Resin tube

Abstract

Provided is a resin tube containing a poly(3-hydroxyalkanoate)-based resin component. The resin component contains a poly(3-hydroxyalkanoate)-based resin (A) having a weight average molecular weight of 100,000 to 700,000 (exclusive of 700,000), and a copolymer (B) of a 3-hydroxybutyrate unit having a weight average molecular weight of at least 700,000 and another hydroxyalkanoate unit. The content ratio of the 3-hydroxybutyrate unit in the copolymer (B) is 76 mol% to 100 mol% (exclusive of 100 mol%). The content of the resin (A) in the total amount of the poly(3-hydroxyalkanoate)-based resin component is 80 wt% to 99 wt%, and the content of the copolymer (B) is 1 wt% to 20 wt%. The 50% fracture energy of the resin tube at 23°C is more than 0.625 J.

Description

Resin tube

[0001] The present invention relates to a resin tube containing a poly(3-hydroxyalkanoate) resin.

[0002] In recent years, the separate collection and composting of food waste has been promoted, particularly in Europe, and there is a demand for plastic products that can be composted together with food waste. Furthermore, with marine pollution caused by microplastics coming to the forefront, there is a desire to develop plastics that can decompose in seawater.

[0003] Poly(3-hydroxyalkanoate) resins are thermoplastic polyesters that are produced and accumulated as energy storage substances within the cells of many microbial species. They are also biodegradable not only in soil but also in seawater, and are therefore attracting attention as materials that can solve the above-mentioned problems.

[0004] The use of such poly(3-hydroxyalkanoate) resins as resin materials for forming resin tubes such as straws has been investigated.

[0005] Patent Documents 1 and 2 disclose resin tubes containing at least two types of poly(3-hydroxyalkanoate) resins that differ from each other in the type of constituent monomer and / or the content ratio of the constituent monomer.

[0006] Furthermore, Patent Document 3 discloses that by using a poly(3-hydroxyalkanoate) resin having a weight-average molecular weight of 300,000 to 500,000 and in which the proportion of components having a weight-average molecular weight of 250,000 or less in the molecular weight distribution is 15 to 40% by weight, it is possible to provide a resin tube that is high in strength and can be molded at high speed.

[0007] International Publication No. 2022 / 009717 Japanese Patent Application Laid-Open No. 2024-8387 International Publication No. 2023 / 100673

[0008] Resin tubes are required to be resistant to cracking during manufacturing, transportation, and use, i.e., to have impact resistance. At the same time, they may also be required to be resistant to deformation even when force is applied. This corresponds to a high measured elastic modulus for the resin tube.

[0009] However, with the poly(3-hydroxyalkanoate) resin compositions disclosed in Patent Documents 1 to 3, it is not easy to obtain a resin tube that has a good balance between impact resistance and elastic modulus.

[0010] In view of the above-mentioned current situation, an object of the present invention is to provide a resin tube which contains a poly(3-hydroxyalkanoate)-based resin component and has a good balance between impact resistance and elastic modulus.

[0011] As a result of intensive research to solve the above problems, the inventors have discovered that a resin tube having a good balance between impact resistance and elastic modulus can be provided by using, as a poly(3-hydroxyalkanoate)-based resin, a resin having a relatively low weight-average molecular weight and a copolymer having a relatively high weight-average molecular weight and a specific monomer composition in combination in specific proportions, and have thereby completed the present invention.

[0012] That is, the present invention relates to a resin tube containing a poly(3-hydroxyalkanoate)-based resin component, wherein the poly(3-hydroxyalkanoate)-based resin component contains: a poly(3-hydroxyalkanoate)-based resin (A) having a weight-average molecular weight of 100,000 or more and less than 700,000; and a copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the copolymer (B) having a weight-average molecular weight of 700,000 or more, the content of 3-hydroxybutyrate units being 76 mol % or more and less than 100 mol % of the total of the 3-hydroxybutyrate units and the other hydroxyalkanoate units; the content of resin (A) being 80 wt % or more and 99 wt % or less, and the content of copolymer (B) being 1 wt % or more and 20 wt % or less, of the total amount of the poly(3-hydroxyalkanoate)-based resin component; and the 50% fracture energy at 23°C exceeds 0.625 J.

[0013] According to the present invention, it is possible to provide a resin tube that contains a poly(3-hydroxyalkanoate)-based resin component and has a good balance between impact resistance and elastic modulus. According to the present invention, it is possible to provide a resin tube containing a poly(3-hydroxyalkanoate)-based resin that is resistant to cracking and deformation. According to the present invention, it is possible to provide a resin tube that has good impact resistance in a temperature range from room temperature to low temperatures. Furthermore, since the resin tube according to the present invention has good solidification properties after melting, it can be produced at a high molding speed. Therefore, it is possible to provide a resin tube that has a good balance between impact resistance and elastic modulus and is highly productive.

[0014] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. One embodiment of the present invention relates to a resin tube containing a poly(3-hydroxyalkanoate)-based resin component.

[0015] (Poly(3-hydroxyalkanoate)-based resin) The poly(3-hydroxyalkanoate)-based resin is a polymer having a 3-hydroxyalkanoate unit, and specifically, is preferably a polymer containing a unit represented by the following general formula (1): [—CHR—CH ２ -CO-O-] (1) In the general formula (1), R is C ｐ H ２ｐ＋１ where p is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. p is preferably an integer of 1 to 10, and more preferably an integer of 1 to 8.

