Poly(3-hydroxybutyrate)-based resin tube and method for producing the same

Abstract

The purpose of the present invention is to provide: a poly(3-hydroxybutyrate)-based resin tube which exhibits excellent resistance to repeated bending; and a method for producing this poly(3-hydroxybutyrate)-based resin tube. The above are achieved by providing a poly(3-hydroxybutyrate)-based resin tube which contains from 95% to 65% by weight of a poly(3-hydroxybutyrate)-based resin and from 5% to 40% by weight of an aliphatic-aromatic polyester resin, while having an elongation at yield point in a tensile test, a tensile elongation of 50% or more in the tensile test and a thickness of from 0.01 to 0.6 mm.

Description

Technical Field

[0001] The present invention relates to a poly(3-hydroxybutyrate)-based resin tube and a method for producing the same.

Background Art

[0002] In recent years, the separation and recycling of food waste and composting have been promoted mainly in Europe, and plastic products that can be composted together with food waste are desired. As an example of such a plastic product, a tubular molded article (tube) such as a straw mainly composed of polylactic acid has been disclosed.

[0003] However, although polylactic acid can be biodegradable in compost, it cannot be expected to decompose in a short period in the ocean where the temperature is low, so there is a problem that it cannot be a countermeasure against marine pollution.

[0004] In response to this problem, poly(3-hydroxybutyrate)-based resin (hereinafter, may be abbreviated as "P3HB-based resin") is a thermoplastic polyester that is produced and accumulated as an energy storage substance in the cells of many microbial species, and is a material that can undergo biodegradation not only in soil but also in seawater. Therefore, it has attracted attention as a material to solve the above problems.

[0005] For example, Patent Document 1 discloses a tubular molded article composed of a P3HB-based resin, an aliphatic polyester-based resin, and an inorganic filler.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, it has been found that the tubular molded article disclosed in Patent Document 1 has room for improvement in repeated bending resistance because it contains an inorganic filler. In this case, for example, there is a problem that bellows processing at room temperature is difficult.

[0008] Therefore, one aspect of the present invention aims to provide a P3HB-based resin tube containing a P3HB-based resin that is a material biodegradable in seawater and having improved properties, and a method for manufacturing the same.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that in a P3HB-based resin tube, which is a material biodegradable in seawater, by including a specific resin in a specific blending ratio, bellows processing at room temperature is possible, and a novel finding that a P3HB-based resin tube excellent in repeated bending resistance can be obtained, and thus the present invention has been completed.

[0010] Therefore, one aspect of the present invention is a poly(3-hydroxybutyrate)-based resin tube containing 95 to 60% by weight of a poly(3-hydroxybutyrate)-based resin and 5 to 40% by weight of an aliphatic-aromatic polyester-based resin, having a yield point elongation in a tensile test, and having a tensile elongation of 50% or more in the tensile test, and having a wall thickness of 0.01 to 0.6 mm.

Effects of the Invention

[0011] According to one aspect of the present invention, it is possible to provide a P3HB-based resin tube capable of bellows processing at room temperature and excellent in repeated bending resistance, and a method for manufacturing the same.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0013] One embodiment of the present invention will be described in detail below. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more and B or less". Also, all the documents described in this specification are incorporated herein by reference.

[0014] 〔1. Outline of the Present Invention〕 A poly(3-hydroxybutyrate)-based resin tube (hereinafter referred to as "this tube") according to one embodiment of the present invention contains 95 to 60% by weight of a poly(3-hydroxybutyrate)-based resin and 5 to 40% by weight of an aliphatic-aromatic polyester-based resin, has a yield point elongation in a tensile test, and has a tensile elongation of 50% or more in the tensile test, and is characterized in that the wall thickness is 0.01 to 0.6 mm.

[0015] P3HB-based resins generally have the characteristic that when heated and plasticized, it is difficult to maintain their shape, and it is difficult to achieve both shape maintenance by heating and moldability, and there is a problem of poor secondary processability. Therefore, as a result of previous studies by the present inventors, by using a P3HB-based resin showing specific melting point behavior, a P3HB-based resin tube that is easily deformable, can be suitably used as a straw, and can be rapidly decomposed even in seawater has been successfully developed.

[0016] However, in further detailed studies on P3HB-based resin tubes, it has been found that the above P3HB-based resin tubes are difficult to bellows process at room temperature, and furthermore, there are new problems in repeated bending resistance.

[0017] Therefore, as a result of intensive studies on P3HB-based resin tubes, the present inventors have found that by including a P3HB-based resin and an aliphatic-aromatic polyester-based resin in a specific blending ratio, (1) it is possible to perform bellows processing at room temperature and obtain a P3HB-based resin tube having excellent repeated bending resistance, and (2) a film formed from resin pellets containing a mixture of a P3HB-based resin and an aliphatic-aromatic polyester-based resin has a yield point elongation and further has a high tensile elongation, for the first time.

