Polyhydroxyalkanoate resin composition and molded body thereof

Abstract

To provide a polyhydroxyalkanoate-based resin composition that contains a polyhydoxyalkanoate resin having seawater decomposability, has both high rigidity and high processing productivity, and suppresses decline of molecular weight in processing.SOLUTION: A polyhydroxyalkanoate-based resin composition containing a polyhydroxyalkanoate-based resin component has a highest melting peak temperature of 148°C or higher and 170°C or lower in differential scan thermal analysis of the resin composition, a total crystal melting enthalpy calculated from all melting peaks in the range of 65 J / g-75 J / g, and a bending elastic modulus of 1,200 MPa or more measured for a multipurpose test piece of 4 mm thickness obtained from the resin composition in accordance with ISO 3167 Type A.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polyhydroxyalkanoate resin composition and a molded article thereof. [Background technology]

[0002] A large amount of petroleum-derived plastics are discarded every year, and the lack of landfill sites and environmental pollution caused by this large amount of waste are being raised as serious issues. In recent years, microplastics have also become a major problem in the marine environment.

[0003] Polyhydroxyalkanoate resins have excellent seawater degradability and are materials that can solve the environmental problems caused by discarded plastics. For example, the processing and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), a copolymer of poly(3-hydroxybutyrate) resins, can be flexibly controlled by changing the composition ratio of 3-hydroxyhexanoate.

[0004] The inventors have previously proposed poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)-based compositions that have improved thermoformability for sheets and secondary processability for straws by defining the melting point behavior (see Patent Documents 1 and 2).

[0005] However, even with these techniques, there is still room for improvement in obtaining processed products with high productivity. In order to process with high productivity, it is necessary to promote crystallization after melting, and it is known that crystallization can be accelerated by increasing the melting point of poly(3-hydroxybutyrate)-based resins (see Non-Patent Document 1). However, if the melting point becomes too high, the temperature during melt processing approaches the thermal decomposition temperature of the resin, which causes a problem of a significant decrease in the molecular weight of the resin during melt processing.

[0006] The inventors have also proposed a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)-based composition that achieves both productivity and mechanical properties by controlling the melting point and enthalpy of fusion (see Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2020 / 195477 [Patent Document 2] International Publication No. 2020 / 040093 [Patent Document 3] International Publication No. 2020 / 195550 [Non-patent literature]

[0008] [Non-Patent Document 1] Yoshiharu Doi, Shiro Kitamura, Hideki Abe, Macromolecules, vol. 22, pp. 4822-4828, (1995) Summary of the Invention [Problem to be solved by the invention]

[0009] The films and sheets obtained by the technique disclosed in Patent Document 3 are flexible, and may be difficult to apply to rigid applications such as food containers that require rigidity.

[0010] In view of the above-mentioned current situation, the object of the present invention is to provide a polyhydroxyalkanoate-based resin composition which contains a polyhydroxyalkanoate-based resin having seawater decomposability, combines high rigidity and processing productivity, and can suppress a decrease in molecular weight during processing. [Means for solving the problem]

[0011] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, it has been found that by configuring a composition containing a polyhydroxyalkanoate resin component so that the highest melting peak temperature in differential scanning calorimetry is 148°C or higher and 170°C or lower, and the total crystalline fusion enthalpy calculated from all of the melting peaks is within a specific range, it is possible to provide a polyhydroxyalkanoate resin composition that combines high rigidity and processing productivity, and in which a decrease in molecular weight during processing can be suppressed, and thus the present invention has been completed.

[0012] That is, the present invention relates to a polyhydroxyalkanoate-based resin composition containing a polyhydroxyalkanoate-based resin component, in which, in a differential scanning calorimetry analysis of the resin composition, the highest melting peak temperature is 148°C or higher and 170°C or lower, the total crystalline melting enthalpy calculated from all the melting peaks is in the range of 65 J / g to 75 J / g, and the flexural modulus of elasticity measured on a 4 mm-thick multipurpose test piece obtained from the resin composition in accordance with ISO 3167 Type A is 1200 MPa or higher. Preferably, the polyhydroxyalkanoate resin component is a mixture of at least two kinds of polyhydroxyalkanoate resins differing from each other in the types of constituent monomers and / or the content ratios of the constituent monomers. Preferably, the polyhydroxyalkanoate resin component comprises a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. Preferably, the polyhydroxyalkanoate-based resin component is A copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of the other hydroxyalkanoate units is 1 to 5 mol %, and The copolymer (B) contains 3-hydroxybutyrate units and other hydroxyalkanoate units, and the content of the other hydroxyalkanoate units is 6 to 50 mol % or more. Preferably, the proportion of the copolymer (A) in the total of the copolymer (A) and the copolymer (B) is 70 to 85% by weight, and the proportion of the copolymer (B) is 30 to 15% by weight. Preferably, said other hydroxyalkanoate units are 3-hydroxyhexanoate units. The present invention also relates to a polyhydroxyalkanoate resin composition containing the polyhydroxyalkanoate resin composition and a polybutylene succinate adipate resin or a polycaprolactone resin, in which the proportion of the polyhydroxyalkanoate resin component is 55 to 95% by weight, and the proportion of the polybutylene succinate adipate resin or the polycaprolactone resin is 5 to 45% by weight. The present invention further relates to a molded article made of the polyhydroxyalkanoate resin composition. Effect of the Invention

