Polyvalent carboxylic acid compound, polymer, composition, molded body, method for producing polyvalent carboxylic acid compound, and method for producing polymer

Abstract

The present invention provides: a polymer which exhibits excellent degradability even in water such as seawater; a polyvalent carboxylic acid compound which can be suitably used for the synthesis of the polymer; a composition and a molded body, each of which contains the polymer; a method for producing the polyvalent carboxylic acid compound; and a method for producing the polymer. This polyvalent carboxylic acid compound has a chemical structure in which a sugar compound having four or more hydroxyl groups in each molecule is bonded to a carbonyl compound having a formyl group and a carboxyl group. The chemical structure has a plurality of acetal structures that are each formed between any two of the hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound.

Description

Polyvalent carboxylic acid compound, polymer, composition, molded article, method for producing polyvalent carboxylic acid compound, and method for producing polymer

[0001] Some aspects of the present invention relate to a polyvalent carboxylic acid compound, a polymer, a composition, a molded article, a method for producing a polyvalent carboxylic acid compound, and a method for producing a polymer.

[0002] Polyester is widely used due to its excellent physical properties and durability. However, conventional polyester is difficult to decompose in the natural environment, and particularly in the marine environment, decomposition by microorganisms does not progress over a long period of time, and the environmental load is regarded as a problem.

[0003] In recent years, although biodegradable polyesters have been developed (for example, see Patent Document 1), these have the problem that while they are excellent in decomposability in soil, they are insufficient in decomposability in water such as seawater.

[0004] Japanese Patent Application Laid-Open No. 2000-189183

[0005] The object of some aspects of the present invention is to provide a polymer that exhibits excellent decomposability even in water such as seawater, to provide a polyvalent carboxylic acid compound that can be suitably used for the synthesis of the polymer, to provide a composition and a molded article containing the polymer, to provide a method for producing the polyvalent carboxylic acid compound, and also to provide a method for producing the polymer.

[0006] The polyvalent carboxylic acid compound according to an application example of some aspects of the present invention has a chemical structure in which a sugar compound having four or more hydroxyl groups in the molecule and a carbonyl compound having a formyl group and a carboxyl group are bonded, and the chemical structure has a plurality of acetal structures formed between any two of the hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound.

[0007] In the polyvalent carboxylic acid compound according to an application example of some aspects of the present invention, the polyvalent carboxylic acid compound is preferably represented by the following formula (1).

[0008]

[0009] Polymers according to some embodiments of the present invention are characterized by having a structure in which a polycarboxylic acid compound and a polyhydric alcohol compound according to the above-mentioned embodiments of the present invention are polycondensed.

[0010] Polymers according to some embodiments of the present invention are preferably marine biodegradable.

[0011] In polymers according to some embodiments of the present invention, it is preferable that the polyhydric alcohol compound is represented by the following formula (2).

[0012] (In equation (2), m is an integer greater than or equal to 1, and n is an integer between 2 and 20.)

[0013] In some embodiments of the present invention, the polymer is preferably represented by the following formula (3).

[0014] (In equation (3), l is an integer greater than or equal to 2, m is an integer greater than or equal to 1, and n is an integer between 2 and 20.)

[0015] A composition relating to some aspects of the present invention is characterized by containing the polymer relating to the above-described example of the present invention.

[0016] A molded article relating to some embodiments of the present invention is characterized by containing the polymer relating to the above-described embodiment of the present invention.

[0017] A method for producing polycarboxylic acid compounds according to some embodiments of the present invention is characterized by comprising an acetalization step in which a sugar compound having four or more hydroxyl groups in its molecule and a carbonyl compound having a formyl group and a carboxyl group are dehydrated and condensed under acidic conditions.

[0018] In the method for producing polycarboxylic acid compounds according to some embodiments of the present invention, it is preferable that the sugar compound is xylose.

[0019] In the method for producing polycarboxylic acid compounds according to some embodiments of the present invention, it is preferable that the carbonyl compound is represented by the following formula (4).

[0020] (In equation (4), n is an integer between 0 and 10, inclusive.)

[0021] A polymer production method according to some embodiments of the present invention is characterized by comprising: an acetalization step to obtain a polycarboxylic acid compound having an acetal structure by dehydrating and condensing a sugar compound having four or more hydroxyl groups in its molecule with a carbonyl compound having a formyl group and a carboxyl group under acidic conditions; and a polycondensation step to polycondense the polycarboxylic acid compound with a polyhydric alcohol compound.

[0022] According to the present invention, it is possible to provide a polymer that exhibits excellent degradability even in water such as seawater, a polycarboxylic acid compound that can be suitably used in the synthesis of the polymer, a composition and molded article containing the polymer, a method for producing the polycarboxylic acid compound, and a method for producing the polymer.

[0023] Hereinafter, polycarboxylic acid compounds, polymers, compositions, molded articles, methods for producing polycarboxylic acid compounds, and methods for producing polymers will be described in detail based on several embodiments of the present invention (hereinafter referred to as "this embodiment").

