Polymer with sugar chain

Abstract

To provide a biodegradable polymer that exhibits superior hydrolysis properties without impairing mechanical strength (modulus of elasticity) and glass transition temperature, and a method for producing the same.SOLUTION: The present invention relates to a polymer having repeating units derived from a polycarboxylic acid, with sugar chains included in side chains of the polymer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polymer having a sugar chain and a method for producing the same. [Background technology]

[0002] In recent years, microplastics have become a global problem, and it has been reported that they are being ingested by marine organisms such as fish and shellfish. In addition, harmful substances and heavy metals may be adsorbed on microplastics, and it has been pointed out that these substances may be transferred to living organisms. To solve these problems, alternative materials that are easily decomposed in the ocean are required. As one of the alternative materials, non-petroleum-derived biodegradable plastics have attracted attention. Examples include polyhydroxyalkanoate (PHA), polylactic acid (PLA), and polybutylene succinate (PBS). Among them, polybutylene succinate (PBS) is a biodegradable plastic synthesized from succinic acid and 1,4-butanediol obtained from renewable resources. It has good processability and balanced mechanical properties, so it is used for various applications such as mulch films, medical devices, and the food industry.

[0003] For example, Patent Documents 1 and 2 disclose polyurethanes with sugar chains introduced into the main chain. However, because the main chain is not a biodegradable polymer, marine degradability cannot be expected. In order to achieve excellent marine degradability, it is necessary to use a biodegradable polymer as the main chain and further improve biodegradability (hydrolysis characteristics). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2007-40163 [Patent Document 2] International Publication No. 2007-88784 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a biodegradable polymer that is excellent in hydrolysis properties without impairing mechanical strength (elastic modulus) and a decrease in glass transition temperature, and a method for producing the same. [Means for solving the problem]

[0006] As a result of intensive research aimed at solving the above problems, the inventors have discovered that the above problems can be solved by introducing a sugar chain into the side chain of a polymer having a repeating unit derived from a polycarboxylic acid, and have thus completed the present invention.

[0007] That is, the present invention (1) is a polymer having a repeating unit derived from a polyvalent carboxylic acid and containing a sugar chain in the side chain of the polymer.

[0008] The present invention (2) relates to the polymer according to the present invention (1), in which the polycarboxylic acid is an aliphatic polycarboxylic acid.

[0009] The present invention (3) relates to a compound represented by the following formula: HOOC-R 1 (-SR 2 -SUG)-COOH (In the formula, R 1 and R 2 are each independently a divalent linear hydrocarbon group having 1 to 6 carbon atoms, and SUG is a monovalent group formed by removing a hydrogen atom from the hydroxyl group of an oligosaccharide. The polymer according to the present invention (2) is a carboxylic acid represented by the formula:

[0010] The present invention (4) is the polymer according to any one of the present inventions (1) to (3), further having a repeating unit derived from a polyhydric alcohol.

[0011] The present invention (5) is the polymer according to any one of the present inventions (1) to (4), wherein the repeating unit derived from the polycarboxylic acid is a repeating unit derived from a polycarboxylic acid having no sugar chain on a side chain and a repeating unit derived from a polycarboxylic acid having a sugar chain on a side chain.

[0012] The present invention (6) is the polymer according to any one of the present inventions (1) to (5), which has a weight-average molecular weight of 5,000 or more.

[0013] The present invention (7) is the polymer according to any one of the present inventions (1) to (6), wherein after immersing 0.5 g of the polymer in 30 g of a phosphate buffer solution having a liquid temperature of 63° C. and a pH of 7 for 30 days, the weight of the polymer is 85% or less of the weight before the immersion.

[0014] The present invention (8) is a film containing the polymer according to any one of the present inventions (1) to (7).

[0015] The present invention (9) is a method for producing a polymer, which comprises a step of polymerizing a monomer containing a polycarboxylic acid having a sugar chain on the side chain.

[0016] The present invention (10) is the method for producing a polymer according to the present invention (9), wherein the polycarboxylic acid is a mixture of 95 to 99 mol % of a polycarboxylic acid having no sugar chain on a side chain and 1 to 5 mol % of a polycarboxylic acid having a sugar chain on a side chain.

[0017] The present invention (11) is a method for producing a polymer according to the present invention (9) or (10), wherein the monomer further contains a polyhydric alcohol.

[0018] The present invention (12) is a method for producing a polymer according to any one of the present inventions (9) to (11), wherein the polymerization temperature is 150° C. or lower.