[0013] According to the present invention, it is possible to provide a polyhydroxyalkanoate-based resin composition which contains a polyhydroxyalkanoate-based resin having seawater decomposability, has high rigidity and processing productivity, and is capable of suppressing a decrease in molecular weight during processing. The polyhydroxyalkanoate-based resin composition according to the present invention is a material capable of resolving the environmental problems caused by plastics, which have become an issue in recent years. [Brief description of the drawings]

[0014] [Figure 1] 1 is a graph showing the DSC curve of the polyhydroxyalkanoate resin composition obtained in Example 1, as well as the highest melting peak temperature and total crystalline melting enthalpy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described, however, the present invention is not limited to the following embodiment.

[0016] [Polyhydroxyalkanoate resin composition] The polyhydroxyalkanoate resin composition according to the present embodiment has a highest melting peak temperature of 148°C to 170°C in differential scanning calorimetry, and a total crystalline melting enthalpy calculated from all melting peaks is in the range of 65 J / g to 75 J / g. A flexural modulus of 1200 MPa or more is measured on a multipurpose test piece having a thickness of 4 mm according to ISO 3167 Type A obtained from the resin composition. Furthermore, the polyhydroxyalkanoate resin composition contains at least one polyhydroxyalkanoate resin component, and may further contain components other than the resin component.

[0017] (Polyhydroxyalkanoate resin component) The polyhydroxyalkanoate resin component constituting the main component of the polyhydroxyalkanoate resin composition may be a single polyhydroxyalkanoate resin or a combination of two or more polyhydroxyalkanoate resins. The polyhydroxyalkanoate resin may be, for example, a polymer having a 3-hydroxyalkanoate structural unit (monomer unit) and / or a 4-hydroxyalkanoate structural unit that is decomposable in seawater. In particular, a poly(3-hydroxyalkanoate) resin having a 3-hydroxyalkanoate structural unit, specifically a resin containing a structural unit represented by the following general formula (1), is preferred. [-CHR-CH 2 -CO-O-] (1)

[0018] 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 1 to 10, and more preferably 1 to 8.

[0019] As the poly(3-hydroxyalkanoate)-based resin, a poly(3-hydroxyalkanoate)-based resin produced from a microorganism is particularly preferred. In the poly(3-hydroxyalkanoate)-based resin produced from a microorganism, all of the 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0020] 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 constituent units. The poly(3-hydroxyalkanoate) resin may contain only one or more types of 3-hydroxyalkanoate units as the constituent units of the polymer, or may contain other units (e.g., 4-hydroxyalkanoate units, etc.) in addition to one or more types of 3-hydroxyalkanoate units.

[0021] 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 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units. It is also preferable that the poly(3-hydroxyalkanoate) resin is a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0022] 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 viewpoint of mechanical properties of molded articles and processing productivity, etc., 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.

[0023] From the viewpoint of providing a polyhydroxyalkanoate resin composition that combines high rigidity and processing productivity and that can suppress a decrease in molecular weight during processing, the poly(3-hydroxyalkanoate) resin component is preferably a mixture of at least two types of polyhydroxyalkanoate resins differing from each other in the types of constituent monomers and / or the content ratios of the constituent monomers, and more preferably contains at least one type of highly crystalline poly(3-hydroxyalkanoate) resin and at least one type of low crystalline poly(3-hydroxyalkanoate) resin.

[0024] The highly crystalline poly(3-hydroxyalkanoate) resin is a copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units. The content of 3-hydroxybutyrate units in the highly crystalline poly(3-hydroxyalkanoate) resin is preferably higher than the average content of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin component. Specifically, the content of other hydroxyalkanoate units in the copolymer (A) is preferably 1 mol% or more and 5 mol% or less, more preferably 2 mol% or more and 4 mol% or less.