[0016] The poly(3-hydroxyalkanoate) resin is preferably a poly(3-hydroxyalkanoate) resin produced by a microorganism, in which all 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0017] The poly(3-hydroxyalkanoate) resin preferably contains 3-hydroxyalkanoate units (particularly units represented by general formula (1)) in an amount of 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more of the total structural units. The poly(3-hydroxyalkanoate) resin may contain only 3-hydroxyalkanoate units as structural units of the polymer, or may contain one or more types of 3-hydroxyalkanoate units as well as other units (e.g., 4-hydroxyalkanoate units).

[0018] The poly(3-hydroxyalkanoate) resin may be a homopolymer or copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units. In particular, it is preferable that all of the 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units. Furthermore, it is preferable that the poly(3-hydroxyalkanoate) resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0019] Specific examples of poly(3-hydroxyalkanoate) resins include poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH). , poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), etc. In particular, from the viewpoints of productivity and mechanical properties of molded articles, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0020] When the poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units, the average content of 3-hydroxybutyrate units in the total monomer units (i.e., the total of 3-hydroxybutyrate units and other hydroxyalkanoate units) in the entire poly(3-hydroxyalkanoate) resin component contained in the resin tube according to the present disclosure is preferably 65 to 98 mol%, more preferably 75 to 96 mol%, even more preferably 80 to 95 mol%, and particularly preferably 85 to 96 mol%, from the viewpoint of achieving both the mechanical properties and productivity of the resin tube.

[0021] The average content of 3-hydroxybutyrate units in the total number of monomer units in the entire poly(3-hydroxyalkanoate) resin component can be determined by a method known to those skilled in the art, for example, the method described in paragraph

[0047] of WO 2013 / 147139. The content of 3-hydroxybutyrate units in each copolymer or resin described below can also be determined in a similar manner.

[0022] The weight average molecular weight measured for the entire poly(3-hydroxyalkanoate) resin component contained in the resin tube according to the present disclosure is preferably 100,000 to 1,500,000, more preferably 200,000 to 1,000,000, and particularly preferably 300,000 to 800,000, from the viewpoint of achieving both mechanical properties and productivity of the resin tube.

[0023] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin component can be measured in terms of polystyrene using gel permeation chromatography (HPLC GPC system manufactured by Shimadzu Corporation) using a chloroform solution. A column suitable for measuring weight-average molecular weights can be used as the column for gel permeation chromatography. The weight-average molecular weights of the copolymers or resins described below can also be determined in the same manner.

[0024] The poly(3-hydroxyalkanoate) resin component contained in the resin tube according to the present disclosure is preferably not cross-linked using a cross-linking agent such as an organic peroxide, i.e., it is preferable that it does not have a cross-linked structure.

[0025] The resin tube according to the present disclosure contains at least two types of poly(3-hydroxyalkanoate) resins having different weight-average molecular weights as the poly(3-hydroxyalkanoate) resin component, thereby providing a resin tube with a good balance between impact resistance and elastic modulus.

[0026] Specifically, the poly(3-hydroxyalkanoate) resin component contained in the resin tube according to the present disclosure contains at least the following two types of resin: a poly(3-hydroxyalkanoate) resin (A) having a weight-average molecular weight of 100,000 or more and less than 700,000, and a copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units having a weight-average molecular weight of 700,000 or more.

[0027] As described above, by using a poly(3-hydroxyalkanoate) resin (A) having a relatively low weight-average molecular weight in combination with a 3-hydroxybutyrate unit-containing copolymer (B) having a relatively high weight-average molecular weight, it is possible to achieve a good balance between the impact resistance and elastic modulus of the resin tube.

[0028] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin (A) is 100,000 or more and less than 700,000. By using a poly(3-hydroxyalkanoate) resin with such a relatively low molecular weight, fluidity during melt processing can be ensured, enabling resin tubes to be produced with high productivity. From the viewpoint of resin tube productivity, the molecular weight is preferably 650,000 or less. While there is no particular lower limit, from the viewpoint of the impact resistance or elastic modulus of the resin tube, a molecular weight of 200,000 or more is preferred, and 300,000 or more is more preferred. When the poly(3-hydroxyalkanoate) resin (A) contains multiple types of resins, the weight-average molecular weight of each of the multiple resins may be within the aforementioned range.

[0029] The poly(3-hydroxyalkanoate) resin (A) preferably contains a homopolymer of 3-hydroxybutyrate units or a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. It may contain both a homopolymer and a copolymer. Furthermore, the copolymer may contain at least two types of copolymers that differ from each other in the types of constituent monomers and / or the content ratios of the constituent monomers.

[0030] In an embodiment in which the poly(3-hydroxyalkanoate) resin (A) contains at least a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, the average content of 3-hydroxybutyrate units in the total monomer units (i.e., the total of 3-hydroxybutyrate units and other hydroxyalkanoate units) in the entire resin (A) is preferably 65 to 98 mol %, more preferably 75 to 96 mol %, even more preferably 80 to 95 mol %, and particularly preferably 85 to 96 mol %, from the viewpoint of achieving both impact resistance and elastic modulus of the resin tube.