[0018] The disclosure of a P3HB-based resin tube having the above characteristics is novel, and the present invention is extremely useful in various fields of use.

[0019] 〔2. Poly(3-hydroxybutyrate)-based resin tube〕 (Poly(3-hydroxybutyrate)-based resin) This tube contains a poly(3-hydroxybutyrate)-based resin.

[0020] In the present specification, the P3HB-based resin is an aliphatic polyester resin that can be produced from microorganisms and has 3-hydroxybutyrate as a repeating unit.

[0021] In one embodiment of the present invention, the P3HB-based resin may be poly(3-hydroxybutyrate) having only 3-hydroxybutyrate as a repeating unit, or a copolymer of 3-hydroxybutyrate and another hydroxyalkanoate.

[0022] In one embodiment of the present invention, the P3HB-based resin may be a mixture of a homopolymer and one or more copolymers, or a mixture of two or more copolymers. The form of copolymerization is not particularly limited and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, or the like.

[0023] In one embodiment of the present invention, examples of the P3HB-based resin include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (P3HB3HD), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), and the like. Among them, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially.

[0024] Also, by changing the composition ratio of the repeating units, the melting point and crystallinity can be changed, and as a result, physical properties such as Young's modulus and heat resistance can be changed, and it is possible to impart physical properties between polypropylene and polyethylene. From the viewpoint that it is easy to produce industrially as described above and is a physically useful resin, P3HB3HH, which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred. In particular, among P3HB-based resins having the property of being easily thermally decomposed under heating at 180°C or higher, P3HB3HH is also preferred from the viewpoint that it can lower the melting point and enables molding processing at low temperatures.

[0025] The melting point, Young's modulus, etc. of the above P3HB3HV change depending on the ratio of the 3-hydroxybutyrate component and the 3-hydroxyvalerate component. However, since both components co-crystallize, the crystallinity is as high as 50% or more. Therefore, although P3HB3HV is softer than P3HB, the improvement of brittleness is insufficient.

[0026] P3HB-based resins can be produced, for example, by microorganisms. The microorganisms for producing P3HB-based resins are not particularly limited as long as they have the ability to produce P3HB-based resins. For example, as P3HB-producing bacteria, Bacillus megaterium discovered in 1925 was the first, and other natural microorganisms such as Cupriavidus necator (formerly classified: Alcaligenes eutrophus, Ralstonia eutropha), Alcaligenes latus, etc. are also included. It is known that P3HB accumulates in the cells of these microorganisms.

[0027] In addition, as bacteria for producing copolymers of hydroxybutyrate and other hydroxyalkanoates, Aeromonas caviae, which is a P3HB3HV and P3HB3HH-producing bacterium, Alcaligenes eutrophus, which is a P3HB4HB-producing bacterium, etc. are known. In particular, regarding P3HB3HH, in order to increase the productivity of P3HB3HH, strains such as Alcaligenes eutrophus AC32 strain (Alcaligenes eutrophus AC32, FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)), into which genes of the P3HA synthase group have been introduced, are more preferable, and microbial cells in which P3HB3HH has been accumulated in the cells by culturing these microorganisms under appropriate conditions are used. In addition to the above, depending on the P3HB-based resin to be produced, genetically modified microorganisms into which various P3HB-based resin synthesis-related genes have been introduced may be used, or the culture conditions including the type of substrate may be optimized.

[0028] In addition, P3HB3HH can also be produced, for example, by the method described in International Publication No. 2010 / 013483. Examples of commercially available P3HB3HH include "Kaneka Biodegradable Polymer PHBH (registered trademark)" of Kaneka Corporation (for example, X131A and 151C used in the examples).

[0029] In one embodiment of the present invention, from the viewpoint of the balance between flexibility and strength, the composition ratio of the repeating units of P3HB3HH is preferably such that the composition ratio of 3-hydroxybutyrate units / 3-hydroxyhexanoate units is 80 / 20 to 99 / 1 (mol / mol), more preferably 85 / 15 to 97 / 3 (mol / mol). When the composition ratio of 3-hydroxybutyrate units / 3-hydroxyhexanoate units is 99 / 1 (mol / mol) or less, sufficient flexibility can be obtained, and when it is 80 / 20 (mol / mol) or more, sufficient hardness can be obtained.

[0030] In one embodiment of the present invention, the weight average molecular weight of the P3HB-based resin (hereinafter sometimes referred to as "Mw") is not particularly limited, but is preferably 150,000 to 800,000, more preferably 200,000 to 700,000, and even more preferably 250,000 to 600,000. When the weight average molecular weight is 150,000 or more, sufficient mechanical properties and the like can be obtained, and when it is 800,000 or less, a sufficient crystallization rate can be obtained, and good moldability can be achieved. The weight average molecular weight of the P3HB-based resin can be determined as the molecular weight in terms of polystyrene by gel permeation chromatography (GPC) (using "Shodex GPC-101" manufactured by Showa Denko) with polystyrene gel ("Shodex K-804" manufactured by Showa Denko) used for the column and chloroform used as the mobile phase.

