Resin compositions and fibers containing poly(3-hydroxybutyric acid)

Abstract

The present invention provides a new resin composition containing PHB that can prevent adhesion to metal parts during fiber formation. [Solution] A resin composition containing poly(3-hydroxybutyric acid) (also referred to as "PHB") and polyglycerin unsaturated fatty acid ester.

Description

Technical Field

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

Background Art

[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), which is produced by bacteria inhabiting the sea and 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] PHB possesses biodegradability and biocompatibility, is insoluble in water, is resistant to hydrolysis, and has characteristics that differ from conventional biodegradable plastics that are susceptible to moisture. Furthermore, while many biodegradable resins only decompose effectively under aerobic conditions, PHB decomposes rapidly even under anaerobic conditions such as lake bottom sediment. For this reason, PHB is being considered for use in various molded products such as fibers and films. In particular, fibers made from PHB are expected to be in high demand as medical devices such as surgical sutures, fishing equipment such as fishing lines and nets, clothing materials such as fibers, building materials such as nonwoven fabrics and ropes, and packaging materials for food and other products, due to their biodegradability and biocompatibility.

[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, wherein the PHB is 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. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 8-158158 [Patent Document 2] International Publication No. WO2006 / 038373 [Patent Document 3] International Publication No. 2014 / 020838 [Patent Document 4] International Publication No. 2017 / 122679 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] One method for producing 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 using metal rollers, unwinding them from the paper tube and 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 could be increased, problems such as the resin composition adhering to the metal roller and causing thread breakage occurred, for example, when the resin composition was melt-extruded, the strand-like molten resin was cooled and solidified to form fibers, and then wound 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. [Means for solving the problem]

[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 comprising a crystal nucleating agent in any one of the first to third aspects. [5] A fifth aspect of the present invention is a resin composition comprising the resin composition of 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. [Effects of the Invention]

[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.

Mode for Carrying Out the Invention

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

[0018] <The 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 containing poly(3-hydroxybutyric acid) (PHB) and polyglycerol unsaturated fatty acid ester.

[0019] (PHB) The method for producing and obtaining PHB is arbitrary. It is possible to produce it by a known method, or commercially available PHB can also be used.

[0020] Examples of the method for producing PHB include, for example, a fermentation synthesis method in which a microorganism having PHB-producing ability is cultured and PHB accumulated in the cells is recovered, and a poly(-3-hydroxybutyric acid) homopolymer can be obtained by such a method. Examples of microorganisms having PHB-producing ability, that is, PHB-producing bacteria include, for example, Bacillus megaterium, Cupriavidus necator (formerly classified: Alcaligenes eutrophus, Ralstonia eutropha), Alcaligenes latus, and the like. Among them, strains of bacterial species belonging to the genus Methylobacterium, specifically Methylobacterium extorquens ATCC55366, can be mentioned as those 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, if necessary, other organic components. Methods for recovering PHB from the cells include extraction with an organic solvent such as chloroform, or decomposing the cell components with an enzyme such as lysozyme and then filtering off the PHB granules. Another method of fermentation synthesis 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 direct cultivation of Ralstonia eutropha, the transformed microorganisms 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 interfere with 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 can be maintained when it is fiberized. From this viewpoint, it is preferable that the mass-average molecular weight (Mw) of PHB is 50,000 or more, more preferably 100,000 or more, and even 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 processability can be maintained and fiberization does not become difficult. From this viewpoint, it is preferable that the mass-average molecular weight (Mw) of PHB is 5,000,000 or less, more preferably 4,000,000 or less, and even 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] (Polyglycerol 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] A polyglycerol unsaturated fatty acid ester can be any ester formed from polyglycerol and an unsaturated fatty acid. The unsaturated fatty acids constituting the above polyglycerol unsaturated fatty acid ester are not particularly limited as long as they are fatty acids containing double bonds in the bonds between carbon atoms. Examples include palmitoleic acid, oleic acid, elaidic acid, linoleic acid, γ-linolenic acid, α-linolenic acid, arachidonic acid, ricinoleic acid, condensed ricinoleic acid, and the like. Among these, from the viewpoint of further reducing the adhesiveness when the resin composition of the present invention is formed 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 polyglycerol unsaturated fatty acid ester is preferably 3 to 9, and more preferably 6 or higher or 8 or lower. When the HLB value of the polyglycerin unsaturated fatty acid ester is within the above range, a favorable balance of lipophilicity and hydrophilicity is achieved in the resin composition.