[0025] As the copolymer (A), the above-mentioned copolymer containing 3-hydroxybutyrate units 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.

[0026] The low-crystalline poly(3-hydroxyalkanoate) resin is a copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units. The content of 3-hydroxybutyrate units contained in the low-crystalline poly(3-hydroxyalkanoate) resin is preferably lower than the average content of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin component. Specifically, the content of other hydroxyalkanoate units in the copolymer (B) is preferably 6 mol% or more and 50 mol% or less, more preferably 8 mol% or more and 40 mol% or less, and even more preferably 10 mol% or more and 30 mol% or less.

[0027] As the copolymer (B), the above-mentioned copolymer containing 3-hydroxybutyrate units 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.

[0028] The ratio of copolymer (A) to the total of copolymer (A) and copolymer (B) is preferably 70% by weight or more and 85% by weight or less, and the ratio of copolymer (B) is preferably 15% by weight or more and 30% by weight or less. By using copolymer (A) and copolymer (B) in this range in combination, the highest melting point peak temperature, total crystalline melting enthalpy, and flexural modulus can be controlled within a predetermined range, and it becomes easy to provide a polyhydroxyalkanoate-based resin composition that has both high rigidity and processing productivity, and can suppress the decrease in molecular weight during processing. It is more preferable that the ratio of copolymer (A) is 73% by weight or more and 84% by weight or less, and the ratio of copolymer (B) is 16% by weight or more and 27% by weight or less, and it is even more preferable that the ratio of copolymer (A) is 75% by weight or more and 83% by weight or less, and the ratio of copolymer (B) is 17% by weight or more and 25% by weight or less.

[0029] The poly(3-hydroxyalkanoate) resin component may contain only the copolymer (A) and the copolymer (B), or may further contain another poly(3-hydroxyalkanoate) resin in addition to the copolymer (A) and the copolymer (B). The other poly(3-hydroxyalkanoate) resin may be a homopolymer of 3-hydroxybutyrate, or may be a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units in which the content of the other hydroxyalkanoate units does not fall within the definition of either the copolymer (A) or the copolymer (B).

[0030] The average content ratio of 3-hydroxybutyrate units and other hydroxyalkanoate units in all monomer units constituting the poly(3-hydroxyalkanoate)-based resin component is preferably 3-hydroxybutyrate units / other hydroxyalkanoate units=98 / 2 to 93 / 7 (mol % / mol %), and more preferably 97 / 3 to 95 / 5 (mol % / mol %), from the viewpoints of achieving high rigidity of molded bodies, good processing productivity, and suppression of molecular weight reduction during processing.

[0031] The average content ratio of each monomer unit in all monomer units constituting the poly(3-hydroxyalkanoate)-based 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 average content ratio means the molar ratio of each monomer unit in all monomer units in the entire poly(3-hydroxyalkanoate)-based resin component, and means the molar ratio of each monomer unit contained in the entire mixture of two or more poly(3-hydroxyalkanoate)-based resins constituting the poly(3-hydroxyalkanoate)-based resin component.

[0032] The weight average molecular weight of the poly(3-hydroxyalkanoate) resin component is not particularly limited, but from the viewpoint of achieving high rigidity of the molded body, good processing productivity, and suppression of molecular weight reduction during processing, it is preferably 50,000 to 3,000,000, more preferably 100,000 to 1,000,000, and even more preferably 120,000 to 700,000.

[0033] In addition, the weight average molecular weight of each poly(3-hydroxyalkanoate) resin constituting the poly(3-hydroxyalkanoate) resin component is not particularly limited. However, the weight average molecular weight of the copolymer (A), which is a highly crystalline poly(3-hydroxyalkanoate) resin, is preferably 50,000 to 3,000,000, more preferably 100,000 to 1,000,000, and even more preferably 120,000 to 700,000, from the viewpoint of achieving high rigidity of the molded body, good processing productivity, and suppression of molecular weight reduction during processing. On the other hand, the weight average molecular weight of the copolymer (B), which is a low-crystalline poly(3-hydroxyalkanoate) resin, is preferably 50,000 to 3,000,000, more preferably 100,000 to 1,000,000, and even more preferably 120,000 to 700,000, from the viewpoint of achieving high rigidity of the molded body, good processing productivity, and suppression of molecular weight reduction during processing.

[0034] The weight average molecular weight of the poly(3-hydroxyalkanoate) resin or poly(3-hydroxyalkanoate) resin component can be measured in terms of polystyrene using gel permeation chromatography (Shodex GPC-101 manufactured by Showa Denko) using a chloroform solution. As the column for the gel permeation chromatography, a column suitable for measuring the weight average molecular weight may be used.

