Method for manufacturing polymer molded products

Abstract

The present invention addresses the problem of providing a method for producing a polymer molded product that does not cause significant loss of molecular weight during melt molding, even with polymers that easily lose molecular weight in a molten state. The present invention provides a method for producing a polymer molded product where the method includes performing melt molding in a temperature range in which some lamella crystals, in a polymer that includes lamella crystals having different lamella thicknesses, are melted and fluidized, and the remaining lamella crystals remain without being melted.

Description

[Technical Field]

[0001] The present invention relates to a method for molding a crystalline thermoplastic polymer having lamellar crystals of different thicknesses, lengths, widths, and degrees of crystallinity in a partially molten state, rather than melting all the crystals and then molding the polymer. That is, the present invention relates to a method for melt-molding a polymer at a temperature at which the lamellar crystals on the higher melting point side are difficult to melt, and at which the lamellar crystals on the lower melting point side and the amorphous regions melt and become fluid. Furthermore, if the melting point of a polymer is close to the thermal decomposition temperature at which a molecular weight reduction occurs due to heating, the molecular weight of the polymer may decrease in the molten state. The present invention relates to a molding method that does not cause a significant molecular weight reduction during molding, even for such polymers. The present invention also relates to a spinning method that prevents fibers from sticking together during the melt spinning process due to slow crystallization. Furthermore, the present invention also relates to a spinning method that prevents sticking even when using polymers that have a glass transition point lower than room temperature and tend to stick together when being turned into fibers. Sticking is a state in which the fibers stick together due to the strong adhesiveness of the polymer, making it difficult to unwind the fibers. [Background technology]

[0002] Polyhydroxyalkanoates (polyhydroxyalkanoic acids, hereafter abbreviated as PHA) are thermoplastic polyesters that are accumulated by microorganisms. They have attracted attention as biodegradable, biocompatible, and bioabsorbable plastics, and extensive research has been conducted on them (Non-Patent Document 1). More than 100 types of monomer units that make up PHA are known. A typical PHA is poly-3-hydroxybutyrate (hereafter abbreviated as P(3HB)), which is composed of (R)-3-hydroxybutyrate (also called (R)-3-hydroxybutyric acid, hereafter abbreviated as 3HB) (Non-Patent Document 1).

[0003] The melting point of P(3HB) is approximately 175 to 180°C, which is as high as that of polypropylene (hereinafter abbreviated as PP). The breaking strength of P(3HB) is similar to that of PP, but the breaking elongation is 5% or less, and the glass transition point is 4°C (below room temperature).

[0004] Because P(3HB) is a highly crystalline, hard, and brittle material, it is often not used as a single molded body such as a film. When attempting to use PHA industrially, methods known to improve its physical properties (crystallinity, mechanical properties, etc.) include introducing a second component monomer unit to form a copolymer, increasing the molecular weight, and compounding with different polymeric materials.

[0005] PHAs, including P(3HB), are susceptible to thermal decomposition. While significant weight loss does not occur near the melting point of P(3HB), chain scission is known to cause molecular weight degradation, resulting in a significant problem of molecular weight degradation in the molten state. Furthermore, the crystallization rate of PHAs is significantly slower than that of traditional industrial polymers, with their glass transition temperatures below room temperature. When PHAs are molded after being heated and molten, they present several processing challenges, including long cooling times for solidification, poor productivity, slow crystallization during melt spinning, resulting in amorphous fiber winding, which can lead to fiber sticking. To avoid sticking, the fibers must be wound without overlapping. Furthermore, the long cooling times required for solidification (crystallization) after winding are also significant. Furthermore, slow crystallization rates lead to large spherulite growth, which can lead to deterioration of the molded product's physical properties and aging. Copolymerization can further reduce the nucleation density, i.e., the crystallization rate, and the above processing challenges persist. Furthermore, increasing the molecular weight poses another problem: excessively high melt viscosity.

[0006] In the melt processing of thermoplastic polymeric materials such as polyester, various crystal nucleating agents have been investigated to improve the crystallization rate.

[0007] Known crystal nucleating agents include, for example, the following for specific polyesters: Inorganic elements such as Zn powder, Al powder, graphite, and carbon black; Metal oxides such as ZnO, MgO, Al2O3, TiO2, MnO2, SiO2, Fe3O4; nitrides such as aluminum nitride, silicon nitride, titanium nitride, and boron nitride; inorganic salts such as Na2CO3, CaCO3, MgCo3, CaSO4, CaSiO3, BaSO4, Ca3(PO4)3; Clays such as talc, kaolin, clay, and white clay; Organic salts such as calcium oxalate, sodium oxalate, calcium benzoate, calcium phthalate, calcium tartrate, magnesium stearate, polyacrylates; Polymers such as polyester, polyethylene, and polypropylene: It is known to add the following (Patent Document 1).