[0030] Polyglycerin unsaturated fatty acid ester is preferably blended in a ratio of 1 to 10 parts by mass per 100 parts by mass of PHB. A blending amount of polyglycerin unsaturated fatty acid ester of 1 part by mass or more per 100 parts by mass of PHB is preferable because it reduces the adhesion of PHB. From this viewpoint, the blending amount of polyglycerin unsaturated fatty acid ester is preferably 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 blended is 10 parts by mass or less per 100 parts by mass of PHB, as this suppresses bleed-out, and more preferably 7 parts by mass or less, and even more preferably 4 parts by mass or less.

[0031] (Hydroxy fatty acid esters or their derivatives) The resin composition of the present invention may optionally further contain hydroxy fatty acid esters or derivatives thereof. By further including a hydroxy fatty acid ester or a derivative thereof in the resin composition of the present invention, it is possible to lower the melt viscosity and further increase fluidity, as well as improve stringability. For example, when the resin composition of the present invention is made into fibers, it becomes possible to wind it at a higher speed.

[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 their spinnability.

[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, as this 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 even more preferably 3 parts by mass or more. On the other hand, if the amount of hydroxy fatty acid ester or its derivative is 25 parts by mass or less per 100 parts by mass of PHB, it is preferable because the mass loss during heating is suppressed. From this viewpoint, the amount of hydroxy fatty acid ester or its derivative is preferably 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] (Crystallizing agent) The resin composition of the present invention may optionally further contain a nucleating agent (also simply referred to as "nucleating agent"). The inclusion of a nucleating agent in the resin composition of the present invention can promote (or improve) the crystallization of the resin, further increasing the crystallization rate of the resin composition and improving its crystallinity.

[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 added in a ratio of 0.01 to 5 parts by mass per 100 parts by mass of PHB. A crystal nucleating agent is preferable if its concentration is 0.01 parts by mass or more per 100 parts by mass of PHB, as this increases the crystallization rate of the PHB resin composition during molding, making it easier to form fibers. From this viewpoint, it is preferable that the concentration of the crystal nucleating agent be 0.01 parts by mass or more per 100 parts by mass of PHB, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more. On the other hand, if the amount of nucleating agent is 5 parts by mass or less per 100 parts by mass of PHB, the dispersibility of the resin composition does not decrease, which is preferable because the fibers are less likely to break when fiberized. From this viewpoint, the 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 even 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 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 list is not limited to these. These can 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 preferable because it makes it easier to adjust the D / L ratio of the polylactic acids. In this case, the average D / L ratio of multiple lactic acid polymers should fall within the above range. Depending on the application, a balance between heat resistance and thermal shrinkage properties can be achieved by blending two or more polylactic acids with different D / L ratios and adjusting their crystallinity.

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

[0042] A PLA with a mass-average molecular weight of 20,000 or more is preferable because it allows for adequate resin cohesive force and maintains the film's elongation strength. On the other hand, a mass-average molecular weight of 400,000 or less is preferable from the viewpoint of manufacturing and productivity improvement because it allows for a reduction in melt viscosity. From this viewpoint, the mass-average molecular weight of PLA is preferably 20,000 or more, more preferably 40,000 or more, and even 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 even more preferably 300,000 or less.

[0043] It is preferable to blend PLA in a ratio of 10 to 80 parts by mass per 100 parts by mass of PHB. A PLA content of 10 parts by mass or more per 100 parts by mass of PHB is preferable because it improves the thermal stability of the PHB. From this viewpoint, a PLA content of 10 parts by mass or more per 100 parts by mass of PHB is preferable, and more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more. On the other hand, if the amount of PLA is 80 parts by mass or less per 100 parts by mass of PHB, the biodegradability is not significantly impaired, which is preferable. From this viewpoint, the amount of PLA is preferably 70 parts by mass or less per 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 ingredients) The resin composition of the present invention can further contain various additives. The amount of these components added is not particularly limited, as long as it does not impair the properties of the PHB fibers. Examples include plasticizers, lubricants, inorganic fillers, antioxidants, UV absorbers, colorants such as dyes and pigments, and antistatic agents. However, it is not limited to these.

[0045] <Application> The resin composition of the present invention contains PHB as its main component resin, and therefore possesses biodegradability and biocompatibility, as well as resistance to hydrolysis. Furthermore, it has the characteristic of rapidly decomposing even under anaerobic conditions such as lake bottom sediment. Moreover, the resin composition of the present invention can be plasticized without reducing the crystallization rate, and its adhesiveness can be reduced, making it possible to industrially manufacture films, fibers, and other molded products. In particular, the resin composition of the present invention is suitable as a raw material for fibers because it can be plasticized without reducing the crystallization rate, and its adhesiveness can be reduced, preventing it from adhering to metal parts when it is fiberized.

