Resin composition containing poly(3-hydroxybutyrate) and fibers

Abstract

Provided is a novel resin composition containing poly(3-hydroxybutyrate) (also referred to as "PHB") and being capable of preventing adhesion to a metal part during fiberization.　The resin composition contains poly(3-hydroxybutyrate) and a polyglycerol unsaturated fatty acid ester.

Description

Resin composition and fiber containing poly(3-hydroxybutyric acid)

[0001] The present invention relates to a resin composition containing poly(3-hydroxybutyric acid) and a fiber obtained by spinning the resin composition.

[0002] Poly(3-hydroxybutyric acid) (also referred to as "PHB") is known as a "marine biodegradable plastic" that exhibits biodegradability even in the ocean among "biodegradable plastics" that are ultimately completely decomposed into water and carbon dioxide by the action of microorganisms. PHB is a polyester composed of 3-hydroxybutyric acid (a ketone body), is produced from bacteria inhabiting the sea or lakes, and is known to be accumulated as granules in the cytoplasm as an energy substrate in the bacteria. For example, in addition to rhizobia such as the genus Sinorhizobium, it can be produced relatively easily and in large quantities by various bacteria such as the genus Alcaligenes, the genus Athiorhodium, the genus Azotobacter, the genus Bacillus, the genus Nocardia, the genus Pseudomonas, the genus Rhizobium, and the genus Spirillum.

[0003] In addition to having biodegradability and biocompatibility, PHB is insoluble in water, has hydrolysis resistance, and has characteristics different from those of conventional biodegradable plastics that are vulnerable to moisture. Also, while many biodegradable resins are effectively decomposed only under aerobic conditions, PHB has the characteristic of being rapidly decomposed even under anaerobic conditions such as the bottom mud of lakes. Therefore, the use of PHB in various molded products such as fibers and films has been studied. Among them, fibers made from PHB have biodegradability and biocompatibility, so there is great potential demand as medical supplies such as surgical sutures, fishing industry supplies such as fishing lines and fishing nets, clothing materials such as fibers, building materials such as non-woven fabrics and ropes, and food and other packaging materials.

[0004] Various proposals have been made regarding the fiberization of PHB. In particular, PHB has a slower crystallization rate compared to petrochemical resins such as polyethylene terephthalate, which has been an obstacle to the fiberization of PHB, and proposals have been made to solve this problem. For example, Patent Document 1 relates to a biodegradable resin fiber consisting of PHB and PCL, with PHB in the range of 10 to 80 parts by mass, and discloses a manufacturing method in which the temperature of the liquid used to cool the molten yarn is set to -50 to 15°C, preferably -50 to 10°C or lower, and in the subsequent stretching step, the stretching tank temperature is set to 4 to 55°C, preferably 15 to 55°C.

[0005] Patent Document 2 discloses a method for producing fibers, characterized by the following steps for providing high-strength fibers: producing melt-extruded fibers by melt-extruding polyhydroxyalkanoic acid; rapidly cooling and solidifying the melt-extruded fibers to a temperature below the glass transition temperature of polyhydroxyalkanoic acid + 15°C to produce amorphous fibers; leaving the amorphous fibers at a temperature below the glass transition temperature + 15°C to produce crystallized fibers; stretching the crystallized fibers; and further subjecting them to tension heat treatment.

[0006] Patent Document 3 discloses the use of pentaerythritol as a crystal nucleating agent to improve the crystallization of polyhydroxyalkanoates, which are slow to crystallize.

[0007] Patent Document 4 discloses that by blending a specific crystal nucleating agent and a specific lubricant with PHB to form polyester fibers, spinnability and productivity at high draw speeds are improved, and the tensile strength of the fibers is increased.

[0008] Japanese Patent Publication No. Hei 8-158158, International Publication No. WO2006 / 038373, International Publication No. 2014 / 020838, International Publication No. 2017 / 122679

[0009] One method for manufacturing fibers using PHB involves melt-extruding a resin composition containing PHB, cooling and solidifying the strand-like molten resin to form fibers, winding them onto a paper tube through a metal roller, unwinding them from the paper tube, stretching them, and then heat-treating them before winding them onto the paper tube again. However, with regard to resin compositions containing PHB, as mentioned above, even if the crystallization rate can be increased, problems such as the resin composition adhering to the metal roller and causing the threads to break can occur, for example, when the resin composition is melt-extruded, the strand-like molten resin is cooled and solidified to form fibers, and then winding them onto a paper tube through a metal roller.

[0010] Therefore, the object of the present invention is to provide a new resin composition containing PHB that can prevent adhesion to metal parts during fiber formation.

[0011] To solve these problems, the present invention proposes the following embodiments.

[0012] [1] A first aspect of the present invention is a resin composition comprising poly(3-hydroxybutyric acid) (also referred to as "PHB") and a polyglycerin unsaturated fatty acid ester.