[0008] Also, particulate materials such as talc, micronized mica, boron nitride, and calcium carbonate have been tried as crystal nucleating agents for PHA.A more effective method is known in which an organic phosphonic acid such as cyclohexylphosphonic acid or an organic phosphinic acid, or an ester thereof, or a derivative of such an acid or ester, and a metal compound such as an oxide, hydroxide, or saturated or unsaturated carboxylate of a metal of Groups IA to VA or IB to VB of the periodic table are intimately mixed together (Patent Document 2).

[0009] Furthermore, as a nucleating agent for PHA, Sorbitol and sodium benzoate (Patent Document 3); sugar alcohols such as erythritol, D-arabitol, ribitol, xylitol, galactitol, D-mannitol, L-mannitol, D-sorbitol, myo-inositol, and scyllo-inositol (Patent Document 4); Polyvinyl alcohol, chitin, chitosan (Patent Document 5); Polyalkylene oxides such as polyethylene oxide, polypropylene oxide, and polybutylene oxide (Patent Document 6); aliphatic polyesters such as polylactic acid and PHA, aliphatic carboxylic acid amides, aliphatic carboxylic acid salts, aliphatic alcohols, and aliphatic carboxylic acid esters (Patent Documents 7 to 9); fatty acid esters such as dimethyl adipate, di-2-ethylhexyl adipate, diisobutyl adipate, dibutyl adipate, diisodecyl adipate, dibutyl diglycol adipate, dibutyl sebacate, and di-2-ethylhexyl sebacate (Patent Document 10); Cyclic compounds having C═O and a functional group selected from NH, S, and O in the molecule, such as indigo, quinacridone, and quinacridone magenta (Patent Document 11); Ketopyrroles, which are cyclic compounds having a C═O and an NH group in the molecule (Patent Document 12); Sorbitol derivatives such as bisbenzylidene sorbitol and bis(p-methylbenzylidene) sorbitol (Patent Document 13); Compounds containing a nitrogen-containing heteroaromatic nucleus such as pyridine, pyrimidine, pyrazine, pyridazine, triazine, and imidazole (Patent Document 14); Phosphate ester compounds (Patent Document 15); Bisamides of higher fatty acids and metal salts of higher fatty acids (Patent Document 16); Fatty acids and fatty acid amides (Patent Document 17); Branched polylactic acid (Patent Document 18); Pentaerythritol (Patent Document 19); Pentaerythritol and inorganic or organic fillers (Patent Document 20); Sorbitol acetal, compounds having an amide bond, and pentaerythritol (Patent Document 21) Amino acids such as tryptophan, phenylalanine, p-chloro-phenylalanine, m-tyrosine, phenylglycine, p-hydroxyphenylglycine, methionine, o-tyrosine, and valine, and phosphatidylcholine (Patent Documents 22 to 24); Dipeptides such as aspartame (Patent Document 25); and Nucleic acid bases such as uracil and thymine (Patent Document 26) is known.

[0010] These methods have been adopted to accelerate the slow crystallization rate of aliphatic polyesters such as PHA and polylactic acid and improve their processability during molding. However, they are ineffective, resulting in reduced strength and a poor surface appearance of the molded product, and problems remain, such as the need for additional additives. Furthermore, depending on the type of nucleating agent, as crystallization progresses after molding, differences in compatibility and molecular weight can cause the agent to be pushed out of the crystal, resulting in blooming or bleeding. In such cases, additional additives such as dispersants, anti-agglomerating agents, and compatibilizers may be required. The above-mentioned nucleating agents include those made of fatty acids and amino acids that are easily decomposed, absorbed, or metabolized in the body, i.e., non-toxic, for use in the body. However, a truly effective crystal nucleating agent has yet to be discovered.

[0011] Furthermore, attempts have been made to improve the crystallization properties of PHA by blending it with other PHAs or biodegradable polymers. Patent Documents 27 to 29 disclose the addition of P(3HB), which has a higher melting point, as a crystal nucleating agent (nucleating material) to a P(3HB-co-3HV) copolymer consisting of 3HB and 3-hydroxyvalerate (3-hydroxyvaleric acid, hereinafter abbreviated as 3HV), a P(3HB-co-3HHx) copolymer consisting of 3HB and 3-hydroxyhexanoate (3-hydroxyhexanoic acid, hereinafter abbreviated as 3HHx), or a P(3HB-co-3HO) copolymer consisting of 3HB and 3-hydroxyoctanoate (3-hydroxyoctanoic acid, hereinafter abbreviated as 3HO).

