filament

Abstract

To provide a biodegradable filament having an excellent flexibility and an excellent feeder transportability.SOLUTION: There is provided a filament having at least a sheath portion and a core portion, in which the sheath portion comprises a biodegradable polyester and / or a water-soluble polymer, and the core portion comprises a polyester copolymer. When the polyester copolymer has two types of ester bond-forming monomer residues as main structural units, and the two types of ester bond-forming monomers each are designated as "monomer A" and "monomer B", a certain relation is satisfied among a mole fraction (%) of the monomer A residue in the polyester copolymer, a mole fraction (%) of the monomer B residue in the polyester copolymer and a mole fraction (%) of structure in which the monomer A residue and the monomer B residue are adjacent in the polyester copolymer, in which a crystallization rate of at least one of the monomer A residue or the monomer B residue is less than 14%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a filament having at least a sheath portion and a core portion. [Background technology]

[0002] FDM 3D printers, which use a feeder to send out a filament made of thermoplastic resin and then melt it and extrude it from a nozzle to create a shape, are becoming increasingly popular and are widely used not only for personal use but also for industrial purposes such as manufacturing parts.

[0003] The resins that make up the filaments are mainly hard materials such as polylactic acid and ABS, but in recent years there has been a demand for highly flexible materials, and development of elastomer materials such as thermoplastic polyurethane is progressing.

[0004] On the other hand, filaments made of such highly flexible materials are difficult to feed using a feeder due to their high flexibility, and are often sticky, causing problems such as the filaments sticking to each other or to the inner wall of the guide tube that supports the feeding.As a means of solving this problem, filaments with a hard, low-stickiness material arranged on the outer surface have been reported (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-029091 [Patent Document 2] Japanese Patent Application Publication No. 2017-177497 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, 3D printers have also been deployed for medical purposes, and personalized medicine, in which custom-made medical devices are created using 3D printers to fit the unique shapes of bones and organs of each patient and then implanted into the body, is attracting attention.

[0007] However, although the filaments described in Patent Documents 1 and 2 have excellent feeder transportability, they use a non-biodegradable styrene-based elastomer in the core, and the resulting shaped object is non-biodegradable, making them unsuitable for medical devices that are required to decompose and be excreted from the body after completing their role.

[0008] Therefore, an object of the present invention is to provide a biodegradable filament that is excellent in flexibility and feeder transportability. [Means for solving the problem]

[0009] The present invention is intended to solve the above problems as follows.

[0010] A filament having at least a sheath portion and a core portion, the sheath portion comprises a biodegradable polyester and / or a water-soluble polymer; the core portion comprises a polyester copolymer; The polyester copolymer has two types of ester bond-forming monomer residues as main structural units, and when the two types of ester bond-forming monomers are designated as "monomer A" and "monomer B," respectively, the polyester copolymer is a filament that satisfies the following (1) and (2): (1) The R value represented by the following formula is 0.45 or more and 0.99 or less. R = [AB] / (2[A][B]) × 100 [A]: Molar fraction (%) of monomer A residues in the polyester copolymer [B]: Molar fraction (%) of monomer B residues in the polyester copolymer [AB]: mole fraction (%) of structures (AB and BA) in which monomer A residue and monomer B residue are adjacent to each other in the polyester copolymer (2) The crystallinity of at least one of the monomer A residue and the monomer B residue is less than 14%. [Effects of the Invention]

[0011] According to the present invention, it is possible to obtain a molded article or a filament for producing a molded article that is suitable for medical use and has biodegradability or bioabsorbability and particularly excellent flexibility. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of a cross-sectional shape of a filament, where white and black components represent components with different compositions. DETAILED DESCRIPTION OF THE INVENTION

[0013] The filament of the present invention has at least a sheath portion and a core portion. The sheath portion refers to the outer surface of the filament and a region continuous from the outer surface, and the core portion refers to the region not exposed on the outer surface.

[0014] The cross-sectional shape of the filament of the present invention is not particularly limited as long as it has a sheath portion and a core portion. Examples of cross-sectional shapes of the filament of the present invention include a single core portion ( FIG. 1a ), an island-in-the-sea configuration with multiple core portions ( FIGS. 1b and 1c ), and a configuration with a core portion disposed inside a core portion ( FIG. 1d ). A single core portion is preferred ( FIG. 1a ). When multiple core portions are present, their compositions may be different. That is, each of the multiple core portions may contain different components. Furthermore, when multiple core portions are present, and there is a core portion inside another core portion, as in FIG. 1d , the sheath portion and the innermost core portion may have the same composition, i.e., contain the same components. When multiple sheath components are present, their compositions may be different. That is, each of the multiple sheath portions may contain different components.

[0015] The shape of the outer surface of the cross-sectional shape of the filament of the present invention is also not particularly limited, and examples include polygons (FIG. 1e), stars, crosses, ellipses, and perfect circles. However, when used in 3D printer applications, in order to improve the precision of the molded body, it is preferable that the shape of the outer surface of the cross-sectional shape of the filament of the present invention is a perfect circle or close to a perfect circle. Here, a perfect circle refers to a cross-section of the filament cut perpendicular to the longitudinal direction, where the circularity expressed as the ratio of the major axis to the minor axis (major axis / minor axis) is 1.00. If the circularity is greater than 1.00, the shape will be elliptical. However, in order to improve the precision of the molded body for 3D printer applications, the circularity of the shape of the outer surface of the cross-sectional shape of the filament is preferably 1.10 or less, more preferably 1.05 or less, even more preferably 1.03 or less, and most preferably 1.00.

[0016] The sheath portion of the filament of the present invention contains a biodegradable polyester and / or a water-soluble polymer. The content of the biodegradable polyester and / or the water-soluble polymer in the sheath portion is not particularly limited, but the total content of the biodegradable polyester and the water-soluble polymer is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, based on 100% by weight of the entire sheath portion.