[0013] [2] A second aspect of the present invention is a resin composition according to the first aspect, comprising 1 to 10 parts by mass of polyglycerin unsaturated fatty acid ester per 100 parts by mass of PHB.

[0014] [3] A third aspect of the present invention is a resin composition according to the first or second aspect, further comprising a hydroxy fatty acid ester or a derivative thereof. [4] A fourth aspect of the present invention is a resin composition according to any one of the first to third aspects, further comprising a crystal nucleating agent. [5] A fifth aspect of the present invention is a resin composition according to any one of the first to fourth aspects, further comprising polylactic acid (also referred to as "PLA").

[0015] [6] A sixth aspect of the present invention is a fiber made of a resin composition according to any one of the first to fifth aspects.

[0016] The resin composition proposed in this invention can be plasticized without reducing the crystallization rate by adding a polyglycerol unsaturated fatty acid ester to poly(3-hydroxybutyric acid) (PHB), and moreover, its adhesiveness can be reduced. Therefore, it is possible to prevent adhesion to metal parts, such as metal rollers, when forming fibers.

[0017] An example of an embodiment of the present invention will be described below. However, the present invention is not limited to the embodiment described below.

[0018] <Resin Composition of the Present Invention> A resin composition according to an example of an embodiment of the present invention (hereinafter referred to as "the resin composition of the present invention") is a resin composition comprising poly(3-hydroxybutyric acid) (PHB) and polyglycerin unsaturated fatty acid ester.

[0019] (PHB) The method of manufacturing and obtaining PHB is optional. It can be manufactured by known methods, or commercially available PHB can be used.

[0020] One method for producing PHB is a fermentation synthesis method in which microorganisms capable of producing PHB are cultured and the PHB accumulated within the cells is recovered. By this method, poly(-3-hydroxybutyric acid) homopolymer can be obtained. Examples of microorganisms capable of producing PHB, i.e., PHB-producing bacteria, include Bacillus megaterium, as well as Cupriavidus necator (formerly classified as Alcaligenes eutrophus, Ralstonia eutropha), Alcaligenes latus, and others. In particular, strains of bacterial species belonging to the genus Methylobacterium, specifically Methylobacterium extorquens ATCC55366, can be cited as producing high molecular weight PHB with a mass-average molecular weight of 1 million (number-average molecular weight of 500,000) or more (Bourque, D. et al., Appl. Microbiol. Biotechnol (1995)).

[0021] In the aforementioned fermentation synthesis method, these microorganisms can usually accumulate PHB within their cells by culturing them in a conventional culture medium containing a carbon source, a nitrogen source, inorganic ions, and other organic components as needed. Methods for recovering PHB from the cells include extraction with an organic solvent such as chloroform, and a method of decomposing the cell components with an enzyme such as lysozyme and then filtering off the PHB granules. Another aspect of the fermentation synthesis method involves culturing microorganisms transformed by introducing recombinant DNA containing a PHB synthesis gene, and then collecting the PHB produced within the cells. In this method, unlike the direct cultivation of Ralstonia eutropha, the microorganisms transformed by introducing recombinant DNA do not possess PHB-degrading enzymes within their cells, thus enabling the accumulation of significantly higher molecular weight PHB.

[0022] Alternatively, PHB produced by chemical synthesis may be used instead of the fermentation method described above.

[0023] The mass-average molecular weight (Mw) of PHB is not particularly limited as long as it does not hinder the fiber formation process, but it is preferably between 50,000 and 5,000,000. If the mass-average molecular weight (Mw) of PHB is 50,000 or more, the strength when fiberized can be maintained. From this viewpoint, the mass-average molecular weight (Mw) of PHB is preferably 50,000 or more, more preferably 100,000 or more, and more preferably 150,000 or more. On the other hand, if the mass-average molecular weight (Mw) of PHB is 5,000,000 or less, it is preferable because it can maintain processability and does not make fiberization difficult. From this viewpoint, the mass-average molecular weight (Mw) of PHB is preferably 5,000,000 or less, more preferably 4,000,000 or less, and more preferably 3,000,000 or less. The mass-average molecular weight used here can be obtained by measuring the polystyrene-reduced molecular weight distribution using gel permeation chromatography (GPC) with chloroform eluent.

[0024] In the resin composition of the present invention, PHB is included as the main component resin, that is, as the resin with the highest mass percentage among the resins constituting the resin composition of the present invention. In this invention, "resin" refers to an organic substance with a mass-average molecular weight of 10,000 or more. The PHB content in the resin composition of the present invention can be assumed to be 50% by mass or more, more preferably 60% by mass or more, and more preferably 70% by mass or more.