[0031] In one embodiment of the present invention, the P3HB-based resin is preferably a mixture of two or more polymers having different physical properties from the viewpoint of the balance of flexibility, strength, and moldability. In a preferred embodiment, the P3HB-based resin is a mixture of two or more polymers having different degrees of crystallinity. By using two or more polymers having different degrees of crystallinity, in particular, the difference in the melting point temperature of the resin mixture described later tends to be large, so that the effect of facilitating molding processing is achieved.

[0032] The mixing ratio in a mixture of two or more polymers having different degrees of crystallinity is not particularly limited and can be appropriately set according to the types of polymers to be mixed and the like. In the case of a mixture of two polymers, from the viewpoint of moldability, when the mixture is 100% by weight, it is preferable to contain 50% by weight or more of the polymer with a higher degree of crystallinity. In the case of a mixture of three or more polymers, from the viewpoint of moldability, it is preferable to contain 50% by weight or more of the polymer with the highest degree of crystallinity. For example, it is preferable to contain 50% by weight or more of a polymer with a high degree of crystallinity having a 3HB / 3HH molar ratio of 99 / 1 to 93 / 7.

[0033] As a preferred example of mixing two or more polymers having different physical properties, the P3HB-based resin is a mixture of Kaneka biodegradable polymer PHBH (registered trademark) X131A, which is a P3HB-based resin with a high degree of crystallinity, and Kaneka biodegradable polymer PHBH (registered trademark) 151C, which is a P3HB-based resin with a low degree of crystallinity. These mixing ratios are not particularly limited and can be appropriately set according to the types of resins to be mixed and the like. However, from the viewpoint of moldability, it is preferable that the weight ratio of X131A is more than the weight ratio of 151C. Note that X131A has a 3HB / 3HH molar ratio of 94 / 6, an MFR of 3 g / 10 min (160 °C - 5 kgf), and a melting point of 144 °C. 151C has a 3HB / 3HH molar ratio of 89 / 11, an MFR of 3 g / 10 min (160 °C - 5 kgf), and a melting point of 125 °C.

[0034] (Aliphatic-aromatic polyester resin) This tube contains an aliphatic-aromatic polyester resin. As used herein, "aliphatic-aromatic polyester resin" is a polyester polymer having repeating units derived from an aliphatic dicarboxylic acid, repeating units derived from an aromatic dicarboxylic acid, and repeating units derived from a diol.

[0035] Examples of the aliphatic dicarboxylic acid that is a constituent component of the aliphatic-aromatic polyester resin include succinic acid, adipic acid, azelaic acid, sebacic acid, brassilic acid, pimelic acid, suberic acid, fumaric acid, and itaconic acid. These may be used alone or in combination of two or more. Among them, adipic acid, azelaic acid, sebacic acid, and succinic acid are preferred.

[0036] Examples of the aromatic dicarboxylic acid that is a constituent component of the aliphatic-aromatic polyester resin include terephthalic acid, isophthalic acid, and furandicarboxylic acid. These may be used alone or in combination of two or more. Among them, terephthalic acid and furandicarboxylic acid are preferred.

[0037] Examples of the diol that is a constituent component of the aliphatic-aromatic polyester resin include 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol. These may be used alone or in combination of two or more. Among them, 1,4-butanediol is preferred.

[0038] In one embodiment of the present invention, specific examples of the aliphatic-aromatic polyester resin include, for example, polybutylene succinate terephthalate (PBST), polybutylene adipate terephthalate (PBAT), polybutylene sebacate terephthalate (PBSeT), polybutylene azelate terephthalate (PBAzT), and the like. Among them, from the viewpoints of industrial availability, heat resistance, and / or marine degradability, polybutylene adipate terephthalate (PBAT), polybutylene sebacate terephthalate (PBSeT), and polybutylene azelate terephthalate (PBAzT) are particularly preferred.

[0039] In one embodiment of the present invention, a commercially available aliphatic-aromatic polyester resin may be used. For example, Ecoflex® F blend C1200 manufactured by BASF can be used.

[0040] In one embodiment of the present invention, from the viewpoint of mechanical properties, the composition ratio of the repeating units of the aliphatic-aromatic polyester resin is preferably such that the composition ratio of the aliphatic dicarboxylic acid unit / aromatic dicarboxylic acid unit is 95 / 5 to 30 / 70 (mol / mol), more preferably 90 / 10 to 40 / 60 (mol / mol). When the total of the aliphatic dicarboxylic acid unit and the aromatic dicarboxylic acid unit is 100 mol%, if the aromatic dicarboxylic acid unit is 5 mol% or more, the mechanical properties are good. Also, if the aromatic dicarboxylic acid unit is 70 mol% or less, the biodegradability is excellent.