[0035] The method for producing the poly(3-hydroxyalkanoate) resin is not particularly limited, and may be a production method by chemical synthesis or a production method using a microorganism. Among them, a production method using a microorganism is preferable. A known method can be applied to the production method using a microorganism. For example, Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB, are known as bacteria that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates. In particular, with regard to P3HB3HH, in order to increase the productivity of P3HB3HH, it is more preferable to use Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)) or the like, into which genes of P3HA synthase group have been introduced, 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, genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes have been introduced may be used according to the poly(3-hydroxyalkanoate) resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0036] 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. In addition, a blend may be obtained by melt-kneading two or more resins using an extruder, kneader, Banbury mixer, roll, etc., or by dissolving two or more resins in a solvent, mixing, and drying.

[0037] (Melting behavior of the composition) The polyhydroxyalkanoate resin composition according to the present embodiment has a highest melting peak temperature in the range of 148°C to 170°C in differential scanning calorimetry. By satisfying this condition, the molded body obtained by molding the resin composition can be made highly rigid, and the processing productivity can be improved, and the molecular weight reduction during processing can be suppressed. If the highest melting peak temperature is less than 148°C, it may be difficult to obtain a highly rigid and hard molded body, or the processing productivity may be reduced. On the other hand, if it exceeds 170°C, the molecular weight of the resin may be significantly reduced when melting the resin, making it difficult to manufacture the resin composition or molded body. The highest melting peak temperature is preferably 149°C to 165°C, more preferably 150°C to 160°C, and even more preferably 150°C to 155°C.

[0038] The highest melting peak temperature exhibited by the polyhydroxyalkanoate resin composition is measured using a differential scanning calorimeter (DSC25 model manufactured by TA Instruments) by weighing out about 2 mg of the polyhydroxyalkanoate resin composition and heating it from -30°C to 180°C at a heating rate of 10°C / min, and the measured DSC curve is the temperature of the melting peak on the highest temperature side.

[0039] As shown in the DSC curve of FIG. 1, the polyhydroxyalkanoate resin composition according to this embodiment may have, in addition to the melting peak on the highest temperature side, another melting peak in the region lower than this peak, for example, a melting peak below 100° C.

[0040] The polyhydroxyalkanate-based resin composition according to the present embodiment has a total crystalline melting enthalpy calculated from all melting peaks in differential scanning calorimetry measured thereon, which is in the range of 65 J / g to 75 J / g. By making it within this range, the molded body obtained by molding the resin composition can be made highly rigid, and the molecular weight reduction during processing can be suppressed. If the total crystalline melting enthalpy is less than 65 J / g, it is difficult to obtain a highly rigid and hard molded body. On the other hand, if it exceeds 75 J / g, the molecular weight of the resin may be significantly reduced when the resin composition is melted. The total crystalline melting enthalpy is preferably 66 J / g to 74 J / g, more preferably 66 J / g to 73 J / g.

[0041] The total crystalline melting enthalpy calculated from all melting peaks refers to the sum of the crystalline melting enthalpy. Specifically, in the DSC curve obtained as described above, a straight line is drawn between the baselines before the start of melting and after the end of melting, and the total crystalline melting enthalpy is calculated as the area of ​​the melting region (hatched region in Figure 1) enclosed by the straight line and the DSC curve.

[0042] (Production method of the composition) The method for producing the polyhydroxyalkanoate resin composition exhibiting the melting behavior described above includes, for example, a method of appropriately adjusting the copolymerization ratio of each monomer constituting the copolymer when the polyhydroxyalkanoate resin is a copolymer, a method of mixing components other than the polyhydroxyalkanoate resin components such as plasticizers, and a method of mixing at least two polyhydroxyalkanoate resins having different melting behaviors. In particular, a method of mixing at least two polyhydroxyalkanoate resins having different melting behaviors is preferred. Specifically, as described above, it is preferred to mix at least two polyhydroxyalkanoate resins having different types of constituent monomers and / or different content ratios of constituent monomers. This makes it easy to control the highest melting peak temperature of the polyhydroxyalkanoate resin composition in differential scanning calorimetry analysis to 148°C or more and 170°C or less, and the total crystal melting enthalpy calculated from all melting peaks to a range of 65J / g to 75J / g.

[0043] (Flexural modulus) The polyhydroxyalkanoate-based resin composition according to this embodiment is hard. Specifically, a multipurpose test piece having a thickness of 4 mm and conforming to ISO 3167 Type A obtained from the resin composition exhibits a flexural modulus of 1200 MPa or more as measured according to JIS-K7171. The multipurpose test piece can be obtained by injection molding. The flexural modulus is preferably 1400 MPa or more, more preferably 1600 MPa or more, and even more preferably 1700 MPa or more. The upper limit is not particularly limited, but may be, for example, 2500 MPa or less.