[0025] (Polyglycerin unsaturated fatty acid ester) In the resin composition of the present invention, by adding polyglycerin unsaturated fatty acid ester to PHB, plasticization can be achieved without reducing the crystallization rate, and the adhesiveness can be reduced, thus preventing adhesion to metal parts, such as metal rollers, when fiberizing.

[0026] The polyglycerol unsaturated fatty acid ester can be any ester of polyglycerol and an unsaturated fatty acid. The unsaturated fatty acid constituting the above polyglycerol unsaturated fatty acid ester is not particularly limited as long as it is a fatty acid that contains a double bond in the bond between carbon atoms. Examples include palmitoleic acid, oleic acid, elaidic acid, linoleic acid, γ-linolenic acid, α-linolenic acid, arachidonic acid, ricinoleic acid, and condensed ricinoleic acid. Among these, from the viewpoint of further reducing the adhesiveness when the resin composition of the present invention is made into fibers, it is preferable that it be one of oleic acid, ricinoleic acid, and polyricinoleic acid.

[0027] Examples of polyglycerol unsaturated fatty acid esters include polyglycerol oleate ester, polyglycerol ricinoleate ester, and polyglycerol condensed ricinoleate ester.

[0028] There are no particular restrictions on the average degree of polymerization of the polyglycerin constituting the above-mentioned polyglycerin unsaturated fatty acid ester, but examples include those with an average degree of polymerization of 2 to 10, specifically diglycerin (average degree of polymerization 2), triglycerin (average degree of polymerization 3), tetraglycerin (average degree of polymerization 4), hexaglycerin (average degree of polymerization 6), octaglycerin (average degree of polymerization 8), or decaglycerin (average degree of polymerization 10).

[0029] The HLB value of the polyglycerin unsaturated fatty acid ester is preferably 3 to 9, and more preferably 6 or higher or 8 or lower. Having the HLB value of the polyglycerin unsaturated fatty acid ester within this range provides a favorable balance between lipophilicity and hydrophilicity in the resin composition.

[0030] It is preferable to blend polyglycerin unsaturated fatty acid ester in a ratio of 1 to 10 parts by mass per 100 parts by mass of PHB. It is preferable that the amount of polyglycerin unsaturated fatty acid ester is 1 part by mass or more per 100 parts by mass of PHB because it reduces the adhesion of PHB. From this viewpoint, it is preferable that the amount of polyglycerin unsaturated fatty acid ester is 1 part by mass or more per 100 parts by mass of PHB, more preferably 1.5 parts by mass or more, and more preferably 2 parts by mass or more. With this blending ratio, it is also possible to prevent the fibers from adhering to the metal part without reducing the crystallization rate during fiber formation. On the other hand, it is preferable that the amount of polyglycerin unsaturated fatty acid ester is 10 parts by mass or less per 100 parts by mass of PHB because it suppresses bleed-out, and more preferably 7 parts by mass or less, and more preferably 4 parts by mass or less.

[0031] (Hydroxy fatty acid ester or derivative thereof) The resin composition of the present invention may further contain a hydroxy fatty acid ester or derivative thereof, as needed. By further containing a hydroxy fatty acid ester or derivative thereof, the resin composition of the present invention can not only lower its melt viscosity and further increase its fluidity, but also improve its spinnability, allowing it to be wound at a higher speed when, for example, the resin composition of the present invention is made into fibers.

[0032] Examples of hydroxy fatty acid esters or their derivatives include citrate esters, tartaric acid esters, and malic acid esters. Specific compounds include triethyl citrate, tributyl citrate, dibutyl malate, dibutyl tartrate, triethyl O-acetylcitrate, and tributyl O-acetylcitrate. Among these, tributyl O-acetylcitrate and triethyl O-acetylcitrate are preferred from the viewpoint of being compatible with polyglycerol unsaturated fatty acid esters and further enhancing the stringiness.

[0033] It is preferable to blend the hydroxy fatty acid ester or its derivative in a ratio of 1 to 25 parts by mass per 100 parts by mass of PHB. It is preferable that the amount of hydroxy fatty acid ester or its derivative is 1 part by mass or more per 100 parts by mass of PHB because it reduces the melt viscosity. From this viewpoint, it is preferable that the amount of hydroxy fatty acid ester or its derivative is 1 part by mass or more per 100 parts by mass of PHB, more preferably 2 parts by mass or more, and more preferably 3 parts by mass or more. On the other hand, it is preferable that the amount of hydroxy fatty acid ester or its derivative is 25 parts by mass or less per 100 parts by mass of PHB because it suppresses the mass loss during heating. From this viewpoint, it is preferable that the amount of hydroxy fatty acid ester or its derivative is 25 parts by mass or less per 100 parts by mass of PHB, more preferably 23 parts by mass or less, and more preferably 22 parts by mass or less.