[0046] (The fiber of the present invention) A fiber according to an example of an embodiment of the present invention (referred to as "the fiber of the present invention") is a fiber manufactured 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, after being extruded from a spinning nozzle as described above, it is 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 it; and a spunbond method in which, after being extruded from a spinning nozzle as described above, it is air-stretched with an air ejector and sprayed onto a take-up roll or belt to obtain a nonwoven fabric. One particularly preferred example is a manufacturing 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 either manufacturing method, the resin composition of the present invention does not adhere to metal parts such as metal rollers when fibrous, thus enabling the industrial production of the fibers of the present invention.

[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, etc.> In this invention, when "α~β" (where α and β are arbitrary numbers) is written, unless otherwise specified, it means "α or greater and β or less," and also includes the meaning of "preferably greater than α" or "preferably less than β." Furthermore, when "α or greater" (where α is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than α," and when "β or less" (where β is any number) is written, unless otherwise specified, it also includes the meaning of "preferably less than β." [Examples]

[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, we will explain the measurement methods and evaluation methods for each physical property value shown in the examples and comparative examples.

[0052] (mass average molecular weight) The mass-average molecular weight was determined using gel permeation chromatography (HLC-8320GPC, Tosoh Bioscience Co., Ltd.), with styrene-divinylbenzene columns (two TSKgel GMHHR-H, Tosoh Bioscience Co., Ltd.) and chloroform as the mobile phase, expressed as the molecular weight in polystyrene equivalent. 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, namely the resin and additives, were placed in a small melt extruder (Xplore Instruments "MC15M"), and the maximum load recorded by the machine during mixing was measured. During the melting and mixing process of this equipment, the resin and additives are mixed from top to bottom by a screw inside the equipment and then returned to the top via a circulation line. At this time, the molten resin acquires a 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 to mix at a constant speed is detected as a load by a measuring instrument at the bottom of the equipment, and therefore the value of the load was indirectly used as an indicator of the 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, Hitachi High-Tech Science Corporation). Under conditions of heating rate of 10°C / min and cooling rate of 10°C / min, the temperatures of the reference substance and the sample were 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 heat of exothermic reaction (heat of crystallization J / g) of the DSC calorimeter curve appearing around 100°C in the first cooling region of the chart obtained by the generally known heat of crystallization of perfect crystals of PHB (146 J / g).

[0056] (Bleedout) Bleed-out was evaluated visually by observing the resin surface extracted after kneading 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) × (Failure): Liquid is clearly visible on the resin surface. (Large amount of bleed-out)

[0057] (TG-TDA mass reduction starting 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 decreased by 1 wt% was defined as the "1% mass loss point (°C)."

[0058] (The adhesive properties of the thread) In Examples 1-18 and Comparative Examples 1-6, a jig (made of SUS304) was brought into contact with the surface of the yarn immediately after molding, and the "adhesion of the yarn" was evaluated according to the following criteria by checking whether the yarn was pulled by the jig. ◎ (Pass): Not affected at all. ○ (Pass): There is a slight pull, but it quickly releases. △ (Failure): It pulls, but it lets go when you try to pull it away. × (Failure): They won't let go no matter how hard you try to separate them.

[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 adhesion of the strand was evaluated according to the following criteria by checking whether the strand was pulled by the jig. ○ (Pass): There is a slight pull, but it quickly releases. △ (Failure): It pulls, but it lets go when you try to pull it away. × (Failure): They won't let go no matter how hard you try to separate them.

[0060] (Yarn adhesion after quenching) In Examples 19-21, we checked whether the thread was pulled by a metal (aluminum) traction roller and evaluated the "adhesion of the thread after quenching" according to the following criteria. ○ (Pass): Does not adhere to the metal roller and detaches immediately. △ (Failure): It adheres weakly to the metal roller, but detaches without breaking the thread. × (Failure): The thread breaks due to strong adhesion to the metal roller.

[0061] <Examples 1-3 and Comparative Example 1> The raw materials listed below were placed in a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and mixed for 10 minutes at the temperatures shown in the table below, and after melting and mixing, a 1 cm strand was extruded from the outlet of the mixing 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] [Table 1]

[0064] (Consideration) It was found that adding polyglycerol oleate ester to PHB allows for plasticization of PHB without reducing the crystallization rate. Furthermore, it was found that this reduces adhesion to metal parts and also lowers the load during melt mixing. The lower limit for the amount of polyglycerin oleate added is considered to be around 0.5% by mass.