[0031] On the other hand, the weight-average molecular weight of the copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units is 700,000 or more. By using such a copolymer with a relatively high molecular weight in combination with the resin (A), the impact resistance of the resin tube can be improved while maintaining the elastic modulus within a good range. Furthermore, by using the high molecular weight copolymer (B) in combination with the resin (A), the solidification property of the poly(3-hydroxyalkanoate)-based resin component is improved, and the molding speed of the resin tube can be increased.

[0032] The weight average molecular weight of the copolymer (B) is preferably 750,000 or more. Although the upper limit is not particularly limited, from the viewpoint of productivity, it is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. When the copolymer (B) contains multiple types of copolymers, it is sufficient that the weight average molecular weight of each of the multiple types of copolymers is within the above-mentioned range.

[0033] The difference in weight-average molecular weight between the resin (A) and the copolymer (B) is not particularly limited, but is preferably 100,000 or more, more preferably 200,000 or more, and particularly preferably 250,000 or more, in order to more easily exhibit the respective effects of (A) and (B).

[0034] As the copolymer (B), only one type may be used, or at least two types of copolymers differing from each other in the types of constituent monomers and / or the content ratios of the constituent monomers may be used in combination.

[0035] In copolymer (B), the content of 3-hydroxybutyrate units in the total of 3-hydroxybutyrate units and other hydroxyalkanoate units is set in the range of 76 mol% or more and less than 100 mol% in order to achieve the effect of improving the impact resistance of the resin tube by blending copolymer (B). The content is preferably 78 mol% or more and 95 mol% or less, more preferably 80 mol% or more and 92 mol% or less, even more preferably 82 mol% or more and 90 mol% or less, and particularly preferably 85 mol% or more and 89 mol% or less.

[0036] As the copolymer (B), the copolymers described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred.

[0037] In the resin tube according to the present disclosure, the content of resin (A) is set to a range of 80% by weight to 99% by weight, and the content of copolymer (B) is set to a range of 1% by weight to 20% by weight, based on the total amount of the poly(3-hydroxyalkanoate)-based resin component. By using both resins in this range, a good balance between the impact resistance and elastic modulus of the resin tube can be achieved. If the amount of copolymer (B) is less than 1% by weight, it becomes difficult to achieve an improvement in impact resistance. On the other hand, if it exceeds 20% by weight, the melt viscosity of the poly(3-hydroxyalkanoate)-based resin component increases, which tends to reduce the productivity of the resin tube.

[0038] The lower limit of the content of resin (A) is preferably 85% by weight or more, more preferably 90% by weight or more, even more preferably 92% by weight or more, and particularly preferably 93% by weight or more. The upper limit of the content of resin (A) is preferably 98% by weight or less, more preferably 97% by weight or less, even more preferably 96% by weight or less, and particularly preferably 95% by weight or less.

[0039] The upper limit of the content of copolymer (B) is preferably 15% by weight or less, more preferably 10% by weight or less, even more preferably 8% by weight or less, and particularly preferably 7% by weight or less. The lower limit of the content of copolymer (B) is preferably 2% by weight or more, more preferably 3% by weight or more, even more preferably 4% by weight or more, and particularly preferably 5% by weight or more.

[0040] Next, a preferred embodiment of the resin (A) having a relatively low weight-average molecular weight will be described. The resin (A) according to the preferred embodiment preferably contains at least a copolymer (A1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 50 mol % or more and 76 mol % or less of the 3-hydroxybutyrate units.

[0041] Copolymer (A1) has a relatively low content of 3-hydroxybutyrate units and is therefore a low-crystalline poly(3-hydroxyalkanoate) resin. Low-crystalline poly(3-hydroxyalkanoate) resins have good toughness. Therefore, by using copolymer (A1), the impact resistance of the resin tube can be further improved.

[0042] In the copolymer (A1), the content of 3-hydroxybutyrate units in the total of 3-hydroxybutyrate units and other hydroxyalkanoate units is 50 mol% or more and 76 mol% or less. From the viewpoint of impact resistance, the upper limit of this percentage is preferably 74 mol% or less, more preferably 72 mol% or less. Furthermore, from the viewpoint of productivity of the copolymer (A1), the lower limit of this percentage is preferably 60 mol% or more, more preferably 70 mol% or more.

[0043] As the copolymer (A1), the copolymers described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0044] The weight-average molecular weight of the copolymer (A1) is in the range of 100,000 or more and less than 700,000, similar to that of the resin (A). The preferred range of the weight-average molecular weight of the copolymer (A1) is also the same as the preferred range of the weight-average molecular weight of the resin (A) described above. However, from the viewpoint of impact resistance, the lower limit of the weight-average molecular weight of the copolymer (A1) is preferably 400,000 or more, more preferably 500,000 or more.

[0045] The content of copolymer (A1) is preferably 10% by weight or more and 30% by weight or less of the total amount of poly(3-hydroxyalkanoate)-based resin components contained in the resin tube according to the present disclosure. By using copolymer (A1) in such an amount, impact resistance can be further improved and the elastic modulus can be maintained within a good range. From the viewpoint of impact resistance, the lower limit is preferably 12% by weight or more, and more preferably 14% by weight or more. From the viewpoint of elastic modulus, the upper limit is preferably 25% by weight or less, more preferably 20% by weight or less, and even more preferably 18% by weight or less.