[0019] The present invention (13) relates to a compound represented by the following formula: HOOC-R 1 (-SR 2 -SUG)-COOH (In the formula, R 1 and R 2 are each independently a divalent linear hydrocarbon group having 1 to 6 carbon atoms, and SUG is a monovalent group formed by removing a hydrogen atom from a hydroxyl group of a disaccharide or oligosaccharide. It is a polyvalent carboxylic acid represented by the formula: Effect of the Invention

[0020] According to the present invention, since the polymer has a sugar chain on the side chain, it is possible to provide a biodegradable polymer having excellent hydrolysis properties without impairing properties such as mechanical strength (elastic modulus) and glass transition temperature, and a method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The polymer of the present invention is a polymer having a repeating unit derived from a polyvalent carboxylic acid, and is characterized by containing a sugar chain in the side chain of the polymer. The polymer of the present invention has high biodegradability, and biodegradation refers to the property of turning into carbon dioxide and water by the action of microorganisms and circulating in the natural world. Examples of the polymer include polybutylene succinate (PBS), polyethylene succinate (PES), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polybutylene succinate lactate (PBSL), etc., with PBS being preferred in terms of biodegradability, heat resistance, and mechanical strength.

[0022] Examples of polycarboxylic acids include aliphatic polycarboxylic acids and aromatic polycarboxylic acids, with aliphatic polycarboxylic acids being preferred because they are biodegradable and not derived from petroleum. Examples of aliphatic polycarboxylic acids include aliphatic polycarboxylic acids having a sugar chain on the side chain and aliphatic polycarboxylic acids having no sugar chain on the side chain. Here, the side chain refers to a branching site bonded to the main chain, which is the central part of the molecule. Polyvalent means divalent or more, meaning having two or more carboxyl groups. The upper limit of the valence is preferably hexavalent or less.

[0023] The aliphatic polycarboxylic acid having a sugar chain on the side chain includes the following formula: HOOC-R 1 (-SR 2 -SUG)-COOH (In the formula, R 1 and R 2 are each independently a divalent linear hydrocarbon group having 1 to 6 carbon atoms, and SUG is a monovalent group formed by removing a hydrogen atom from the hydroxyl group of an oligosaccharide. Examples of the aliphatic polyvalent carboxylic acids include those represented by the formula R 1 and R 2 Examples of the alkyl group include a methylene group, an ethylene group, a propylene group, and a butylene group.

[0024] Examples of sugars constituting the sugar chain include monosaccharides and oligosaccharides such as disaccharides, trisaccharides, and tetrasaccharides, but disaccharides or higher are preferred, and the sugar is preferably highly stable and non-reducing so that side reactions are unlikely to occur. The sugar chain is preferably contained in an amount of 1 mol % or more relative to the repeating unit.

[0025] Examples of monosaccharides include triose, tetrose, pentose, hexose, and heptose.

[0026] Examples of disaccharides include sucrose, lactose, maltose, trehalose, turanose, and cellobiose. Examples of trisaccharides include raffinose, melezitose, and maltotriose. Examples of tetrasaccharides include acarbose, stachyose, and cyclonigerosylnigerose (CNN). Examples of polysaccharides include polysaccharides having glucose as a constituent unit, polysaccharides having fructose as a constituent unit, and polysaccharides having N-acetylglucosamine as a constituent unit.

[0027] The aliphatic polycarboxylic acid having a sugar chain on the side chain can be synthesized by a known method, for example, a method of reacting a tricarboxylic acid with a sugar having an epoxy group introduced therein, a method of reacting a tricarboxylic acid with a sugar having an amino group introduced therein, or a method described in the examples of the present invention.

[0028] Examples of the aliphatic polycarboxylic acid having no sugar chain on the side chain include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc. Among these, succinic acid and adipic acid are preferred in terms of reactivity and processability.

[0029] The polycarboxylic acid constituting the repeating unit derived from the polycarboxylic acid is preferably a mixture of an aliphatic polycarboxylic acid having a sugar chain on the side chain and an aliphatic polycarboxylic acid having no sugar chain on the side chain. The content of the aliphatic polycarboxylic acid having a sugar chain on the side chain is not particularly limited, but is preferably 1 to 10 mol %, more preferably 1 to 5 mol %, based on the total of both polycarboxylic acids (100 mol %). If it is less than 1 mol %, the hydrolysis property becomes insufficient, and if it exceeds 10 mol %, the molecular weight decreases and the polymer tends to become brittle.