[0034] (Crystal Nucleating Agent) The resin composition of the present invention may optionally further contain a crystal nucleating agent (also simply referred to as "nucleating agent"). By including a crystal nucleating agent in the resin composition of the present invention, the crystallization of the resin can be promoted (or improved), the crystallization rate of the resin composition of the present invention can be further increased, and the crystallinity can be improved.

[0035] Examples of nucleating agents include inorganic substances such as boron nitride, titanium dioxide, talc, layered silicates, calcium carbonate, sodium chloride, and metal phosphates, as well as polyvinyl alcohol, chitin, chitosan, cyclodextrin, polyethylene oxide, aliphatic carboxylic acid amides, aliphatic carboxylic acid salts, aliphatic alcohols, aliphatic carboxylic acid esters, dimethyl adipate, dibutyl adipate, diisodecyl adipate, and dibutyl sebacate, erythritol, galactitol, mannitol, and arabitol, pentaerythritol, melamine cyanurate, and cellulose. However, the list is not limited to these.

[0036] The nucleating agent is preferably blended in a ratio of 0.01 to 5 parts by mass per 100 parts by mass of PHB. A blending amount of nucleating agent of 0.01 parts by mass or more per 100 parts by mass of PHB is preferable because it increases the crystallization rate of the PHB resin composition during molding, making it easier to form fibers. From this viewpoint, the blending amount of nucleating agent is preferably 0.01 parts by mass or more per 100 parts by mass of PHB, more preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more. On the other hand, a blending amount of nucleating agent of 5 parts by mass or less per 100 parts by mass of PHB is preferable because it does not reduce the dispersibility of the resin composition, making it less likely for the fibers to break when formed into fibers. From this viewpoint, the blending amount of nucleating agent is preferably 5 parts by mass or less per 100 parts by mass of PHB, more preferably 4 parts by mass or less, and more preferably 3 parts by mass or less.

[0037] (Biodegradable Resin) The resin composition of the present invention may optionally further contain a biodegradable resin. Examples of such biodegradable resins include polylactic acid, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene succinate, poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(lactate-co-3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polyvinyl alcohol, polyglycolic acid, unmodified starch, modified starch, cellulose acetate, chitosan, etc. However, the invention is not limited to these. These may be used individually or in combination of two or more. Among these, polylactic acid (PLA) is preferred from the viewpoint of further reducing the adhesiveness when the resin composition of the present invention is formed into fibers.

[0038] [PLA] By adding PLA to the resin composition of the present invention, the adhesion to metal parts can be further reduced.

[0039] Polylactic acid (PLA) can be any polyester having lactic acid as a constituent monomer. For example, it can be a homopolymer of D-lactic acid or L-lactic acid, or a copolymer thereof. More specifically, it can be any of the following: poly(D-lactic acid) whose structural unit is D-lactic acid, poly(L-lactic acid) whose structural unit is L-lactic acid, and poly(DL-lactic acid) which is a copolymer of L-lactic acid and D-lactic acid, or a mixed resin thereof. It may also be a mixed resin of multiple copolymers having different copolymerization ratios of D-lactic acid and L-lactic acid.

[0040] The copolymer of L-lactic acid and D-lactic acid described above has a copolymerization ratio of D-lactic acid to L-lactic acid (hereinafter abbreviated as "D / L ratio") preferably of "3 / 97" to "15 / 85" or "85 / 15" to "97 / 3", more preferably of "5 / 95" to "15 / 85" or "85 / 15" to "95 / 5", even more preferably of "8 / 92" to "15 / 85" or "85 / 15" to "92 / 8", and particularly preferably of "10 / 90" to "15 / 85" or "85 / 15" to "90 / 10". It is also possible to blend polylactic acids with different D / L ratios, and blending is more preferable because it makes it easier to adjust the D / L ratio of the polylactic acid. In this case, the average value of the D / L ratios of multiple lactic acid polymers should fall within the above range. By blending two or more polylactic acids with different D / L ratios to adjust their crystallinity, it is possible to achieve a balance between heat resistance and thermal shrinkage properties, depending on the intended use.

[0041] Furthermore, as long as the essential properties of PLA are not impaired, a small amount of copolymerizing component may be copolymerized. Examples of such copolymerizing component include at least one selected from the group consisting of α-hydroxycarboxylic acids other than lactic acid, nonaliphatic dicarboxylic acids such as terephthalic acid, aliphatic dicarboxylic acids such as succinic acid, nonaliphatic diols such as ethylene oxide adducts of bisphenol A, and aliphatic diols such as ethylene glycol.

[0042] The mass-average molecular weight of PLA is preferable if the mass-average molecular weight of the polylactic acid resin is 20,000 or more, as this allows for appropriate resin cohesive force and maintains the film's elongation strength. On the other hand, if the mass-average molecular weight is 400,000 or less, the melt viscosity can be reduced, which is preferable from the viewpoint of manufacturing and productivity improvement. From this viewpoint, the mass-average molecular weight of PLA is preferably 20,000 or more, more preferably 40,000 or more, and more preferably 60,000 or more. On the other hand, it is preferable that it be 400,000 or less, more preferably 350,000 or less, and more preferably 300,000 or less.