[0024] In this embodiment, unless otherwise specified, the measurements and processes described are assumed to have been performed at room temperature (23°C).

[0025] [1] Polycarboxylic acid compounds The polycarboxylic acid compounds according to this embodiment have a chemical structure in which a sugar compound having four or more hydroxyl groups in the molecule is bonded to a carbonyl compound having a formyl group and a carboxyl group, and the chemical structure has a plurality of acetal structures formed between any two of the hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound.

[0026] This makes it possible to provide a polycarboxylic acid compound that can be suitably used in the synthesis of polymers that exhibit excellent degradability even in water such as seawater. In other words, the polycarboxylic acid compound of this embodiment can be suitably used as a constituent monomer of polymers that exhibit excellent degradability even in water such as seawater.

[0027] Furthermore, polymers produced using such polycarboxylic acid compounds possess excellent physical properties (e.g., mechanical strength, heat resistance, etc.) similar to conventional plastics.

[0028] Furthermore, the aforementioned chemical structure only needs to satisfy the above conditions within the molecule of the polycarboxylic acid compound, and does not necessarily have to be formed by actually reacting the sugar compound and the carbonyl compound during the synthesis of the polycarboxylic acid compound. In other words, the term "bonded" above is an expression used to describe the chemical structure (state) of the polycarboxylic acid compound, and not an expression used to describe the manufacturing method.

[0029] [1-1] Sugar Compounds The sugar compound units having the above chemical structure will be described below. Sugar compounds have four or more hydroxyl groups in their molecules. Within the molecule of the polycarboxylic acid compound, an acetal structure is formed between any two hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound.

[0030] Specific examples of sugar compounds (sugar compounds that do not form an acetal structure) include monosaccharides such as xylose, mannose, galactose, arabinose, ribose, and glucose, and polysaccharides such as cellulose and starch, but xylose is preferred among them.

[0031] This makes it possible to improve the degradability in water of polymers synthesized using polycarboxylic acid compounds, and to improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of molded articles produced using such polymers.

[0032] [1-2] Carbonyl Compounds The carbonyl compound units having the above chemical structure will be described below. Carbonyl compounds have a formyl group and a carboxyl group. Within the molecule of the polycarboxylic acid compound, an acetal structure is formed between the formyl group of the carbonyl compound and any two hydroxyl groups of the sugar compound.

[0033] Specific examples of carbonyl compounds (carbonyl compounds that do not form an acetal structure) include compounds in which a formyl group and a carboxyl group are bonded to a divalent hydrocarbon group. Among these, compounds in which a formyl group is bonded to one end of an alkylene group and a carboxyl group is bonded to the other end are preferred, the compound represented by the following formula (4) is more preferred, and glyoxylic acid is even more preferred.

[0034] (In equation (4), n is an integer between 0 and 10, inclusive.)

[0035] This makes it possible to improve the degradability in water of polymers synthesized using polycarboxylic acid compounds, and to improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of molded articles produced using such polymers.

[0036] The carbonyl compound is not limited to glyoxylic acid, but any compound having a formyl group and a carboxyl group can be used in the same way. For example, by using a compound in formula (4) where n is between 1 and 3, a polycarboxylic acid compound having multiple acetal structures can be suitably obtained by reacting with multiple hydroxyl groups of a sugar compound.

[0037] [1-3] Overall structure of polycarboxylic acid compounds The polycarboxylic acid compound of this embodiment has a chemical structure having a plurality of acetal structures formed between any two hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound.

[0038] The number of acetal structures in the aforementioned chemical structure may be two or more, or three or more, but it is preferable that there be two.

[0039] As a result, the degradability in water of a polymer synthesized using the polycarboxylic acid compound can be made more excellent, and the physical properties (for example, mechanical strength, heat resistance, etc.) of a molded body produced using the polymer can be made more excellent.

[0040] The structure of the polycarboxylic acid compound is determined by the type of sugar compound, the type of carbonyl compound, the number of acetal structures in the chemical structure, etc., but it is preferably the one represented by the following formula (1).

[0041]

[0042] As a result, the degradability in water of a polymer synthesized using the polycarboxylic acid compound can be made more excellent, and the physical properties (for example, mechanical strength, heat resistance, etc.) of a molded body produced using the polymer can be made more excellent.

[0043] In the above description, the case where the polycarboxylic acid compound has a free carboxyl group (—COOH) has been typically described. However, the polycarboxylic acid compound according to the present invention may have a carboxyl group in the form of a salt. The scope of the polycarboxylic acid compound according to the present invention shall include esterified products such as activated esters. By using such an esterified product, for example, it can be preferably used in the production of the polymer of the present invention described in detail later.