[0046] In a preferred embodiment, the resin (A) preferably contains at least poly(3-hydroxybutyrate) (A2) and / or a copolymer (A3) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the copolymer having a 3-hydroxybutyrate unit content of more than 90 mol % and not more than 99 mol %. While either (A2) or (A3) may be used alone, it is more preferable to contain both (A2) and (A3).

[0047] Although the copolymer (A1) may be omitted and (A2) and / or (A3) may be used, it is preferable to use (A1) in combination with (A2) and / or (A3). In particular, from the viewpoint of the balance between impact resistance and elastic modulus of the resin tube, it is most preferable to use the three components (A1), (A2), and (A3).

[0048] Poly(3-hydroxybutyrate) (A2) and copolymer (A3) have a high content of 3-hydroxybutyrate units, making them highly crystalline poly(3-hydroxyalkanoate)-based resins. Highly crystalline poly(3-hydroxyalkanoate)-based resins have good strength. This makes it easier to maintain the elastic modulus of the resin tube within a favorable range. Furthermore, the use of (A2) can improve the productivity of resin tubes.

[0049] The poly(3-hydroxybutyrate) (A2) refers to a homopolymer of 3-hydroxybutyrate or a polymer containing, in addition to 3-hydroxybutyrate units, a small amount of hydroxyalkanoate units other than 3-hydroxybutyrate units. Specifically, the poly(3-hydroxybutyrate) (A2) preferably contains 3-hydroxybutyrate units in a proportion of more than 99 mol % and not more than 100 mol % of all of its constituent monomers.

[0050] The hydroxyalkanoate unit other than the 3-hydroxybutyrate unit that can be contained in the poly(3-hydroxybutyrate) (A2) is not particularly limited as long as it is copolymerizable with the 3-hydroxybutyrate unit, and examples thereof include a 3-hydroxyalkanoate unit other than the 3-hydroxybutyrate unit and a hydroxyalkanoate unit other than the 3-hydroxyalkanoate unit (for example, a 4-hydroxyalkanoate unit). In particular, a 3-hydroxyhexanoate unit is preferred.

[0051] In copolymer (A3), the content of 3-hydroxybutyrate units in the total of 3-hydroxybutyrate units and other hydroxyalkanoate units is more than 90 mol% and not more than 99 mol%. From the viewpoint of elastic modulus, the lower limit of this percentage is preferably 92 mol% or more, more preferably 94 mol% or more. The upper limit of this percentage may be 98 mol% or less, or may be 97 mol% or less.

[0052] As the copolymer (A3), the copolymers described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0053] Furthermore, the copolymer (A3) may be a mixture of at least two copolymers differing in the type and / or content of the constituent monomers, as long as the content of the 3-hydroxybutyrate unit in each of the copolymers falls within the above-mentioned range.

[0054] The total content of poly(3-hydroxybutyrate) (A2) and copolymer (A3) is preferably 50% by weight or more and 90% by weight or less of the total amount of poly(3-hydroxyalkanoate)-based resin components contained in the resin tube according to the present disclosure. Using (A2) and / or (A3) in such amounts facilitates maintaining the elastic modulus of the resin tube within a favorable range and improves the productivity of the resin tube. The upper limit is preferably 88% by weight or less, more preferably 85% by weight or less, and even more preferably 80% by weight or less. The lower limit is preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 75% by weight or more, and particularly preferably 78% by weight or more.

[0055] The content of poly(3-hydroxybutyrate) (A2) is preferably 1% by weight or more and 20% by weight or less of the total amount of poly(3-hydroxyalkanoate)-based resin components contained in the resin tube according to the present disclosure. Using (A2) in such an amount improves the productivity of the resin tube and enables the production of a resin tube with a good appearance. The upper limit is preferably 15% by weight or less, more preferably 10% by weight or less. The lower limit is preferably 3% by weight or more, more preferably 5% by weight or more.

[0056] The weight-average molecular weights of the poly(3-hydroxybutyrate) (A2) and the copolymer (A3) are each in the range of 100,000 or more and less than 700,000, similar to that of the resin (A). The preferred ranges of the weight-average molecular weights of (A2) and (A3) are also the same as the preferred range of the weight-average molecular weight of the resin (A) described above. However, from the viewpoint of the elastic modulus and productivity of the resin tube, the upper limit of the weight-average molecular weights of the poly(3-hydroxybutyrate) (A2) and the copolymer (A3) is preferably 600,000 or less, and more preferably 500,000 or less.

[0057] The method for producing poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a production method using chemical synthesis or a production method using a microorganism. Among these, a production method using a microorganism is preferred. Known methods can be applied to the production method using a microorganism. For example, known bacteria that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, in order to increase the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)) or the like into which genes encoding P3HA synthases have been introduced is more preferred, and microbial cells obtained by culturing these microorganisms under appropriate conditions and allowing P3HB3HH to accumulate within the cells are used. In addition to the above, genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes have been introduced may be used depending on the poly(3-hydroxyalkanoate) resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0058] The method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a method for obtaining a blend by microbial production or a method for obtaining a blend by chemical synthesis. Alternatively, a blend may be obtained by melt-kneading two or more resins using an extruder, kneader, Banbury mixer, roll, or the like, or by dissolving two or more resins in a solvent, mixing, and drying the resins.