[0044] (Other resins) The polyhydroxyalkanoate-based resin composition according to one embodiment may contain other resins than the poly(3-hydroxyalkanoate)-based resin, as long as the effect of the invention is 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. Aliphatic polyester-based resins are preferred, and polybutylene succinate adipate or polycaprolactone are more preferred. Only one type of other resin may be contained, or two or more types may be contained.

[0045] The content of the other resin is not particularly limited, but from the viewpoint of seawater decomposability, it is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less, relative to 100 parts by weight of the total of the poly(3-hydroxyalkanoate)-based resin components. The lower limit of the content of the other resin is not particularly limited, and may be 0 parts by weight.

[0046] On the other hand, from the viewpoint of improving the impact resistance of the polyhydroxyalkanoate resin, the proportion of the polyhydroxyalkanoate resin component in the total of the polyhydroxyalkanoate resin component and the other resins is preferably 55 to 95% by weight and the proportion of the other resins is preferably 5 to 45% by weight, more preferably 60 to 90% by weight and 10 to 40% by weight, and even more preferably 65 to 85% by weight and 15 to 35% by weight. The melting behavior of the polyhydroxyalkanoate resin composition described above is a measured value that does not include the contribution of the other resins.

[0047] (Layered clay minerals) The polyhydroxyalkanoate-based resin composition according to one embodiment may further contain a layered clay mineral. Here, the layered clay mineral refers to a mineral containing layered silicate as a main component.

[0048] The layered clay mineral is not particularly limited and any known one can be used, but since it is easy to obtain an improvement effect on processing productivity, one or more selected from the group consisting of smectite, mica, talc, pyroferrite, vermiculite, chlorite, kaolinite, and serpentine are preferred. From the viewpoint of versatility, mica, talc, and kaolinite are preferred, and talc is particularly preferred.

[0049] Examples of the mica include wet-ground mica and dry-ground mica, and specific examples include mica manufactured by Yamaguchi Mica Co., Ltd. and Keiwa Rozai Co., Ltd.

[0050] Examples of the talc include general-purpose talc and surface-treated talc. Specific examples include "Microace" (registered trademark) manufactured by Nippon Talc Co., Ltd., "Talcan Powder" (registered trademark) manufactured by Hayashi Kasei Co., Ltd., and talc manufactured by Takehara Chemical Industry Co., Ltd. and Maruo Calcium Co., Ltd.

[0051] Examples of the kaolinite include dry kaolin, calcined kaolin, wet kaolin, etc., and specific examples include "TRANSLINK" (registered trademark), "ASP" (registered trademark), "SANTINTONE" (registered trademark), and "ULTREX" (registered trademark) manufactured by Hayashi Kasei Co., Ltd., and kaolinite manufactured by Keiwa Rozai Co., Ltd.

[0052] The average particle size of the layered clay mineral is preferably 0.1 to 50 μm, more preferably 0.3 to 30 μm, further preferably 0.5 to 15 μm, and particularly preferably 1 to 10 μm, in order to obtain excellent mechanical properties and processing productivity of the molded body. The average particle size can be measured using a laser diffraction / scattering device such as "Microtrac MT3100II" manufactured by Nikkiso Co., Ltd.

[0053] The content of the layered clay mineral is not particularly limited, but may be, for example, 5 parts by weight or more and 45 parts by weight or less relative to 100 parts by weight of the poly(3-hydroxyalkanoate)-based resin component in total. The content is preferably 10 parts by weight or more and 40 parts by weight or less, more preferably 10 parts by weight or more and 35 parts by weight or less, and even more preferably 15 parts by weight or more and 30 parts by weight or less.

[0054] (Additives) The polyhydroxyalkanoate resin composition according to one embodiment may contain additives within the range that does not impair the effects of the invention. Examples of additives that can be used depending on the purpose include crystallization nucleating agents, lubricants, plasticizers, antistatic agents, flame retardants, conductive agents, heat insulating agents, crosslinking agents, antioxidants, ultraviolet absorbers, colorants, inorganic fillers, organic fillers, and hydrolysis inhibitors. Additives having biodegradability are particularly preferred.

[0055] Examples of the crystallization nucleating agent include pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among them, pentaerythritol is preferred because it is particularly effective in promoting the crystallization of the poly(3-hydroxyalkanoate) resin component. The amount of the crystallization nucleating agent used 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 a total of 100 parts by weight of the poly(3-hydroxyalkanoate) resin component. In addition, one type of crystallization nucleating agent may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted depending on the purpose.