[0044] The polycarboxylic acid compound according to the present invention is not limited to the form having a free carboxyl group, and may be in the form of an alkali metal salt or an organic base salt. Also, the scope of the polycarboxylic acid compound may include esterified products containing activated esters and the like. These forms can be selected from the viewpoints of purification property, storage stability, handling property, easiness of introduction into the polycondensation step, etc.

[0045] Further, the polyvalent carboxylic acid compound of the present invention may have a structure other than the above chemical structure. For example, among the hydroxyl groups of the sugar compound constituting the polyvalent carboxylic acid compound that do not form an acetal structure, chemical modifications such as esterification and etherification may be performed.

[0046] The polyvalent carboxylic acid compound according to an embodiment of the present invention includes a first structure that is a first five-membered ring or a first six-membered ring containing at least one oxygen atom, a second structure that is a second five-membered ring or a second six-membered ring that shares a first carbon-carbon bond among the first five-membered ring or the first six-membered ring, and a third structure that is a third five-membered ring or a third six-membered ring that shares a second carbon-carbon bond among the first five-membered ring or the first six-membered ring, a first carboxyl group or a first ester group directly or indirectly bonded to the second structure via a first linking group, and a second carboxyl group or a second ester group directly or indirectly bonded to the third structure via a second linking group. The second five-membered ring or the second six-membered ring contains two oxygen atoms, and the third five-membered ring or the third six-membered ring contains two oxygen atoms.

[0047] The first structure is preferably the first six-membered ring.

[0048] Further, the second structure is preferably the second five-membered ring. In particular, when the first structure is the first six-membered ring, the second structure is preferably the second five-membered ring.

[0049] Further, the third structure is preferably the third five-membered ring. In particular, when the first structure is the first six-membered ring and the second structure is the second five-membered ring, the third structure is preferably the third five-membered ring.

[0050] Further, each of the two oxygen atoms contained in the second five-membered ring is preferably directly bonded to different carbon atoms of the first carbon-carbon bond.

[0051] [[ID=I8]] Further, each of the two oxygen atoms contained in the third five-membered ring is preferably directly bonded to different carbon atoms of the second carbon-carbon bond.

[0052] [2] Method for producing polycarboxylic acid compounds Next, the method for producing the polycarboxylic acid compounds described above will be explained.

[0053] The method for producing a polycarboxylic acid compound according to this embodiment includes an acetalization step in which a sugar compound having four or more hydroxyl groups in its molecule and a carbonyl compound having a formyl group and a carboxyl group are dehydrated and condensed under acidic conditions.

[0054] This provides a method for producing polycarboxylic acid compounds that can be suitably used in the synthesis of polymers that exhibit excellent degradability even in water such as seawater.

[0055] [2-1] Acetalization process In the acetalization process, a sugar compound having four or more hydroxyl groups in its molecule and a carbonyl compound having a formyl group and a carboxyl group are subjected to dehydration condensation under acidic conditions.

[0056] [2-1-1] Sugar Compounds Specific examples of sugar compounds used in this process include monosaccharides such as xylose, mannose, galactose, arabinose, ribose, and glucose, and polysaccharides such as cellulose and starch. Furthermore, the sugar compounds used in this process may have some of their hydroxyl groups (for example, hydroxyl groups that do not contribute to the formation of the acetal structure) protected by a protecting group. Among these, xylose is preferred as the sugar compound used in this process.

[0057] This makes it possible to improve the decomposability of the polymer in water, and also improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of the molded article produced using the polymer.

[0058] [2-1-2] Carbonyl Compounds Examples of carbonyl compounds used in this process include compounds in which a formyl group and a carboxyl group are bonded to a divalent hydrocarbon group. Alternatively, compounds in which the carboxyl group has been esterified may be used. Among these, compounds in which a formyl group is bonded to one end of an alkylene group and a carboxyl group is bonded to the other end are preferred, the compound represented by the following formula (4) is more preferred, and glyoxylic acid is even more preferred.

[0059] (In equation (4), n is an integer between 0 and 10, inclusive.)

[0060] This creates two cyclic structures that share at least two sides of the sugar backbone, which improves, for example, the standard strength and chemical stability of the resulting polymer of the compound.

[0061] The amount of carbonyl compound used in this process is preferably 2 to 20 times, more preferably 1.5 to 8 times, and even more preferably 3 to 6 times, relative to the amount of sugar compound used, with respect to the stoichiometry of the target polycarboxylic acid compound (the polycarboxylic acid compound to be produced).

[0062] This makes it possible to improve the decomposability of the polymer in water, and also improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of the molded article produced using the polymer.

[0063] [2-1-3] The composition subjected to the solvent acetalization step may contain at least the sugar compound and carbonyl compound described above, but usually it contains a solvent that dissolves them.

[0064] Examples of solvents include water; alcoholic solvents such as methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol; esteric solvents such as ethyl acetate; ketone solvents such as acetone; etheric solvents such as dioxane; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; aromatic solvents such as benzene and toluene; nitrile solvents such as acetonitrile; and halogenated solvents such as methylene chloride, chloroform, and dichloroethane. One or more of these can be selected and used in combination.