[0059] (Other Resins) The resin tube according to the present disclosure may contain other resins besides the poly(3-hydroxyalkanoate)-based resin component, as long as the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester-based resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate, polybutylene sebacate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.

[0060] The content of the other resin is not particularly limited, but is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, even more preferably 10 parts by weight or less, and particularly preferably 5 parts by weight or less, relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate) resin component. It may even be 1 part by weight or less. The lower limit of the content of the other resin is not particularly limited, and may even be 0 part by weight.

[0061] (Plasticizer (C)) The resin tube according to the present disclosure preferably contains a plasticizer (C) in addition to the poly(3-hydroxyalkanoate)-based resin component. By blending the plasticizer (C), the impact resistance (particularly impact resistance at low temperatures) of the resin tube can be improved.

[0062] The plasticizer (C) is not particularly limited, but from the viewpoint of compatibility with the poly(3-hydroxyalkanoate)-based resin component, it is preferable to use an ester compound having an ester bond in the molecule.

[0063] Examples of ester compounds that can be used as plasticizers include modified glycerin compounds, dibasic acid ester compounds, adipate compounds, polyether ester compounds, benzoate ester compounds, citrate ester compounds, isosorbide ester compounds, and polycaprolactone compounds. Among these, modified glycerin ester compounds, dibasic acid ester compounds, adipate ester compounds, polyether ester compounds, and isosorbide ester compounds are preferred. The ester compounds can be used alone or in combination of two or more. When two or more compounds are used in combination, the mixing ratio of the ester compounds can be appropriately adjusted.

[0064] As the modified glycerin compound, a glycerin ester compound is preferred. As the glycerin ester compound, any of glycerin monoesters, diesters, and triesters can be used, but from the viewpoint of compatibility with the poly(3-hydroxyalkanoate) resin component, a glycerin triester is preferred. Among the glycerin triesters, glycerin diacetomonoester is particularly preferred. Specific examples of glycerin diacetomonoesters include glycerin diacetomonolaurate, glycerin diacetomonooleate, glycerin diacetomonostearate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate. Examples of the modified glycerin compound include Riken Vitamin Co., Ltd.'s "Rikemal" PL series and "BIOCIZER."

[0065] Specific examples of dibasic acid ester compounds include dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis(2-ethylhexyl) azelate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, diethyl succinate, and mixed-group dibasic acid ester compounds.

[0066] Examples of the adipate compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

[0067] Examples of polyether ester compounds include polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate.

[0068] As the ester compound, a modified glycerin-based compound is preferred from the viewpoints of cost, versatility, and high biomass content. In particular, from the viewpoint of food contact, a glycerin triester is more preferred, a glycerin diacetomonoester is even more preferred, and glycerin diacetomonolaurate is particularly preferred.

[0069] The content of the plasticizer (C) in the resin tube according to the present disclosure may be set as appropriate taking into consideration the moldability, impact resistance, and modulus of elasticity of the resin tube, but is preferably 0.1 to 10 parts by weight relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component. From the viewpoint of improving impact resistance, the lower limit of the content is preferably 1 part by weight or more, preferably 2 parts by weight or more, and more preferably 3 parts by weight or more. Furthermore, from the viewpoint of maintaining the modulus of elasticity within a good range, the upper limit of the content is preferably 8 parts by weight or less, more preferably 6 parts by weight or less, and even more preferably 4 parts by weight or less.

[0070] (Additives) The resin tube according to the present disclosure may contain additives to the extent that the effects of the invention are not impaired. Examples of additives that can be used depending on the purpose include crystallization nucleating agents, lubricants, antistatic agents, flame retardants, conductive agents, heat insulating agents, crosslinking agents, antioxidants, UV absorbers, colorants, inorganic fillers, organic fillers, and hydrolysis inhibitors. Biodegradable additives are particularly preferred.

[0071] Examples of crystallization nucleating agents include sugar alcohols such as pentaerythritol, galactitol, and mannitol; talc; fatty acid amides; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, sugar alcohols are preferred, and pentaerythritol is particularly preferred, because they are particularly effective in promoting the crystallization of the poly(3-hydroxyalkanoate) resin component. One type of crystallization nucleating agent may be used, or two or more types may be used, and the ratio of use can be appropriately adjusted depending on the purpose.

[0072] When a crystallization nucleating agent is used, its content is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component.

[0073] However, the resin tube according to the present disclosure may be substantially free of sugar alcohols such as pentaerythritol. "Substantially free of sugar alcohols" means that the sugar alcohol content is less than 0.1 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component. It may even be less than 0.01 parts by weight. In an embodiment that is substantially free of sugar alcohols, it is possible to avoid the problems of bleed-out of sugar alcohols and the resulting contamination of the manufacturing equipment.

[0074] When sugar alcohols are not substantially blended, it is preferable to blend talc and / or fatty acid amide as a crystallization nucleating agent. By using these crystallization nucleating agents, productivity of the resin tube can be improved even when sugar alcohols are not substantially blended. Specific examples of fatty acid amides are as described below in detail as lubricants. The fatty acid amide blended in the resin tube according to the present disclosure can function as both a crystallization nucleating agent and a lubricant.