[0017] Biodegradability refers to the property of being broken down in the body, and biodegradable polyesters are polyesters that have such a property. Polyesters are polymers in which monomers are linked primarily by ester bonds. Terms that can be used interchangeably with biodegradability include bioabsorbability and biocompatibility.

[0018] Whether a polyester is biodegradable or not can be evaluated according to the method specified in JIS K6950 (2000), for example, as follows: Specifically, an inorganic salt solution (300 mL), activated sludge (9 mg), and polyester (30 mg) are added to a culture bottle and stirred at 25°C for 90 days. The degree of biodegradation is calculated according to the following formula based on the amount of oxygen consumed, and polyesters with a degree of biodegradation of 60% or higher are considered to be biodegradable. Biodegradability (%)=(BOD-B) / TOD ×100 BOD: Oxygen consumption of polyester B: Blank oxygen consumption TOD: Theoretical oxygen consumption required for complete oxidation of polyester Examples of biodegradable polyesters include, but are not limited to, polylactic acid, polycaprolactone, polybutylene succinate, polybutylene adipate, polybutylene succinate adipate, polydioxanone, polyglycolic acid, polybutyrolactone, polyvalerolactone, etc. Although mixtures of these may be used, it is preferable to use a single biodegradable polyester.

[0019] The biodegradable polyester contained in the sheath portion of the filament of the present invention is different from the polyester copolymer contained in the core portion of the filament of the present invention. That is, the biodegradable polyester contained in the sheath portion of the filament of the present invention is composed of a polyester that has the property of being degraded in vivo, and further does not satisfy at least one of the following conditions (1) (the R value represented by the formula described below is 0.45 to 0.99) and (2) (the crystallinity of at least one of the monomer A residues or monomer B residues is less than 14%). Therefore, when a biodegradable polyester satisfies both the following conditions (1) (the R value represented by the formula described below is 0.45 to 0.99) and (2) (the crystallinity of at least one of the monomer A residues or monomer B residues is less than 14%), the polyester is determined to fall under the category of the polyester copolymer described below.

[0020] Water-soluble polymers refer to polymers that dissolve in water. Examples of water-soluble polymers include polyethylene glycol, polyvinyl alcohol, polypropylene glycol, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylpyrrolidone, polyvinylacetamide, polymaleic acid, polysulfonic acid, polyethyleneimine, hydroxypropylmethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, alginic acid, polyphosphate, starch, agar, gelatin, pullulan, dextrin, xanthan gum, and salts, copolymers, or copolymer salts thereof, and mixtures thereof may also be used. Among these, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone are more preferred, and polyethylene glycol is particularly preferred.

[0021] Whether a polymer is water-soluble or not can be evaluated, for example, by the following method: 1 g of polymer is added to 100 mL of water heated to 37°C and stirred. The polymer is confirmed to be dissolved visually within 24 hours, and is deemed to be water-soluble.

[0022] The water-soluble polymer contained in the sheath portion of the filament of the present invention is different from the polyester copolymer contained in the core portion of the filament of the present invention. That is, when the water-soluble polymer contained in the sheath portion of the filament of the present invention is a polyester, it is a polyester that is soluble in water and does not satisfy at least one of the following conditions (1) (the R value represented by the formula below is 0.45 to 0.99) and (2) (the crystallinity of at least one of the monomer A residues or the monomer B residues is less than 14%). Therefore, when a water-soluble polyester satisfies both the following conditions (1) (the R value represented by the formula below is 0.45 to 0.99) and (2) (the crystallinity of at least one of the monomer A residues or the monomer B residues is less than 14%), the polyester is determined to be a polyester copolymer described below.

[0023] The core portion of the filament of the present invention contains a polyester copolymer, which has two types of ester bond-forming monomer residues as main structural units, and when the two types of ester bond-forming monomers are designated as "monomer A" and "monomer B," respectively, satisfies the following (1) and (2):

[0024] (1) The R value represented by the following formula is 0.45 or more and 0.99 or less. R = [AB] / (2[A][B]) × 100 [A]: Molar fraction (%) of monomer A residues in the polyester copolymer [B]: Molar fraction (%) of monomer B residues in the polyester copolymer [AB]: mole fraction (%) of structures (AB and BA) in which monomer A residue and monomer B residue are adjacent to each other in the polyester copolymer (2) The crystallinity of at least one of the monomer A residue and the monomer B residue is less than 14%.

[0025] The amount of the polyester copolymer contained in the core portion of the filament of the present invention is not particularly limited as long as it contains the polyester copolymer, but it is preferable that the core portion contains 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, based on 100% by weight of the entire core portion.

[0026] In this specification, the two types of ester bond-forming monomers may be referred to as "monomer A" and "monomer B," respectively.

[0027] The term "ester bond-forming monomer" refers to a monomer that, after polymerization, produces a polymer in which the monomer units are linked by ester bonds, i.e., a polyester.

[0028] As the ester bond-forming monomer, a hydroxycarboxylic acid is preferably used. Also preferably used are lactones, which are cyclic compounds formed by intramolecular dehydration condensation of the hydroxy group and the carboxyl group of a hydroxycarboxylic acid, and lactides, which are cyclic compounds formed by dehydration condensation of the hydroxy group and the carboxyl group of two molecules of hydroxycarboxylic acid.

[0029] As the hydroxycarboxylic acid, it is particularly preferable to use an aliphatic hydroxycarboxylic acid, such as lactic acid, glycolic acid, or hydroxybutyric acid. , Hi Examples thereof include hydroxypentanoic acid, hydroxycaproic acid, and hydroxyheptanoic acid, and particularly preferred are lactic acid, glycolic acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyoctanoic acid, hydroxynonanoic acid, hydroxydecanoic acid, hydroxyundecanoic acid, hydroxydodecanoic acid, and (2-hydroxyethoxy)acetic acid.