[0043] It is preferable to blend PLA in a proportion of 10 to 80 parts by mass with respect to 100 parts by mass of PHB. If the blending amount of PLA is 10 parts by mass or more with respect to 100 parts by mass of PHB, the thermal stability of PHB is improved, which is preferable. From this perspective, the blending amount of PLA is preferably 10 parts by mass or more with respect to 100 parts by mass of PHB, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more. On the other hand, if the blending amount of PLA is 80 parts by mass or less with respect to 100 parts by mass of PHB, the biodegradability is not significantly impaired, which is preferable. From this perspective, the blending amount of PLA is preferably 70 parts by mass or less with respect to 100 parts by mass of PHB, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less.

[0044] (Other components) Various additives can be further blended in the resin composition of the present invention. The addition amounts of these components are not particularly limited as long as the properties of the PHB fibers are not impaired. For example, plasticizers, lubricants, inorganic fillers, antioxidants, ultraviolet absorbers, colorants such as dyes and pigments, antistatic agents, etc. can be mentioned. However, it is not limited to these.

[0045] <Uses> Since the resin composition of the present invention contains PHB as the main component resin, it has biodegradability and biocompatibility, and also has hydrolysis resistance. In addition, it has the characteristic of being rapidly decomposed even under anaerobic conditions such as the bottom mud of lakes. Moreover, the resin composition of the present invention can be plasticized without reducing the crystallization rate, and the adhesiveness can be reduced, so films, fibers, and other molded products can be industrially manufactured. Among them, the resin composition of the present invention can be plasticized without reducing the crystallization rate, and the adhesiveness can be reduced, and it can prevent adhesion to metal parts during fiberization, so it is suitable as a raw material for fibers.

[0046] (The fiber of the present invention) The fiber according to an example of an embodiment of the present invention (referred to as "the fiber of the present invention") is a fiber produced using the resin composition of the present invention as a raw material.

[0047] As a method for producing the fibers of the present invention, currently known melt spinning methods can be employed. Examples include a melt spinning method in which the resin composition of the present invention is melted using a melt extruder, extruded from a spinning nozzle, and then drawn up while being stretched by a traction roll; an in-line stretch spinning method in which, as described above, the material is extruded from a spinning nozzle, drawn up by a traction roll, and then sequentially wound and stretched by multiple rolls that take up at a higher speed, thereby continuously stretching the material; and a spunbond method in which, as described above, the material is extruded from a spinning nozzle, air-stretched with an air ejector, and sprayed onto a take-up roll or belt to obtain a nonwoven fabric. A particularly preferred example is a method that involves melting the resin composition of the present invention, cooling and solidifying the strand-like molten resin to form fibers, winding them onto a paper tube through a metal roller, unwinding them from the paper tube and stretching them, and then heat-treating them before winding them onto the paper tube again. In any of these manufacturing methods, the fibrous resin composition of the present invention does not adhere to metal parts such as metal rollers, so the fibers of the present invention can be manufactured industrially.

[0048] Metal rollers used in the spinning process can be made from materials such as stainless steel, aluminum, copper alloys, titanium alloys, chrome-plated steel, and tool steel. These metals and other metals can be selected according to the operating environment and required characteristics.

[0049] <Explanation of Terms> In this invention, when "α to β" (where α and β are arbitrary numbers) is written, unless otherwise specified, it includes the meaning of "α or greater and β or less," as well as "preferably greater than α" or "preferably less than β." Similarly, when "α or greater" (where α is an arbitrary number) is written, unless otherwise specified, it includes the meaning of "preferably greater than α," and when "β or less" (where β is an arbitrary number) is written, unless otherwise specified, it also includes the meaning of "preferably less than β."

[0050] The following describes an example of an embodiment of the present invention. However, the present invention is not limited to the embodiment described below.

[0051] <Methods for measuring and evaluating physical properties> First, the methods for measuring and evaluating each physical property shown in the examples and comparative examples will be explained.

[0052] (Mass-average molecular weight) The mass-average molecular weight was determined using gel permeation chromatography (HLC-8320GPC, manufactured by Tosoh Bioscience Co., Ltd.), with styrene-divinylbenzene columns (two TSKgel GMHHR-H columns, manufactured by Tosoh Bioscience Co., Ltd.) and chloroform as the mobile phase, expressed as the molecular weight in terms of polystyrene. Calibration curves were created using polystyrene with mass-average molecular weights of 5,430, 37,900, 225,000, 812,000, 3,480,000, 9,760,000, and 20,600,000.