[0065] [2-1-4] Other Components The composition subjected to the acetalization process may contain components other than those listed above. Hereinafter in this section, such components will also be referred to as "other components".

[0066] Other components include acidic substances such as sulfuric acid, nitric acid, and acetic acid.

[0067] [2-1-5] Reaction Conditions This step is carried out under acidic conditions. The pH of the system in which this step is carried out is preferably between 1 and 7, more preferably between 2 and 7, and even more preferably between 4 and 7. This allows the desired reaction to proceed more favorably.

[0068] The reaction temperature in this process is not particularly limited, but is preferably 40°C to 120°C, more preferably 50°C to 100°C, and even more preferably 60°C to 95°C. This allows the desired reaction to proceed more effectively.

[0069] The reaction time in this process is not particularly limited, but is preferably 0.2 hours or more and 24 hours or less, more preferably 0.5 hours or more and 18 hours or less, and even more preferably 1 hour or more and 9 hours or less.

[0070] [2-2] Other steps The method for producing polycarboxylic acid compounds according to this embodiment may have at least the acetalization step described above, but may also have other steps. Examples of such steps include various pretreatment steps and posttreatment steps.

[0071] Examples of post-treatment steps for the acetal process include neutralization and purification.

[0072] [3] Polymer The polymer according to this embodiment has a structure in which the polycarboxylic acid compound and the polyol compound described above are polycondensed.

[0073] This makes it possible to provide polymers that exhibit excellent degradability even in water such as seawater.

[0074] Furthermore, these polymers possess excellent physical properties (e.g., mechanical strength, heat resistance, etc.) similar to conventional plastics.

[0075] Furthermore, the polymer in this embodiment only needs to have a structure in which the aforementioned polycarboxylic acid compound and polyhydric alcohol compound are polycondensed within its molecule, and it does not necessarily have to be obtained by actually reacting the aforementioned polycarboxylic acid compound and polyhydric alcohol compound during the synthesis of the polymer. In other words, the above-mentioned "polycondensed structure" is a description of the structure (state) that the polymer possesses, and not a description of the manufacturing method.

[0076] The polymer according to this embodiment exhibits excellent degradability even in water, but it is particularly preferable that it is degradable in seawater, that is, has marine degradability.

[0077] This allows for a more effective solution to the marine pollution problem associated with conventional plastics.

[0078] The degradability in seawater can be evaluated by immersing a test specimen in artificial or natural seawater and measuring at least one of the following: weight loss rate, molecular weight change, mechanical property change, and surface morphology change. The test temperature is preferably between 10°C and 40°C, and more preferably between 20°C and 35°C. The immersion period can be set according to the application and purpose of the test.

[0079] [3-1] Polycarboxylic acid compounds The polycarboxylic acid compounds that polymers possess will be described below.

[0080] The polycarboxylic acid compound units in the polymer correspond to the polycarboxylic acid compounds described in [1] above. By satisfying the conditions described in [1] above, the same effects as described above can be obtained.

[0081] The polymer of this embodiment may include units corresponding to multiple types of polycarboxylic acid compounds as the polycarboxylic acid compound units.

[0082] [3-2] Polyhydric alcohol compounds The polyhydric alcohol compound units of polymers will be described below.

[0083] The polyhydric alcohol compound may be any compound having two or more hydroxyl groups in its molecule, and may have three or more hydroxyl groups, but it is preferable that it is a compound having two hydroxyl groups.

[0084] This makes it possible to improve the decomposability of the polymer in water, and also improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of the molded article produced using the polymer.

[0085] Polyhydric alcohol compounds may have two or more hydroxyl groups within their molecule, as well as other functional groups. Examples of such functional groups include carboxyl groups, ester groups, ether groups, and the like.

[0086] Specific examples of polyhydric alcohol compounds include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and tartaric acid. Among these, those represented by the following formula (2) are preferred.

[0087] (In equation (2), m is an integer greater than or equal to 1, and n is an integer between 2 and 20.)

[0088] This makes it possible to improve the decomposability of the polymer in water, and also improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of the molded article produced using the polymer.

[0089] The properties of polymers and molded articles can be adjusted by selecting polyhydric alcohol compounds. For example, increasing the proportion of ethylene glycol-derived units can improve heat resistance, and including polyethylene glycol-derived units can improve degradability in aqueous environments.

[0090] The polymer of this embodiment may include units corresponding to multiple types of polyhydric alcohol compounds as the polyhydric alcohol compound units.

[0091] [3-3] Units of other compounds The polymer of this embodiment may have the polycarboxylic acid compound units and polyhydric alcohol compound units described above, but may also have units of other compounds.

