JP2006183042A - New multiblock copolymer, method for producing the same, and its utilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new multiblock copolymer utilizable as a material of a biodegradable resin applicable to many kinds of applications. <P>SOLUTION: The new multiblock copolymer having more improved mechanical characteristics without damaging the biodegradability has the first block comprising a polylactic acid having hydroxy groups at both terminals, and the second block comprising a polymer having mobility higher than that of the polylactic acid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel multi-block copolymer and use thereof, and more particularly to a novel multi-block copolymer excellent in flexibility that can be used for a biodegradable resin material and use thereof.

  In recent years, biodegradable materials have attracted attention due to the growing awareness of environmental issues. A biodegradable material is a material that is decomposed into carbon dioxide and water by microorganisms. Therefore, the biodegradable material has a small load on the environment when discarded.

  As such a biodegradable resin material, for example, a material made of aliphatic polyester or polylactic acid is known. For example, Patent Document 1 discloses that a biodegradable thermoplastic elastomer can be prepared by chemically linking aliphatic polyesters prepared by condensation polymerization.

  Further, in Patent Document 2, as a method for producing a completely alternating block copolymer (ABA) n, a cyclic diester is polymerized from a hydroxy or amino group of a pre-generated B block, and then a dihydroxy ABA block is difunctionalized. It is described to react with a binder to repeat the ABA structure along the copolymer chain.

  Polylactic acid is a polymer obtained by ring-opening polymerization of L-lactide, which is a cyclic diester monomer of lactic acid, and is the most widely used biodegradable resin material. A biodegradable resin prepared from this polylactic acid has biocompatibility and high strength. On the other hand, however, polylactic acid has the disadvantage that it is fragile, flexible and difficult to handle.

  In order to eliminate such disadvantages of polylactic acid, many attempts have been made to develop a new multi-block copolymer in which polylactic acid (hard segment) and other highly mobile polymer (soft segment) are combined.

  For example, Non-Patent Document 1 discloses a multi-block copolymer composed of polylactic acid and polycaprolactone (hereinafter sometimes referred to as “PCL”).

More specifically, Non-Patent Document 1 discloses that polylactic acid-based polymer obtained by reacting L-lactide with hexanediol using tin octylate as a catalyst and PCL having hydroxyl groups at both ends are subjected to condensation polymerization. The resulting multi-block copolymer is described.
JP-A-6-239984 (Publication date: August 30, 1994) Patent 2984374 (Registration date: September 24, 1999) Oju Jeon, et al., Macromolecules 2003, 36, 5585-5592

  The multi-block copolymer disclosed in Non-Patent Document 1 has considerably improved mechanical properties as compared with the case of polylactic acid alone.

  However, even the multi-block copolymer disclosed in Non-Patent Document 1 cannot be said to have sufficient mechanical properties, and still has much room for improvement.

  For this reason, there has been a strong demand for the development of a novel multi-block copolymer that has excellent mechanical properties and can be used as a biodegradable resin material that can be applied to various applications.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a novel multi-block copolymer having improved mechanical properties without impairing biodegradability and use thereof There is to do.

As a result of intensive studies to solve the above problems, the inventors of the present invention obtained trisborohydride, neodymium, tritetrahydrofuran (hereinafter sometimes referred to as Nd (BH ₄ ) ₃ (THF) ₃ ) from L-lactide. Has found that polylactic acid represented by the following general formula (I) and having hydroxyl groups at both ends is synthesized. Furthermore, we synthesized a multi-block copolymer containing this new polylactic acid as a hard segment and evaluated its function. It was confirmed that mechanical properties such as flexibility were significantly improved without impairing biodegradability. The headline and the present invention have been completed. The present invention has been completed based on the above-described novel findings and includes the following inventions.

(1) A multi-block copolymer having at least a first block and a second block, wherein the first block is polylactic acid having hydroxyl groups at both ends;
The second block is a multi-block copolymer that is a polymer having higher mobility than the polylactic acid.

  (2) The multiblock copolymer according to (1), wherein the first block is polylactic acid represented by the following general formula:

(In the general formula (I), k is a natural number.)
(3) The second block is a polymer including a repeating unit having at least one of an aliphatic hydrocarbon skeleton, 1 to 3 ester bonds, 1 to 3 ether bonds, or a combination thereof (1). Or the multiblock copolymer as described in (2).

  (4) The second block is at least one monomer selected from the group consisting of ε-caprolactone, ethylene glycol, propylene glycol, δ-valerolactone, β-butyrolactone, β-propiolactone, glycolide, and butylene glycol. The multiblock copolymer according to any one of (1) to (3), which is a polymer comprising:

  (5) The multiblock copolymer according to any one of (1) to (4), wherein the second block is a polymer having hydroxyl groups at both ends.

  (6) The multiblock copolymer according to any one of (1) to (5), which further has a chain extension site composed of a chain extender.

  (7) The multi-block copolymer according to (6), wherein the chain extender is a compound having an isocyanate group.

  (8) Hexamethylene diisocyanate, n-xylene diisocyanate, 1,4-cyclohexylene diisocyanate, tetramethylene diisocyanate, octamethylene diisocyanate, isophorone diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4- (6) or (7) which is at least one compound selected from the group consisting of TDI (tolylene 2,4-diisocyanate), 2,5-TDI, and 2,6-TDI, or a mixture of two or more. The described multi-block copolymer.

