JP2011168644A - Lactic acid polymer and aliphatic polyester copolymer, method for producing those, and molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lactic acid polymer suitable for a raw material to produce an aliphatic polyester copolymer and a method for producing the polymer, as well as to provide the aliphatic polyester copolymer containing the lactic acid polymer and a molded product. <P>SOLUTION: This lactic acid polymer, when measured for proton nuclear magnetic resonance spectrum using heavy chloroform as a solvent, has a number average molecular weight of ≥500 calculated from an integrated intensity ratio of signals which appear at 5.2 ppm and 4.4 ppm; and has the integrated intensity of ≤0.003 of the signal which appears at 2.5 ppm, provided that the integrated intensity of the signal at 5.2 ppm is 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lactic acid polymer as a raw material for an aliphatic polyester copolymer, a method for producing the same, an aliphatic polyester copolymer containing the lactic acid polymer, and a molded article.

  Aliphatic polyesters are generally known as environmentally friendly polymer materials because they have so-called biodegradability, which is degraded by the action of microorganisms, enzymes, and the like in the environment, in other words, in water and in the ground. For example, aliphatic polyester containing lactic acid as a constituent element is naturally decomposed in the environment, but it is also decomposed in the living body, and the lactic acid produced by the decomposition is originally present in the living body, so it is highly safe. . Therefore, development of medical materials is expected as one application of this type of polymer.

  For example, Patent Document 1 discloses a biocompatible porous sheet using an aliphatic polyester copolymer having lactic acid as one of the constituent elements.

JP 2008-36134 A

  Lactic acid homopolymers are hard and brittle and have limited applications. Therefore, a method for modifying this property by copolymerization is known. That is, a method is known in which aliphatic diol, aliphatic dicarboxylic acid, aliphatic oxycarboxylic acid and the like are copolymerized with lactic acid to obtain an aliphatic polyester copolymer. Moreover, in order to use as a material, it is necessary for mechanical properties, such as intensity | strength, to be excellent, For that purpose, it is preferable that the molecular weight of an aliphatic polyester copolymer is high. In this case, it is preferable to use a lactic acid polymer as a raw material rather than using a lactic acid monomer as a raw material, and generally use a high molecular weight lactic acid polymer as a raw material. Preferred for obtaining a coalescence.

  However, according to the study by the present inventors, depending on the molecular weight and properties of this lactic acid polymer, the aliphatic polyester copolymer produced using this as a raw material cannot be made sufficiently high in molecular weight, It has become clear that there is room for improvement. For example, Patent Document 1 discloses a method of adjusting an aliphatic polyester copolymer using a lactic acid polymer (lactic acid oligomer) as a raw material, but even if a lactic acid polymer (lactic acid oligomer) is adjusted by this method, The number average molecular weight of the lactic acid polymer (lactic acid oligomer) is as low as less than 500. And the molecular weight of the aliphatic polyester copolymer manufactured using this lactic acid polymer as a raw material cannot be made high.

  Therefore, the present invention aims to provide a lactic acid polymer suitable as a raw material for producing an aliphatic polyester copolymer and a method for producing the same, and an aliphatic polyester copolymer containing the lactic acid polymer, It aims at providing a molded object.

As a result of intensive studies in view of the above-mentioned problems, the present inventors have determined that the chemical shift when tetramethylsilane is 0.0 ppm when the NMR spectrum is measured using deuterated chloroform as a solvent is 5.2 ppm and 4.4 ppm. The number average molecular weight of the polymer calculated from the ratio of the integral intensity of the signal appearing in Fig. 5 is 500 or more, and the integral intensity of the signal appearing at 2.5 ppm when the integral intensity of the 5.2 ppm signal is 1 is 0. The lactic acid polymer which is 003 or less was found.

In addition, the lactic acid polymer can be produced by carrying out the polymerization reaction under conditions where the reaction temperature is higher than 150 ° C. and lower than 230 ° C. and the final degree of vacuum is higher than 0.5 kPa and lower than 10 kPa. I found it.
Then, gel permeation chromatography (hereinafter referred to as GPC) containing the lactic acid polymer.
An aliphatic polyester copolymer having a number average molecular weight of 30000 or more and a molded product were measured.