[0030] Examples of repeating units that constitute the polymer together with the repeating units derived from polyvalent carboxylic acids include repeating units derived from polyhydric alcohols and repeating units derived from polyvalent amines. If the repeating units derived from polyhydric alcohols are present, the polymer becomes a polyester, and if the repeating units derived from polyvalent amines are present, the polymer becomes a polyamide.

[0031] Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanediol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, and sorbitol.

[0032] Examples of polyvalent amines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, inorganic salts or organic salts (such as azithinium salts) of these polyvalent amine compounds, and polysaccharides having an amino group such as chitin.

[0033] The weight average molecular weight of the polymer of the present invention is preferably 5000 or more, more preferably 10000 or more. If it is less than 5000, it tends to be brittle. On the other hand, although there is no particular upper limit, it is preferably 100000 or less. The weight average molecular weight is a polystyrene-equivalent molecular weight measured by gel permeation chromatography.

[0034] The glass transition temperature of the polymer of the present invention is not particularly limited, but is preferably from -20 to 0° C., more preferably from -15 to -5° C. In addition, the melting point of the polymer is not particularly limited, but is preferably from 70 to 130° C., more preferably from 80 to 120° C.

[0035] The polymer of the present invention is preferably such that the weight of 0.5 g of the polymer, which is melted at 150° C. and molded into pellets, after immersion for 30 days in 30 g of a phosphate buffer having a liquid temperature of 63° C. and a pH of 7, is 85% or less, and more preferably 80% or less, of the weight before immersion. Biodegradability can be evaluated by measuring the weight.

[0036] The film of the present invention is characterized by containing the polymer of the present invention. The thickness of the film is preferably from 10 to 500 μm, more preferably from 50 to 200 μm.

[0037] The method for producing a polymer of the present invention is characterized by including a step of polymerizing a monomer containing a polycarboxylic acid containing one or more sugar chains in the side chain. The polymer of the present invention can be synthesized by this method. The polycarboxylic acid used in the method for producing a polymer of the present invention is as described above. Since the polycarboxylic acid alone does not polymerize, it is polycondensed together with the polyhydric alcohol or polyamine described above. The polymerization is preferably carried out in the presence of a polymerization catalyst. Examples of the polymerization catalyst include scandium triflate (ScOTf), scandium triflyl imide, tin octylate, tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, and other tetraalkoxy titanates. These polymerization catalysts may be used alone or in combination of two or more kinds. The amount of the catalyst used is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the total monomers.

[0038] The polymerization temperature during polymerization is not particularly limited, but is preferably 200° C. or less, more preferably 180° C. or less. If the temperature exceeds 200° C., the yield tends to decrease and coloring tends to become stronger. The polymerization reaction is preferably carried out under reduced pressure in order to efficiently proceed with the deglycolization reaction.

[0039] The polyvalent carboxylic acid of the present invention is represented by the following formula: HOOC-R 1 (-SR 2 -SUG)-COOH (In the formula, R 1 and R 2 are each independently a divalent linear hydrocarbon group having 1 to 6 carbon atoms, and SUG is a monovalent group formed by removing a hydrogen atom from a hydroxyl group of an oligosaccharide. The polyvalent carboxylic acid of the present invention is as described above.

[0040] The polycarboxylic acid can be synthesized by reacting a saccharide with a halogenated compound having a carbon-carbon double bond in the presence of an alkali to introduce a carbon-carbon double bond into the sugar chain, and then reacting the saccharide with a polycarboxylic acid having a thiol group in the presence of a radical reaction initiator. Examples of the halogenated compound having a carbon-carbon double bond include allyl bromide and allyl chloride. Examples of the polycarboxylic acid having a thiol group include mercaptosuccinic acid and dimercaptosuccinic acid. The radical reaction initiator is not particularly limited as long as it is a compound that generates radicals by heating and initiates a chain polymerization reaction, and organic peroxides, azo compounds, sulfates, and the like can be used. Examples of the azo compound include azobisisobutyronitrile (AIBN), examples of the peroxide include benzoyl peroxide, and examples of the sulfates include potassium persulfate, sodium sulfate, and ammonium sulfate. These polymerization catalysts may be used alone or in combination of two or more. The amount of the catalyst used is preferably 0.05 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the total monomers. EXAMPLES