  (9) A method for producing a multi-block copolymer comprising a step of chemically bonding a polylactic acid having hydroxyl groups at both ends and a polymer having higher mobility than the polylactic acid.

  (10) Polylactic acid represented by the following general formula (I).

(In the general formula (I), k is a natural number.)
(11) A method for producing polylactic acid, comprising a step of polymerizing L-lactide in the presence of tris borohydride, neodymium, or tritetrahydrofuran.

  (12) A resin composition comprising the multiblock copolymer according to any one of (1) to (8).

  (13) A thermoplastic elastomer comprising the multiblock copolymer according to any one of (1) to (8).

  (14) A resin modifier comprising the multiblock copolymer according to any one of (1) to (8).

  (15) A resin composition comprising the polylactic acid according to (10).

  The multi-block copolymer according to the present invention has an effect that mechanical properties such as mechanical strength, flexibility, and extensibility are excellent as compared with conventional multi-block copolymers having polylactic acid as a hard segment. Furthermore, since a biodegradable material such as polylactic acid is used, good biodegradability is exhibited.

  Therefore, the multi-block copolymer according to the present invention can be used for various uses as a biodegradable resin material and is very useful. For example, it can be utilized as a thermoplastic elastomer (TPE) by taking advantage of its good flexibility.

  The present invention also includes a method for producing the multiblock copolymer according to the present invention, polylactic acid which is an intermediate compound for producing the multiblock copolymer, and a method for producing the same. Needless to say, the polylactic acid and the method for producing the same according to the present invention are very useful because they are used for producing the multi-block copolymer.

  The present invention relates to a novel flexible multi-block copolymer, a production method thereof, an intermediate thereof, a production method thereof, and use thereof. Therefore, in the following, a novel multi-block copolymer will be described first, then a production method thereof, further an intermediate compound polylactic acid and a production method thereof, and finally a utilization method thereof will be explained.

<1. Multiblock Copolymer According to the Present Invention>
The multiblock copolymer according to the present invention is a multiblock copolymer having at least a first block and a second block. That is, it is only necessary to have the first block and the second block, and other components, its composition, molecular weight, presence / absence of a crosslinking agent and a polymerization initiator, and various conditions such as the concentration of each component can be appropriately set. There is no particular limitation.

  The first block and the second block may be, for example, a multiblock copolymer that is bonded in any order directly and / or without a chain extender described later. The kind of chemical bond) and the order are not particularly limited.

  The first block is polylactic acid having hydroxyl groups at both ends. In this specification, the term “polylactic acid” refers to a polymer in which L-lactic acid, D-lactic acid, and a mixture thereof are polymerized in an arbitrary amount. The specific structure, molecular weight, number of bonds, and the like are as follows. Although not particularly limited, it is particularly preferable that L-lactic acid is polymerized alone.

  The term “both ends” refers to both terminal portions of the polymer, and “has hydroxyl groups at both ends” means that both terminal portions of the polymer are hydroxyl groups (—OH).

  For example, examples of the first block include polylactic acid represented by the general formula (I). Here, in general formula (I), k is a natural number, but more preferably, k is in the range of 10 to 10,000.

The polylactic acid according to the present invention may contain a diol in addition to L-lactic acid and D-lactic acid. An example of the structure of such polylactic acid is shown in the following general formula (III). In general formula (III), p and q are natural numbers. In the following general formula (III), —R— represents — (CH ₂ ) _x — (x = 2 to 20) or — (CH ₂ CH ₂ O) _y CH ₂ CH ₂ — (y = 1 to 20). However, -R- preferably has a structure different from that of the second block.

  The second block only needs to have a polymer having higher mobility than the polylactic acid, and other components, composition, molecular weight, presence / absence of chain extender (crosslinking agent), type of chain extender, Various conditions such as the concentration of each component can be appropriately set and are not particularly limited.

  Here, “a polymer having a higher mobility than polylactic acid” improves the disadvantages of “brittleness and low flexibility” of a polymer composed only of polylactic acid by combining (or bonding) with polylactic acid. Any polymer having such a property can be used, which means a so-called soft segment. That is, for example, a polymer having low crystallinity and high flexibility as compared with polylactic acid can be mentioned.

  In addition, “a polymer having higher mobility than polylactic acid” can also be defined as having a higher degree of freedom of rotation of bonds in the molecule, in particular, higher degree of freedom of rotation of the carbon main chain than polylactic acid. . Examples of such a polymer include those having a larger number of single bonds between carbons in the carbon main chain than polylactic acid.

  Moreover, as a polymer used as a 2nd block, the polymer provided with the repeating unit which has at least 1 among an aliphatic hydrocarbon frame | skeleton, an ester bond, an ether bond, or those combinations can be used suitably, for example. In addition, a polymer having an aliphatic hydrocarbon skeleton having 2 to 20 carbon atoms is preferable for use as the second block because it has particularly high mobility. Moreover, the ester bond and the ether bond are preferably polymers each having 1 to 3 repeating units. Such polymers are preferred because of their particularly high mobility.

  As a polymer suitable as the second block, at least selected from the group consisting of ε-caprolactone, ethylene glycol, propylene glycol, δ-valerolactone, β-butyrolactone, β-propiolactone, glycolide, and butylene glycol Mention may be made of polymers consisting of one monomer.

  In the multi-block copolymer of the present invention, the polymer to be the second block is not limited to one type, and two or more different polymers may be included as the second block in one molecule of the multi-block copolymer. .