[0041] In one embodiment of the present invention, the weight average molecular weight of the aliphatic-aromatic polyester resin is not particularly limited, but is preferably 10,000 to 500,000, more preferably 20,000 to 400,000. If the weight average molecular weight is 500,000 or less, processing becomes easy, and if it is 10,000 or more, the physical properties are excellent. The weight average molecular weight of the aliphatic-aromatic polyester resin can be determined by the same method as the weight average molecular weight of the P3HB resin.

[0042] (Poly(3-hydroxybutyrate) resin tube) This tube contains the above poly(3-hydroxybutyrate) resin and the above aliphatic-aromatic polyester resin in a specific blending ratio, and is a tube having a wall thickness of 0.01 mm or more and 0.6 mm or less.

[0043] In this specification, the "tube" means an elongated cylindrical molded product having a substantially constant wall thickness, composed of a wall surface with a substantially circular cross-sectional shape, and having a hollow inside.

[0044] The wall thickness of this tube is not particularly limited, but since it will not be crushed by suction when drinking a beverage through a straw, it is in the range of 0.01 mm or more. Also, when forming the tube by melt extrusion as described later, in order to maintain the strength to withstand water pressure in the resin solidification process in water, the wall thickness of this tube is preferably 0.05 mm or more, more preferably 0.1 mm or more, and still more preferably 0.12 mm or more.

[0045] Also, since the wall thickness of this tube has appropriate flexibility, it is not easily broken, is not likely to cause injury when prodded with a fingertip, etc., and is easily biodegradable even in seawater, it is in the range of 0.6 mm or less, and more preferably 0.4 mm or less.

[0046] In one embodiment of the present invention, the blending ratio of the P3HB-based resin and the aliphatic-aromatic polyester-based resin in this tube is, for example, a ratio containing 95 to 60% by weight of the P3HB-based resin and 5 to 40% by weight of the aliphatic-aromatic polyester-based resin, preferably a ratio containing 94 to 62% by weight of the P3HB-based resin and 6 to 38% by weight of the aliphatic-aromatic polyester-based resin, more preferably a ratio containing 93 to 65% by weight of the P3HB-based resin and 7 to 35% by weight of the aliphatic-aromatic polyester-based resin, and still more preferably a ratio containing 92 to 67% by weight of the P3HB-based resin and 8 to 33% by weight of the aliphatic-aromatic polyester-based resin. When the blending ratio of the P3HB-based resin and the aliphatic-aromatic polyester-based resin is within the above range, this tube can be bellows processed at room temperature, and furthermore, it has the effect of excellent repeated bending resistance. The repeated bending resistance of this tube is measured and evaluated by the method described in the examples.

[0047] In one embodiment of the present invention, this tube has a top temperature (Tm a ) of the crystal melting curve in the range of 130 to 155°C in differential scanning calorimetry, and an end temperature (Tm bA mixture of a poly(3-hydroxybutyrate) resin and an aliphatic-aromatic polyester resin, having a difference (hereinafter sometimes referred to as "difference at melting point temperature") of 10 °C or more from

[0048] In one embodiment of the present invention, the difference at melting point temperature is 10 °C or more, preferably 12 °C or more, more preferably 15 °C or more, and still more preferably 17 °C or more. When within the above range, it becomes easy to melt the P3HB resin and the aliphatic-aromatic polyester resin while leaving some crystals unmelted. As a result, when the tube is secondary processed, while heating and plasticizing a predetermined portion of the tube, the overall shape of the tube can be maintained, and it becomes possible to easily mold the tube by secondary processing. That is, it is possible to achieve both shape maintenance by heating and moldability, and excellent secondary processability can be achieved. As a result, it is possible to easily provide the straw with a bent portion or an expandable and contractible structure, and a highly convenient straw can be provided. Furthermore, the above tube can be made to have the property of being excellent in repeated bending resistance.

[0049] In addition to the above-described excellent secondary processability, when molding a tube by melt extrusion as described later, there is also an advantage that solidification of the P3HB resin and the aliphatic-aromatic polyester resin in water after extrusion is accelerated, making it easier to avoid flattening of the tube due to water pressure.

[0050] Regarding the upper limit, although not particularly limited, from the viewpoint of ease of manufacturing the mixture of the P3HB resin and the aliphatic-aromatic polyester resin, for example, it is 50 °C or less, more preferably 40 °C or less, still more preferably 35 °C or less, and particularly preferably 30 °C or less.

