° C. or in the air as a catalyst. ing. As a specific example, as a ring-opening polymerization method of ε-caprolactone (2-oxepanone), a method of heating to 100 ° C. or more, or a ring-opening polymerization of caprolactone using an aluminum metal compound, for example, aluminum isopropoxide. (Non-Patent Document 1). In the ring-opening polymerization of ε-caprolactone using this aluminum isopropoxide as a catalyst, living polymerization proceeds and polycaprolactone having a narrow molecular weight distribution can be obtained.

  However, aluminum compounds used as catalysts are unstable when exposed to moisture and oxygen, and the reaction system must be fully dried and the monomers, catalysts and additives must be highly purified and dried. Furthermore, these polymerization reactions had to be performed under a nitrogen atmosphere. Recently, energetic studies have been conducted on enzyme ring-opening polymerization using a reverse reaction of lipase, which is a hydrolase, for the purpose of controlling mild conditions and stereoregularity (Non-patent Documents 2 and 3). However, there are still many points to be solved for practical use, such as the fact that the enzyme is expensive and it is difficult to remove the enzyme from the produced polymer.

On the other hand, the present inventors have developed a method for polymerizing lactones with a rare earth metal compound that is stable in air or a small amount of water having a polymerization activity in the range from about room temperature to about 100 ° C. (Application 2002-118374)
However, this method requires a long reaction time of 60 ° C. and 48 hours in the ring-opening polymerization of caprolactone, and there are still points to be improved.

(C. Jacobs, Ph. Dubois, R. Jerome, and Ph. Teyssie, "Macromolecular Engineering of Polylactones and Polylactides. 5.", Macromolecules, 24, 3027-3034 (1991)) H. Uyama and S. Kobayashi, Chem. Lett., 1149 (1993) R. T. MacDonald, S. K. Pulapura, Y. Y. Svirkin and R. A. Gross, "Enzyme Catalyzed ε-CaprolactoneRing-Opening Polymerization", Macromolecules, 28, 73-78 (1995).) M. Kunioka, Y. Wang, S. Onozawa, “Polymerization ofpoly (ε-caprolactone) using yttrium triflate”, PolymerJ., 35, 422-429 (2003).)

  In view of the circumstances as described above, the problem of the present invention is that the activity is not lowered by a minute amount of water remaining in the reaction medium such as a monomer or oxygen in the air, and the activity is higher in the range from about room temperature to about 100 degrees. The present invention provides a novel ring-opening polymerization catalyst for producing a polyester, and further intends to advantageously produce a polyester using the catalyst.

  As a result of intensive studies to solve the above problems, the present inventors have developed a lactone and a lactide by using a compound comprising three perfluoroalkyl group ligand moieties and an aluminum metal as a catalyst. In the ring polymerization, the polymerization reaction can proceed in a simple system and with energy saving in the range from about room temperature to around 100 degrees, without using advanced conditions for raw material monomers and special conditions such as under nitrogen atmosphere. In addition, the inventors have found that when a cyclic acid anhydride and a cyclic ether are used as raw material monomers, the polymerization reaction proceeds to produce a polyester, and the present invention has been completed.

That is, the present invention relates to the following (1) to (5).
(1) The following general formula I
Al (OSO ₂ R ¹ ) (OSO ₂ R ² ) (OSO ₂ R ³ ) .. General formula I
^{(Wherein, R 1, R 2, R} 3 are each the same or different which may be a perfluoroalkyl group, Al represents aluminum.)
A catalyst for ring-opening polymerization of lactones or lactides, which is used for the production of polyester, comprising an aluminum compound represented by the formula:
(2) A process for producing a polyester from a lactone or lactide by a ring-opening polymerization reaction, wherein the aluminum compound described in (1) above is used as a catalyst.
(3) The method for producing a polyester as described in (2) above, wherein the lactone or lactide to be subjected to the ring-opening polymerization reaction is each alone or a mixture of plural kinds.
(4) The method for producing a polyester as described in (2) or (3) above, wherein the ring-opening polymerization reaction system contains water or a monovalent or polyhydric alcohol.

  According to the present invention, when a polyester is produced by ring-opening polymerization, as in the past, the polymerization reaction is carried out in a nitrogen atmosphere, or a purification process such as removing traces of moisture or impurities from the raw material monomer, or drying of the catalyst Since a process such as a process is not required and the polymerization temperature may be relatively low, the polyester can be produced with an extremely simple system and energy saving. In addition, by using the method for producing a polyester of the present invention, it is possible to produce and provide a polyester in which an enzyme containing a trace amount of water and various drugs are dispersed in a polymer, and application to a drug delivery system can be expected.