  That is, the second block includes a polymer composed of a single repetition of the above monomers and a polymer composed of a repetition of two or more combinations of the above monomers. More specifically, a group consisting of a combination of two or more of the above-described monomers, polycaprolactone, polyethylene glycol, polypropylene glycol, polyvalerolactone, polybutyrolactone, polypropiolactone, polyglycolide, and polybutylene glycol. There may be mentioned at least one polymer or a combination of two or more polymers more selected.

The polycaprolactone can be obtained, for example, by polymerizing ε-caprolactone with Nd (BH ₄ ) ₃ (THF) ₃ (FIG. 1). Can be obtained.

The polycaprolactone may contain ε-caprolactone and other diols as shown in FIG. In FIG. 4, r and s are natural numbers. Further, -R'- is - in _{- '(y CH 2 CH 2} ' = 1~20) (CH 2) x '- - (x' = 2~20), or _(CH 2 CH 2 O) _y Preferably there is. As shown in FIG. 4, such a polymer can be obtained by polymerizing ε-caprolactone in the presence of a catalyst using a diol as a polymerization initiator. Examples of the catalyst include tin octylate and DBDL (dibutyltin dilaurate).

  The polymer contained in the second block is preferably a polymer having hydroxyl groups at both ends.

  In other words, the multi-block copolymer according to the present invention includes a hard segment (first block) having high crystallinity represented by the general formula (I) and a soft segment (second block) having lower crystallinity than the hard segment. Can be said to be a multi-block copolymer linked at random directly or via a chain extender.

  Here, when both the first block and the second block have a hydroxyl group at both ends, a multi-block copolymer obtained by randomly polymerizing the first block and the second block by using a predetermined chain extender is used. It is highly preferred because it can be prepared.

  The multiblock copolymer according to the present invention may further have a chain extender. In the present specification, the term “chain extender” refers to those that chemically bond the first block and the second block, the first block, the second block, and a combination thereof (crosslinking agent, polymerization accelerator). ) And its specific configuration is not particularly limited.

  That is, as the chain extender, a conventionally known bifunctional chain extender can be used. For example, when the second block is a polymer having hydroxyl groups at both ends, a conventionally known chain extender for chemically bonding hydroxyl groups can be suitably used. As such a chain extender, those capable of forming a urethane bond, for example, diisocyanate compounds, diepoxides, and dichlorosilanes can be used.

  In particular, a diisocyanate compound may be used in which the isocyanate group forms a urethane bond with the hydroxyl group of the two types of prepolymers, the hard segment and the soft segment described above. Specifically, hexamethylene diisocyanate, n-xylene diisocyanate, 1,4-cyclohexylene diisocyanate, tetramethylene diisocyanate, octamethylene diisocyanate, isophorone diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2, Mention may be made of at least one compound selected from the group consisting of 4-TDI (tolylene 2,4-diisocyanate), 2,5-TDI, and 2,6-TDI, or a mixture of two or more.

  Further, in the present specification, the term “chain extension site composed of a chain extender” is a portion derived from the above-described chain extender in the multiblock copolymer of the present invention. In the block copolymer, the portion excluding the first block and the second block. That is, it can be said that the “chain extension site composed of a chain extender” is a “linker” part connecting the first block and the second block.

  That is, the multiblock copolymer according to the present invention can be represented by, for example, the following general formula (II).

  Here, in general formula (II), n and m are natural numbers, but it is more preferable that n and m are in the range of 10 to 10,000, respectively.

  Further, in the general formula (II), the “chain extension site composed of a chain extender” is a portion described on the rightmost side.

  In the above general formula (II), as an example of the multi-block copolymer according to the present invention, an example using polycaprolactone as the soft segment and HMDI (hexamethylene diisocyanate) as the chain extender is given as an example. The block copolymer is not limited to this. That is, as already described, as the soft segment, in addition to polycaprolactone, the above-described polyethylene glycol, polypropylene glycol, and the like can be suitably used.

  As chain extenders, HMDI, n-xylene diisocyanate, 1,4-cyclohexylene diisocyanate, tetramethylene diisocyanate, octamethylene diisocyanate, isophorone diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2 , 4-TDI, 2,5-TDI, and 2,6-TDI, at least one compound, or a mixture of two or more can be used. In other words, the present invention can include a wide variety of multi-block copolymers by appropriately combining the above polylactic acid with a soft segment and a chain extender.

  As described above, the multiblock copolymer according to the present invention has very characteristic properties because it has, as a hard segment, polylactic acid having hydroxyl groups at both ends. That is, in the conventional multi-block copolymer having polylactic acid as a hard segment, one end of polylactic acid is a hydroxyl group and the other end is a carboxyl group (—COOH). Even when a polymer having hydroxyl groups at both ends (specifically, PCL) is used as the soft segment, the diversity of the composition of the obtained multi-block copolymer was naturally limited.

  However, the polylactic acid used in the multiblock copolymer according to the present invention has hydroxyl groups at both ends. Therefore, when a polymer having a hydroxyl group at both ends is used as the soft segment, the diversity of the composition of the resulting multi-block copolymer is very wide. Therefore, as shown in the examples to be described later, the multi-block copolymer according to the present invention has remarkably superior mechanical characteristics as compared with the conventional multi-block copolymer having polylactic acid as a hard segment.