[0030] Although L-lactic acid, D-lactic acid, and mixtures thereof can be used as lactic acid, it is preferable to use L-lactic acid in terms of the physical properties and biocompatibility of the resulting polymer. When a mixture is used as a monomer, the L-lactic acid content is preferably 85% or more, and more preferably 95% or more.

[0031] Lactones include caprolactone and dioxepanone. , Ji Oxanone, 1,4-dioxane-2,3-dione, trimethylene carbonate, β-propiolactone, δ-valerolactone, β-propiolactone, β-butyrolactone, γ-butyrolactone, pivalolactone, etc. can be used, with caprolactone and δ-valerolactone being particularly preferred.

[0032] As lactide, dilactide obtained by dehydration condensation of two molecules of lactic acid, glycolide obtained by dehydration condensation of two molecules of glycolic acid, and tetramethyl glycolide can be used.

[0033] As the ester bond-forming monomer, derivatives of the above-exemplified monomers can also be used.

[0034] Among these, the present invention is directed to a method for producing a lactic acid-based monomer and a hydroxybutyric acid-based monomer, wherein the monomer A and the monomer B are lactic acid, glycolic acid, or hydroxybutyric acid. , Hi Hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid, caprolactone, dioxepanone , Ji More preferably, the monomer A is a compound selected from the group consisting of oxanone, 1,4-dioxane-2,3-dione, trimethylene carbonate, β-propiolactone, δ-valerolactone, β-propiolactone, β-butyrolactone, γ-butyrolactone, pivalolactone, dilactide, glycolide, and tetramethylglycolide. Furthermore, it is particularly preferred that Monomer A is lactic acid or glycolic acid, and it is particularly preferred that Monomer B is caprolactone or δ-valerolactone.

[0035] In this specification, of the two types of ester-bonding monomers, the one with high crystallinity of the homopolymer composed only of the monomer residues is referred to as Monomer A, and the one with low crystallinity is referred to as Monomer B. The crystallinity of the homopolymer can be measured using a differential scanning calorimeter (DSC) as follows.

[0036] The homopolymer is collected on an aluminum pan and measured using a differential scanning calorimeter (EXTAR 6000, manufactured by Seiko Instruments Inc.) under the following condition A by the DSC method to calculate the heat of fusion. A higher heat of fusion per unit weight indicates higher crystallinity. For example, the heat of fusion per unit weight of polylactic acid, determined using the above method, is 93 J / g. (Condition A) Device name: EXSTAR 6000 (Seiko Instruments Inc.) Temperature conditions: 25℃→250℃(10℃ / min) Standard material: α-alumina In the present invention, the crystallinity of at least one of the monomer A residue and the monomer B residue is less than 14%. If the crystallinity is less than 14%, an increase in Young's modulus is suppressed, and a filament suitable for medical material applications can be obtained. The crystallinity of the monomer A residue or the monomer B residue is preferably 10% or less, and more preferably 5% or less.

[0037] The crystallinity ratio of a monomer residue referred to here is the ratio of the heat of fusion per unit weight of the monomer residue in the polyester copolymer of the present invention to the product of the heat of fusion per unit weight of a homopolymer consisting only of a certain monomer residue and the weight fraction of that monomer residue in the polyester copolymer. In other words, the crystallinity ratio of a monomer A residue is the ratio of the heat of fusion per unit weight of the monomer A residue in the polyester copolymer to the product of the heat of fusion per unit weight of a homopolymer consisting only of monomer A and the weight fraction of the monomer A residue in the polyester copolymer of the present invention. The crystallinity ratios of the monomer A residue and the monomer B residue indicate the proportion of the monomer A residue or the monomer B residue in the polyester copolymer of the present invention that form a crystalline structure, respectively.

[0038] In particular, when the monomer A residue is a lactic acid residue and the monomer B residue is a caprolactone residue, the crystallinity of the lactic acid residue and the caprolactone residue is preferably less than 14%, more preferably 10% or less. The crystallinity is specifically determined by the following method.

[0039] The polyester copolymer was dissolved in chloroform to a concentration of 5% by weight, and the solution was transferred to a Teflon petri dish and dried overnight at room temperature under normal pressure. This was then dried under reduced pressure to obtain a polyester copolymer film. The resulting polyester copolymer film was placed on an alumina PAN and measured using a differential scanning calorimeter under the following conditions using the DSC method. The heat of fusion was calculated from the measurement results under temperature conditions (D) and (E). The crystallization ratio was calculated using the following formula:

[0040] Crystallization rate of lactic acid residues = (heat of fusion per unit weight of lactic acid residues in polyester copolymer) / {(heat of fusion per unit weight of homopolymer consisting only of lactic acid residues) × (weight fraction of lactic acid residues in polyester copolymer)} × 100 (%) Crystallinity ratio of caprolactone residue=(Heat of fusion per unit weight of caprolactone residue in polyester copolymer) / {(Heat of fusion per unit weight of homopolymer consisting of only caprolactone residue)×(Weight fraction of caprolactone residue in polyester copolymer)}×100(%) Device name: EXSTAR 6000 (Seiko Instruments Inc.) Temperature conditions: (A) 25℃ → (B) 250℃ (10℃ / min) → (C) 250℃ (5min) → (D) -70℃ (10℃ / min) → (E) 250℃ (10℃ / min) → (F) 250℃ (5min) → (G) 25℃ (100℃ / min) Standard material: Alumina In this specification, the term "monomer residue" generally refers to a repeating unit of a chemical structure derived from a monomer in the chemical structure of a copolymer obtained by polymerizing two or more monomers including the monomer. For example, a copolymer of lactic acid (CH3CH(OH)COOH) and caprolactone (ε-caprolactone: formula below)

[0041] [ka]

[0042] When polymerized to form a copolymer of lactic acid and caprolactone,

[0043] [ka]

[0044] is a lactic acid monomer residue, and the unit represented by the following formula is a caprolactone monomer residue.