[0041] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0042] Production Example 1 (Synthesis of Compound 1) 5.0 g (15 mmol) of trehalose, which had been dried overnight at 100°C under reduced pressure, and 1.2 g (29 mmol) of sodium hydroxide were dissolved in 100 ml of anhydrous DMSO and stirred at room temperature for 30 minutes. Then, 1.9 g (161 mmol) of allyl bromide was slowly added dropwise and reacted at 40°C for 24 hours to obtain 4.6 g of trehalose with allyl groups introduced. IR showed a peak at 1660 cm originating from the allyl groups. -1An absorption peak of 1660 cm was confirmed. 3.0 g (8 mmol) of the obtained compound and 1.2 g (8 mmol) of mercaptosuccinic acid were dissolved in 5 ml of methanol, and 0.02 g (0.4 mmol) of azobisisobutyronitrile (AIBN) was added. The mixture was reacted at 60°C for 24 hours, and then concentrated with an evaporator. The residue was dissolved in 50 g of methanol, filtered, and concentrated with an evaporator to obtain 3.1 g of compound 1, which is represented by the following formula and has trehalose introduced into the side chain of mercaptosuccinic acid. IR showed an absorption peak of 1660 cm originating from the allyl group. -1 Absorption and disappearance of 1680cm from carboxylic acid -1 , 3420cm from the hydroxyl group of trehalose -1 The absorption was confirmed.

[0043] [ka]

[0044] Production Example 2 (Synthesis of Compound 2) 5.0 g (15 mmol) of sucrose and 1.2 g (29 mmol) of sodium hydroxide were dissolved in 100 ml of anhydrous DMSO and stirred at room temperature for 30 minutes. Then, 1.9 g (161 mmol) of allyl bromide was slowly added dropwise and reacted at 40°C for 24 hours to obtain 4.2 g of sucrose with an allyl group. IR showed an allyl group-derived peak of 1660 cm -1 An absorption peak of 1660 cm was confirmed. Next, 3.0 g (8 mmol) of the obtained compound and 1.2 (8 mmol) g of mercaptosuccinic acid were dissolved in 5 ml of distilled water, and 0.02 g (0.1 mmol) of potassium sulfate was added. The mixture was reacted at 80°C for 24 hours, and then concentrated with an evaporator. The residue was dissolved in 50 g of methanol, filtered, and concentrated with an evaporator to obtain 2.7 g of compound 2, which has sucrose introduced into the side chain of mercaptosuccinic acid and is represented by the following formula. IR showed an absorption peak of 1660 cm originating from the allyl group. -1 Absorption and disappearance of 1680cm from carboxylic acid -1 , 3420cm from the hydroxyl group of sucrose -1 The absorption was confirmed. [ka]

[0045] Production Example 3 (Synthesis of Compound 3) Cyclonigerosylnigerose (5.0 g, 8.0 mmol) dried overnight at 100°C under reduced pressure and sodium hydroxide (0.6 mmol) were dissolved in 100 ml of anhydrous DMSO and stirred at room temperature for 30 minutes. Then, allyl bromide (1.0 g, 8.5 mmol) was slowly added dropwise and reacted at 40°C for 24 hours to obtain 3.4 g of a compound in which an allyl group was introduced into cyclonigerosylnigerose. IR showed a peak at 1660 cm originating from the allyl group. -1 An absorption peak of 1660 cm was confirmed. 3.0 g of the obtained compound and 0.7 g of mercaptosuccinic acid were dissolved in 5 ml of distilled water, and 0.07 g (0.2 mmol) of potassium sulfate was added. The mixture was reacted at 80°C for 24 hours, and then concentrated with an evaporator. The residue was dissolved in 50 g of methanol, filtered, and concentrated with an evaporator to obtain 2.4 g of compound 3, which is represented by the following formula and has cyclonigerosylnigerose introduced into the side chain of mercaptosuccinic acid. IR showed an absorption peak of 1660 cm originating from the allyl group. -1 The disappearance of the absorption peak at 1680 cm -1 , 3420cm from the hydroxyl group of cyclonigerosylnigerose -1 The absorption was confirmed. [ka]

[0046] Examples 1 to 4 and Comparative Example 1 The monomers having the weights shown in Table 1 were reacted at 60°C for 3 hours using scandium triflate (ScOTf) as a polymerization catalyst and 7 ml of acetonitrile as a solvent, and then polymerized at 125°C for 48 hours under a reduced pressure of 3 mmHg or less. The polymers obtained were dissolved in 15 g of chloroform and reprecipitated with methanol to obtain polymers of each of the Examples and Comparative Examples. IR showed a 3420 cm peak derived from the hydroxyl groups of trehalose. -1 and the ester group-derived 1710cm -1 An absorption peak was confirmed near the

[0047] The physical properties of the obtained polymer were measured by the following methods. The elastic modulus and glass transition temperature were measured using a test piece having a thickness of 2 mm and dimensions of 10 mm x 50 mm, which was prepared by melting the obtained polymer at 150°C and molding it. The results are shown in Table 1.