[0065] <Examples 1, 4-6 and Comparative Examples 2-3> The raw materials listed below were placed in a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and mixed at 175°C for 10 minutes, and after melting and mixing, a 1 cm strand was extruded from the outlet of the mixing 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, "Tirabazole VR-01" manufactured by Taiyo Kagaku Co., Ltd., 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] [Table 2]

[0068] (Consideration) It was found that while PHB resin compositions containing isobutyl oleate or glyceryl stearate result in the fibrous threads adhering to SUS304, PHB resin compositions containing polyglyceryl oleate, an unsaturated fatty acid polyglyceryl, result in less adhesion of the fibrous threads to SUS304.

[0069] <Example 7 and Comparative Example 4> The raw materials listed below were placed in a small melting extruder in the mass ratios shown in the table below, melted and mixed at 175°C for 10 minutes, and then extruded in a strand-like manner from the outlet of the mixing device. The mixture was then pulled vigorously by hand to form a thread-like material.

[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] [Table 3]

[0072] (Consideration) In a composition in which polyglyceryl ester of stearic acid, a saturated fatty acid, was added to PHB, the resulting fibers adhered to SUS304. However, in a composition in which polyglyceryl ester of oleic acid, an unsaturated fatty acid, was added to PHB, the crystallization rate increased, and it was found that the fibers could be formed without adhering to SUS304.

[0073] <Examples 8-12 and Comparative Examples 5-7> The raw materials listed below were placed in a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and mixed at 175°C for 10 minutes, and after melting and mixing, a 1 cm strand was extruded from the outlet of the mixing 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 ester, "SY Glystar PO-3S" manufactured by Sakamoto Pharmaceutical Co., Ltd., degree of polymerization 4) • Acetyl triethyl citrate (Jungbunzlauer "CITROFOL AII") or acetyl tributyl citrate (Jungbunzlauer "CITROFOL BII")

[0075] [Table 4]

[0076] (Consideration) PHB with a mass-average molecular weight exceeding 1.5 million has a high melt viscosity and places a heavy 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 fibers to be formed without adhering to SUS304.

[0077] <Examples 13-18> The raw materials listed below were placed in a small melt extruder (Xplore Instruments "MC15M") in the mass ratios shown in the table below, melted and mixed at 175°C for 10 minutes, and after melting and mixing, a 1 cm strand was extruded from the outlet of the mixing 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 ester, "SY Glystar PO-3S" manufactured by Sakamoto Pharmaceutical Co., Ltd., degree of polymerization 4) • Polyglycerin unsaturated fatty acid ester (polyglycerin ricinoleate ester, "SY Glister CRS-75" manufactured by Sakamoto Pharmaceutical Co., Ltd., degree of polymerization 6) • Polyglycerin unsaturated fatty acid ester (polyglycerin ricinoleate ester, "Tirabazole D-818M" manufactured by Taiyo Kagaku Co., Ltd., degree of polymerization 6) • Nucleating agent (talc, "D-600" manufactured by Nippon Talc Co., Ltd., 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] [Table 5]

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

[0081] <Example 19> The raw materials listed below were fed 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 fed into a miniature single-screw extruder (AIKI Riotec "ALM-E10-ALT"), melted and kneaded at 175°C for 10 minutes, and the molten resin was extruded in strand form from a Φ1mm 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] [Table 6]

[0084] (Consideration) We confirmed that monofilaments can be spun by adding polyglyceryl oleate to PHB. It was found that adding polyglyceryl oleate to PHB allows for processing of PHB resin compositions in pellet molding and monofilament spinning without suppressing adhesion to metals or impairing moldability.

[0085] <Examples 20-21> 96.9 wt% of the following PHB, 3.0 wt% of the following polyglycerol unsaturated fatty acid ester, and 0.1 wt% of the following nucleating agent were placed in a twin-screw fusion extruder and melted and kneaded at 175°C for 10 minutes to produce PHB-containing pellets. The obtained PHB-containing pellets and the PLA listed below were fed into a miniature single-screw extruder (AIKI Riotec "ALM-E10-ALT") in the mass ratio shown in the table below, melted and kneaded at 175°C for 10 minutes, and the molten resin was extruded in strand form 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 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, Nissan Chemical Corporation "MC-6000", average particle size 2.0 μm) • PLA (polylactic acid, manufactured by Maeda Chemicals Co., Ltd., "L-105", Mw 170,000, melting point 170-180℃, Tg 55-60)

[0087] [Table 7]

[0088] (Consideration) It was found that incorporating PLA further reduced the adhesive properties of the thread.

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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