[0012] In Patent Documents 27 to 29, Dry mixing involves mixing the blended dry powder PHA either directly or in the presence of dry ice; Solution mixing in which the polymer is partially or completely dissolved in a solvent such as chloroform and then stirred and mixed, and then the solvent is evaporated to precipitate the polymer, or the polymer is precipitated in a poor solvent; and 1. Mix the high-melting P(3HB) to be added at a temperature that does not melt the PHA, but melts the PHA (P(3HB-co-3HV), P(3HB-co-3HHx), or P(3HB-co-3HO) in the examples) to be added, by thoroughly stirring and mixing the PHA, i.e., partial melt mixing, at a temperature that does not melt the PHA; The above mixing methods are described, but it is mentioned that it is necessary for a small amount of P(3HB) on the high melting point side to be mixed to be finely and uniformly dispersed in the PHA copolymer on the low melting point side.

[0013] Each of the above mixing methods has its own disadvantages. Dry mixing, even when mixing polymer powders, limits the ability to achieve uniform mixing below the powder particle size. Solution mixing requires large amounts of good solvents such as chloroform, and when reprecipitation is performed, even larger amounts of poor solvents—5 to 10 times the amount of good solvent—are required. Furthermore, differences in solubility during reprecipitation can lead to uneven precipitation of the polymer species. Even when the blend is partially molten, the added P(3HB) has high crystallinity and a high melting point, making it unsuitable for forming small, uniform crystal nuclei because the P(3HB) particles remain largely unchanged and are mixed without melting. While the method of elevating the temperature above the melting point of P(3HB) to achieve uniform blending is common in melt mixing, PHAs, including P(3HB), inevitably suffer from thermal decomposition, deterioration due to agitation, and molecular weight loss near the melting point of P(3HB).

[0014] Instead of promoting crystallization by blending P(3HB) extracted from the cells with a PHA copolymer, a method has been reported in which P(3HB) or 3HB-rich PHA, which can serve as crystal nuclei, is produced as a blend within the cells during culture together with other PHA copolymers, eliminating the need to blend P(3HB) and PHA after extracting the PHA from the cells. Patent Document 30 describes a method in which the carbon source supply is changed during culture to produce P(3HB) or P(3HB-co-3HHx) with a low 3HHx ratio together with P(3HB-co-3HHx) with an increased 3HHx ratio. Patent Documents 31 and 32 disclose methods for producing PHA blends with different melting points within the same cells by using genetic engineering to contain multiple PHA synthases with different substrate specificities within the same cells. Although it is also stated that molding can be performed at temperatures below 170°C, it is unclear what temperature range is possible for molding. In known molding processes, it is common to melt the polymer at a temperature above its melting point and then mold it. In this document, the purpose is also to improve the solidification rate (crystallization rate) of the PHA blend once it has been melted.

[0015] Non-patent documents 2 to 4 do not aim to demonstrate that P(3HB) can serve as a crystal nucleus, but they do describe PHA-producing wild-type strains that produce a blend of P(3HB) and PHA copolymers within the same bacterium, and describe the production of a blend of P(3HB) homopolymer and C4 to C12 PHA copolymers by naturally maintaining PHA polymerizing enzymes with different substrate specificities within the same bacterium.

[0016] On the other hand, there are also reports using ultra-high molecular weight P(3HB) and reports on controlling crystal formation independently of molecular weight to achieve high strength. For example, ultra-high molecular weight P(3HB) with a number-average molecular weight of 1.5 million or more (weight-average molecular weight of 3 million) was synthesized using genetically modified Escherichia coli, and P(3HB) films with improved physical properties were obtained using this ultra-high molecular weight P(3HB) (Patent Document 33 and Non-Patent Document 5).