The aluminum metal compound used as the ring-opening polymerization catalyst for producing the polyester of the present invention is represented by the following general formula I
Al (OSO ₂ R ¹ ) (OSO ₂ R ² ) (OSO ₂ R ³ ) .. General formula I
(In the formula, R ¹ , R ² and R ³ each represent a perfluoroalkyl group which may be the same or different, and Al represents aluminum.)
It is represented by the chemical structure represented by
As apparent from the general formula I, the compound is a compound characterized in that a perfluoroalkylsulfonic acid ligand moiety and an aluminum atom are bonded.

These perfluoroalkyl groups may be different or the same, but it is preferable that three R ¹ , R ² and R ³ are preferably the same. The perfluoroalkyl group may be either a linear or branched perfluoroalkyl group or a cyclic perfluoroalkyl group. The carbon number of the perfluoroalkyl group is 1 to 10, preferably 1 to 6, and more preferably 1 to 3. Specific examples of the alkyl group include a trifluoromethyl group, a pentafluoroethyl group, a perfluoropropyl group, and a perfluorocyclohexyl group.

（式中、Ｒ^４はアルキレン基を示す）
（２）以下の一般式ＩＩＩで表される環状ジエステル構造を有するラクチド類

（式中、Ｒ^５はアルキレン基を示す。） The ring-opening polymerization method of the polyester using the aluminum compound catalyst of the present invention is a novel polymerization method not described in any document. According to the polymerization method, for example, a polyester is produced using the following cyclic monomers as raw materials.
(1) Lactones represented by the following general formula II

(Wherein R ⁴ represents an alkylene group)
(2) Lactides having a cyclic diester structure represented by the following general formula III

(In the formula, R ⁵ represents an alkylene group.)

（但し、式中Ｒ^６はアルキレン基を示す。）

（但し、式中Ｒ^７はアルキレン基を示す。）
本発明の上記アルミニウム金属化合物触媒は、特に、上記（１）、（２）式に示したラクトン類、ラクチド類から、開環重合により、ポリエステルを製造し得るという点にその機能上の特徴を有する。 (3) A cyclic acid anhydride obtained by dehydrating and cyclizing a dicarboxylic acid represented by the following general formula IV and a cyclic ether obtained by dehydrating and cyclizing a diol represented by the following general formula V

(In the formula, R ⁶ represents an alkylene group.)

(In the formula, R ⁷ represents an alkylene group.)
The aluminum metal compound catalyst of the present invention has a functional feature in that a polyester can be produced by ring-opening polymerization from the lactones and lactides shown in the above formulas (1) and (2). Have.

In the present invention, the lactones represented by the general formula II, which is a raw material monomer that undergoes ring-opening polymerization with an aluminum metal compound, is preferably a compound having 3 to 15 carbon atoms in the formula, preferably 4 to 14 carbon atoms. More preferred are compounds.
Specific examples of the alkylene group include, for example, tetramethylene, pentamethylene, decamethylene, tetradeca (14) methylene and the like. Specific compound names include δ-valerolactone, ε-caprolactone, oxacyclododecane- 2-one, oxacyclohexadecan-2-one and the like.

  As the lactides represented by the general formula III, the alkylene group in the formula is a linear or branched alkylene group having 1 or 2 carbon atoms, and specific examples of the alkylene group include, for example, Examples include methylene and methylmethylene, and specific compound names include glycolide and lactide.

  As the cyclic acid anhydride of the general formula IV, the alkylene group in the formula is a linear alkylene group, preferably having 2 or 3 carbon atoms, more preferably having 2 carbon atoms. Specific examples of the group include, for example, ethylene, propene and the like, and specific compound names include succinic anhydride, glutaric anhydride and the like.

  As the cyclic ether of the general formula V, the alkylene group in the formula is a linear alkylene group, preferably having 3 to 5 carbon atoms, more preferably having 4 carbon atoms. Specific examples include propene, butene, pentene and the like, and specific compound names include oxetane, tetrahydrofuran, tetrehydropyran and the like.

In the ring-opening polymerization using the aluminum metal compound catalyst of the present invention, water or a monovalent or polyhydric alcohol can be contained in the reaction system in order to improve the polymerization rate and to control the molecular weight. These may be added to the reaction system, or may be contained in the reaction system as a result accompanying the use of an unpurified raw material monomer as a raw material. In this specification, a polyhydric alcohol refers to a compound having two or more hydroxyl groups.
As alcohol used by this invention, a C1-C10 alcohol is preferable, More preferably, a C1-C4 lower aliphatic alcohol is mentioned. The number of hydroxyl groups is preferably 1 to 4.