That is, the gist of the present invention is as follows.
(1) When the proton nuclear magnetic resonance spectrum is measured using deuterated chloroform as a solvent, the number average molecular weight of the polymer calculated from the ratio of the integral intensities of signals appearing at 5.2 ppm and 4.4 ppm is 500 or more, and A lactic acid polymer, wherein the integrated intensity of a signal appearing at 2.5 ppm when the integrated intensity of a signal of 5.2 ppm is 1, is 0.003 or less.
(2) characterized in that it comprises a step of carrying out a polymerization reaction under conditions where the reaction temperature is higher than 150 ° C. and lower than 230 ° C. and the pressure reduction degree is higher than 0.5 kPa and lower than 10 kPa.
A method for producing a lactic acid polymer.
(3) A lactic acid polymer obtained by the production method according to (2).
(4) An aliphatic polyester copolymer comprising the lactic acid polymer according to (1) or (3) in its structure.
(5) A method for producing an aliphatic polyester copolymer, wherein the lactic acid polymer according to (1) or (3) is used as a raw material.
(6) The method for producing an aliphatic polyester copolymer according to (5), wherein polyalkylene glycol and aliphatic carboxylic acid are further used as raw materials for copolymerization.
(7) The aliphatic polyester copolymer (8) obtained by the production method according to (5) or (6) is characterized in that the number average molecular weight measured by gel permeation chromatography is 30000 or more. The aliphatic polyester copolymer according to (4) or (7).
(9) A molded product comprising the aliphatic polyester copolymer according to (4), (7) or (8).

  By using the lactic acid polymer of the present invention as a raw material for the production of an aliphatic polyester copolymer, the molecular weight of the resulting copolymer can be made sufficiently high. Further, by using the lactic acid polymer of the present invention as a raw material for the production of an aliphatic polyester copolymer, the strength of the obtained copolymer can be increased, and a material excellent in mechanical properties that is difficult to break is provided. be able to. Moreover, according to the manufacturing method of the lactic acid polymer of this invention, the said lactic acid polymer can be manufactured simply and efficiently.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified by these contents.
[Lactic acid polymer and production method thereof]
In the lactic acid polymer of the present invention, when the NMR spectrum was measured using deuterated chloroform as a solvent, the chemical shift when tetramethylsilane was 0.0 ppm, the integrated intensity of the signal appearing at 5.2 ppm and 4.4 ppm The number average molecular weight of the polymer calculated from the ratio of the integrated intensities of the appearing signals is 500 or more. More preferably, it is 800 or more. If the number average molecular weight is too small, it is difficult to increase the molecular weight of the copolymer when an aliphatic polyester copolymer is produced using this lactic acid polymer as a raw material.

The 5.2 ppm signal is due to the methine proton in the ester bond of the lactic acid polymer, and the 4.4 ppm signal is due to the methine proton adjacent to the hydroxyl terminal. Therefore, the molecular weight of the lactic acid polymer can be calculated by dividing the former integrated intensity by the latter integrated intensity.
The lactic acid polymer is characterized in that the integrated intensity of the signal appearing at 2.5 ppm when the integrated intensity of the 5.2 ppm signal is 1 is 0.003 or less. Preferably it is 0.002 or less, More preferably, it is 0.001 or less. When the value of the integral strength is too large, it is difficult to increase the molecular weight of the copolymer when an aliphatic polyester copolymer is produced using this lactic acid polymer as a raw material.

  The signal appearing at 2.5 ppm can be presumed to be caused by a methine proton adjacent to the aldehyde group or a methine proton adjacent to a carbonyl group having a ketone structure when an aldehyde group is present at the terminal. In order to make such a structure (heterogeneous structure), the carboxyl group at the end of the lactic acid polymer must cause a side reaction, which means that the end of the carboxyl group is reduced. That is, a decrease in carboxyl group terminals leads to a loss of terminal balance between the hydroxyl group and the carboxyl group. Therefore, when an aliphatic polyester copolymer is produced using a lactic acid polymer having such properties as a raw material, It can be presumed that it is difficult to increase the molecular weight. Although there is no limitation in particular in manufacturing the lactic acid polymer of this invention, it is preferable to melt-polymerize a lactic acid monomer. As the lactic acid monomer, a commercially available 50 to 90% aqueous solution can be used. In order to produce a lactic acid polymer, it is preferable to have a polymerization reaction step for controlling the reaction temperature and the range of the degree of vacuum.