[0017] In addition, a molecular weight-independent method for producing P(3HB) fibers has been described in Patent Documents 34 and 35. The method involves melt-extruding P(3HB), rapidly cooling it to a temperature below the glass transition temperature +15°C, and solidifying it to produce amorphous fibers. The amorphous fibers are then cold-stretched to orient the molecular chains of the amorphous fibers, followed by heat treatment (hereinafter also referred to as the "cold stretching method"). Patent Documents 34 and 35 also disclose a fiber production method (hereinafter also referred to as the "microcrystalline nucleus stretching method") in which the melt-extruded fibers are rapidly cooled to a temperature below the glass transition temperature of the PHA +15°C and solidified to produce amorphous fibers. The amorphous fibers are then left at a temperature below the glass transition temperature +15°C to form microcrystalline nuclei (isothermal crystallization) to produce crystallized fibers. The crystallized fibers are then stretched and further heat-treated under tension (hereinafter also referred to as the "microcrystalline nucleus stretching method") (Patent Document 36).

[0018] However, the above methods are industrially disadvantageous for several reasons: the production efficiency of ultra-high molecular weight P(3HB) is low and the costs are high; the cold drawing method requires rapid cooling to a low temperature near the glass transition temperature to obtain amorphous fibers; and the microcrystalline nucleus drawing method requires rapid cooling to a low temperature near the glass transition temperature and then maintaining it at that low temperature for a long period of time to generate microcrystals of the molten P(3HB).

[0019] Ultra-high molecular weight P(3HB) with a weight-average molecular weight of 2.7 million produced by genetically modified E. coli was added to P(3HB) derived from ordinary microorganisms with a weight-average molecular weight of 520,000, and the mixture was dissolved in chloroform and cast into a film. The film was hot-pressed at 200°C, quenched in ice water, and then cold-stretched. Observation of crystal growth in the P(3HB) film containing trace amounts of the ultra-high molecular weight P(3HB) after reheating to 200°C suggests that the ultra-high molecular weight P(3HB) behaves like a nucleating agent and promotes nucleation (Non-Patent Document 6). In one study, a small amount of ultra-high molecular weight P(3HB) with a weight-average molecular weight of 3.47 million was added to P(3HB) with a weight-average molecular weight of 520,000, and melt-spun at 180°C, 190°C, and 200°C (Non-Patent Document 7). While the molecular weight decreased upon heating above the melting point, the addition of ultra-high molecular weight P(3HB) suppressed the initial thermal decomposition of P(3HB) and improved the processability of melt spinning. It was reported that blended P(3HB) fibers containing 5% by weight of ultra-high molecular weight P(3HB) exhibited a strength of 740 MPa after melt spinning and two-stage cold drawing. While this process required only a small amount of ultra-high molecular weight P(3HB), the two-stage cold drawing at 4°C was necessary, making the process unsuitable for industrialization.

[0020] It has also been reported that when a molding material primarily composed of a biodegradable polyester having a melting point within a specific range is melt-molded at a specific heating temperature range to produce a melt-molded product, the cold crystallization heat and the sum of the heat of fusion and the cold crystallization heat are set within specific ranges as indicators of the crystallization ability and degree of crystallization of the resulting melt-molded product (Patent Document 37). It has also been reported that a copolymer of 3HB and 3-hydroxyhexanoate is processed at a temperature (around 160°C) that does not completely melt the crystals (Non-Patent Document 8). Furthermore, a tube made of a poly(3-hydroxybutyrate) resin has been reported in which the difference between the melting point peak temperature and the melting point peak end temperature in differential scanning calorimetry analysis of the poly(3-hydroxybutyrate) resin is 10°C or more (Patent Document 38). Furthermore, a method for producing a biodegradable resin molded article has been reported, in which, when a biodegradable resin composition containing poly(3-hydroxyalkanoate) is heated, melted, and kneaded to form a molded article, the amount of crystals remaining at the outlet of the molding machine after the heating, melting, and kneading is confirmed by near-infrared spectroscopy, and the amount of crystals remaining at the outlet of the molding machine is adjusted so that a crystallization peak by near-infrared spectroscopy of the molded article is observed within 200 seconds after molding (Patent Document 39). However, there is no description of setting the melt molding temperature to a temperature higher than the flow initiation temperature measured by a flow tester heating method and showing that crystalline melting is completely completed as measured by a differential scanning calorimeter (in particular, a temperature lower than the extrapolated melting end temperature). [Prior art documents] [Patent documents]