  Preferred alcohols include, for example, monohydric alcohols such as methanol, ethanol, and propanol, dihydric alcohols such as 1,3-propanediol, 1,4 butanediol, and 1,5-hexanediol, trihydric alcohols such as glycerin, and the like. And tetrahydric alcohols such as pentaerythritol. Moreover, you may use the mixture with said alcohol mixture and water.

Among these, in the ring-opening polymerization using the aluminum metal compound catalyst of the present invention, it is more preferable to add glycerin for the purpose of obtaining the maximum yield and molecular weight.
Moreover, the addition amount of water or alcohol is 0.01-10 wt% with respect to the weight of the added monomer, Preferably it is 0.5-2 wt%, More preferably, it is 1 wt%.

  When the reaction is carried out, the polymerization reaction (bulk polymerization) is usually performed using the monomer liquid as a medium without using a reaction solvent, but a general organic solvent may be used. When using an organic solvent, aromatic hydrocarbons such as toluene and xylene, ethers such as diethyl ether, dibutyl ether and tetrahydrofuran, aliphatic saturated hydrocarbons such as pentane and hexane, methylene chloride, chloroform and the like Chlorinated hydrocarbons, acetone, 1,4-dioxane, dimethylformamide, dimethyl sulfoxide and the like can be mentioned. Moreover, you may use the mixed suspension solvent which mixed water with said organic solvent.

The aluminum metal compound used as a catalyst in the present invention is a compound that is stable in the air and is not decomposed by moisture or oxygen remaining in the air or in the monomer to be added. Furthermore, it has extremely advantageous properties in that a lactide or a cyclic acid anhydride and a cyclic ether can be subjected to ring-opening polymerization to produce a polyester. In addition, when the monomer is a lactone that is liquid at room temperature, this catalyst has a very high polymerization activity even from room temperature to around 60 ° C., so that it has excellent properties in that it enables production of polyester at a low cost and safety, energy saving. Have
Next, the present invention will be described more specifically with reference to examples.

  In a 10 mL vial with a glass lid, 1140 mg (10 mmol) of commercially available ε-caprolactone, 9.5 mg (0.02 mmol) of aluminum trifluoromethanesulfonic acid, 6.2 mg (0.067 mmol) of glycerin were left unpurified. Put in an air atmosphere, cover and mix well, then place in a constant temperature bath at 60 ° C. to conduct the polymerization reaction, take out every predetermined time, take out the contents, dissolve in 10 mL of chloroform, and then add 300 mL of By mixing with methanol, the precipitated polymer is recovered by filtering with a filter paper. The obtained polymer is dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent. The yield was calculated by weighing the dried polymer and dividing by the added monomer weight. The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). Table 1 shows the polyester yield, Mn, and Mw / Mn obtained for each reaction time.

  As is apparent from the results in Table 1, the yield molecular weight reached a steady state in only 3 hours of reaction time, and the yield was about 85%, which was almost the highest value for bulk polymerization. Moreover, the high molecular weight body whose molecular weight is about 16500 was obtained. The molecular weight distribution dispersity was about 2.0.

  The unpurified ε-caprolactone reagent contains, as impurities, oligomers obtained by reacting a small amount of water or a few cyclic monomers. Generally used ε-caprolactone polymerization catalysts (for example, tin dioctanoate and aluminum alkoxide) lose their polymerization activity due to moisture contained as impurities, and cannot polymerize unpurified ε-caprolactone. The aluminum trifluoromethanesulfonic acid used in this example did not lose its polymerization ability due to impurities.

Polymerization was carried out using aluminum trifluoromethanesulfonic acid as a catalyst in the same manner as in Example 1 except that purified ε-caprolactone was used as the lactone raw material.
Purified ε-caprolactone was purified by putting 100 mL of ε-caprolactone into a 500 mL eggplant type flask, mixing about 3 g of calcium hydride, stirring for 24 hours at room temperature, and then vacuum distillation at 10 mmHg and about 100 degrees. I got it.

  Place 1140 mg (10 mmol) of purified ε-caprolactone, 9.5 mg (0.02 mmol) of aluminum trifluoromethanesulfonic acid, and 6.2 mg (0.067 mmol) of glycerin in a 10 ml vial with a glass lid under an air atmosphere. Then, after mixing well, put in a constant temperature bath at 60 degrees, perform polymerization reaction, take out every predetermined time, take out the contents, dissolve in 10 mL chloroform, and then mix with 300 mL methanol to precipitate The polymer thus obtained was recovered by filtering with filter paper.