[0056] Examples of the lubricant include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauramide, ethylenebiscapricamide, p-phenylenebisstearamide, and polycondensates of ethylenediamine, stearic acid, and sebacic acid. Among them, behenamide or erucamide is preferred because of its particularly excellent lubricant effect on poly(3-hydroxyalkanoate)-based resin components. The amount of the lubricant used 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 of poly(3-hydroxyalkanoate)-based resin components. Furthermore, one type of lubricant may be used, or two or more types may be used, and the ratio of use can be appropriately adjusted depending on the purpose.

[0057] [Molded body] The polyhydroxyalkanoate resin composition according to the present embodiment can be melt-kneaded with each component, and pelletized as necessary, and then molded by various molding methods such as inflation molding, extrusion molding, injection molding, blow molding, and calendar molding. The polyhydroxyalkanoate resin composition according to the present embodiment has high processing productivity, and can be suitably used in molding methods that continuously perform melt processing, such as inflation molding and extrusion molding. Each molding method will be specifically described below.

[0058] First, a poly(3-hydroxyalkanoate)-based resin component, other resins as necessary, and optional additives are added, and melt-kneaded using an extruder, kneader, Banbury mixer, roll, etc. to prepare a resin composition, which is extruded into a strand shape and then cut to obtain pellets having a particle shape such as a cylindrical shape, an elliptical cylindrical shape, a spherical shape, a cubic shape, a rectangular parallelepiped shape, etc. The prepared pellets are desirably sufficiently dried at 40 to 80°C to remove moisture, and then molded.

[0059] The temperature at which the melt kneading is carried out cannot be generally specified because it depends on the melting point, melt viscosity, etc. of the resin used. In the case of extrusion pelletization, however, it is preferable to set the cylinder temperature to 100 to 160°C, and the adapter and die temperatures to 140 to 160°C.

[0060] The pellets produced by the above method are rapidly crystallized, and thus molded articles can be produced with high productivity. Preferred molding methods include, for example, T-die extrusion, cast extrusion, profile extrusion, tube extrusion, inflation molding, calendar molding, injection molding, vacuum molding, compressed air molding, foam molding, and melt spinning.

[0061] The polyhydroxyalkanoate resin composition can be processed into a film or sheet by known methods such as inflation molding and extrusion molding using a T-die. Specific conditions may be appropriately set, but for example, in inflation molding, it is preferable to dry the pellets with a dehumidifying dryer or the like before molding until the moisture content of the pellets is 500 ppm or less, set the cylinder temperature to 100°C to 160°C, and set the adapter and die temperatures to 130°C to 160°C.

[0062] There is no particular restriction on the thickness of the film or sheet, but generally, a thickness of about 1 to 100 μm is called a film, and a thickness of more than 100 μm up to about 2 mm is called a sheet.

[0063] The film or sheet obtained from the polyhydroxyalkanoate-based resin composition according to the present embodiment has excellent biodegradability, and therefore can be suitably used in the fields of agriculture, fishery, forestry, horticulture, medicine, sanitary products, food industry, clothing, non-clothing, packaging, automobiles, building materials, and other fields, such as partitions, trays, containers, lids, plates, blister packaging, and PTP packaging.

[0064] The pellets can also be subjected to injection molding to form an injection molded article. Injection molding is a method in which a heated and melted resin composition is injected into a mold, the resin composition is cooled and solidified in the mold, the mold is opened, and the molded article is released to obtain a molded article. As the injection molding method, in addition to the injection molding method generally used when molding a thermoplastic resin, injection blow molding, gas-assisted molding, injection compression molding, and other injection molding methods can be used. In addition, in-mold molding, gas press molding, two-color molding, sandwich molding, PUSH-PULL, SCORIM, and the like can also be used. However, the injection molding methods that can be used are not limited to the above methods.

[0065] The temperature at which the mold is cooled after injection can be appropriately determined by one skilled in the art, but is preferably 20 to 70°C, more preferably 25 to 60°C, further preferably 30 to 50°C, and particularly preferably 35 to 45°C.