  Specifically, as an example of the multi-block copolymer according to the present invention, the mechanical properties when PCL was used as the second block were examined, and as shown in the examples described later, as the amount of PCL was increased. “Tensile Strength (MPa)” was 20.6 MPa to 26.3 MPa, and “Elongation at break (%)” was 805% to 1910%.

  On the other hand, the conventional multi-block copolymer disclosed in Non-Patent Document 1 similarly uses a polylactic acid-based polymer as a hard segment and PCL as a soft segment, and its “Tensile Strength (MPa)” is 6. 93 MPa to 20.02 MPa, and “Elongation at break (%)” was 512% to 738%.

  Thus, it can be seen that the mechanical strength and flexibility of the multi-block copolymer according to the present invention are remarkably improved as compared with the conventional multi-block copolymer. Since the multi-block copolymer according to the present invention has such unique properties, it can be used for various uses as described later and is very useful.

  The most characteristic part of the present invention is to obtain a flexible multi-block copolymer by bonding a polylactic acid having a hydroxyl group at both ends and a soft segment. Therefore, the compound used as the soft segment (second block) and the chain extender can be appropriately changed. By changing these compounds, the properties of the multi-block copolymer change, so that these compounds may be appropriately selected so as to meet the purpose of use of the multi-block copolymer.

  Moreover, the property of the said multiblock copolymer can be changed by changing the molar ratio of the hard segment contained in the multiblock copolymer which concerns on this invention, and a soft segment. That is, the flexibility of the multi-block copolymer can be further increased by increasing the molar ratio of the soft segment. Therefore, this molar ratio may be determined in accordance with the purpose of use of the multi-block copolymer.

<2. Method for producing multi-block copolymer according to the present invention>
The method for producing a multiblock copolymer according to the present invention includes a step of chemically bonding polylactic acid having hydroxyl groups at both ends and a polymer (soft segment) having higher mobility than the polylactic acid. There are no particular limitations on other conditions, such as the presence or absence of a chain extender, the type of chain extender, temperature, material, catalyst, production equipment / equipment, etc.

  That is, the method for producing a multi-block copolymer according to the present invention is a method for producing the multi-block copolymer described in the section <1>. In addition, as a soft segment, the thing of the said <1> column can be used conveniently.

  The above production method will be described in more detail. For example, polylactic acid (for example, a compound represented by the above general formula (I)) serving as a hard segment and a polymer serving as a soft segment are individually synthesized, and then the prepolymer Can be mentioned by a chain extender. In addition, according to the chemical structure and type of the soft segment to be selected, the mode of bonding and the chain extender (crosslinking agent) can be set as appropriate. For example, when a polymer having hydroxyl groups at both ends (for example, PCL or polyethylene glycol) is used as the soft segment, an appropriate chain extender such as HMDI may be selected and used as shown in the examples described later. it can. In addition, as a chain extender used for this method, the thing as described in said <1> column can be used conveniently.

  Moreover, in the Example mentioned later, as a manufacturing method of the above-mentioned <1> column multiblock copolymer, the two types of prepolymers (first block and second block) described above are polymerized using a chain extender, A method including a step of synthesizing a multi-block copolymer is employed.

  Moreover, the conventionally well-known thing can be used suitably for the catalyst in this manufacturing method, It does not specifically limit. For example, tin octylate or DBDL can be used as the catalyst in the above step.

  According to the method for producing a multi-block copolymer according to the present invention as described above, the multi-block copolymer can be obtained simply and efficiently.

  Specifically, the production scheme shown in FIG. 1 can be used as the production method of the multi-block copolymer according to the present invention. Further, instead of the polycaprolactone shown in FIG. 1, a polymer obtained by the production scheme shown in FIG. 4 can also be used.

<3. Polylactic acid (intermediate) and production method thereof according to the present invention>
The polylactic acid according to the present invention is useful as an intermediate compound for producing at least the above multiblock copolymer. Therefore, the present invention includes polylactic acid having hydroxyl groups at both ends. Examples of such polylactic acid include polylactic acid represented by the above general formula (I).

  Unlike the polylactic acid obtained by ring-opening polymerization of L-lactide, the polylactic acid has hydroxyl groups at both ends, and such a polylactic acid has not yet been reported. Therefore, since the polylactic acid according to the present invention has a chemical structure different from that of the conventional polylactic acid, the polylactic acid has various usefulness in applications other than the intermediate in producing the multiblock copolymer. Conceivable. For example, it can be used as a crosslinking agent or a gelling agent.

  The method for producing the polylactic acid according to the present invention, for example, the compound represented by the general formula (I), is one of the methods for producing the multiblock copolymer according to the present invention described in the section <1> above. This is a very useful process. Therefore, the present invention also includes a method for producing the above-mentioned polylactic acid (intermediate) and a method for producing the multi-block copolymer in the above-mentioned <1> column, which includes a step for producing the intermediate.

As shown in FIG. 1, the method for producing polylactic acid represented by the general formula (I) is a step of polymerizing L-lactide in the presence of Nd (BH ₄ ) ₃ (THF) ₃ , that is, Nd (BH ₄ ) ₃ (THF) ₃ may be included as a polymerization initiator, as long as it includes a step of polymerizing L-lactide, and other conditions such as steps, materials, temperature, equipment used and equipment can be set as appropriate. There is no particular limitation.