[0092] Examples of such compounds include compounds having one carboxyl group and one hydroxyl group in the molecule (e.g., lactic acid, 6-hydroxycaproic acid, etc.), and polycarboxylic acid compounds other than those described in [1] above.

[0093] If the polymer of this embodiment has units of other compounds in addition to the polycarboxylic acid compound units and polyhydric alcohol compound units described above, the proportion of the units of the other compounds to the entire polymer is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0094] [3-4] The weight-average molecular weight of the polymer in this embodiment is preferably 5,000 to 5 million, more preferably 10,000 to 3 million, and even more preferably 100,000 to 2 million.

[0095] The glass transition temperature of the polymer in this embodiment is preferably 40°C to 200°C, more preferably 60°C to 150°C, and even more preferably 80°C to 120°C.

[0096] This makes it possible to improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of molded articles manufactured using polymers.

[0097] The polymer of this embodiment is preferably represented by the following formula (3).

[0098] (In equation (3), l is an integer greater than or equal to 2, m is an integer greater than or equal to 1, and n is an integer between 2 and 20.)

[0099] This makes it possible to improve the decomposability of the polymer in water, and also improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of the molded article produced using the polymer.

[0100] A polymer according to an embodiment of the present invention has a plurality of structural units, each of which comprises a first structure which is a first six-membered ring containing at least one oxygen atom, a second structure which is a second five-membered ring sharing a first carbon-carbon bond with the first six-membered ring, and a third structure which is a third five-membered ring sharing a second carbon-carbon bond with the first six-membered ring, wherein the second five-membered ring or the second six-membered ring contains two oxygen atoms, and the third five-membered ring or the third six-membered ring contains two oxygen atoms.

[0101] Preferably, each of the plurality of structural units further comprises a first carboxylate group directly or via a first linking group to the second structure.

[0102] Furthermore, it is preferable that each of the plurality of structural units further comprises a second carboxylate group directly or via a second linking group to the third structure.

[0103] Furthermore, it is preferable that each of the plurality of structural units further comprises a third linking group bonded to the oxygen atom of the first carboxylate group, and that adjacent structural units among the plurality of structural units are bonded to each other via the third linking group.

[0104] Furthermore, it is preferable that the third linking group contains at least one oxygen atom.

[0105] Furthermore, it is preferable that the at least one oxygen atom is contained within the hydroxyl group.

[0106] Furthermore, it is preferable that at least one oxygen atom is bonded to two carbon atoms included in the main chain of the third linking group.

[0107] [4] Method for producing polymers Next, the method for producing polymers as described above will be explained.

[0108] The polymer production method according to this embodiment comprises an acetalization step to obtain a polycarboxylic acid compound having an acetal structure by dehydrating and condensing a sugar compound having four or more hydroxyl groups in its molecule with a carbonyl compound having a formyl group and a carboxyl group under acidic conditions, and a polycondensation step to polycondense the polycarboxylic acid compound with a polyhydric alcohol compound.

[0109] This makes it possible to provide a method for producing polymers that exhibit excellent degradability even in water such as seawater.

[0110] [4-1] Acetalization process In the acetalization process, a sugar compound having four or more hydroxyl groups in its molecule and a carbonyl compound having a formyl group and a carboxyl group are subjected to dehydration condensation under acidic conditions.

[0111] The acetal process can be carried out in the same manner as described in [2-1] above. This will yield the same effects as described above.

[0112] [4-2] Polycondensation process In the polycondensation process, the polycarboxylic acid compound and the polyhydric alcohol compound obtained in the acetal process are polycondensed.

[0113] [4-2-1] Polycarboxylic acid compounds The polycarboxylic acid compounds were obtained in the acetal step.

[0114] It is preferable that such polycarboxylic acid compounds satisfy the conditions described in [1] above. This will yield the same effects as described above.

[0115] In this process, multiple types of polycarboxylic acid compounds may be used in combination.

[0116] Furthermore, the polycarboxylic acid compound obtained in the acetal step may be subjected to the polycondensation step as is, or it may be subjected to the polycondensation step after chemical transformation.

[0117] [4-2-2] Polyhydric alcohol compounds Polyhydric alcohol compounds are compounds that have two or more hydroxyl groups in their molecule.

[0118] By using a polyhydric alcohol compound that satisfies the conditions described in [3-2] above, the same effects as described above can be obtained.

[0119] In this process, multiple types of polyhydric alcohol compounds may be used in combination.

[0120] The amount of polyhydric alcohol compound used in this process is preferably 2 to 10 times, more preferably 2.2 to 5 times, and even more preferably 2.4 to 4 times, relative to the amount of polyhydric carboxylic acid compound used, with respect to the stoichiometry of the target polymer (polymer to be produced).

[0121] This makes it possible to improve the decomposability of the polymer in water, and also improve the physical properties (e.g., mechanical strength, heat resistance, etc.) of the molded article produced using the polymer.