The obtained polymer was dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent, the dried polymer was weighed, and the yield was calculated by dividing by the monomer weight.
The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). The results are shown in Table 2.

表２の重合結果は、未精製のε−カプロラクトンから開環重合したものに比べ、若干、分子量が高いもののそれほど大きく差異は無かった。この結果は、精製課程があまり有効でなく、未精製のε−カプロラクトンが充分使用できることを示しており、工業的に精製工程を省略できることになり、非常に有効である。

The polymerization results in Table 2 were slightly higher in molecular weight than those obtained by ring-opening polymerization from unpurified ε-caprolactone, but were not so different. This result shows that the purification process is not very effective, and that unpurified ε-caprolactone can be used sufficiently, and the purification step can be omitted industrially, which is very effective.

In this example, in order to obtain the optimum value of the catalyst concentration, the results of testing by changing several concentrations of aluminum trifluoromethanesulfonic acid under the conditions of Example 1 above are shown.
In a 10 ml vial with a glass lid, 1140 mg (10 mmol) of crude ε-caprolactone, 6.2 mg (0.067 mmol) of glycerin, and 4.8-38 mg (0.01-0.8 mmol) of a predetermined amount of aluminum trifluoromethanesulfonic acid. ) In an air atmosphere, capped, mixed well, and then placed in a thermostatic bath at 60 degrees to conduct the polymerization reaction. After 6 hours, the contents were taken out and dissolved in 10 mL of chloroform, followed by 300 mL of methanol. And the precipitated polymer was recovered by filtering with a filter paper.

  The obtained polymer was dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent, the dried polymer was weighed, and the yield was calculated by dividing by the monomer weight. The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). The results are shown in Table 3.

  As is apparent from this result, the polymerization activity of this aluminum trifluoromethanesulfonic acid is very high, and when it is added to the polymerization system of only 4.8 mg (0.4 wt% relative to the monomer), the yield and molecular weight are almost the same. The maximum value was obtained.

This example shows the results of testing the influence of alcohol addition in the polymerization reaction of ε-caprolactone with aluminum trifluoromethanesulfonic acid.
1-3-valent alcohol calculated so that 1140 mg (10 mmol) of unpurified ε-caprolactone, 9.5 mg (0.02 mmol) of aluminum trifluoromethanesulfonic acid, and 0.2 mmol of hydroxyl groups are contained in a 10 ml vial with a glass lid. Is put in an air atmosphere, covered, mixed well, and then placed in a thermostatic bath at 60 ° C. to conduct the polymerization reaction. After 6 hours, the contents are taken out and dissolved in 10 mL of chloroform, and then 300 mL of methanol and By mixing, the precipitated polymer was recovered by filtering with a filter paper. The obtained polymer was dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent, the dried polymer was weighed, and the yield was calculated by dividing by the monomer weight.

  The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). The results are shown in Table 4.

  As is clear from this result, when no initiator is added, no polymer is obtained at a reaction time of 6 hours. However, by adding a small amount of alcohol such as 2-propanol to the polymerization reaction system, aluminum trifluoromethanesulfone is obtained. It has been found that the polymerization reaction of ε-caprolactone with acid is greatly accelerated. Glycerin having three hydroxyl groups in one molecule has the most accelerating effect, and the one having the largest molecular weight was obtained. This is believed to be due to the increased molecular weight of the resulting polymer as multiple polymer chains extend from one initiator molecule.

This example shows the results of testing the temperature dependence of the polymerization reaction of ε-caprolactone with aluminum trifluoromethanesulfonic acid.
In a 10 ml vial with a glass lid, 1140 mg (10 mmol) of unpurified ε-caprolactone, 9.5 mg (0.02 mmol) of aluminum trifluoromethanesulfonic acid, and 6.2 mg (0.067 mmol) of glycerin were placed in an air atmosphere. After mixing well, place in a thermostatic bath at 40, 60, and 80 degrees, perform the polymerization reaction, remove the contents after 6 hours, dissolve in 10 mL of chloroform, and then mix with 300 mL of methanol. The precipitated polymer was recovered by filtering with a filter paper. The obtained polymer was dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent, the dried polymer was weighed, and the yield was calculated by dividing by the monomer weight.

  The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). The results are shown in Table 5.

  As is apparent from the results, the catalyst system used in the present invention was found to give a polymer having a maximum molecular weight at a polymerization temperature of 60 ° C.