[0075] Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauricamide, ethylenebiscapricamide, p-phenylenebisstearamide, and polycondensates of ethylenediamine, stearic acid, and sebacic acid. Among these, behenamide and erucamide are preferred because of their particularly excellent lubricating effect on poly(3-hydroxyalkanoate)-based resin components. One or more types of lubricants may be used, and the ratio of use can be adjusted appropriately depending on the purpose.

[0076] When a lubricant is used, its content is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component. The resin tube according to the present disclosure preferably contains a lubricant, but does not necessarily need to contain one.

[0077] The resin tube according to the present disclosure may contain a filler. The inclusion of a filler can increase strength. The filler may be either an inorganic filler or an organic filler, or both may be used in combination. The inorganic filler is not particularly limited, but examples include talc, silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, carbon black, etc. Only one type of inorganic filler may be used, or two or more types may be used in combination.

[0078] When the filler is used, its content is not particularly limited, but is preferably 0.5 to 100 parts by weight, more preferably 1 to 80 parts by weight, even more preferably 3 to 70 parts by weight, and even more preferably 5 to 60 parts by weight, relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin components. However, the resin tube according to the present disclosure may be substantially free of a filler. "Substantially free of a filler" means that the filler content is less than 1 part by weight relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin components. It may also be less than 0.1 part by weight.

[0079] (Resin tube) In this specification, a tube refers to a long, thin cylindrical molded product having a substantially uniform wall thickness, a substantially circular cross-sectional shape, and a hollow interior. The tube can be used as a straw or a pipe, but its uses are not limited to these.

[0080] When the resin tube according to the present disclosure is used as a straw, the thickness of the resin tube is preferably 0.01 mm or more and 0.6 mm or less, more preferably 0.05 mm or more and 0.5 mm or less, and even more preferably 0.1 mm or more and 0.4 mm or less, because the resin tube will not collapse when sucked when using it as a straw to drink a beverage, has appropriate flexibility so is unlikely to break, is unlikely to cause injury when poking a fingertip, and is rapidly biodegradable even in seawater.

[0081] Furthermore, when the resin tube according to the present disclosure is used as a straw, the outer diameter of the resin tube is not particularly limited, but from the perspective of ease of use when using it as a straw to drink beverages, it is preferably 2 to 10 mm, more preferably 4 to 8 mm, and even more preferably 5 to 7 mm.

[0082] When the resin tube according to the present disclosure is used as a pipe, the wall thickness of the resin tube can be appropriately set by a person skilled in the art, but is preferably 0.7 mm to 10 mm, more preferably 1 mm to 8 mm. The pipe can be suitably used in marine product farming and fishing.

[0083] The cross-sectional shape of the resin tube according to the present disclosure is generally circular, but from the viewpoint of usability as a straw or pipe, the closer to a perfect circle the better. Therefore, the flatness of the cross-sectional shape of the tube [100 × (maximum outer diameter − minimum outer diameter) / maximum outer diameter] is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and even more preferably 3% or less. A flatness of 0% means that the cross-sectional shape is a perfect circle.

[0084] The length of the resin tube according to the present disclosure is not particularly limited. However, when the resin tube is used as a straw, the length of the resin tube is preferably 50 to 350 mm, more preferably 70 to 300 mm, and even more preferably 90 to 270 mm, from the viewpoint of ease of use when using the resin tube as a straw to drink a beverage.

[0085] The resin tube used as a straw may be a tube that has not undergone secondary processing, or may be a tube that has undergone secondary processing such as the formation of a stopper portion or a bellows portion.

[0086] The resin tube according to the present disclosure has a 50% fracture energy measured at 23°C of greater than 0.625 J. When the 50% fracture energy is greater than 0.625 J, the resin tube exhibits good impact resistance and is less likely to crack during manufacture, transportation, use, etc. The 50% fracture energy is preferably 0.7 J or more, more preferably 1 J or more, and even more preferably 1.4 J or less. The upper limit is not particularly limited, but may be, for example, 10 J or less, 5 J or less, or 3 J or less.

[0087] A resin tube that satisfies the 50% fracture energy condition can be achieved by using, as the poly(3-hydroxyalkanoate)-based resin component, a resin (A) that exhibits a relatively low weight-average molecular weight and a copolymer (B) that exhibits a relatively high weight-average molecular weight and has a specific monomer composition, in specific proportions, as described above. The wall thickness and diameter of the resin tube may be set to satisfy the 50% fracture energy condition. Details of the method for measuring the 50% fracture energy are provided in the Examples section.

[0088] The resin tube according to the present disclosure has a good balance between impact resistance and elastic modulus, and the elastic modulus is maintained within a good range. Specifically, the tensile modulus measured in the MD direction of the resin tube at 23°C is preferably 1430 MPa or more, more preferably 1450 MPa or more, even more preferably 1480 MPa or more, and particularly preferably 1500 MPa or more. The upper limit is not particularly limited, but may be, for example, 2500 MPa or less or 2100 MPa or less.

[0089] The resin tube according to the present disclosure can be produced by a known method, for example, by melting a blend of a poly(3-hydroxyalkanoate)-based resin component and other components in an extruder, extruding the blend through an annular die connected to the outlet of the extruder, and pouring it into water to solidify it into a tubular shape. Alternatively, the blend may be melt-extruded to form pellets, and the resulting pellets may be used to form a tube.