[0122] [4-2-3] The composition subjected to the solvent polycondensation step may contain at least the polycarboxylic acid compound and polyol compound described above, but may also contain, for example, a solvent that dissolves them.

[0123] Examples of solvents include water; alcoholic solvents such as methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol; esteric solvents such as ethyl acetate; ketone solvents such as acetone; etheric solvents such as dioxane; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; aromatic solvents such as benzene and toluene; nitrile solvents such as acetonitrile; and halogenated solvents such as methylene chloride, chloroform, and dichloroethane. One or more of these can be selected and used in combination.

[0124] Furthermore, the polycondensation process is not limited to a configuration that includes a solvent, but may also be carried out in a configuration that does not include a solvent (a substantially solvent-free configuration).

[0125] [4-2-4] Other polymerizable components The composition subjected to the polycondensation step may contain the above-mentioned polycarboxylic acid compounds (polycarboxylic acid compounds having a chemical structure in which a sugar compound having four or more hydroxyl groups in the molecule is bonded to a carbonyl compound having a formyl group and a carboxyl group, and the chemical structure has a plurality of acetal structures formed between any two of the hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound) and polyhydric alcohol compounds, but may also contain other polymerizable components. Hereinafter in this section, such components will also be referred to as "other polymerizable components".

[0126] Other polymerizable components include, for example, compounds having one carboxyl group and one hydroxyl group in the molecule (e.g., lactic acid, 6-hydroxycaproic acid, etc.), and polycarboxylic acid compounds other than those described in [1] above.

[0127] [4-2-5] Other Components The composition subjected to the polycondensation step may contain components other than those listed above. Hereinafter in this section, such components will also be referred to as "other components".

[0128] Other components include catalysts (catalytic components) such as antimony trioxide and tetraethoxytitanium. These may be used individually or in combination of two or more.

[0129] The content of these components in the composition subjected to the polycondensation process can be appropriately set according to the molecular weight of the target polymer, the reaction rate, and the physical properties of the target molded article.

[0130] [4-2-6] Reaction Conditions The reaction conditions in this step, more specifically, for example, the reaction temperature and reaction time, may be set according to the target polymer.

[0131] The reaction temperature in this process is not particularly limited, but is preferably 70°C to 280°C, more preferably 100°C to 250°C, and even more preferably 130°C to 220°C. This allows the desired reaction to proceed more effectively.

[0132] The reaction time in this process is not particularly limited, but is preferably between 1 hour and 48 hours, more preferably between 2 hours and 36 hours, and even more preferably between 3 hours and 18 hours.

[0133] Furthermore, in this process, for example, the temperature can be increased in stages, and the reaction can be carried out under reduced pressure as needed. More specifically, as shown in the examples below, one method is to heat and stir at around 150°C, then increase the temperature to around 200°C, and then carry out the reaction under reduced pressure.

[0134] [4-3] Other steps The method for producing a polycarboxylic acid compound according to this embodiment may have at least the acetalization step and polycondensation step described above, but may also have other steps.

[0135] Examples of such processes include various pretreatment processes, intermediate processing processes such as deprotection processes and chemical modification processes, and post-processing processes such as purification processes, mixing processes, and pelletizing processes.

[0136] [5] Composition The composition according to this embodiment contains the polymer described in [3] above.

[0137] This makes it possible to provide a composition containing a polymer that exhibits excellent degradability even in water, such as seawater. As a result, for example, molded articles produced using this composition can exhibit excellent degradability in water.

[0138] [5-1] The polymer content in the composition of this embodiment (the polymer described in [3] above) is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. This allows the effects described above to be exhibited more significantly.

[0139] [5-2] Constituent monomers of the polymer The composition of this embodiment may, in addition to the polymer (the polymer described in [3] above), include, for example, constituent monomers that make up the polymer.

[0140] Such constituent monomers may be, for example, unreacted components during the production of the polymer, or decomposition products of the polymer.

[0141] [5-3] Solvent The composition of this embodiment may contain a solvent that dissolves the polymer (the polymer described in [3] above).

[0142] Examples of such solvents include water; alcoholic solvents such as methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol; esteric solvents such as ethyl acetate; ketone solvents such as acetone; etheric solvents such as dioxane; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; aromatic solvents such as benzene and toluene; nitrile solvents such as acetonitrile; and halogenated solvents such as methylene chloride, chloroform, and dichloroethane. One or more of these can be selected and used in combination.

[0143] [5-4] Other Components The composition of this embodiment may contain components other than those listed above. Hereinafter, in this section, such components will also be referred to as "other components".

[0144] Other components include polymer components other than the aforementioned polymer (other polymer components), talc, and inorganic compounds such as calcium carbonate.