In addition, as a method for producing the above-mentioned multiblock copolymer in the <1> column via L-lactide, polylactic acid represented by the above general formula (I) serving as the first block is converted from L-lactide to Nd. The first step of synthesis using (BH ₄ ) ₃ (THF) ₃ and the polylactic acid represented by the above general formula (I) and the polymer of the second block are linked by, for example, a chain extender. A method including the second step can be exemplified.

Heretofore, it has not been known that polylactic acid represented by the above general formula (I) can be obtained by polymerizing L-lactide in the presence of Nd (BH ₄ ) ₃ (THF) ₃ . . Presumably, during this polymerization process, Nd (BH ₄ ) ₃ (THF) ₃ reduces the carbonyl group at the starting end of L-lactide, so that the polylactic acid of the present invention in which both ends are hydroxyl groups is synthesized. it is conceivable that.

As described above, the polylactic acid according to the present invention is not only useful as an intermediate in the production of at least the above-mentioned multiblock copolymer, but is also a polylactic acid having an unprecedented structure. Can be expected. In addition, by using Nd (BH ₄ ) ₃ (THF) ₃ , a method for producing polylactic acid including a step of ring-opening polymerization of L-lactide, or polylactic acid obtained by the method, the above multiblock According to the method for producing the copolymer, the polylactic acid or the multi-block copolymer can be produced easily and with high efficiency, so that it is very useful.

  The polylactic acid of the present invention includes polylactic acid represented by the above general formula (III). Examples of the method for producing polylactic acid represented by the general formula (III) include a method of polymerizing lactide in the presence of a catalyst using diol as a polymerization initiator (FIG. 3). Examples of the catalyst include tin octylate and DBDL.

<4. Use of Multiblock Copolymer According to the Present Invention>
Since the multi-block copolymer according to the present invention has the chemical structure as described above, it has a unique function of being significantly more flexible than conventional biodegradable resin materials. Therefore, the following various uses are possible.

  First, it can utilize as a resin composition containing the multiblock copolymer as described in the above-mentioned <1> column. Such a resin composition has much more flexibility than conventional biodegradable resin compositions, is very easy to handle, and can be easily processed into shapes such as sheets and films. It can be used for various applications such as food packaging containers, medical instruments, toys, food containers, and industrial parts.

  Moreover, since the said multiblock copolymer has biodegradability, the resin composition concerning this invention has a small burden on the environment when it discards. Moreover, since it has biocompatibility, it can be suitably applied to a cell scaffold in cell culture or a medical device such as artificial skin.

  Furthermore, the multi-block copolymer according to the present invention has the property of being thermoplastic, that is, softening at a high temperature. For this reason, it can be utilized as a thermoplastic elastomer (TPE; Thermoplastic Elastomers). TPE is generally a so-called multi-block copolymer in which at least two types of prepolymers of a hard segment having high crystallinity and a soft segment having lower crystallinity than this hard segment are linked.

  TPE has the characteristics of rubber at normal temperatures, but at high temperatures, as its name suggests, it can be easily molded by plastic processing machines such as softening, compression, extrusion, and injection, just like thermoplastics. It is. Cross-linking is not required, the molding cycle is short, and other elastomers (for example, vulcanized rubber) can be recycled, which is almost impossible. It is a stretched material.

  As a biodegradable TPE, a block copolymer (multi-block copolymer) in which a high-melting point aliphatic polyester block (hard segment) and a low-melting point aliphatic polyester block (soft segment) are linked is disclosed in Patent Document 1 above. It is disclosed.

  However, the polymer disclosed in Patent Document 1 cannot be said to have sufficiently high flexibility, which is one of important performances required as TPE, and has room for improvement.

  The multi-block copolymers of the present invention have a higher flexibility than these conventional TPEs. Therefore, the multi-block copolymer according to the present invention is a very flexible TPE and is very useful when used as a thermoplastic elastomer. Furthermore, unlike conventional vulcanized rubber, etc., it has the effect of being recyclable.

  Furthermore, the multi-block copolymer of the present invention can be used as a resin modifier for improving the flexibility and impact resistance of a resin such as a thermoplastic resin. For example, as described above, conventional polylactic acid known as a biodegradable thermoplastic resin has the advantages of being biocompatible and having high strength. However, this conventional polylactic acid has the disadvantage that it is brittle and lacks flexibility. Since the multiblock copolymer of the present invention has the first block made of polylactic acid, it is excellent in miscibility with polylactic acid. Therefore, the multiblock copolymer of the present invention is highly effective in improving the disadvantages of polylactic acid as described above by adding it as a modifier to such polylactic acid.

  Therefore, for example, when it is desired to increase the flexibility of a resin such as a thermoplastic resin material, a highly flexible biodegradable thermoplastic resin is produced by adding the resin modifier according to the present invention including the multi-block copolymer. can do.

  Moreover, the resin composition containing polylactic acid having a hydroxyl group at both ends is also included in the present invention. Since the above-mentioned polylactic acid has an unprecedented structure, it is considered very useful when used as a resin composition.

  Hereinafter, examples will be shown, and the embodiment of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Furthermore, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the embodiments obtained by appropriately combining the respective technical means disclosed are also included in the present invention. It is included in the technical scope of the invention.

  In this example, both ends hydroxylated polylactic acid (hereinafter simply referred to as polylactic acid) as a hard segment, and both ends hydroxylated polycaprolactone (hereinafter simply referred to as polycaprolactone in this example) as a soft segment. ) Was used as a chain extender. Other compounds such as catalysts used will be described in the following description.