[0021] [Patent Document 1] Japanese Patent Application Publication No. 07-126496 [Patent Document 2] Japanese Patent Application Publication No. 03-024151 [Patent Document 3] WO2006 / 012917 publication [Patent Document 4] WO2008 / 099586 publication [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-077232 [Patent Document 6] Japanese Patent Application Laid-Open No. 2010-229407 [Patent Document 7] Japanese Patent Application Publication No. 09-278991 [Patent Document 8] Japanese Patent Application Publication No. 11-005849 [Patent Document 9] Japanese Patent Application Publication No. 07-188537 [Patent Document 10] Japanese Patent Application Publication No. 11-116783 [Patent Document 11] Japanese Patent Application Laid-Open No. 2003-238779 [Patent Document 12] Japanese Patent Application Laid-Open No. 2003-327803 [Patent Document 13] Japanese Patent Application Publication No. 10-158369 [Patent Document 14] Special Publication No. 2007-517126 [Patent Document 15] Japanese Patent Application Laid-Open No. 2003-192884 [Patent Document 16] Japanese Patent Application Publication No. 6-299054 [Patent Document 17] Japanese Patent Application Publication No. 8-27363 [Patent Document 18] Japanese Patent Application Laid-Open No. 2009-024058 [Patent Document 19] Japanese Patent Application Laid-Open No. 2017-101256 [Patent Document 20] WO2015 / 052876 publication [Patent Document 21] WO2014 / 068943 publication [Patent Document 22] Japanese Patent Application Laid-Open No. 2006-282940 [Patent Document 23] Japanese Patent Application Publication No. 06-345950 [Patent Document 24] Special Publication No. 10-504583 [Patent Document 25] Japanese Patent Application Publication No. 2019-119839 [Patent Document 26] Japanese Patent Application Publication No. 2019-119840 [Patent Document 27] Special Publication No. 08-510498 [Patent Document 28] WO2002 / 055581 publication [Patent Document 29] WO2002 / 050461 publication [Patent Document 30] Japanese Patent Application Laid-Open No. 2004-250629 [Patent Document 31] WO2015 / 146195 publication [Patent Document 32] WO2017 / 056442 publication [Patent Document 33] Japanese Patent Application Publication No. 10-176070 [Patent Document 34] Japanese Patent Application Laid-Open No. 2003-328230 [Patent Document 35] Japanese Patent Application Laid-Open No. 2003-328231 [Patent Document 36] WO2006 / 038373 publication [Patent Document 37] Patent No. 4245306 [Patent Document 38] WO2020 / 040093 publication [Patent Document 39] Japanese Patent Application Laid-Open No. 2010-241075 [Non-patent literature]

[0022] [Non-Patent Document 1] Alistair J. Anderson et al.,Microbiological Reviews,Vol.54,No.4,450-472,1990 [Non-patent document 2] H. Abe, et al., International Journal of Biological Macromolecules, 1994, vol. 16, 115-119. [Non-patent document 3] M.Kato et Aal.,Bull.Chem.Soc.Jpn,1996,vol.69,515-520. [Non-patent document 4] H.Matsusaki et al., Journal of bacteriology, 1998, vol.180, 6459-6467. [Non-Patent Document 5] Kusaka et al., Appl. Microbiol. Biotechnol., 47 140-143 (1997). Molecular mass of poly[(R)-3-hydroxybutyric acid] produced in a recombinant Escherichia coli. [Non-patent document 6] T. Kabe et al., Macromolecules, 2012, 45, 1858-1865. [Non-Patent Document 7] T. Kabe en al., ACS symposium series on Biobased Monomers, Polymers, and Materials,Chapter 5,63-75. [Non-patent document 8] Journal of the Japan Society of Packaging Science, Vol. 28, No. 2 (2019) 109-115 Summary of the Invention [Problem to be solved by the invention]

[0023] As mentioned above, conventional methods have been developed with the aim of rapidly forming primary nuclei after melting a slow-crystallizing crystalline polymer (polyester), preventing the formation of large, defective spherulites, crystallizing to increase strength, and solidifying and crystallizing to facilitate processing. In the melt-molding of biodegradable crystalline polymers, various attempts have been made to promote crystallization in order to improve the poor processability caused by the slow crystallization rate and to increase strength, but there is still room for improvement.