[0090] When the resin tube according to the present disclosure is subjected to secondary processing, the secondary processing may be performed at room temperature or under heating. The resin tube according to the present disclosure can be suitably subjected to secondary processing involving heating. The heating temperature during secondary processing can be appropriately set, and may be, for example, about 100 to 150°C.

[0091] The following items list preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] A resin tube containing a poly(3-hydroxyalkanoate)-based resin component, wherein the poly(3-hydroxyalkanoate)-based resin component contains: a poly(3-hydroxyalkanoate)-based resin (A) having a weight-average molecular weight of 100,000 or more and less than 700,000; and a copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the copolymer (B) having a weight-average molecular weight of 700,000 or more, the content of 3-hydroxybutyrate units being 76 mol % or more and less than 100 mol % of the total of the 3-hydroxybutyrate units and the other hydroxyalkanoate units; the content of resin (A) being 80 wt % or more and 99 wt % or less, and the content of copolymer (B) being 1 wt % or more and 20 wt % or less, of the total amount of the poly(3-hydroxyalkanoate)-based resin component; and the resin tube having a 50% fracture energy at 23°C of more than 0.625 J. [Item 2] The resin tube according to Item 1, wherein copolymer (B) has a 3-hydroxybutyrate unit content of 50 mol% or more and 92 mol% or less. [Item 3] The resin tube according to Item 1 or 2, wherein the content of resin (A) is 90 wt% or more and the content of copolymer (B) is 10 wt% or less of the total amount of the poly(3-hydroxyalkanoate)-based resin component. [Item 4] The resin tube according to any of Items 1 to 3, wherein resin (A) contains a copolymer (A1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 50 mol% or more and 76 mol% or less of 3-hydroxybutyrate units, and the content of copolymer (A1) is 10 wt% or more and 20 wt% or less of the total amount of the poly(3-hydroxyalkanoate)-based resin component.[Item 5] The resin tube according to Item 4, wherein the resin (A) comprises poly(3-hydroxybutyrate) (A2) and / or a copolymer (A3) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of 3-hydroxybutyrate units being more than 90 mol% and not more than 99 mol%, and the total content of poly(3-hydroxybutyrate) (A2) and copolymer (A3) is 70% by weight or more and 90% by weight or less of the total amount of the poly(3-hydroxyalkanoate)-based resin component. [Item 6] The resin tube according to any one of Items 1 to 5, further containing a plasticizer (C). [Item 7] The resin tube according to any one of Items 1 to 6, wherein the tensile modulus in the machine direction at 23°C is 1,430 MPa or more. [Item 8] The resin tube according to any one of Items 1 to 7, wherein the wall thickness is 0.01 mm or more and 10 mm or less.

[0092] The present invention will be specifically explained below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0093] The substances used in the examples and comparative examples are shown below. [Poly(3-hydroxyalkanoate)-based resin] Copolymer (A1): P3HB3HH-30:P3HB3HH (average content ratio 3HB / 3HH=70.5 / 29.5 (mol % / mol %), weight-average molecular weight 640,000 g / mol) Produced in accordance with the method described in Example 9 of WO 2019 / 142845.

[0094] Poly(3-hydroxybutyrate) (A2): PHB: poly(3-hydroxybutyrate) (weight average molecular weight: 300,000 g / mol) Produced according to the method described in Comparative Example 1 of WO 2004 / 041936.

[0095] Copolymer (A3): P3HB3HH-3: P3HB3HH (average content ratio 3HB / 3HH = 97.1 / 2.9 (mol% / mol%), weight average molecular weight is 300,000 g / mol) Produced in accordance with the method described in Example 2 of WO 2019 / 142845. P3HB3HH-6: P3HB3HH (average content ratio 3HB / 3HH = 94.0 / 6.0 (mol% / mol%), weight average molecular weight is 500,000 g / mol) Produced in accordance with the method described in WO 2008 / 010296.

[0096] Copolymer (B): P3HB3HH-11H:P3HB3HH (average content ratio 3HB / 3HH=89.0 / 11.0 (mol % / mol %), weight average molecular weight 750,000 g / mol) was produced in accordance with the method described in WO 2008 / 010296.

[0097] [Additives] Additive-1: Behenic acid amide (manufactured by Nippon Fine Chemicals Co., Ltd.: BNT-22H) Additive-2: Erucic acid amide (manufactured by Nippon Fine Chemicals Co., Ltd.: Neutron-S)

[0098] [Plasticizer] Plasticizer: Glycerin diacetomonolaurate (BIOCIZER, manufactured by Riken Vitamin Co., Ltd.)

[0099] The evaluation methods used in the Examples and Comparative Examples are described below. [Measurement of Impact Resistance of Tube Molded Articles] Tubes with an inner diameter of 5.6 mm, a thickness of 0.2 mm, and a length of 40 mm were prepared using the resin compositions described in the Examples and Comparative Examples. The tubes were cured for two hours in a thermostatic chamber set to one of the temperatures listed in Table 1 (23°C, 15°C, or 10°C). After curing, the tubes were quickly removed from the thermostatic chamber and placed on a 2-mm-thick rubber sheet with their axes horizontal. A 300-g rectangular weight was allowed to freely fall onto the tube from a height arbitrarily set above the top of the tube. The weight was dropped so that it contacted the entire tube. Based on the fracture results, the fracture height with a 50% probability was estimated, and the potential energy of the weight before the weight was dropped was calculated as the 50% fracture energy.