The polymerization reaction process may be accompanied by temperature increase and / or pressure reduction.
The polymerization reaction temperature of the lactic acid polymer of the present invention is higher than 150 ° C. and lower than 230 ° C. The lower limit is preferably 160 ° C, more preferably 170 ° C, and the upper limit is preferably 220 ° C, more preferably 210 ° C. If the polymerization temperature is too low, there is a problem in that a lactic acid polymer having a high molecular weight cannot be obtained. On the other hand, if it is too high, by-products such as cyclic dimers and the above heterogeneous structure are likely to be formed, and the former case has a problem in that the yield of lactic acid polymer is lowered, and in the latter case, lactic acid heavy There is a problem in that it is difficult to increase the molecular weight of the copolymer to be produced, because it leads to the loss of the terminal balance of the hydroxyl group and carboxyl group of the coalescence.

  Further, the degree of reduced pressure of the polymerization reaction is characterized by being a pressure higher than 0.5 kPa and lower than 10 kPa. The lower limit is preferably 0.6 kPa, more preferably 0.7 kPa, and the upper limit is preferably 9 kPa, more preferably 8 kPa. If the degree of vacuum is too low, there is a problem in that the yield of the lactic acid polymer is likely to be generated, and a lactic acid polymer having a high molecular weight is formed if the degree of vacuum is too high. There is a problem in that it cannot be obtained.

Moreover, you may use a catalyst when performing this manufacture. Catalysts include tin octylate, tin oxide, tin chloride, tin lactate, tin powder and other metal tin or tin compounds, zinc powder, zinc oxide, zinc sulfate and other metal zinc or zinc compounds, aluminum oxide, aluminum chloride, sulfuric acid Examples thereof include metal aluminum such as aluminum or aluminum compound. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Among these, tin compounds and the like are preferable as the catalyst, and tin octylate is more preferable.
The amount of the catalyst used is not particularly limited, but is usually 0.0001% by weight or more, preferably 0.001% by weight or more, and usually 10% by weight or less, preferably 5% by weight or less as a ratio to the total amount of raw material components. It is a range.

[Aliphatic polyester copolymer and production method thereof]
The aliphatic polyester copolymer of the present invention is a polyester containing the lactic acid polymer of the present invention. The production method is not particularly limited, but it can be produced by polymerizing a raw material component composed of a lactic acid polymer, an aliphatic diol, an aliphatic dicarboxylic acid, an aliphatic oxycarboxylic acid or the like.

  Examples of the aliphatic diol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, Examples include diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytrimethylene ether glycol, and polytetramethylene ether glycol.

Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, sebacic acid, 1,10-decanedicarboxylic acid, and the like.
Examples of the aliphatic oxycarboxylic acid include glycolic acid, polycaprolactone, malic acid, and citric acid.
In order to produce the aliphatic polyester copolymer of the present invention, the polymerization reaction is preferably performed in the presence of a catalyst. As a kind and usage-amount of a catalyst, you may use the method similar to the manufacturing method of said lactic acid polymer.

The polymerization reaction is preferably performed by solution polymerization. The polymerization reaction can be carried out by mixing the raw material components, the catalyst, and the solvent in the reactor. The order of mixing is not particularly limited, and can be adopted as appropriate.
The aliphatic polyester copolymer obtained by solution polymerization can be purified and recovered by a so-called reprecipitation method in which the copolymer is dissolved in a solvent capable of dissolving the copolymer, if necessary, and then introduced into a poor solvent.

  The number average molecular weight of the aliphatic polyester copolymer thus obtained is preferably 30000 or more, more preferably 35000 or more, further preferably 40000 or more, and most preferably 45000 or more. If the number average molecular weight is too small, mechanical properties such as strength and elongation at break will be poor, and there is a possibility that the field where the material can be used is restricted.

[Molded body]
The molded article of the present invention can be obtained by molding the aliphatic polyester copolymer obtained above. Although there is no restriction | limiting in the shaping | molding method, Usually, it can carry out by the method currently performed with polyester, for example, injection molding, extrusion molding, blow molding, press molding, the cast molding using a solvent. Various moldings, sheets, films, foams and the like can be obtained by such a method.
An example of a cast molding method using a solvent is a method in which an aliphatic polyester copolymer is dissolved in a suitable solvent, cast on a Teflon (registered trademark) sheet, and then formed into a film using an applicator.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited by a following example, unless the summary is exceeded.
In the following description, “parts” means “parts by weight” unless otherwise specified.
[NMR measurement]
The instrument was an AVANCE 400 manufactured by Bruker and measured at room temperature using deuterated chloroform as a solvent.
For the chemical shift, the value when tetramethylsilane was 0.0 ppm was adopted.