[0045] [ka]

[0046] However, as an exception, when a dimer such as lactide is used as a monomer, the term "monomer residue" refers to one of the two repeating structures derived from the dimer. For example, dilactide (L-(-)-lactide: formula below)

[0047] [ka]

[0048] When lactic acid is polymerized with caprolactone, the chemical structure of the copolymer is formed with two repeats of the structure shown in formula (R1) above as dilactide residues. In this case, one of the lactic acid units is considered to be a "monomer residue," and two "monomer residues," i.e., two lactic acid residues, are considered to have been formed derived from the dilactide.

[0049] The phrase "a polyester copolymer having two types of ester-bonding monomer residues as its "main structural units"" means that the sum of the number of the two types of monomer residues is 50 mol % or more, where the sum of all the number of monomer residues in the entire polymer, including other monomer residues, is 100 mol %, and each of these residues accounts for 20 mol % or more, where the sum of all the number of monomer residues in the entire polymer is 100 mol %. For example, the phrase "a polyester copolymer having monomer A residues and monomer B residues as its main structural units" means that the sum of the number of monomer A residues and monomer B residues is 50 mol % or more, where the sum of all the number of monomer residues in the entire polymer is 100 mol %, and that the monomer A residues account for 20 mol % or more and the monomer B residues account for 20 mol % or more. Here, the molar fractions of the monomer A residues, monomer B residues, and other residues can be determined by nuclear magnetic resonance (NMR) measurement from the area values ​​of the signals derived from each residue. For example, when the monomer A residues are lactic acid residues and the monomer B residues are caprolactone residues, measurement can be performed using the method described in Measurement Example 1 below.

[0050] The sum of the monomer A residues and the monomer B residues is, as defined above, 50 mol % or more, preferably 75 mol % or more, and more preferably 90 mol % or more, where the sum of all the monomer residues contained in the entire polymer, including other monomer residues, is 100 mol %. Also, as defined above, the sum of the monomer A residues and the monomer B residues is 20 mol % or more, preferably 30 mol % or more, and more preferably 40 mol % or more. A particularly preferred embodiment is a polymer in which the sum of the monomer A residues and the monomer B residues is 100 mol % of the entire polymer, i.e., a polymer consisting only of monomer A and monomer B.

[0051] The polyester copolymer may further contain another monomer copolymerizable with the two ester bond-forming monomers constituting the main structural units, as long as the effect of the present invention is not impaired. Such a monomer may be another of the above-mentioned ester bond-forming monomers.

[0052] Copolymerization of a monomer that functions as a linker is also a preferred embodiment. Examples of the monomer that functions as a linker include hydroxycarboxylic acids other than the two ester bond-forming monomers that constitute the main structural units, dialcohols, dicarboxylic acids, amino acids, diamines, diisocyanates, and diepoxides.

[0053] In this specification, the term "polyester copolymer" also includes copolymers that contain monomers other than ester bond-forming monomers as constituent units, and thereby contain constituent units that are linked in part by bonds other than ester bonds.

[0054] The polyester copolymer is preferably biodegradable or bioabsorbable. Those skilled in the art will be able to synthesize copolymers that exhibit appropriate biodegradability or bioabsorbability depending on the application by appropriately combining the above-exemplified monomers and adjusting the ratio of the monomers within the ranges specified in the present invention.

[0055] The R value is used as an index of the randomness of the arrangement of monomer residues in a polyester copolymer whose main structural units are two types of ester bond-forming monomer residues, i.e., monomer A residue and monomer B residue. For example, a random copolymer in which the monomer arrangement is completely random has an R value of 1. In addition, the R value for a block copolymer is 0 to 0.44.

[0056] The R value can be determined by quantifying the ratio of combinations of two adjacent monomers (AA, BB, AB, BA) by nuclear magnetic resonance (NMR) measurement, and specifically, it is measured by the method described in Measurement Example 1 below.

[0057] If the R value is less than 0.45, the crystallinity will be high, and the molded product of the copolymer will be hard and the Young's modulus may increase. On the other hand, if the R value exceeds 0.99, the molded product of the copolymer will be too soft and sticky, which may reduce handleability. From the same viewpoint, in the present invention, the R value of the polyester copolymer is preferably 0.45 to 0.99, more preferably 0.45 to 0.85 or 0.50 to 0.99, even more preferably 0.45 to 0.80 or 0.50 to 0.85, and most preferably 0.50 to 0.80.

[0058] In this specification, when a multiplication step is carried out in which the obtained polyester copolymers are linked together or the monomer A and the monomer B are added to the polyester copolymer solution obtained in the synthesis step to multiply the polyester copolymer, for convenience, the polyester copolymer before linking or before addition is referred to as a "macromer."

[0059] The polyester copolymer may be a linear polymer in which macromer units are linearly linked, or a branched polymer in which macromer units are branched and linked.

[0060] A linear polyester copolymer can be synthesized, for example, by bonding one molecule of a macromer to each end of a macromer via the ends.

[0061] A preferred embodiment of the polyester copolymer of the present invention is a copolymer having a structure in which two or more macromer units having a composition gradient in the backbone are linked, each consisting of a residue of monomer A and a residue of monomer B. In this specification, for convenience, such a structure may be referred to as a "multigradient" and a copolymer having a multigradient structure may be referred to as a "multigradient polymer."

[0062] That is, the polyester copolymer is preferably a multi-gradient copolymer, and the multi-gradient copolymer preferably has a structure in which two or more, and more preferably three or more, macromer units are linked together, each having a gradient structure in which monomer A residues and monomer B residues form a composition gradient in the skeleton. The upper limit of the number of linked macromer units having a gradient structure in which monomer A residues and monomer B residues form a composition gradient in the skeleton is preferably 80 or less, more preferably 40 or less, and even more preferably 20 or less.