[0051] In this specification, "the top temperature (Tm a ) of the crystal melting curve in differential scanning calorimetry" and "the end temperature (Tm b)」 is defined as follows. 4 to 10 mg of the resin sample is filled into an aluminum pan, and using a differential scanning calorimeter, the temperature of the resin sample is raised from 30°C to 180°C at a rate of 10°C / min under a nitrogen stream to melt the resin sample and obtain an endothermic curve. In the obtained endothermic curve, for the melting point peak existing in the range of 130 to 155°C, the top temperature of the melting point peak at which the endothermic amount is maximum is defined as Tm a and the temperature at which no endotherm is observed is defined as Tm b . If there is another melting point peak on the higher temperature side than Tm a , the temperature at which no endotherm is observed for that peak is defined as Tm b . For example, "the top temperature (Tm a ) of the crystal melting curve in differential scanning calorimetry" and "the end temperature (Tm b ) of the crystal melting curve" indicate the respective positions shown in FIGS. 1 to 3. Specifically, FIG. 1 schematically shows a DSC chart in which Tm a exists in the range of 130 to 155°C, and the difference between Tm b and Tm a is 10°C or more. Also, FIG. 2 schematically shows a DSC chart in which Tm a exists in the range of 130 to 155°C, but the difference between Tm b and Tm a is less than 10°C. FIG. 3 schematically shows a DSC chart in which Tm a exists in the range of 130 to 155°C, there is another melting point peak on the higher temperature side than Tm a , and the difference between Tm b and Tm a is 10°C or more.

[0052] In one embodiment of the present invention, for Tm a and Tm b in a mixture of a P3HB-based resin and an aliphatic-aromatic polyester-based resin, for example, (i) when Tm a = 130 to 155°C, Tm b = 160 to 180°C, and (ii) more preferably when Tm a = 140 to 145°C, Tm b= It is 165 to 175 °C. When the melting point of the mixture of the P3HB-based resin and the aliphatic-aromatic polyester-based resin is within the above range, in the temperature range not exceeding 180 °C, which is the thermal decomposition temperature of the mixture of the P3HB-based resin and the aliphatic-aromatic polyester-based resin, processing that leaves some crystals while sufficiently melting the resin becomes easy, excellent secondary processability can be achieved, and the property of being excellent in repeated bending resistance can be imparted.

[0053] In differential scanning calorimetry, the top temperature (Tm a ) of the crystal melting curve in the range of 130 to 155 °C and the difference from the end temperature (Tm b ) of the crystal melting curve are measured by the method described in the examples below.

[0054] In one embodiment of the present invention, as the mixture of the P3HB-based resin and the aliphatic-aromatic polyester-based resin that satisfies the difference in melting point temperature, for example, the mixture of the commercially available P3HB-based resin and the aliphatic-aromatic polyester-based resin described above can be used. As the P3HB-based resin, for example, Kaneka Corporation's "Kaneka Biodegradable Polymer PHBH (registered trademark)" (for example, X131A and 151C used in the examples) etc. are used. Also, as the aliphatic-aromatic polyester-based resin, for example, Ecoflex (registered trademark) F blend C1200 manufactured by BASF etc. are used.

[0055] In one embodiment of the present invention, this tube can use one type of P3HB-based resin alone, or can use a combination of two or more types of P3HB-based resins. When using a combination of two or more types of P3HB-based resins, for example, the resins described in the above section (poly(3-hydroxybutyrate)-based resin) are used.

[0056] Also, in one embodiment of the present invention, the tube may contain one or more biodegradable resins other than poly(3-hydroxybutyrate) - based resins and aliphatic - aromatic polyester - based resins within the scope where the effects of the present invention are achieved. Examples of such other resins include aliphatic polyester - based resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid. The addition amount of these resins is not particularly limited, but is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, based on 100 parts by weight of the P3HB - based resin. The lower limit is not particularly limited and may be 0 parts by weight.

[0057] Further, the tube may contain additives commonly used in the art within the scope where the effects of the present invention are achieved. Examples of such additives include colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, plasticizers, antioxidants, oxidation inhibitors, weather resistance improvers, ultraviolet absorbers, crystal nucleating agents, lubricants, mold release agents, water repellents, antibacterial agents, sliding property improvers, etc. Among them, the processability can be significantly improved by adding a crystal nucleating agent. Examples of such crystal nucleating agents include pentaerythritol. As the additive, only one kind may be included, or two or more kinds may be included. The content of these additives can be appropriately set by those skilled in the art according to the purpose of use.

[0058] On the other hand, it has been found in the present invention that when an inorganic filler is added to the mixture of the above - mentioned P3HB - based resin and aliphatic - aromatic polyester - based resin, the resulting tube has high rigidity, does not exhibit yield point elongation, and has a reduced tensile elongation. Such a tube is inferior in bellows formability and repeated bending resistance. Therefore, it is preferable that the tube substantially does not contain an inorganic filler. More specifically, the content of the inorganic filler in the tube is preferably less than 5% by weight, more preferably less than 3% by weight, and even more preferably less than 1% by weight. Specific examples of the above - mentioned inorganic filler include talc, calcium carbonate, mica, silica, titanium oxide, alumina, zeolite, clay, etc.

[0059] This tube has a yield point elongation. Due to the tube having a yield point elongation, the tube has excellent repeated bending resistance.

[0060] In this specification, "yield point elongation" means a state where elongation continues even after exceeding the yield point in a tensile test. The yield point elongation of this tube is evaluated by the tensile test described in the examples.