[Measurement of molecular weight]
1. Lactic acid polymer The same NMR apparatus as described above was used. The molecular weight was calculated from the ratio of integral intensities of signals appearing at 5.2 ppm and 4.4 ppm. Aliphatic polyester copolymer Measured by GPC. The apparatus was GPC8020 manufactured by Tosoh Corporation, the column was TSKgelGMHXL-N, and the measurement was performed at 40 ° C. using THF as an eluent. The molecular weight was a standard polystyrene equivalent value.
[Tensile test]
Using a desktop material testing machine STA-1225 manufactured by Orientec Co., Ltd., tensile speed 50 mm / min
Measured with

[Example 1]
A reaction vessel equipped with a stirrer, a nitrogen inlet, a heating device, a thermometer, and a vacuum port was charged with 150 parts by weight of L-lactic acid monomer (Purac 88% aqueous solution) as a raw material, and the polymerization reaction was carried out as follows. It was.

  Nitrogen gas was introduced into the container while stirring the contents of the container, and the inside of the system was changed to a nitrogen atmosphere by vacuum replacement. While stirring the system, the temperature was raised to 150 ° C. in 30 minutes while maintaining normal pressure (first step (temperature increase)), and the reaction was carried out at this temperature for 2 hours to distill water (second step (dehydration)). . Next, the temperature was raised to 200 ° C. over 1.5 hours, and the temperature was kept at 200 ° C. for 1.5 hours (third step (temperature rise / depressurization). (The third step (temperature increase / depressurization), and then further reduced to 2.7 kPa over 2 hours at 200 ° C. (fourth step (decompression)), and the polymerization reaction was continued for 2 hours as it was ( 5th step (final reaction)).

  After completion of the reaction, the contents were taken out to obtain a colorless and transparent lactic acid polymer. This lactic acid polymer had a number average molecular weight of 870. The integral intensity of the signal that appeared at 2.5 ppm when the integral intensity of the 5.2 ppm signal by NMR was 1 was 0.0008.

[Example 2]
The same procedure as in Example 1 was performed except that the last reaction time (fifth step (final reaction)) was changed to 6 hours.
After completion of the reaction, the contents were taken out to obtain a colorless and transparent lactic acid polymer. This lactic acid polymer had a number average molecular weight of 1800. Further, the integral intensity of the signal appearing at 2.5 ppm when the integral intensity of the 5.2 ppm signal by NMR was set to 1 was 0.0007.

Example 3
Example 1 except that 0.25 parts by weight of tin octylate (manufactured by Nacalai Tesque) was added as a catalyst and the final reaction at 200 ° C. and 2.7 kPa (fifth step (final reaction)) was performed for 4 hours. The same was done.

  After completion of the reaction, the contents were taken out to obtain a colorless and transparent lactic acid polymer. This lactic acid polymer had a number average molecular weight of 2400. Further, the integrated intensity of the signal appearing at 2.5 ppm when the integrated intensity of the 5.2 ppm signal by NMR was set to 1 was 0.0005.

[Comparative Example 1]
For the purpose of following the method of Patent Document 1, the following experiment was conducted.
The condition of the third step (temperature increase / decompression) is constant at a temperature of 150 ° C., the pressure is reduced to 13 kPa in 0.5 hours and held for 2 hours, and the condition of the fourth step (decompression) is 4 kPa in 0.5 hours. The process was carried out in the same manner as in Example 1 except that the pressure in the fifth step (final reaction) was reduced to 2.7 kPa in 0.5 hours and the reaction was continued for 2 hours.
After completion of the reaction, the contents were taken out to obtain a colorless and transparent lactic acid polymer. This lactic acid polymer had a number average molecular weight of 430. Further, the integrated intensity of the signal appearing at 2.5 ppm when the integrated intensity of the 5.2 ppm signal by NMR was set to 1 was 0.0005.

[Comparative Example 2]
The temperature of the third step (temperature increase / decompression) is raised to a temperature of 230 ° C., and at the same time, the pressure reduction is applied and the pressure is reduced to 8 kPa over 3 hours. The pressure was reduced to 4 kPa, and the reaction was carried out in the same manner as in Example 1 except that the reaction was continued for 1 hour and 30 minutes under the condition of the fifth step (final reaction).