[0145] As other polymer components, various polymers can be used, but for example, biodegradable plastics such as cellulose acetate, cellulose propionate acetate, polyhydroxyalkanoic acid, polyhydroxybutyrate hexanoate, polylactic acid, polycaprolactone, polybutylene succinate, polyethylene succinate, polybutylene succinate adipate, polyvinyl alcohol, polyglycolic acid, poly(caprolactone / butylene succinate), poly(butylene succinate / adipate), and polyhydroxybutyrate / hydroxyhexanoate can be suitably used. In this case, the composition of this embodiment may contain, for example, other polymer components (biodegradable plastics) in a content of 50% to 99% by weight. When other polymer components (biodegradable plastics) are included in a content of 75% to 99% by weight, they function as additives such as plasticizers, lubricants, and especially flow improvers that improve MFR. They also function as biomass content improvers.

[0146] Furthermore, the composition of this embodiment may also contain, as other polymer components, ordinary plastics such as polymethyl methacrylate, polycarbonate, cyclic olefin polymer, polystyrene, polyethylene, polypropylene, and polyethylene terephthalate. In particular, it may contain transparent plastics. In this case, the composition of this embodiment may contain, for example, other polymer components (ordinary plastics) in a content of 50% to 99% by weight. When other polymer components (ordinary plastics) are included in a content of 75% to 99% by weight, they function as additives such as plasticizers, lubricants, and especially flow improvers that improve MFR.

[0147] For example, if the composition of this embodiment includes other polymer components in addition to the polymer according to this embodiment, the composition of this embodiment may include these compounded products.

[0148] [5-5] Form of Composition The form of the composition of this embodiment is not particularly limited, but examples include liquid, pelletized, particulate, powdered, etc.

[0149] [6] Molded article The composition according to this embodiment contains the polymer described in [3] above.

[0150] This makes it possible to provide a molded article containing a polymer that exhibits excellent degradability even in water such as seawater. For this reason, the molded article according to this embodiment can be suitably applied to applications where degradability in water such as seawater is required. More specifically, it can be suitably applied to, for example, fishing materials that may be released into the marine environment.

[0151] The content of the polymer (the polymer described in [3] above) in the molded article of this embodiment is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. This allows the effects described above to be exhibited more significantly.

[0152] The molded article of this embodiment can be manufactured, for example, using the composition described in [5] above.

[0153] The molded article of this embodiment only needs to have at least a portion of the part containing the polymer (the polymer described in [3] above), and may also have a portion that does not contain the polymer (the polymer described in [3] above) in addition to such a portion.

[0154] Furthermore, the molded body of this embodiment may be an assembly made up of multiple parts. In such a case, it is sufficient that at least one of the parts constituting the assembly contains the polymer (the polymer described in [3] above).

[0155] The molded body of this embodiment may be in any shape, such as particulate, powdery, sheety, platey, fibrous, stringy, rody, columnar, spherical, ellipsoidal, or any other three-dimensional shape.

[0156] The molded article of this embodiment can be manufactured using various molding methods, such as extrusion molding, compression molding, injection molding, and three-dimensional molding. Furthermore, the molded article of this embodiment may be molded into a predetermined shape and then subjected to shape adjustments by machining or other methods.

[0157] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto.

[0158] The present invention will be described in detail below based on specific examples, but the present invention is not limited thereto. In the following examples, processes and measurements where temperature conditions are not specified were performed at room temperature (23°C), and those where pressure conditions are not specified were performed under atmospheric pressure (normal pressure).

[0159] [7] Production of polycarboxylic acid compounds Polycarboxylic acid compounds were produced as follows.

[0160] (Example A1) 63.0 g of xylose, a sugar compound having four or more hydroxyl groups in its molecule, 126.0 g of a 50% by mass aqueous solution of glyoxylic acid, a carbonyl compound having a formyl group and a carboxyl group, and 2.1 g of 98% by mass sulfuric acid were weighed into a 500 mL flask and stirred at 90°C and 2 kPa for 3 hours.

[0161] Next, 0.3 g of 98% by mass sulfuric acid and 120 g of methanol were added, and the mixture was heated and stirred at 80°C for 3 hours.

[0162] Next, the reaction mixture was cooled to room temperature, neutralized with an aqueous sodium bicarbonate solution, and then the precipitate was removed by filtration.

[0163] The obtained solution was concentrated, dissolved in ethyl acetate, and washed with distilled water to remove water-soluble impurities. Ethyl acetate was removed from this solution by distillation, and the mixture was dried under reduced pressure to obtain a polycarboxylic acid compound having multiple acetal structures formed between the two hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound within the molecule. This polycarboxylic acid compound is the compound shown in formula (1) above.

[0164] [8] Production of polymer (Example B1) 6.0 g of the polycarboxylic acid compound obtained in Example A1, 3.2 g of tartaric acid (a polyhydric alcohol compound), and 0.026 g of antimony trioxide were weighed into a 200 mL separable flask, heated and stirred at 150°C for 2 hours, then heated and stirred at 200°C for 2 hours, and further heated and stirred at 200°C and 10 Pa for 2 hours.