[0100] [Evaluation of Tensile Modulus] The produced tube molded article was cut into a No. 7 dumbbell shape conforming to JIS K 6251 to obtain a test piece. A tensile test was carried out in the MD direction of the tube in accordance with JIS K 7127 using a tensile tester (Shimadzu Corporation: EZ-LX 1kN) at a temperature of 23°C and a tension speed of 100 mm / min. The tensile modulus was calculated based on the S-S curve obtained from the tensile test.

[0101] Example 1: 0.33 kg of P3HB3HH-30, 0.148 kg of PHB, 0.27 kg of P3HB3HH-3, 1.196 kg of P3HB3HH-6, and 0.056 kg of P3HB3HH-11H were blended to obtain the resin composition shown in Table 1, and then 20 g of additive-1 and 10 g of additive-2 were blended and blended. To prepare resin composition pellets, melt extrusion was performed using a φ26 mm co-rotating twin-screw extruder. The cylinder temperature and die temperature were each set to 150 °C, and the resulting resin material (resin mixture) was added and extruded. The extruded strand-shaped resin material was passed through a water tank filled with hot water at 40 °C and cut with a pelletizer to obtain resin composition pellets. For tube molding, a circular die (outer diameter 15 mm, inner diameter 13.5 mm) was connected to a φ50 mm single-screw extruder and extrusion molding was performed. The cylinder temperature and die temperature were each set to 160°C, and the resin composition pellets were added and extruded into a tube. The extruded tube was passed through a water bath at 40°C and taken up at 30 m / min to form a tube with an inner diameter of 5.6 mm and a thickness of 0.2 mm.

[0102] (Examples 2 to 7, Comparative Examples 1 to 3) Resin composition pellets and tubes were prepared in the same manner as in Example 1, except that the formulation was changed as shown in Table 1, and evaluations were carried out in the same manner as in Example 1. The results are summarized in Table 1.

[0103]

[0104] The following can be seen from Table 1. Comparative Example 1 does not contain the high molecular weight copolymer (B). Although the tensile modulus is high, the 50% breaking energy value is insufficient, and it is clear that the balance between impact resistance and modulus is poor.

[0105] Comparative Example 2 also did not contain the high molecular weight copolymer (B) but contained a plasticizer instead. The incorporation of the plasticizer improved the 50% breaking energy, but the tensile modulus was significantly reduced to 1,400 MPa, resulting in a poor balance between impact resistance and modulus.

[0106] On the other hand, Examples 1 to 7, which contained a high molecular weight copolymer (B), all exhibited a tensile modulus of 1,430 MPa or more and a relatively high 50% breaking energy, demonstrating a good balance between impact resistance and modulus. Of these, Examples 3 to 5, which contained a plasticizer (C) in addition to the copolymer (B), exhibited higher tensile moduli than Comparative Example 2. In Comparative Example 3, the content of the high molecular weight copolymer (B) exceeded 20% by weight, and the tensile modulus fell to less than 1,430 MPa.

Claims

1. A resin tube containing a poly(3-hydroxyalkanoate) resin component, wherein the poly(3-hydroxyalkanoate) resin component contains: a poly(3-hydroxyalkanoate) resin (A) having a weight-average molecular weight of 100,000 or more but less than 700,000; and a copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units having a weight-average molecular weight of 700,000 or more, wherein the content of 3-hydroxybutyrate units in copolymer (B) is 76 mol % or more but less than 100 mol % of the total of the 3-hydroxybutyrate units and other hydroxyalkanoate units; the content of resin (A) is 80 wt % or more but less than 99 wt %, and the content of copolymer (B) is 1 wt % or more but less than 20 wt % of the total amount of the poly(3-hydroxyalkanoate) resin component; and the 50% fracture energy at 23°C exceeds 0.625 J.

2. The resin tube according to claim 1, wherein the copolymer (B) contains 3-hydroxybutyrate units in an amount of 80 mol % or more and 92 mol % or less.

3. A resin tube according to claim 1 or 2, wherein the content of resin (A) is 90% by weight or more and the content of copolymer (B) is 10% by weight or less of the total amount of the poly(3-hydroxyalkanoate)-based resin component.

4. A resin tube according to claim 1 or 2, wherein resin (A) contains a copolymer (A1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 50 mol% or more and 76 mol% or less of 3-hydroxybutyrate units, and the content of copolymer (A1) is 10 wt% or more and 30 wt% or less of the total amount of the poly(3-hydroxyalkanoate)-based resin component.

5. The resin tube according to claim 4, wherein the resin (A) comprises poly(3-hydroxybutyrate) (A2) and / or a copolymer (A3) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is more than 90 mol% and not more than 99 mol%; and the total content of poly(3-hydroxybutyrate) (A2) and copolymer (A3) is 50% by weight or more and 90% by weight or less of the total amount of the poly(3-hydroxyalkanoate)-based resin component.

6. The resin tube according to claim 1 or 2, further comprising a plasticizer (C).

7. A resin tube according to claim 1 or 2, having a tensile modulus in the machine direction at 23°C of 1,430 MPa or more.

8. The resin tube according to claim 1 or 2, having a wall thickness of 0.01 mm or more and 10 mm or less.