[0063] As mentioned above, polyester copolymers in which the monomer A residue is a lactic acid residue and the monomer B residue is a caprolactone residue are particularly preferred embodiments of the present invention.

[0064] The polyester copolymer is preferably a polyester copolymer having a structure in which two or more macromer units are linked together, and in which, where VX represents the faster initial polymerization rate of monomer A or monomer B and VY represents the slower initial polymerization rate, the macromer units are preferably polyester copolymers having monomer A residues and monomer B residues as main structural units that satisfy the relationship 1.1≦VX / VY≦40. By using the polyester copolymer having a structure in which two or more macromer units are linked together, each of which is a polyester copolymer having monomer A residues and monomer B residues as main structural units that satisfy the relationship 1.1≦VX / VY≦40, the macromer units can have a gradient structure, and as a result, the polyester copolymer has a multi-gradient structure, which is preferable.

[0065] Here, VX, which is the faster initial polymerization rate for monomer A or monomer B, and VY, which is the slower initial polymerization rate, can be determined by the following method. Monomer A and monomer B are mixed in equimolar amounts, and a solvent and catalyst are added as necessary. The polymerization reaction is initiated by adjusting conditions such as temperature so that the R value, described below, of the final polyester copolymer synthesized or to be synthesized is the same as that of the polyester copolymer to be synthesized within a 10% error range. Periodic sampling is performed during the polymerization to measure the remaining amounts of monomer A and monomer B. The remaining amounts are measured, for example, by chromatography or nuclear magnetic resonance (NMR) measurement. The amount of monomer used in the polymerization reaction is determined by subtracting the remaining amount from the charged amount. When the amount of monomer used in the polymerization reaction is plotted against the sampling time, the initial slope of the curve is VX and VY.

[0066] When such monomer A and monomer B are reacted, if the initial polymerization rate of monomer A is VX and the initial polymerization rate of monomer B is VY, there is a high probability that monomer A will bond to the polymer end during polymerization in the early stages of polymerization. Meanwhile, in the later stages of polymerization, when monomer A is consumed and its concentration in the reaction solution decreases, there is a high probability that monomer B will bond to the polymer end during polymerization. As a result, a gradient polymer is obtained in which the proportion of monomer A residues gradually decreases from one end. Such a gradient polymer has low crystallinity and a suppressed increase in Young's modulus. To facilitate the formation of such a gradient structure, VX / VY is preferably 1.3 or more, and even more preferably 1.5 or more. On the other hand, if the difference in the polymerization rates of monomer A and monomer B is too large, the resulting structure may resemble a block polymer in which only monomer A is polymerized followed by monomer B, resulting in high crystallinity and an increase in Young's modulus. Therefore, VX / VY is more preferably 30 or less, even more preferably 20 or less, and even more preferably 10 or less.

[0067] Preferred combinations of such monomer A and monomer B include dilactide and ε-caprolactone, glycolide and ε-caprolactone, glycolide and dilactide, dilactide and dioxepanone, ethylene oxalate and dilactide, dilactide and δ-valerolactone, and glycolide and δ-valerolactone.

[0068] The filament of the present invention has a sheath containing the biodegradable polyester and / or water-soluble polymer and a core containing the polyester copolymer, resulting in excellent feeder transportability. Feeder transportability is an indicator of whether the filament can be easily fed to the nozzle of an FDM 3D printer, and is one of the factors for improving the accuracy of the model, i.e., 3D printability.

[0069] The cross-sectional area ratio of the core portion to the sheath portion of the filament of the present invention is preferably such that the area of ​​the core portion in the cross section / the area of ​​the sheath portion in the cross section is 20 / 80 to 99 / 1. By setting the cross-sectional area ratio of the core portion to the sheath portion to be such that the area of ​​the core portion in the cross section / the area of ​​the sheath portion in the cross section is 20 / 80 to 99 / 1, a filament with excellent feeder transportability can be obtained. The cross-sectional area ratio of the core portion to the sheath portion is more preferably such that the area of ​​the core portion in the cross section / the area of ​​the sheath portion in the cross section is 50 / 50 to 99 / 1 or 20 / 80 to 97 / 3, and even more preferably 80 / 20 to 99 / 1 or 20 / 80 to 95 / 5.

[0070] The cross-sectional area ratio of the core and sheath portions of a filament can be determined by calculating the cross-sectional areas of the core and sheath portions from cross-sectional images of the filament obtained using an optical microscope or electron microscope, and then calculating the ratio. The average of the area ratios obtained from cross-sectional images of 10 arbitrary points on the filament is taken as the "cross-sectional area ratio of the core and sheath portions." If there are multiple core portions, the area of ​​the core portion is taken as the total area of ​​the multiple core portions. Similarly, if there are multiple sheath portions, the area of ​​the sheath portion is taken as the total area of ​​the multiple sheath portions.

[0071] The diameter of the filament of the present invention is preferably 1.0 mm to 5.0 mm. By setting the diameter of the filament of the present invention to 1.0 mm to 5.0 mm, the filament can be suitably used for 3D printer applications. From the viewpoint of use in 3D printer applications, the diameter of the filament is more preferably 1.5 mm to 3.5 mm, even more preferably 1.6 mm to 3.3 mm, and most preferably 1.7 mm to 3.0 mm. The diameter of the filament is defined as the longest linear distance between any two points on the circumference of a cross section of the filament cut perpendicular to the longitudinal direction. The diameter of the filament in the present invention refers to the average value of 10 points measured using the method described below.

[0072] A 3D printer is a device that prints three-dimensional objects by layering resin or metal one layer at a time based on three-dimensional data.There are various methods for this, such as fused deposition modeling (FDM), stereolithography (SLA or DLP), inkjet, powder sintering (SLS or SLM), and powder bonding, but the filament of the present invention is particularly suitable for use in fused deposition modeling (FDM) 3D printers.