[0165] The reaction system was then cooled to room temperature and dissolved in N-methyl-2-pyrrolidone (NMP). The resulting solution was added dropwise to methanol, reprecipitation occurred, and then it was filtered by suction. Polymer 1 was obtained by drying under reduced pressure.

[0166] (Example B2) 6.0 g of the polycarboxylic acid compound obtained in Example A1, 8.4 g of polyethylene glycol (PEG) (molecular weight 400 g / mol), a polyhydric alcohol compound, and 0.026 g of antimony trioxide were weighed into a 200 mL separable flask. The mixture was heated and stirred at 150°C for 2 hours, then heated and stirred at 200°C for 2 hours, and finally heated and stirred at 200°C and 10 Pa for 10 hours.

[0167] The reaction system was then cooled to room temperature and dissolved in N-methyl-2-pyrrolidone (NMP). The resulting solution was added dropwise to methanol, reprecipitated, and then collected by suction filtration. Polymer 2 was obtained by drying under reduced pressure. Polymer 2 is represented by formula (3) above.

[0168] [9] Evaluation Polymers 1 and 2 obtained as described above were subjected to the following treatments, and their decomposability in water (in liquids containing water) was evaluated.

[0169] [9-1] Degradability in distilled water First, 1 g of the target polymer and 50 mL of distilled water were weighed into each sample bottle. With the lid closed, the bottles were stirred every 12 hours, and otherwise left to stand at room temperature for one week. After that, the samples in the sample bottles were filtered, and the solid matter on the filter paper was dried under reduced pressure and its weight was measured to determine the amount of polymer that remained without degradation. From there, the weight loss rate (degradation rate) of the polymer was further determined.

[0170] [9-2] The evaluation was carried out in the same manner as in [9-1] above, except that instead of biodegradable distilled water in the artificial seawater, artificial seawater prepared by dissolving Nisso's "Nisso Perfect Marine Pure (NQB-103)" in distilled water to the specified concentration was used. The results are shown in Table 1.

[0171]

[0172] As is clear from Table 1, excellent results were obtained in each embodiment.

[0173] Furthermore, polymers 1 and 2 were mixed and kneaded with titanium dioxide, a white pigment, respectively, to obtain compositions containing the polymers and titanium dioxide. Using these compositions, sheet-like molded articles were obtained by extrusion molding (T-die method).

[0174] When these molded articles were evaluated in the same manner as described in [9] above, they also showed excellent decomposition properties, similar to those described above.

[0175] According to the present invention, it is possible to provide a polymer that exhibits excellent degradability even in water such as seawater, a polycarboxylic acid compound that can be suitably used in the synthesis of the polymer, a composition and molded article containing the polymer, a method for producing the polycarboxylic acid compound, and a method for producing the polymer. Therefore, the present invention has industrial applicability.

Claims

1. A polycarboxylic acid compound having a chemical structure in which a sugar compound having four or more hydroxyl groups in its molecule is bonded to a carbonyl compound having a formyl group and a carboxyl group, wherein the chemical structure has a plurality of acetal structures formed between any two of the hydroxyl groups of the sugar compound and the formyl group of the carbonyl compound.

2. The polycarboxylic acid compound according to claim 1, wherein the polycarboxylic acid compound is represented by the following formula (1).

3. A polymer characterized by having a structure obtained by polycondensation of a polycarboxylic acid compound and a polyhydric alcohol compound as described in claim 1 or 2.

4. The polymer according to claim 3, which is marine biodegradable.

5. The polymer according to claim 3, wherein the polyhydric alcohol compound is represented by the following formula (2). (In formula (2), m is an integer of 1 or more, and n is an integer of 2 or more and 20 or less.) 6. The polymer according to claim 5, wherein the polymer is represented by the following formula (3). (In equation (3), l is an integer greater than or equal to 2, m is an integer greater than or equal to 1, and n is an integer between 2 and 20.) 7. A composition characterized by comprising the polymer described in claim 3.

8. A molded article characterized by containing the polymer described in claim 3.

9. A method for producing a polycarboxylic acid compound, characterized by comprising an acetalization step in which a sugar compound having four or more hydroxyl groups in its molecule and a carbonyl compound having a formyl group and a carboxyl group are dehydrated and condensed under acidic conditions.

10. The method for producing a polycarboxylic acid compound according to claim 9, wherein the sugar compound is xylose.

11. The method for producing a polycarboxylic acid compound according to claim 9 or 10, wherein the carbonyl compound is represented by the following formula (4). (In equation (4), n is an integer between 0 and 10, inclusive.) 12. A method for producing a polymer, comprising: an acetalization step to obtain a polycarboxylic acid compound having an acetal structure by dehydrating and condensing a sugar compound having four or more hydroxyl groups in its molecule with a carbonyl compound having a formyl group and a carboxyl group under acidic conditions; and a polycondensation step to polycondense the polycarboxylic acid compound with a polyhydric alcohol compound.

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