  First, the production method of the multi-block copolymer according to the present invention will be described with specific examples, and then the properties of the multi-block copolymer (Example) obtained by the production method and the comparative example will be shown.

  In this example, a multi-block copolymer was produced according to the production scheme shown in FIG.

[A] Synthesis of tris borohydride, neodymium, tritetrahydrofuran (Nd (BH ₄ ) ₃ (THF) ₃ ) 8.07 mmol) and sodium borohydride (1.06 g, 26.6 mmol). Next, tetrahydrofuran (50 ml) was added and reacted at 60 ° C. for 48 hours. Nd (BH ₄ ) ₃ (THF) ₃ was obtained as pale purple crystals by removing insolubles by centrifugation and concentrating and cooling the supernatant. The yield was 62%.

[B] Synthesis of polylactic acid (poly L-lactic acid) (B-1) Synthesis of polylactic acid-1
To a tetrahydrofuran (29 ml) solution of L-lactide (10.8 g, 75.1 mmol) in a tetrahydrofuran (29 ml) solution of Nd (BH ₄ ) ₃ (THF) ₃ (0.145 g, 0.36 mmol) obtained in [A] above. 1 ml) solution was added and the polymerization reaction was carried out at 60 ° C. for 1 hour. After the polymerization was stopped by adding ion-exchanged water, the product was dissolved in chloroform and poured into methanol to precipitate a polymer (polylactic acid). The yield was 90.0%.

  The number average molecular weight and molecular weight distribution of the polylactic acid thus obtained were 9970 and 1.3, respectively, according to gel permeation chromatography / multi-angle light scattering. The nuclear magnetic resonance spectrum and matrix-assisted laser absorption ionization time-of-flight mass spectrometry showed that this polylactic acid has hydroxyl groups at both ends and has a structure represented by the above general formula (I).

(B-2) Synthesis of polylactic acid-2
Except the amount of L- lactide and _{Nd (BH 4) 3 (THF} ) 3 , the above (B-1) by performing the same operation as column, to obtain a polylactic acid. Details are as follows.

To a solution of L-lactide (5.3 g, 36.8 mmol) in tetrahydrofuran (28 ml), Nd (BH ₄ ) ₃ (THF) ₃ (0.226 g, 0.56 mmol) obtained in [A] above in tetrahydrofuran ( 2 ml) solution was added and the polymerization reaction was carried out at 60 ° C. for 1 hour. After the polymerization was stopped by adding ion-exchanged water, the product was dissolved in chloroform and poured into methanol to precipitate a polymer (polylactic acid). The yield was 91.2%.

  The number average molecular weight and molecular weight distribution of the polylactic acid thus obtained were 3300 and 1.4, respectively, according to gel permeation chromatography / multi-angle light scattering. The nuclear magnetic resonance spectrum and matrix-assisted laser absorption ionization time-of-flight mass spectrometry showed that this polylactic acid has hydroxyl groups at both ends and has a structure represented by the above general formula (I).

[C] Synthesis of polycaprolactone (poly (ε-caprolactone)) (C-1) Synthesis of polycaprolactone-1
In a tetrahydrofuran (45 ml) solution of ε-caprolactone (14.02 ml, 123 mmol), Nd (BH ₄ ) ₃ (THF) ₃ (0.382 g, 0.943 mmol) obtained in the above [A] was added in tetrahydrofuran (5 ml). The solution was added and the polymerization reaction was carried out at room temperature for 5 minutes. After the polymerization was stopped by adding ion exchange water, the product was dissolved in chloroform and then poured into methanol to precipitate a polymer (polycaprolactone). The yield was 82.5%. The number average molecular weight and molecular weight distribution of the obtained polycaprolactone were 11300 and 1.2, respectively, according to gel permeation chromatography / multi-angle light scattering. The nuclear magnetic resonance spectrum and matrix-assisted laser absorption ionization time-of-flight mass spectrometry showed that this polycaprolactone has hydroxyl groups at both ends and has a structure as shown in FIG.

(C-2) Synthesis of polycaprolactone-2
except the amount of ε- caprolactone and _{Nd (BH 4) 3 (THF} ) 3 , the above (B-1) by performing the same operations as column, to obtain a polylactic acid. Details are as follows.

To a tetrahydrofuran (45 ml) solution of ε-caprolactone (7.01 ml, 61 mmol), Nd (BH ₄ ) ₃ (THF) ₃ (0.188 g, 0.466 mmol) obtained in the above [A] was added to tetrahydrofuran (5 ml). The solution was added and the polymerization reaction was carried out at room temperature for 5 minutes. After the polymerization was stopped by adding ion exchange water, the product was dissolved in chloroform and then poured into methanol to precipitate a polymer (polycaprolactone). The yield was 83.7%. The number average molecular weight and molecular weight distribution of the obtained polycaprolactone were 4000 and 2.3, respectively, according to gel permeation chromatography / multi-angle light scattering. The nuclear magnetic resonance spectrum and matrix-assisted laser absorption ionization time-of-flight mass spectrometry showed that this polycaprolactone has hydroxyl groups at both ends and has a structure as shown in FIG.