[0066] Applications of the injection molded article according to one embodiment are not particularly limited, but examples include tableware such as plates, cups, lid trays, etc., cutlery such as spoons, forks, knives, stirrers, etc., capsules such as coffee capsules and toy containers, toys, agricultural supplies, office automation parts, home appliance parts, automotive parts, various containers and boxes, daily necessities, stationery, and bottle molded products. EXAMPLES

[0067] The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0068] The substances used in the examples and comparative examples are shown below. [Polyhydroxyalkanoate resin] P3HB3HH-1: P3HB3HH (average content ratio 3HB / 3HH = 97 / 3 (mol% / mol%), weight average molecular weight is 650,000 It was produced in accordance with the method described in Example 2 of International Publication WO2019 / 142845. P3HB3HH-2: P3HB3HH (average content ratio 3HB / 3HH = 89 / 11 (mol% / mol%), weight average molecular weight is 580,000 It was produced in accordance with the method described in Example 5 of International Publication WO2019 / 142845. P3HB3HH-3: P3HB3HH (average content ratio 3HB / 3HH = 72 / 28 (mol% / mol%), weight average molecular weight is 1 million It was produced in accordance with the method described in Example 9 of International Publication WO2019 / 142845. P3HB3HH-4: P3HB3HH (average content ratio 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight is 580,000 It was produced in accordance with the method described in Example 1 of International Publication WO2019 / 142845. P3HB: Weight average molecular weight is 700,000 g / mol It was produced in accordance with the method described in Production Example 1 of International Publication WO2015 / 146194.

[0069] When a mixture of two or more polyhydroxyalkanoate resins is used as the polyhydroxyalkanoate resin component, the average ratio (3HB / 3HH) in Table 1 is the average value calculated from the average 3HB / 3HH content ratio in each resin and the weight proportion of each resin.

[0070] [Aliphatic polyester resin] PBSA: Polybutylene succinate adipate (Mitsubishi Chemical Corporation, Bio-PBS FD92PM, glass transition temperature -45°C) PCL: Polycaprolactone (Perstorp, CAPA6800, glass transition temperature -55°C)

[0071] [Additives] Additive: Behenamide (Nippon Fine Chemicals: BNT-22H)

[0072] Next, the evaluation methods used in the examples and comparative examples will be described. [Measurement of melting peak temperature and total crystalline melting enthalpy in differential scanning calorimetry] About 2 mg of the polyhydroxyalkanoate resin composition obtained in each Example or Comparative Example was weighed out using a differential scanning calorimeter (TA Instruments, DSC25 model), and the temperature was raised from -30°C to 180°C at a heating rate of 10°C / min. The temperature of the maximum melting peak in the DSC curve obtained was taken as the melting point. In addition, in the DSC curve, a straight line was drawn between the baselines before the start of melting and after the end of melting, and the total heat amount calculated as the area of ​​the melting region surrounded by the straight line and the DSC curve was determined as the total crystalline melting enthalpy.

[0073] [Weight-average molecular weight measurement by gel permeation chromatography] The weight average molecular weight was evaluated by converting it into a polystyrene standard using a gel permeation chromatography system (Shodex GPC-101, manufactured by Showa Denko) connected with two columns (Shodex K-804, manufactured by Showa Denko) and chloroform as the mobile phase.

[0074] [Evaluation of processing productivity] The cylinder temperature and die temperature of a φ40 mm single screw extruder connected to a 500 mm wide T-die were set to the melting point of the resin + 15°C, and polyhydroxyalkanoate resin pellets were fed into the extruder hopper and extruded from the T-die, sandwiched between two cooling rolls temperature-controlled at 50°C, and taken up at a constant speed by a take-up machine to produce a sheet with a thickness of 0.4 mm. When forming this sheet, the maximum speed (linear speed) at which it could be taken up without sticking to the cooling rolls was evaluated as processing productivity.

[0075] [Evaluation of weight average molecular weight retention rate] The weight average molecular weight measured for the resin sheet obtained in the processing productivity evaluation using the T-die was divided by the weight average molecular weight measured for the resin pellets before the processing productivity evaluation was performed to calculate the retention of the weight average molecular weight during sheet processing.

[0076] [Evaluation of bending modulus] Preparation of test specimens The obtained pellets were used as raw material and injection molded using an injection molding machine (PLASTAR Si-100IV, manufactured by Toyo Machinery & Metals Co., Ltd.) to form multipurpose test pieces with a thickness of 4 mm conforming to ISO 3167 Type A. The cylinder temperature of the molding machine was set to 160 to 190°C, and the mold temperature was set to 45°C. Measurement of flexural modulus The flexural modulus was measured in accordance with JIS-K7171 using a three-point bending tester (Autograph AG-10TB: manufactured by Shimadzu Corporation). The test conditions were a test speed of 2 mm / min, a distance between supports of 64 mm, and a radius of the indenter and the support of 5.0 mm. The measurement atmosphere was 23°C and 50% RH.