[0073] A molded article can be produced by using the filament of the present invention through the following steps. That is, the method for producing a molded article of the present invention is a method for producing a molded article having the following steps.

[0074] Step 1: A step of melting the filament of the present invention in a temperature-controllable nozzle portion.

[0075] Step 2: A step of forming layers by ejecting the resin composition that constitutes the molten filaments while moving the nozzle part horizontally, and laminating the resin composition.

[0076] In step 1, in order to melt the filament of the present invention, the temperature at the nozzle is preferably 50 to 300°C, more preferably 100 to 280°C, and even more preferably 150 to 250°C.

[0077] In step 2, the speed at which the molten resin composition constituting the filament of the present invention is extruded is preferably 1 to 100 mm / s, more preferably 5 to 80 mm / s, and even more preferably 10 to 50 mm / s, in order to form a uniform layer.

[0078] In the present invention, the term "molded article" refers to an object molded into various shapes by conventional methods depending on the intended purpose. Examples include membranes (membranes, films, sheets), boards, rods, pipes, tubes, filaments, meshes, bags, woven fabrics, and nonwoven fabrics. The term "medical molded article" refers to the above molded article used for medical purposes. Medical applications include sutures, artificial bones, artificial skin, wound dressings, stents, DDS carriers, microneedles, and scaffolding materials for tissue and organ regeneration.

[0079] In the filament of the present invention, the difference in melting point between the sheath portion and the core portion is preferably 0 to 50°C. The difference in melting point between the sheath portion and the core portion is the absolute value of (melting point of the sheath portion) - (melting point of the core portion). By setting the difference in melting point between the sheath portion and the core portion of the present invention to 0 to 50°C, 3D printability can be improved. If the difference in melting point between the sheath portion and the core portion is greater than 50°C, it becomes difficult to appropriately set the nozzle temperature during 3D printing. Specifically, if the nozzle temperature is set to match a component with a low melting point, the component with a high melting point will not melt, or if the nozzle temperature is set to match a component with a high melting point, the component with a low melting point will drip or decompose, resulting in reduced 3D printability.

[0080] When there are multiple core portions, the difference in melting point between the sheath portion and the core portion for at least one core portion is preferably 0 to 50°C, and most preferably the difference in melting point between the sheath portion and the core portion for all core portions is 0 to 50°C. When there are multiple sheath portions, the difference in melting point between the sheath portion and at least one core portion is preferably 0 to 50°C, and most preferably the difference in melting point between the sheath portion and the core portion for all core portions is 0 to 50°C. The same applies when there are multiple sheath portions.

[0081] In this specification, the melting point can be determined by the measurement method described below.

[0082] The internal structure of the filament of the present invention is not particularly limited and may be either a solid structure or a hollow structure, but for use in 3D printers, a solid structure is preferred in order to increase the precision of the molded body. [Example]

[0083] EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0084] (Measurement Example 1: Measurement of the mole fraction and R value of each residue by nuclear magnetic resonance (NMR)) The purified polyester copolymer was dissolved in deuterated chloroform. 1 The ratios of lactic acid monomer residues and caprolactone monomer residues in the polyester copolymer were calculated by H-NMR. 1 Using H homospin decoupling, the peak areas of the methine group of lactic acid (near 5.10 ppm), the α-methylene group of caprolactone (near 2.35 ppm), and the ε-methylene group (near 4.10 ppm) were separated by the signals derived from the adjacent monomer residues of lactic acid or caprolactone, and the peak areas were quantified. When δ-valerolactone was used instead of ε-caprolactone, the peak areas of the methine group of lactic acid (near 5.10 ppm), the α-methylene group of valerolactone (near 2.35 ppm), and the δ-methylene group of valerolactone (near 4.10 ppm) were similarly separated by the signals derived from the adjacent monomer residues of lactic acid or valerolactone, and the peak areas were quantified.

[0085] From the peak area ratios, [AB] was calculated and the R value was calculated. Here, [AB] is the molar fraction of structures in which lactic acid residues are adjacent to caprolactone residues or valerolactone residues, specifically the ratio of the number of AB and BA to the total number of AA, AB, BA, and BB. The results are shown in the table. Device name: JNM-ECZ400R (manufactured by JEOL Ltd.) 1 H homospin decoupling irradiation position: 1.66 ppm Solvent: deuterated chloroform Measurement temperature: room temperature (Measurement Example 2: Measurement of Crystallinity by Differential Scanning Calorimetry (DSC)) The polyester copolymer was dissolved in chloroform to a concentration of 5% by weight, and the solution was transferred to a Teflon petri dish and dried overnight at room temperature under normal pressure. This was then dried under reduced pressure to obtain a film with a thickness of approximately 100 μm.

[0086] The obtained film (approximately 10 mg) was collected on an alumina PAN and measured by the DSC method using a differential scanning calorimeter under the following conditions. The crystallization rate was calculated from the measurement results under temperature conditions (D) to (E) using the following equations 1 and 2. The results are shown in the table.