  After completion of the reaction, the contents were taken out to obtain a colorless and transparent lactic acid polymer. This lactic acid polymer had a number average molecular weight of 900. The integrated intensity of the signal that appeared at 2.5 ppm when the integrated intensity of the 5.2 ppm signal by NMR was 1 was 0.0036.

[Comparative Example 3]
The same procedure as in Example 3 was performed except that the temperature of the third step (temperature increase / decompression) was 230 ° C., the temperature of the fifth step (final reaction) was 230 ° C., and the reaction was continued for 2.5 hours. .
After completion of the reaction, the contents were taken out to obtain a colorless and transparent lactic acid polymer. This lactic acid polymer had a number average molecular weight of 13,000. The integrated intensity of the signal appearing at 2.5 ppm when the integrated intensity of the 5.2 ppm signal by NMR was 1 was 0.0048.
The production examples and results of the lactic acid polymer are summarized in Table 1.

[Production example of aliphatic polyester copolymer]
Example 4
In a flask equipped with a stirrer and a condenser with an oil-liquid separator, 3 parts of polyethylene glycol (number average molecular weight 4000, manufactured by Wako Pure Chemical Industries, Ltd.), 0.118 part of succinic acid, 17 parts of the lactic acid polymer produced in Example 1 Then, 0.14 part of tin octylate and 9 parts of diphenyl ether were charged, the pressure was reduced over 1 hour, and polymerization was carried out for 16 hours under conditions of 2.7 kPa and 180 ° C. During the polymerization, the cooling water was set to 60 ° C., the condensed water was discharged out of the system, and the solvent was returned into the system. After dissolving the obtained polymerization solution in chloroform, throwing it into a large amount of methanol and reprecipitating it, collecting the polymer by filtration, dissolving it in chloroform again, and then throwing it again into a large amount of methanol The product polymer was purified by repeating the above and dried with a hot air dryer to obtain a white copolymer.

Moreover, about this copolymer, the number average molecular weight calculated | required by GPC measurement was 45000, and the weight average molecular weight was 87000.
[Examples 5 and 6, Comparative Examples 4 to 6]
It carried out similarly to Example 4 except having used the lactic acid polymer shown in Table 2 instead of the lactic acid polymer manufactured in Example 1. FIG. The results are shown in Table 1.

  In addition, 10 parts by weight of the aliphatic polyester copolymer of the present invention was dissolved in 30 parts by weight of chloroform, then cast on a Teflon (registered trademark) sheet, and a film was formed using a 100 μm applicator. After the film was vacuum-dried at 60 ° C. for 24 hours, a 10 mm-wide strip was cut out and subjected to a tensile test. Copolymer production examples and results are shown in Table 2.

  The lactic acid polymer of the present invention and the aliphatic polyester copolymer containing the lactic acid polymer can be used as an environmentally friendly polymer material having biodegradability. In addition, this aliphatic polyester copolymer is decomposed even in vivo, and lactic acid produced by decomposition is highly safe, so the molded product can be used as a medical material and is very useful industrially. It is.

Claims (9)

  When the proton nuclear magnetic resonance spectrum was measured using deuterated chloroform as a solvent, the number average molecular weight of the polymer calculated from the ratio of the integral intensities of signals appearing at 5.2 ppm and 4.4 ppm was 500 or more, and 5.2 ppm A lactic acid polymer, wherein the integrated intensity of a signal appearing at 2.5 ppm when the integrated intensity of the signal is 1 is 0.003 or less.   A method for producing a lactic acid polymer, comprising a step of performing a polymerization reaction under conditions where the reaction temperature is higher than 150 ° C. and lower than 230 ° C., and the degree of vacuum is higher than 0.5 kPa and lower than 10 kPa. .   A lactic acid polymer obtained by the production method according to claim 2.   An aliphatic polyester copolymer comprising the lactic acid polymer according to claim 1 or 3 in its structure.   A method for producing an aliphatic polyester copolymer, wherein the lactic acid polymer according to claim 1 or 3 is used as a raw material.   The method for producing an aliphatic polyester copolymer according to claim 5, wherein polyalkylene glycol and aliphatic carboxylic acid are further used as raw materials for copolymerization.   An aliphatic polyester copolymer obtained by the production method according to claim 5 or 6.   The aliphatic polyester copolymer according to claim 4 or 7, wherein the number average molecular weight measured by gel permeation chromatography is 30000 or more.   A molded product comprising the aliphatic polyester copolymer according to claim 4, 7 or 8.