[0077] [Impact resistance evaluation] A rectangular sample measuring 80mm x 10mm x 4mm was cut from the center of the dumbbell test piece specified by the ISO, and a notch was further machined using a dedicated notch cutting machine specified by the ISO so that the remaining white space of the V-notch was 8mm. Using this standard sample, the impact resistance was evaluated in a Charpy impact test at 23℃.

[0078] Example 1 75% by weight of P3HB3HH-1 and 25% by weight of P3HB3HH-2 were dry-blended with 1 part by weight of additive, and the mixture was fed into a φ26 mm co-rotating twin-screw extruder with cylinder and die temperatures set to 150°C, extruded, passed through a water tank filled with hot water at 45°C to solidify the strands, and cut with a pelletizer to obtain resin composition pellets. The resin composition had a melting peak temperature of 152° C., a crystal melting enthalpy of 71 J / g, and a weight average molecular weight of 590,000 as measured by differential scanning calorimetry.

[0079] The resin composition pellets were evaluated for processing productivity in a T-die of 10 m / min, the weight average molecular weight after T-die processing was 540,000, the retention rate of the weight average molecular weight was 92%, and the flexural modulus was 1,850 MPa. The evaluation results are shown in Table 1.

[0080] (Example 2, Comparative Examples 1 to 4) Resin composition pellets were prepared in the same manner as in Example 1 except that the formulation was changed as shown in Table 1, and various evaluations were carried out. The results are shown in Table 1.

[0081] [Table 1]

[0082] From Table 1, it can be seen that the polyhydroxyalkanoate resin composition of each Example has a high flexural modulus and is hard, has a high linear speed and good processing productivity, and has a high retention of weight average molecular weight when secondary processed into a sheet.

[0083] On the other hand, in Comparative Example 1, the total crystalline melting enthalpy was large at 76 J / g, and it is understood that the molecular weight was significantly reduced during secondary processing into a sheet. It is clear that Comparative Example 2 has an excessively low melting point, and therefore has a low linear speed and low processing productivity. The melting point of Comparative Example 3 was too high, and it was necessary to raise the cylinder and die temperatures to 170°C to melt the resin during the preparation of the resin pellets, but the molecular weight was significantly reduced during this process, making it difficult to draw the resin into strands. Therefore, it was not possible to obtain resin composition pellets, and it was not possible to carry out each evaluation. It is clear that Comparative Example 4 has a low total crystalline fusion enthalpy of 50 J / g, and is a soft resin composition having a low flexural modulus.

[0084] (Examples 3 to 4) As shown in Table 2, resin composition pellets were prepared in the same manner as in Example 1, except that the resin composition pellets obtained in Example 1 and PBSA or PCL were used, and each evaluation was carried out. The results are shown in Table 2.

[0085] [Table 2]

[0086] From Examples 3 to 4 in Table 2, it can be seen that by blending polybutylene succinate adipate resin or polycaprolactone resin with the polyhydroxyalkanoate resin composition of Example 1, it is possible to improve impact resistance without significantly impairing processing productivity or weight average molecular weight retention.

Claims

1. A polyhydroxyalkanoate-based resin composition containing a polyhydroxyalkanoate-based resin component, The polyhydroxyalkanoate resin component is A copolymer (A) of 3-hydroxybutyrate units and 3-hydroxyhexanoate units, in which the content of 3-hydroxyhexanoate units is 1 to 5 mol %, and The copolymer (B) contains 3-hydroxybutyrate units and 3-hydroxyhexanoate units, and the content of the 3-hydroxyhexanoate units is 6 to 50 mol % or more. the proportion of the copolymer (A) in the total of the copolymer (A) and the copolymer (B) is 70 to 85% by weight, and the proportion of the copolymer (B) is 30 to 15% by weight; In a differential scanning calorimetry analysis of the resin composition, the highest melting peak temperature is 148° C. or more and 170° C. or less, and the total crystalline melting enthalpy calculated from all the melting peaks is in the range of 65 J / g to 75 J / g; A polyhydroxyalkanoate-based resin composition having a flexural modulus of 1200 MPa or more as measured on a multipurpose test piece having a thickness of 4 mm in accordance with ISO 3167 Type A obtained from the resin composition.

2. A polyhydroxyalkanoate-based resin composition comprising the polyhydroxyalkanoate-based resin composition according to claim 1 and a polybutylene succinate adipate resin or a polycaprolactone resin, the proportion of the polyhydroxyalkanoate-based resin composition being 55 to 95% by weight, and the proportion of the polybutylene succinate adipate resin or the polycaprolactone resin being 5 to 45% by weight.

3. A molded article comprising the polyhydroxyalkanoate resin composition according to claim 1 or 2.

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