[0061] The tensile elongation of this tube is 50% or more, preferably 55% or more, more preferably 75% or more, and even more preferably 100% or more. When the tensile elongation of this tube is 50% or more, it has excellent bellows formability. The upper limit of the tensile elongation of this tube is not particularly limited as long as the effects of the present invention are achieved. For example, it is 500%. The tensile elongation of this tube is measured by the tensile test described in the examples.

[0062] The outer diameter of this tube is not particularly limited, but from the viewpoint of ease of use when drinking a beverage as a straw, 2 to 10 mm is preferable, 4 to 8 mm is more preferable, and 5 to 7 mm is even more preferable.

[0063] The cross-sectional shape of this tube is substantially circular, but from the viewpoint of usability as a straw, the closer it is to a perfect circle, the more preferable. Therefore, the flatness ratio [100×(maximum outer diameter - minimum outer diameter) / maximum outer diameter] of the cross-sectional shape of this tube is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and particularly preferably 3% or less. Note that "flatness of 0%" means that the cross-sectional shape is a perfect circle.

[0064] The length of this tube is not particularly limited, but from the viewpoint of ease of use when drinking a beverage as a straw, 50 to 350 mm is preferable, 70 to 300 mm is more preferable, and 90 to 270 mm is even more preferable.

[0065] This tube can be suitably used as a straw. The tube used as a straw may be an unprocessed tube or a tube that has been subjected to secondary processing such as the formation of a stopper portion or a bellows portion.

[0066] [3. Manufacturing method] The manufacturing method of the poly(3-hydroxybutyrate)-based resin tube according to an embodiment of the present invention (hereinafter referred to as "the manufacturing method of this tube") is a method for manufacturing the poly(3-hydroxybutyrate)-based resin tube described above (the poly(3-hydroxybutyrate)-based resin tube), and after melting a mixture of the above poly(3-hydroxybutyrate)-based resin and the above aliphatic-aromatic polyester-based resin in an extruder, it includes a step of extruding from an annular die and introducing it into water, and the temperature of the above annular die is the above Tm a and Tm b is set to a temperature between and.

[0067] Generally, compared with other crystalline resins such as polypropylene, the P3HB-based resin has an extremely slow crystallization rate. Therefore, for cooling and solidification, the P3HB-based resin tube tends to be flattened under the influence of water pressure in water (in other words, the above flattening rate tends to increase). In particular, the larger the outer diameter of the P3HB-based resin tube and the thinner the wall thickness, the more prominent the flattening due to water pressure tends to be. Therefore, it has been difficult to manufacture a thin-walled tube containing a P3HB-based resin and having a cross-sectional shape close to a perfect circle.

[0068] In order to easily realize the forming process of a thin-walled tube with suppressed flattening, in the manufacturing method of this tube, the temperature of the above annular die is set to the top temperature (Tm a ) of the crystal melting curve in the range of 130 to 155°C in the differential scanning calorimetry of the mixture of the above P3HB-based resin and the aliphatic-aromatic polyester-based resin, and the end temperature (Tm b) It is preferable to set the temperature to be between ( ). By adopting this condition, the P3HB-based resin formed from the mixture of the above P3HB-based resin and the aliphatic-aromatic polyester-based resin can be melted to a level where it can be molded, and at the same time, a part of the crystals will remain in the molten resin. As a result, the crystallization solidification in water after extrusion can proceed rapidly, so it is possible to suppress the flattening of the tube due to the influence of water pressure.

[0069] Further, in the method for manufacturing this tube, as the P3HB-based resin, it is preferable to use a P3HB-based resin having a melt viscosity of 10,000 poise or more at 160 °C. By using a P3HB-based resin with such a high melt viscosity, the influence of water pressure in water during solidification can be suppressed, and thereby, the flattening of the tube in water can be further suppressed. The above melt viscosity is more preferably 11,000 poise or more, further preferably 12,000 poise or more, and particularly preferably 13,000 poise or more. The upper limit of the above melt viscosity is not particularly limited, but from the viewpoints of the surface smoothness of the tube and preventing the pressure increase in the annular die, it is preferably 30,000 poise or less. Note that the above melt viscosity is a value measured for the entire P3HB-based resin contained in the P3HB-based resin tube (in the case of a tube containing an additive, for the entire resin including the additive).

[0070] In one embodiment of the present invention, the manufacturing method is a method for manufacturing the poly(3-hydroxybutyrate)-based resin tube described in the above (poly(3-hydroxybutyrate)-based resin tube), and is characterized by including a step of shaping the poly(3-hydroxybutyrate)-based resin tube at room temperature. Since this tube can be bellows processed at room temperature and has excellent repeated bending resistance, according to this embodiment, a molded product processed into a desired shape can be easily obtained.