[0087] Device name: EXSTAR 6000 (Seiko Instruments Inc.) Temperature conditions: (A) 25℃ → (B) 250℃ (10℃ / min) → (C) 250℃ (5min) → (D) -70℃ (10℃ / min) → (E) 250℃ (10℃ / min) → (F) 250℃ (5min) → (G) 25℃ (100℃ / min) Standard material: Alumina Crystallinity ratio of monomer A = (heat of fusion per unit weight of monomer A residue in polyester copolymer) / {(heat of fusion per unit weight of homopolymer consisting of only monomer A residue) × (weight fraction of monomer A residue in polyester copolymer)} × 100 Equation 1 Crystallinity ratio of monomer B = (heat of fusion per unit weight of monomer B residue in polyester copolymer) / {(heat of fusion per unit weight of homopolymer consisting of only monomer B residue) × (weight fraction of monomer B residue in polyester copolymer)} × 100 Equation 2 The heat of fusion of a homopolymer per unit weight can be calculated as follows: The homopolymer is dissolved in chloroform to a concentration of 5% by weight, and the solution is transferred to a Teflon petri dish and dried overnight at room temperature and atmospheric pressure. This is then dried under reduced pressure to obtain a film. The obtained film is placed on an alumina PAN and measured using a differential scanning calorimeter by the DSC method under the following conditions. The heat of fusion is read from the area of ​​the melting peak on the graph obtained from the measurement results under temperature conditions (D) to (E).

[0088] Device name: EXSTAR 6000 (Seiko Instruments Inc.) Temperature conditions: (A) 25℃ → (B) 250℃ (10℃ / min) → (C) 250℃ (5min) → (D) -70℃ (10℃ / min) → (E) 250℃ (10℃ / min) → (F) 250℃ (5min) → (G) 25℃ (100℃ / min) Standard material: Alumina (Measurement Example 3: Melting Point Measurement by Differential Scanning Calorimetry (DSC)) The sheath or core was dissolved in chloroform to a concentration of 5% by weight, and the solution was transferred to a Teflon petri dish and dried overnight at room temperature under normal pressure. This was then dried under reduced pressure to obtain a film approximately 100 μm thick.

[0089] The obtained film (approximately 10 mg) was collected on an alumina PAN and measured by the DSC method using a differential scanning calorimeter under the following conditions. The temperature at which a melting peak was observed under the measurement results under temperature conditions (D) to (E) was taken as the melting point.

[0090] When the components constituting the sheath or core are a mixture, if the polymers contained as components are compatible with each other, a single melting point is obtained, and this value was taken as the melting point of the component.

[0091] On the other hand, when the polymers contained in that portion are incompatible with each other, multiple melting points derived from the individual polymers are obtained, and the melting point derived from the polymer with the highest weight ratio was taken as the melting point of that portion.

[0092] Furthermore, when no clear melting peak was observed in the core or sheath portion, the polymer that constitutes the sheath or core portion did not have a clear melting point, and the temperature determined by the method described in Measurement Example 4 was used as the melting point.

[0093] When there were multiple cores, the melting point of each core was recorded as the "melting point of the core." When there were multiple sheaths, the melting point of each sheath was recorded as the "melting point of the sheath." The results are shown in the table.

[0094] Device name: EXSTAR 6000 (Seiko Instruments Inc.) Temperature conditions: (A) 25℃ → (B) 250℃ (10℃ / min) → (C) 250℃ (5min) → (D) -70℃ (10℃ / min) → (E) 250℃ (10℃ / min) → (F) 250℃ (5min) → (G) 25℃ (100℃ / min) Standard material: Alumina (Measurement Example 4: Melting point measurement method when there is no clear melting point) A fragment (approximately 10 mg) of the sheath or core was placed on a heated hot plate, left to stand for 3 minutes, and then picked up with tweezers. The same procedure was repeated at 5°C intervals, and the lowest temperature at which the fragment deformed when picked up with tweezers and did not return to its original shape was determined as the melting point of that component.

[0095] When there were multiple cores, the melting point of each core was recorded as the "melting point of the core." When there were multiple sheaths, the melting point of each sheath was recorded as the "melting point of the sheath." The results are shown in the table.

[0096] (Measurement Example 5: Filament diameter measurement) The diameter of the filament was measured at 10 random points using a digital caliper, and the average value was taken as the diameter of the filament. The results are shown in the table.

[0097] (Measurement Example 6: Evaluation of filament feeder transportability) The evaluation was carried out using an Ultimaker S5 (manufactured by Ultimaker). The "Load Filament" program was selected from the touch panel, and the prepared filament was loaded as instructed. If the filament was fed to the nozzle without any problems and melted and ejected from the nozzle, the evaluation was "Good." If the filament was not properly fed and melted and ejected from the nozzle due to clogging or other reasons, the evaluation was "Bad." The results are shown in the table.

[0098] (Measurement example 7: Evaluation of 3D printability) The evaluation was carried out using a fused deposition modeling (FDM) 3D printer. The 3D printer has a temperature-controllable nozzle, which moves horizontally while ejecting a resin composition that forms a molten filament to form layers. The resin composition was then layered to create a cube with a side length of 1 cm.

[0099] In this case, the 3D printability of filaments that produced clean cubes with a height of 0.8 cm or more was rated "good," while the 3D printability of filaments that produced cubes with a height of 0.8 cm or more but with some defects was rated "fairly good." 3D printability of filaments that did not qualify as "good" or "fairly good" due to clogging or other reasons that prevented the resin composition from being properly layered was rated "poor." The results are shown in the table.

[0100] (Synthesis Example 1) 50.0 g of L-lactide (PURASORB L; manufactured by PURAC) and 39.6 g of ε-caprolactone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a separable flask as monomers, and 0.45 g of hydroxypivalic acid was used as an initiator. Under an argon atmosphere, 0.27 g of tin(II) octoate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 5.8 mL of toluene (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a catalyst. The mixture was reacted at 150°C for 9.5 hours to obtain a crude copolymer.

[0101] The resulting crude copolymer was dissolved in 200 mL of chloroform and added dropwise to 3000 mL of hexane under stirring to obtain a precipitate, which was then dried under reduced pressure at 50°C to obtain a macromer.

[0102] 50 g of the macromer, 2.1 g of the catalyst 4,4-dimethylaminopyridinium p-toluenesulfonate (synthetic product), and 0.87 g of 4,4-dimethylaminopyridine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were collected and dissolved in 200 mL of dichloromethane (dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) under an argon atmosphere. 1.7 mL of the condensation agent diisopropylcarbodiimide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and condensation polymerization was carried out at room temperature overnight.