This example shows the results of polymerizing L-lactide with the catalyst system used in the present invention.
In a 50 ml vial with a glass lid, 1440 mg (10 mmol) of commercially available L-lactide, 9.5 mg (0.02 mmol) of aluminum trifluoromethanesulfonic acid, and 6.2 mg (0.067 mmol) of glycerin were left unpurified. Put in an air atmosphere, cover, mix well, put in a 100 ° C thermostatic chamber, perform polymerization reaction, take out after a predetermined time, take out the contents, dissolve in 10 mL of chloroform, and then add 300 mL of methanol and By mixing, the precipitated polymer was recovered by filtering with a filter paper. The obtained polymer is dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent. The yield was calculated by weighing the dried polymer and dividing by the monomer weight.

  The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). The results are shown in Table 6.

  As is apparent from this result, it was found that the catalyst system used in the present invention has a polymerization temperature of 100 ° C. capable of polymerizing lactide to polylactic acid, and its efficiency is considerably high. It was found that the yield almost reached the maximum after 6 hours of polymerization, and the molecular weight gradually increased with the polymerization time. The catalyst system of the present invention was also effective for the polymerization reaction of lactide using renewable resources, and polylactic acid having a molecular weight of about 10,000 could be obtained.

This example shows the results of testing the effect of polymerization temperature when L-lactide is polymerized with the catalyst system used in the present invention.
In a 50 ml vial with a glass lid, 1440 mg (10 mmol) of commercially available L-lactide, 9.5 mg (0.02 mmol) of aluminum trifluoromethanesulfonic acid, and 6.2 mg (0.067 mmol) of glycerin were left unpurified. Put in an air atmosphere, cover, mix well, put in a thermostatic bath at 100, 120, 140 degrees, perform polymerization reaction, take out after 6 hours, take out the contents, dissolve in 10 mL chloroform By mixing with 300 mL of methanol, the precipitated polymer was recovered by filtering with a filter paper.

  The obtained polymer is dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent. The yield was calculated by weighing the dried polymer and dividing by the monomer weight. The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). The results are shown in Table 7.

  As is apparent from the results, the yield and molecular weight of the catalyst system of the present invention decreased when the polymerization reaction was carried out at a temperature of 140 ° C. or higher, and it was found that the optimum polymerization temperature was from 100 to 120 ° C.

Reference example 1

This Reference Example 1 shows the results when a polyester is polymerized from a cyclic acid anhydride and a cyclic ether in the catalyst system used in the present invention.
Commercially available succinic acid 1 g (10 mmol) and tetrahydrofuran 1 g (14 mmol), aluminum trifluoromethanesulfonic acid 9.5 mg (0.02 mmol), 1,3- 7 mg (0.10 mmol) of propanediol was put in an air atmosphere, covered, mixed well, then placed in a constant temperature bath at 100 ° C. to carry out the polymerization reaction, taken out after a predetermined time, the contents taken out, 10 mL of chloroform After being dissolved in the solution, it was mixed with 300 mL of methanol, and the precipitated polymer was recovered by filtering with a filter paper.

  The obtained polymer is dried under reduced pressure at room temperature for 24 hours to remove the remaining solvent. The yield was calculated by weighing the dried polymer and dividing by the monomer weight. The number average molecular weight (Mn) and molecular weight distribution dispersity (Mw / Mn) of the obtained polymer were measured by gel permeation chromatography (GPC). The results are shown in Table 8.

  As is apparent from this result, it was found that the catalyst system of the present invention polymerizes a mixture of anhydrous cyclic compounds, which are dehydrating compounds of dicarboxylic acid and diol, and can synthesize the polymer with high efficiency. Although the optimum reaction time was slightly longer, a yield of about 80 wt% could be obtained in 2 days. The purified polymer was found to be polybutylene succinate (PBS), which is a biodegradable polyester, from the peak position of the NMR spectrum and the melting point measured by DSC.

Claims (4)

The following general formula I
Al (OSO ₂ R ¹ ) (OSO ₂ R ² ) (OSO ₂ R ³ ) .. General formula I
(In the formula, R ¹ , R ² and R ³ each represent a perfluoroalkyl group which may be the same or different, and Al represents aluminum.)
A catalyst for ring-opening polymerization of lactones or lactides, which is used for the production of polyester, comprising an aluminum compound represented by the formula: A process for producing a polyester from a lactone or lactide by a ring-opening polymerization reaction, wherein the aluminum compound according to claim 1 is used as a catalyst. The method for producing a polyester according to claim 2, wherein the lactones or lactides to be subjected to the ring-opening polymerization reaction are each alone or a mixture of plural kinds. The method for producing a polyester according to claim 2 or 3, wherein the ring-opening polymerization reaction system contains water or a monovalent or polyhydric alcohol.