[0053] (Load) The raw materials for each example and comparative example, i.e., the resin and additives, were fed into a small melt extruder (Xplore Instruments "MC15M") and the maximum load recorded by the machine during mixing was measured. In the melt mixing process of this machine, the resin and additives are mixed from top to bottom by a screw inside the machine and returned to the top by a circulation line. At this time, the molten resin becomes a melt viscosity dependent on the resin and additives, and a corresponding shear stress is applied to the screw. Furthermore, the force corresponding to the shear stress applied by the screw in order to mix at a constant speed is detected as a load by a measuring instrument at the bottom of the machine, so the load value was indirectly used as an indicator of melt viscosity.

[0054] (Cold Crystallization Temperature) The cold crystallization temperature of the resin compositions made from the raw materials of each example and comparative example was measured using a differential scanning calorimeter (DSC7020, manufactured by Hitachi High-Tech Science Corporation). Under conditions of heating rate of 10°C / min and cooling rate of 10°C / min, the temperature of the reference substance and the sample was measured during the first heating (30°C to the temperature listed in the table (185°C in Table 1)), isothermal holding for the time listed in the table (e.g., 185°C in Table 1, 5 min), first cooling (temperature listed in the table (185°C in Table 1) to -20°C), and second heating (-20°C to the temperature listed in the table (185°C in Table 1)). In the chart obtained here, the top of the exothermic peak in the DSC calorimeter curve that appears around 100°C in the first cooling region was observed as the cold crystallization temperature.

[0055] (Degree of Crystallinity) The degree of crystallinity of the resin compositions made from the raw materials of each example and comparative example was measured using a differential scanning calorimeter (DSC7020, manufactured by Hitachi High-Tech Science Corporation). Under conditions of heating rate of 10°C / min and cooling rate of 10°C / min, the temperature of the reference substance and the sample was measured during the first heating (30°C to the temperature listed in the table (185°C in Table 1)), isothermal holding for the time listed in the table (e.g., 185°C, 5 min), first cooling (temperature listed in the table (185°C in Table 1) to -20°C), and second heating (-20°C to the temperature listed in the table (185°C in Table 1)). The degree of crystallinity was obtained by dividing the amount of heat of crystallization (heat of crystallization J / g) of the DSC calorimeter curve that appears around 100°C in the first cooling region in the chart obtained here by the generally known heat of crystallization of perfect crystals of PHB (146 J / g).

[0056] (Bleed-out) Bleed-out was evaluated visually by observing the resin surface extracted after mixing in each example and comparative example. ○ (Pass): No liquid is visible on the resin surface. △ (Pass): No liquid is visible on the resin surface, but liquid adheres to the hand when touched. (Small amount of bleed-out) × (Fail): Liquid is clearly visible on the resin surface. (Large amount of bleed-out)

[0057] (TG-TDA Mass Loss Initiation Point) The mass loss initiation point of the resin composition (sample) consisting of the raw materials of each example and comparative example was determined by measuring the reference substance and the sample in the range of 40 to 500°C using a thermal mass differential thermal analyzer (STA7200, Hitachi High-Tech Science Corporation) at a heating rate of 10°C / min. The temperature at which the mass loss begins was defined as the "mass loss initiation point (°C)," and the temperature at which the total mass of the sample has decreased by 1 wt% was defined as the "1% mass loss point (°C)."

[0058] (Yarn Adhesion) In Examples 1 to 18 and Comparative Examples 1 to 6, a jig (made of SUS304) was brought into contact with the surface of the yarn immediately after molding, and the "yarn adhesion" was evaluated according to the following criteria by checking whether the yarn was pulled by the jig. ◎ (Pass): Not pulled at all. 〇 (Pass): Pulled slightly, but quickly detaches. △ (Fail): Pulled, but detaches when attempted to pull apart. × (Fail): Cannot be detached even when attempted to pull apart.

[0059] (Strand Adhesion) The raw materials for each example and comparative example, i.e., the resin and additives, were fed into a twin-screw molten extruder (Toyo Seiki "Laboplast Mill 3S150" and "Small Twin-Screw Segment Extruder 2D15W"), and the molten and kneaded strands were continuously extruded. Ten minutes after the start of extrusion, a jig (made of SUS304) was brought into contact with the surface of the strand, and the "strand adhesion" was evaluated according to the following criteria to see if the strand was pulled by the jig. ○ (Pass): It is pulled slightly, but quickly separates. △ (Fail): It is pulled, but separates when attempted to separate. × (Fail): It does not separate even when attempted to separate.

[0060] (Adhesion of the thread after quenching) In Examples 19 to 21, the "adhesion of the thread after quenching" was evaluated according to the following criteria by checking whether the thread was pulled by the metal (aluminum) traction roller. ○ (Pass): Does not adhere to the metal roller and detaches immediately. △ (Fail): Adheres weakly to the metal roller but detaches without breaking the thread. × (Fail): Adheres strongly to the metal roller and breaks the thread.