[0103] The reaction mixture was diluted with 220 mL of chloroform, and 470 mL of 0.5 M hydrochloric acid was added. The mixture was stirred for 30 minutes, and the aqueous layer was removed by decantation. This process of adding 470 mL of ion-exchanged water, stirring for 10 minutes, and removing the aqueous layer by decantation was repeated until the pH of the removed aqueous layer reached 7. The remaining organic layer was added dropwise to 2200 mL of stirred methanol to obtain a precipitate. This precipitate was dried under reduced pressure at 50°C to obtain the purified polyester copolymer of Synthesis Example 1.

[0104] Example 1 The polyester copolymer of Synthesis Example 1 was chopped into pieces 5 mm square or smaller and used to produce filaments using an extruder (FilabotEx2; manufactured by Filabot). The filaments were passed through a polylactic acid (manufactured by Nature3D) / chloroform solution and then dried overnight at room temperature and atmospheric pressure, taking care to prevent the filaments from sticking together. The resulting filaments were then dried overnight under reduced pressure at 50°C to obtain the filaments of Example 1, which have the cross-sectional shape shown in Figure 1a.

[0105] Example 2 The polyester copolymer of Synthesis Example 1 was chopped into 5 mm squares or less and filaments were produced using an extrusion molding machine (FilabotEx2; manufactured by Filabot). The filaments were passed through a polylactic acid (Nature3D) / chloroform solution and then dried overnight at room temperature and atmospheric pressure, taking care not to stick the filaments together. The resulting filaments were then dried overnight under reduced pressure at 50°C, after which they were passed through a polylactic acid (Nature3D) / chloroform solution again and dried overnight under room temperature and atmospheric pressure, taking care not to stick the filaments together. The resulting filaments were then dried overnight under reduced pressure at 50°C to obtain the filaments of Example 2, which have the cross-sectional shape shown in Figure 1a.

[0106] Example 3 The same procedure as in Example 1 was carried out, except that a polycaprolactone (Sigma-Aldrich) / chloroform solution was used instead of a polylactic acid (Nature3D) / chloroform solution, to obtain a filament of Example 3 having a cross-sectional shape as shown in Figure 1a.

[0107] Example 4 The same procedure as in Example 1 was carried out, except that a polybutylene succinate (Nature3D) / chloroform solution was used instead of a polylactic acid (Nature3D) / chloroform solution, to obtain a filament of Example 4 having a cross-sectional shape as shown in Figure 1a.

[0108] (Comparative Example 1) The polyester copolymer of Synthesis Example 1 was chopped into pieces of 5 mm square or less, and filaments were produced using an extrusion molding machine (FilabotEx2; manufactured by Filabot).

[0109] The filaments of Examples 1 to 4 and Comparative Example 1 were subjected to the measurements described in Measurement Examples 5 and 6. The results are shown in the table.

[0110] [Table 1]

[0111] [Table 2] [Industrial Applicability]

[0112] The filament of the present invention is particularly suitable as a filament for 3D printers. Other applications of the filament of the present invention and molded articles obtained therefrom include woven fabrics, knitted fabrics, nonwoven fabrics, and the like; containers for disposable toiletries and cosmetics; and films for packaging films, agricultural mulch films, tapes, and the like. Medical applications include sutures, artificial bones, artificial skin, wound dressings, DDS carriers, microneedles, stents, and scaffolding materials for tissue and organ regeneration. Furthermore, the filament can be used as a binder for toners and thermal transfer inks.

Claims

1. A filament having at least a sheath portion and a core portion, the sheath portion comprises a biodegradable polyester and / or a water-soluble polymer; the core portion comprises a polyester copolymer; The polyester copolymer has two types of ester bond-forming monomer residues as main structural units, and when the two types of ester bond-forming monomers are designated as "monomer A" and "monomer B," respectively, the polyester copolymer has the following structure: the monomer A is lactic acid or glycolic acid, and the monomer B is caprolactone or δ-valerolactone; A filament that satisfies the following (1) and (2): (1) The R value represented by the following formula is 0.45 or more and 0.99 or less. R=[AB] / (2[A][B])×100 [A]: Molar fraction (%) of monomer A residues in the polyester copolymer [B]: Molar fraction (%) of monomer B residues in the polyester copolymer [AB]: mole fraction (%) of structures in which a monomer A residue and a monomer B residue are adjacent to each other (AB and BA) in the polyester copolymer (2) The crystallinity of at least one of the monomer A residue and the monomer B residue is less than 14%.

2. 10. The filament of claim 1, having a diameter of 1.0 mm to 5.0 mm.

3. The biodegradable polyester is polylactic acid, polycaprolactone, polybutylene succinate, polybutylene adipate, polybutylene succinate adipate, polydioxanone, polyglycolic acid, polybutyrolactone, polyvalerolactone, or a mixture thereof. Alternatively, the filament according to claim 1 or 2, wherein the water-soluble polymer is polyethylene glycol.

4. 4. The filament according to claim 1, wherein the difference in melting point between the sheath portion and the core portion is 0 to 50°C.

5. The filament according to any one of claims 1 to 4, wherein the area ratio of the core portion to the sheath portion in the cross section is: area of ​​the core portion in the cross section / area of ​​the sheath portion in the cross section = 20 / 80 to 99 / 1.

6. A method for producing a molded body, comprising the following steps: Step 1: A step of melting the filament according to any one of claims 1 to 5 in a temperature-controllable nozzle portion. Step 2: A step of forming a layer by ejecting the molten resin composition that constitutes the filament while moving the nozzle part horizontally, and laminating the resin composition to form a molded body.

7. The filament according to any one of claims 1 to 5, which is used for a 3D printer.

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