[Example 1] Synthesis of multi-block copolymer (lactic acid unit / lactone unit = 24/76) Polylactic acid (0.195 g) obtained in (B-1) above and obtained in (C-1) above To a dry dichloromethane (2 ml) solution containing polycaprolactone (0.51 g), tin octylate (3.55 mg, 7.9 μmol) and HMDI (0.011 g, 0.065 mmol) were added, Time reaction was performed. The reaction product was dissolved in chloroform and poured into methanol to precipitate the polymer. The yield was 97.9%.

  The number average molecular weight and molecular weight distribution of the resulting multi-block copolymer were 64000 and 1.8, respectively, according to gel permeation chromatography / multi-angle light scattering. From the nuclear magnetic resonance spectrum, it was shown that this multi-block copolymer contains a lactic acid unit, which is a hard segment made of polylactic acid, and a lactone unit, which is a soft segment made of polycaprolactone, in a molar ratio of 24/76.

Example 2 Synthesis of Multiblock Copolymer (Lactic Acid Unit / Lactone Unit = 40/60) A multiblock copolymer was obtained in the same manner as in Example 1 except that polylactic acid and polycaprolactone were used. Details are as follows.

  To a solution of polylactic acid obtained in (B-1) (0.3065 g) and polycaprolactone (0.3474 g) obtained in (C-1) above in dry dichloromethane (2 ml), tin octylate ( 3.2 mg, 7.8 mmol) and HMDI (0.01 g, 0.061 mmol) were added, and the reaction was performed at 60 ° C. for 12 hours. The reaction product was dissolved in chloroform and poured into methanol to precipitate the polymer. The yield was 92.7%.

  The number average molecular weight and molecular weight distribution of the resulting multi-block copolymer were 54000 and 1.8, respectively, according to gel permeation chromatography / multi-angle light scattering. Nuclear magnetic resonance spectra showed that the multiblock copolymer contained lactic acid units and lactone units in a molar ratio of 40/60.

Example 3 Synthesis of Multiblock Copolymer (Lactic Acid Unit / Lactone Unit = 61/39) A multiblock copolymer was obtained in the same manner as in Example 1 except that polylactic acid and polycaprolactone were used. Details are as follows.

  To a solution of polylactic acid (0.3588 g) obtained in (B-1) above and polycaprolactone (0.17440 g) obtained in (C-1) above in a dry dichloromethane (2 ml) solution, tin octylate ( 2.66 g, 6.6 μmol) and HMDI (0.009 g, 0.051 mmol) were added, and the reaction was performed at 60 ° C. for 12 hours. The reaction product was dissolved in chloroform and poured into methanol to precipitate the polymer. The yield was 91.7%.

  The number average molecular weight and molecular weight distribution of the resulting multi-block copolymer were 49000 and 1.7, respectively, according to gel permeation chromatography / multi-angle light scattering. Nuclear magnetic resonance spectra showed that this multi-block copolymer contained lactic acid units and lactone units in a molar ratio of 61/39.

  In Examples 1 to 3 described above, the lactic acid unit (soft segment), the lactone unit (hard segment), and the HMDI unit (chain extension site) were bonded at random to form a multi-block copolymer.

[Example 4] Multiblock copolymer (Synthesis of lactic acid unit / lactone unit = 34/66, except that polylactic acid obtained in (B-2) above and polycaprolactone obtained in (C-2) above were used Obtained a multi-block copolymer by the same operation as in Example 1. The details are as follows.

  To a solution of polylactic acid (0.190 g) obtained in (B-2) above and polycaprolactone (0.537 g) obtained in (C-2) above in a dry dichloromethane (2 ml) solution, tin octylate ( 10.5 mg, 26 μmol) and HMDI (0.032 g, 0.192 mmol) were added, and the reaction was performed at 60 ° C. for 12 hours. The reaction product was dissolved in chloroform and poured into methanol to precipitate the polymer. The yield was 79.2%.

  The number average molecular weight and molecular weight distribution of the resulting multi-block copolymer were 15000 and 1.8, respectively, according to gel permeation chromatography / multi-angle light scattering. Nuclear magnetic resonance spectra indicated that this multi-block copolymer contained lactic acid units and lactone units in a 34/66 molar ratio.

[Example 5] Multiblock copolymer (synthesis of lactic acid unit / lactone unit = 53/47) A multiblock copolymer was obtained in the same manner as in Example 4 except that polylactic acid and polycaprolactone were used. It is as follows.

  Into a dry dichloromethane (2 ml) solution containing polylactic acid (0.312 g) obtained in (B-2) and polycaprolactone (0.378 g) obtained in (C-2) above, tin octylate was added. (9.2 mg, 23 mmol) and HMDI (32 mg, 0.189 mmol) were added and reacted at 60 ° C. for 12 hours. The reaction product was dissolved in chloroform and poured into methanol to precipitate the polymer. The yield was 73.4%.

  The number average molecular weight and molecular weight distribution of the resulting multi-block copolymer were 14700 and 2.1, respectively, according to gel permeation chromatography / multi-angle light scattering. Nuclear magnetic resonance spectra showed that the multiblock copolymer contained lactic acid units and lactone units in a 53/47 molar ratio.

Example 6 Synthesis of Multiblock Copolymer (Lactic Acid Unit / Lactone Unit = 74/26) A multiblock copolymer was obtained in the same manner as in Example 4 except that polylactic acid and polycaprolactone were used. Details are as follows.