[0048] <Weight average molecular weight> The measurement was performed by gel permeation chromatography (Alliance 2695, manufactured by Waters Corporation), and the weight average molecular weight was calculated in terms of polystyrene.

[0049] <Melting point> Measurements were performed using a differential scanning calorimeter (EXSTAR6000, manufactured by Hitachi High-Tech Science Corporation) in a nitrogen atmosphere at a temperature range of 30 to 300° C. and a heating rate of 10° C. / min.

[0050] <Elastic modulus and glass transition temperature> The dynamic viscoelasticity was measured using a dynamic viscoelasticity analyzer (DMS-6100, manufactured by SII Nano Technology Co., Ltd.) under conditions of a temperature range of -50 to 100°C, a heating rate of 2°C / min, and a frequency of 1 MHz. The elastic modulus shown in Table 1 is the elastic modulus at 25°C.

[0051] <Hydrolysis weight loss rate> 0.5 g of a polymer that had been melted at 150°C and formed into pellets having a thickness of 2 mm and a diameter of 18 mm was immersed in 30 g of a phosphate buffer solution having a liquid temperature of 63°C for 30 days, and the weights before and after immersion were measured, and the weight after immersion was divided by the weight before immersion to calculate the rate of weight loss due to hydrolysis.

[0052] [Table 1]

[0053] The polymer polymerized in Comparative Example 1 had a hydrolysis weight loss rate of only 12%, and did not have sufficient biodegradability. On the other hand, the polymers of Examples 1 to 4 in which sugar chains were introduced into the polymer showed significantly improved hydrolysis properties and maintained other physical properties, despite only about 1 mol % of sugar chains being introduced.

Claims

1. A polymer having a repeating unit derived from a polycarboxylic acid, the polymer including a sugar chain on a side chain of the polymer.

2. The polymer according to claim 1 , wherein the polycarboxylic acid is an aliphatic polycarboxylic acid.

3. The aliphatic polycarboxylic acid has the following formula: P.S. １ (-S-R ２ -SUG)-COOH (In the formula, R １ and R ２ are each independently a divalent linear hydrocarbon group having 1 to 6 carbon atoms, and SUG is a monovalent group formed by removing a hydrogen atom from a hydroxyl group of an oligosaccharide.

3. The polymer according to claim 2, wherein the carboxylic acid is represented by the formula:

4. 3. The polymer according to claim 1, further comprising a repeating unit derived from a polyhydric alcohol.

5. The polymer according to claim 1 or 2, wherein the repeating units derived from the polycarboxylic acid are a repeating unit derived from a polycarboxylic acid having no sugar chain on its side chain and a repeating unit derived from a polycarboxylic acid having a sugar chain on its side chain.

6. 3. The polymer according to claim 1, which has a weight average molecular weight of 5,000 or more.

7. 3. The polymer according to claim 1, wherein the weight of 0.5 g of the polymer after immersion in 30 g of a phosphate buffer solution having a pH of 7 at a liquid temperature of 63° C. for 30 days is 85% or less of the weight before immersion.

8. A film comprising the polymer according to claim 1 or 2.

9. A method for producing a polymer, comprising a step of polymerizing a monomer containing a polycarboxylic acid having a sugar chain on the side chain.

10. The method for producing a polymer according to claim 9, wherein the polycarboxylic acid is a mixture of 95 to 99 mol % of a polycarboxylic acid having no sugar chain on a side chain and 1 to 5 mol % of a polycarboxylic acid having a sugar chain on a side chain.

11. The method for producing a polymer according to claim 9 or 10, wherein the monomer further comprises a polyhydric alcohol.

12. The method for producing a polymer according to claim 9 or 10, wherein the polymerization temperature is 150° C. or lower.

13. The following formula: P.S. １ (-S-R ２ -SUG)-COOH (In the formula, R １ and R ２ are each independently a divalent linear hydrocarbon group having 1 to 6 carbon atoms, and SUG is a monovalent group formed by removing a hydrogen atom from a hydroxyl group of an oligosaccharide. A polycarboxylic acid represented by the formula:

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