[0071] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention. <1> containing 95 to 60% by weight of a poly(3-hydroxybutyrate) resin and 5 to 40% by weight of an aliphatic-aromatic polyester resin, having a yield point elongation in a tensile test and a tensile elongation in the tensile test of 50% or more, A poly(3-hydroxybutyrate) resin tube having a wall thickness of 0.01 to 0.6 mm. <2> The aliphatic-aromatic polyester resin has a structural unit derived from an aliphatic dicarboxylic acid, a structural unit derived from an aromatic dicarboxylic acid, and a structural unit derived from a diol, The aliphatic dicarboxylic acid is at least one selected from the group consisting of succinic acid, adipic acid, azelaic acid, sebacic acid, brassilic acid, pimelic acid, suberic acid, fumaric acid, and itaconic acid, The aromatic dicarboxylic acid is at least one selected from the group consisting of terephthalic acid, isophthalic acid, and furandicarboxylic acid, The poly(3-hydroxybutyrate) resin tube according to <1>, wherein the diol is at least one selected from the group consisting of 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol. <3> In differential scanning calorimetry, the mixture of the poly(3-hydroxybutyrate) resin and the aliphatic-aromatic polyester resin has a difference between the top temperature (Tm a ) of the crystal melting curve in the range of 130 to 155 °C and the end temperature (Tm b ) of the crystal melting curve of 10 °C or more. The poly(3-hydroxybutyrate) resin tube according to <1> or <2>. <4> The poly(3-hydroxybutyrate) resin tube according to any one of <1> to <3>, wherein the poly(3-hydroxybutyrate) resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). <5>A method for producing a poly(3-hydroxybutyrate)-based resin tube according to any one of <1> to <4>, comprising a step of melting a mixture of the poly(3-hydroxybutyrate)-based resin and the aliphatic-aromatic polyester-based resin in an extruder, then extruding through an annular die and introducing into water, setting the temperature of the annular die to a temperature between the Tm a and the Tm b A manufacturing method. <6>A method for producing a poly(3-hydroxybutyrate)-based resin tube according to any one of <1> to <4>, comprising a step of shaping the poly(3-hydroxybutyrate)-based resin tube at room temperature.

Examples

[0072] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0073] 〔Materials〕 In the examples and comparative examples, the following materials were used.

[0074] Resin raw material 1: Manufactured by Kaneka, Kaneka biodegradable polymer PHBH (registered trademark) X131A [poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)] Resin raw material 2: Manufactured by Kaneka, Kaneka biodegradable polymer PHBH (registered trademark) 151C [poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)] Resin raw material 3: Manufactured by BASF, Ecoflex (registered trademark) F blend C1200 [aliphatic-aromatic polyester-based resin (polybutylene adipate terephthalate)] Resin raw material 4: Manufactured by BASF, Ecoflex (registered trademark) FS blend C2200 [aliphatic-aromatic polyester-based resin (polybutylene sebacate terephthalate)] 〔Measurement and evaluation methods〕 The evaluations in the examples and comparative examples were performed by the following methods.

[0075] (Differential Scanning Calorimetry Evaluation) 4 - 10 mg of a resin sample (resin pellets) was filled into an aluminum pan, and using a differential scanning calorimeter, under a nitrogen stream, the temperature was raised from 30°C to 180°C at a rate of 10°C / min, and an endothermic curve obtained when the resin sample melted was obtained. Regarding the melting point peak existing in the range of 130 - 155°C, the top temperature of the melting point peak at which the endothermic quantity became maximum was defined as Tm a and the temperature at which no endotherm was observed was defined as Tm b . Tm a If there is another melting point peak on the higher temperature side than Tm, the temperature at which no endotherm was observed for that peak was defined as Tm b .

[0076] (Tensile Test: Yield Point Elongation and Tensile Elongation) 2 g of a resin sample (resin pellets) and a 120 - μm SUS spacer were sandwiched between release - treated PET, and a film of about 100 μm was produced by pressing with a press machine heated to 170°C at a pressure of 4 MPa. Regarding the produced film, using a tensile testing machine (manufactured by Shimadzu Corporation: EZ - LX 1 kN), in accordance with JIS K 7127, a tensile test was conducted under the condition of a tensile speed of 100 mm / min. Based on the S - S curve obtained from the tensile test, the evaluation of the yield point elongation and the calculation of the tensile elongation were performed. Regarding the evaluation of the yield point elongation, when further elongation occurred beyond the yield point, it was evaluated as "○".

[0077] (Repeated Bending Resistance) The movement of manually bending the resin tube 120 degrees was repeatedly performed until cracks or fractures occurred in the resin tube, and the repeated bending resistance was evaluated. The evaluation was conducted in an environment of room temperature 25°C and humidity 60%. If no cracks or fissures occurred even after 100 or more bending movements, the repeated bending resistance was considered good ("○").

[0078] (Bellows Processing) Bellows processing was performed on the resin tube at room temperature using a bellows processing machine. Those on which bellows processing could be performed were considered to have good bellows formability ("○").

[0079] (Tube forming) When the flatness ratio of the produced tube was 10% or less, the tube formability was considered good (「○」). The flatness ratio (%) is calculated by the following formula.