[0061] <Examples 1-3 and Comparative Example 1> The following raw materials were put into a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and kneaded for 10 minutes at the temperatures shown in the table below, and after melting and kneading, a 1 cm strand was extruded from the outlet of the kneading device, i.e., the discharge port, and then vigorously pulled with a jig to form a thread-like shape.

[0062] • PHB (Mw: 510,000) • Polyglycerin unsaturated fatty acid ester (polyglycerin oleate ester, "Tirabazole VR-01" manufactured by Taiyo Kagaku Co., Ltd., degree of polymerization 10)

[0063]

[0064] (Discussion) It was found that by adding polyglycerol oleate ester to PHB, PHB can be plasticized without reducing the crystallization rate. It was also found that the adhesion to metal parts decreased, as did the load during melt mixing. The lower limit of the amount of polyglycerol oleate ester to add is considered to be around 0.5% by mass.

[0065] <Examples 1, 4-6 and Comparative Examples 2-3> The following raw materials were put into a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and kneaded at 175°C for 10 minutes, and after melting and kneading, a 1 cm strand was extruded from the outlet of the kneading device, i.e., the discharge port, and then vigorously pulled with a jig to form a thread-like shape.

[0066] • PHB (Mw: 510,000) • Polyglycerin unsaturated fatty acid ester (polyglycerin oleate ester, manufactured by Taiyo Kagaku Co., Ltd. "Tirabazole VR-01", degree of polymerization 10) • Polyglycerin unsaturated fatty acid ester (polyglycerin decaoleate ester, manufactured by Sakamoto Pharmaceutical Co., Ltd. "SY Glister DAO-7S", degree of polymerization 10) • Polyglycerin unsaturated fatty acid ester (polyglycerin pentaoleate ester, manufactured by Sakamoto Pharmaceutical Co., Ltd. "SY Glister PO-3S", degree of polymerization 4) • Polyglycerin unsaturated fatty acid ester (polyglycerin pentaoleate ester, manufactured by Sakamoto Pharmaceutical Co., Ltd. "SY Glister PO-5S", degree of polymerization 6) • Fatty acid ester (isobutyl oleate, degree of polymerization 1) • Fatty acid ester (glyceryl stearate, degree of polymerization 1)

[0067]

[0068] (Discussion) It was found that in PHB resin compositions to which isobutyl oleate or glyceryl stearate is added, the fibrous threads adhere to SUS304, but in PHB resin compositions to which polyglyceryl oleate, an unsaturated fatty acid polyglyceryl, is added, the fibrous threads do not adhere to SUS304 easily.

[0069] <Example 7 and Comparative Example 4> The following raw materials were put into a small melting extruder in the mass ratios shown in the table below, melted and kneaded at 175°C for 10 minutes, and extruded in a strand shape from the outlet of the kneading device, and then pulled vigorously by hand to form a thread.

[0070] • PHB (Mw: 510,000) • Polyglycerin unsaturated fatty acid ester (polyglycerin oleate ester, "Tirabazole VR-01" manufactured by Taiyo Kagaku Co., Ltd., degree of polymerization 10)

[0071]

[0072] (Discussion) In a composition in which polyglyceryl ester of stearic acid, a saturated fatty acid, is added to PHB, the resulting fibers adhere to SUS304. However, in a composition in which polyglyceryl ester of oleic acid, an unsaturated fatty acid, is added to PHB, the crystallization rate increases, and the fibers can be formed without adhering to SUS304.

[0073] <Examples 8-12 and Comparative Examples 5-7> The following raw materials were put into a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and kneaded at 175°C for 10 minutes, and after melting and kneading, a 1 cm strand was extruded from the outlet of the kneading device, i.e., the discharge port, and then vigorously pulled with a jig to form a thread-like shape.

[0074] • PHB (Mw: 1.83 million) • PHB (Mw: 2.13 million) • Polyglycerin unsaturated fatty acid ester (polyglycerin pentaoleate, "SY Glister PO-3S" manufactured by Sakamoto Pharmaceutical Co., Ltd., degree of polymerization 4) • Acetyl triethyl citrate ("CITROFOL AII" manufactured by Jungbunzlauer) or acetyl tributyl citrate ("CITROFOL BII" manufactured by Jungbunzlauer)

[0075]

[0076] (Discussion) PHB with a mass-average molecular weight exceeding 1.5 million has a high melt viscosity and places a strong load on the apparatus. However, it was found that adding polyglyceryl oleate and O-acetyl citrate reduces the melt viscosity and makes it easier to form fibers, allowing the yarn to be formed without adhering to SUS304.

[0077] <Examples 13-18> The following raw materials were put into a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and kneaded at 175°C for 10 minutes, and after melting and kneading, a 1 cm strand was extruded from the outlet of the kneading device, i.e., the discharge port, and then vigorously pulled with a jig to form a thread-like shape.