  To a solution of polylactic acid (0.361 g) obtained in (B-2) above and polycaprolactone (0.188 g) obtained in (C-2) above in a dry dichloromethane (2 ml) solution, tin octylate ( 7.4 mg, 18 μmol) and HMDI (26 mg, 0.156 mmol) were added, and the reaction was performed at 60 ° C. for 12 hours. The reaction product was dissolved in chloroform and poured into methanol to precipitate the polymer. The yield was 90.0%.

The number average molecular weight and molecular weight distribution of the resulting multi-block copolymer were 15300 and 1.5, respectively, according to gel permeation chromatography / multi-angle light scattering. Nuclear magnetic resonance spectra indicated that the multiblock copolymer contained lactic acid units and lactone units in a molar ratio of 74/26.
[Comparative Example 1]
The polylactic acid obtained in (B-1) above was used as Comparative Example 1.
[Comparative Example 2]
The polycaprolactone obtained in (C-1) was used as Comparative Example 2.
(Break elongation test)
The multi-block copolymers obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were dissolved in chloroform, and films were prepared by a solution casting method. The film was subjected to a tensile test and examined for mechanical properties. The results are shown in Table 1.

  As shown in Table 1, Examples 1 to 6 in which polylactic acid and polycaprolactone are connected by HMDI are significantly larger in elongation at break than Comparative Example 1 that is polylactic acid and Comparative Example 2 that is polycaprolactone. Degree (Elongation at break (%)). That is, since the multi-block copolymer according to the present example has a lactic acid block and a lactone block, it showed very high flexibility. This is probably because polycaprolactone, which is a semicrystalline polymer, forms a random network in the multi-block copolymer.

Moreover, in the multiblock copolymer which concerns on a present Example, the one where the content rate of polycaprolactone was high had the tendency for a softness | flexibility to be high. In addition, the multiblock copolymer containing polylactic acid and polycaprolactone having higher molecular weight (Examples 1 to 3) showed a higher elongation at break.
[Biodegradability test]
About the said Examples 1-3 and Comparative Examples 1 and 2, the hydrolysis experiment by an enzyme (Protenase K) was done as a biodegradability test.

  Enzymatic hydrolysis was performed at 37 ° C. in Tricine Buffer (pH 8.0).

  The result of hydrolysis is shown in the graph of FIG. In FIG. 2, the horizontal axis is time for hydrolysis (Time (h)), and the vertical axis is the remaining amount after hydrolysis (Weight remaining (%)).

  From FIG. 2, the multi-block copolymers according to Examples 1 to 3 were stably hydrolyzed by the enzyme near normal temperature. That is, it was shown that the multiblock copolymer of this example has biodegradability.

  The multi-block copolymer according to the present invention can be used for cell scaffolds in artificial culture or the like during cell culture in regenerative medicine.

It is a figure which shows an example of the manufacturing scheme of the polyblock copolymer containing the polylactic acid of this invention, and this polylactic acid. It is a graph which shows the result of hydrolyzing the polymer which concerns on the Example and comparative example of this invention by Protenase K. It is a figure which shows the other example of the manufacturing scheme of the polylactic acid of this invention. It is a figure which shows the other example of the manufacturing scheme of the polycaprolactone utilized for manufacture of the multiblock copolymer of this invention.

Claims (15)

A multi-block copolymer having at least a first block and a second block,
The first block is polylactic acid having hydroxyl groups at both ends,
The multi-block copolymer, wherein the second block is a polymer having higher mobility than the polylactic acid. 2. The multiblock copolymer according to claim 1, wherein the first block is polylactic acid represented by the following general formula.

(In the general formula (I), k is a natural number.)   The multi-block copolymer according to claim 1 or 2, wherein the second block is a polymer having an aliphatic hydrocarbon skeleton, an ester bond, an ether bond, or a combination thereof as a repeating unit.   The second block is a polymer comprising at least one monomer selected from the group consisting of ε-caprolactone, ethylene glycol, propylene glycol, δ-valerolactone, β-butyrolactone, β-propiolactone, glycolide, and butylene glycol. The multiblock copolymer according to any one of claims 1 to 3, wherein   The multi-block copolymer according to any one of claims 1 to 4, wherein the second block is a polymer having hydroxyl groups at both ends.   The multiblock copolymer according to any one of claims 1 to 5, further comprising a chain extension site comprising a chain extender.   The multi-block copolymer according to claim 6, wherein the chain extender is a compound having an isocyanate group.   The chain extenders are hexamethylene diisocyanate, n-xylene diisocyanate, 1,4-cyclohexylene diisocyanate, tetramethylene diisocyanate, octamethylene diisocyanate, isophorone diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2 , 4-TDI, 2,5-TDI, and 2,6-TDI selected from the group consisting of at least one compound, or a mixture of two or more. Block copolymer.   A method for producing a multi-block copolymer, comprising a step of chemically bonding a polylactic acid having a hydroxyl group at both ends and a polymer having higher mobility than the polylactic acid. Polylactic acid represented by the following general formula (I):

(In the general formula (I), k is a natural number.)   A method for producing polylactic acid, comprising a step of polymerizing L-lactide in the presence of tris borohydride, neodymium, or tritetrahydrofuran.   A resin composition comprising the multi-block copolymer according to claim 1.   A thermoplastic elastomer comprising the multiblock copolymer according to any one of claims 1 to 8.   A resin modifier comprising the multiblock copolymer according to any one of claims 1 to 8.   A resin composition comprising the polylactic acid according to claim 10.

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