[0080] 100×(maximum outer diameter - minimum outer diameter) / maximum outer diameter 〔Manufacture of resin pellets〕 Resin raw materials 1 to 3 were mixed at the compounding ratios shown in Table 1, and 1 part by weight of pentaerythritol was compounded as a crystal nucleating agent with respect to a total of 100 parts by weight of the resin raw materials and dry-blended. The obtained resin material (resin mixture) was put into a φ26 mm co-rotating twin-screw extruder with the cylinder temperature set at 150°C and the die temperature set at 150°C and extruded. The extruded resin material was passed through a water tank filled with 40°C hot water to solidify the strands, and the resin pellets were obtained by cutting with a pelletizer.

[0081] 〔Example 1〕 The cylinder temperature and die temperature of a φ50 mm single-screw extruder connected with an annular die (outer diameter 15 mm, inner diameter 13.5 mm) were each set at 150°C, and the resin pellets were put in and extruded into a tube shape. The extruded resin pellets were passed through a 30°C water tank located 50 mm away from the annular die to obtain a resin tube with an outer diameter of 6 mm and a wall thickness of 0.13 mm. The evaluation results are shown in Table 1.

[0082] 〔Examples 2 to 9〕 A resin tube with an outer diameter of 6 mm and a wall thickness of 0.2 mm was obtained in the same manner as in Example 1 except that the compounding ratio of the resin pellets was changed as shown in Table 1. The evaluation results are shown in Table 1.

[0083] 〔Comparative Examples 1 to 3〕 A resin tube with an outer diameter of 6 mm and a wall thickness of 0.2 mm was obtained in the same manner as in Example 1 except that the compounding ratio of the resin pellets was changed as shown in Table 1. The evaluation results are shown in Table 1.

[0084]

Table 1

[0085] On the other hand, it was found that the films formed from the resin pellets not containing the aliphatic-aromatic polyester resin of Comparative Examples 1 to 2 did not exhibit yield point elongation and did not exhibit tensile elongation. Therefore, although it is possible to manufacture a tube, the result was inferior in bellows formability and repeated bending resistance. Further, the film formed from the resin pellets not containing the aliphatic-aromatic polyester resin of Comparative Example 3 exhibited yield point elongation, but since the tensile elongation was small, although the repeated bending resistance was good, bellows processing at room temperature was difficult.

Industrial Applicability

[0086] Since this tube can be bellows processed at room temperature and has excellent repeated bending resistance, it can be suitably used in various fields where tubes are required (for example, straws, etc.).

Claims

1. A method for manufacturing a poly(3-hydroxybutyrate)-based resin tube, comprising a step of shaping the poly(3-hydroxybutyrate)-based resin tube at room temperature, wherein the poly(3-hydroxybutyrate)-based resin tube contains 95 to 60% by weight of a poly(3-hydroxybutyrate)-based resin and 5 to 40% by weight of an aliphatic-aromatic polyester-based resin, has a yield point elongation in a tensile test and a tensile elongation in the tensile test of 50% or more, and has a wall thickness of 0.01 to 0.6 mm. A method for manufacturing a poly(3-hydroxybutyrate)-based resin tube.

2. The aliphatic-aromatic polyester-based resin has a repeating unit derived from an aliphatic dicarboxylic acid, a repeating unit derived from an aromatic dicarboxylic acid, and a repeating unit derived from a diol, the aliphatic dicarboxylic acid is at least one selected from the group consisting of succinic acid, adipic acid, azelaic acid, sebacic acid, brassilic acid, pimelic acid, suberic acid, fumaric acid, and itaconic acid, the aromatic dicarboxylic acid is at least one selected from the group consisting of terephthalic acid, isophthalic acid, and furandicarboxylic acid, and the diol is at least one selected from the group consisting of 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol. The method for manufacturing a poly(3-hydroxybutyrate)-based resin tube according to Claim 1.

3. The difference between the top temperature (Tm ａ ) of the crystal melting curve in the range of 130 to 155°C and the end temperature (Tm ｂ ) of the crystal melting curve of the mixture of the poly(3-hydroxybutyrate)-based resin and the aliphatic-aromatic polyester-based resin is 10°C or more. The method for producing a poly(3-hydroxybutyrate)-based resin tube according to claim 1 or 2. ａ ), and the end temperature (Tm ｂ ) of the crystal melting curve is 10°C or more. The method for producing a poly(3-hydroxybutyrate)-based resin tube according to claim 1 or 2. ｂ ).

4. The poly(3-hydroxybutyrate)-based resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). The method for manufacturing a poly(3-hydroxybutyrate)-based resin tube according to any one of Claims 1 to 3.

5. The method includes a step of melting a mixture of the poly(3-hydroxybutyrate)-based resin and the aliphatic-aromatic polyester-based resin in an extruder, then extruding it from an annular die and introducing it into water. Set the temperature of the annular die to a temperature between the Tm ａ and the Tm ｂ The method for producing a poly(3-hydroxybutyrate)-based resin tube according to any one of claims 1 to 4, wherein the temperature is set to a temperature between the Tm and the Tm

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