[0078] • PHB (Mw: 430,000) • Polyglycerin unsaturated fatty acid ester (polyglycerin pentaoleate, manufactured by Sakamoto Pharmaceutical Co., Ltd. "SY Glister PO-3S", degree of polymerization 4) • Polyglycerin unsaturated fatty acid ester (polyglycerin ricinoleate, manufactured by Sakamoto Pharmaceutical Co., Ltd. "SY Glister CRS-75", degree of polymerization 6) • Polyglycerin unsaturated fatty acid ester (polyglycerin ricinoleate, manufactured by Taiyo Kagaku Co., Ltd. "Tirabazole D-818M", degree of polymerization 6) • Nucleating agent (talc, manufactured by Nippon Talc Co., Ltd. "D-600", average particle size 0.6 μm, specific surface area 24 m²) ２ / g) • Nucleating agent (talc, "D-800" manufactured by Nippon Talc Co., Ltd., average particle size 0.8 μm, specific surface area 21 m²) ２ ( / g) • Nucleating agent (boron nitride, "AP-100S" manufactured by MARUKA Corporation, average particle size 3.0 μm, specific surface area 50 m²) ２ / g) • Nucleating agent (melamine cyanurate, Nissan Chemical Corporation "MC-6000", average particle size 2.0 μm)

[0079]

[0080] (Discussion) It was found that polyglyceryl ricinoleate, as an unsaturated fatty acid ester, also produced the desired effect.

[0081] <Example 19> The following raw materials were put into a twin-screw molten extruder in the mass ratios shown in the table below, and melted and kneaded at the temperatures shown in the table below for 10 minutes to produce pellets of PHB resin composition. The obtained pellets were put into an ultra-small single-screw molten extruder (AIKI Riotec "ALM-E10-ALT"), melted and kneaded at 175°C for 10 minutes, and strand-shaped molten resin was extruded from a Φ1 mm single-hole spinning nozzle to form yarn. Next, the extruded yarn was passed through a 30°C water bath for 5 seconds, wound three times around a metal (aluminum) traction roller, and then wound onto a paper tube.

[0082] • PHB (Mw: 1.42 million) • Polyglycerin unsaturated fatty acid ester (polyglycerin oleate ester, "Tirabazole VR-01" manufactured by Taiyo Kagaku Co., Ltd., degree of polymerization 10)

[0083]

[0084] (Discussion) We confirmed that monofilaments can be spun by adding polyglyceryl oleate to PHB. It was found that adding polyglyceryl oleate to PHB suppresses adhesion to metal and allows for processing without impairing moldability in both pellet molding of the PHB resin composition and monofilament spinning.

[0085] <Examples 20-21> 96.9 wt% of the following PHB, 3.0 wt% of the following polyglycerin unsaturated fatty acid ester, and 0.1 wt% of the following nucleating agent were put into a twin-screw molten extruder and melted and kneaded at 175°C for 10 minutes to produce PHB-containing pellets. The obtained PHB-containing pellets and the following PLA were put into an ultra-small single-screw molten extruder (AIKI Riotec "ALM-E10-ALT") in the mass ratios shown in the table below and melted and kneaded at 175°C for 10 minutes. The strand-shaped molten resin was extruded from a Φ1 mm single-hole spinning nozzle to form yarn. Next, the extruded yarn was continuously passed through a 30°C water bath for 5 seconds, wound around a metal traction roller three times, and then wound onto a paper tube.

[0086] • PHB (Mw: 200,000) • Polyglycerin unsaturated fatty acid ester (polyglycerin oleate ester, "Tirabazole VR-01" manufactured by Taiyo Kagaku Co., Ltd., degree of polymerization 10) • Nucleating agent (melamine cyanurate, "MC-6000" manufactured by Nissan Chemical Corporation, average particle size 2.0 μm) • PLA (polylactic acid, "L-105" manufactured by Maeda Kasei Co., Ltd., Mw 170,000, melting point 170-180°C, Tg 55-60)

[0087]

[0088] (Discussion) It was found that the adhesion of the thread further decreases when PLA is added.

Claims

1. A resin composition comprising poly(3-hydroxybutyric acid) (also referred to as "PHB") and polyglycerin unsaturated fatty acid esters.

2. The resin composition according to claim 1, comprising 1 to 10 parts by mass of polyglycerin unsaturated fatty acid ester per 100 parts by mass of PHB.

3. The resin composition according to claim 1, further comprising a hydroxy fatty acid ester or a derivative thereof.

4. The resin composition according to claim 1, further comprising a crystal nucleating agent.

5. The resin composition according to claim 1, further comprising polylactic acid (also referred to as "PLA").

6. A fiber comprising the resin composition according to any one of claims 1 to 5.

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