[0024] An object of the present invention is to provide a method for producing a polymer molded article that does not cause a significant decrease in molecular weight during melt molding, even for polymers that tend to decrease in molecular weight when molten. Another object of the present invention is to provide a method for producing a polymer molded article that shortens the crystallization time of slow-crystallizing polymers (e.g., biodegradable polyesters) and improves the melt processability of polymers in processes such as injection molding, blow molding, film molding, fiber spinning, extrusion foaming, and bead foaming, thereby increasing productivity. [Means for solving the problem]

[0025] As a result of extensive research aimed at solving the above problems, the inventors have found that semi-crystalline PHA copolymers of appropriate composition do not inherently have a single melting point, but rather contain crystals, including lamellar crystals (aggregates of crystalline segments) of various thicknesses, and are therefore aggregates of fine lamellar crystals and amorphous regions with various melting points. The inventors have then discovered that by melting (i.e., partially melting) the copolymer at a temperature lower than that at which the entire copolymer can be melted, yet fluidizing the relatively thin, fine lamellar crystals and amorphous regions with lower melting points, melt processing can be achieved without melting the fine, thick lamellar crystals. Because the thick, unmelted, fine lamellar crystals are already uniformly dispersed within or between the molecular chains, it has been found that molding can be achieved immediately from the partially molten state, without the need to wait for primary crystalline nucleation after melting, as is the case with complete melting. It was also discovered that the poor processing characteristics caused by the stickiness caused by the amorphous state when polyester (PHA) is melt-processed can be dramatically improved, and that significant molecular weight loss can be prevented by molding at a temperature lower than the thermal decomposition temperature of PHA. The present invention was completed based on these findings.

[0026] According to the present invention, the following inventions are provided. <1> A method for producing a polymer molded product, comprising melt molding a polymer containing lamellar crystals having different lamellar thicknesses in a temperature range in which some of the lamellar crystals melt and become fluid, while the remaining lamellar crystals remain unmelted. <2> the temperature range is higher than the flow-out initiation temperature as determined by a flow tester temperature rising method and lower than the temperature at which crystalline melting is completely completed as measured by a differential scanning calorimeter; <1> The method described below. <3> The temperature range is higher than the outflow start temperature measured by a flow tester temperature rising method and lower than the extrapolated melting end temperature. <1> or <2> The method described below. <4> cooling the molten polymer in air within a temperature range in which some lamellar crystals melt and become fluid, while the remaining lamellar crystals remain unmelted; <1> from <3> 1. The method according to claim 1 , <5> The melt molding is molding by melt extrusion; <1> from <4> 1. The method according to claim 1 , <6> The melt molding is molding by melt extrusion spinning. <1> from <5> 1. The method according to claim 1 , <7> Melt molding is performed once. <1> from <6> 1. The method according to claim 1 , <8> The polymer comprises a thermoplastic resin. <1> from <7> 1. The method according to claim 1 , <9> The polymer comprises a polyester. <1> from <8> 1. The method according to claim 1 , <10> The polymer comprises an aliphatic polyester. <1> from <9> 1. The method according to claim 1 , <11> The polymer comprises a biodegradable polymer. <1> from <10> 1. The method according to claim 1 , <12> The polymer is a copolymer containing 3-hydroxybutyric acid as a monomer unit. <1> from <11> 1. The method according to claim 1 , <13> The polymer comprises poly(L-lactic acid), poly(p-dioxanone), polybutylene succinate, polybutylene succinate adipate, or a copolymer of glycolic acid and lactic acid; <1> from <12> 1. The method according to claim 1 , <14> The polymer is a copolymer containing 3-hydroxybutyric acid and 4-hydroxybutyric acid as monomer units, and the proportion of 4-hydroxybutyric acid is 5 mol% or more and 40 mol% or less. <1> from <13> 1. The method according to claim 1 , [Effects of the Invention]

[0027] According to the method for producing a polymer molded product of the present invention, it is possible to suppress the molecular weight reduction during melt molding, even for polymers that tend to reduce in molecular weight when in a molten state. The method for producing a polymer molded product of the present invention shortens the crystallization time of the polymer, improves the melt processability of the polymer in processes such as injection molding, blow molding, film molding, fiber spinning, extrusion foaming, and bead foaming, and thereby improves productivity. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S1 (P(3HB) homopolymer) of Comparative Example 1 measured by a flow tester temperature rising method. [Figure 2] Figure 2 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S2 (P(3HB-co-11.8 mol% 4HB)) measured by a flow tester temperature ramp method in Example 1. The extrapolated melting end temperature (158.7°C) and the temperature at which the DSC curve returns to the baseline (167.0°C) are shown. [Figure 3] Figure 3 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S3 (P(3HB-co-13.1 mol% 4HB)) measured by a flow tester temperature ramp method in Example 2. The extrapolated melting end temperature (135.1°C) and the temperature at which the DSC curve returns to the baseline (155.0°C) are shown. [Figure 4] FIG. 4 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S34 (P(3HB-co-14.7 mol % 4HB)) obtained by the flow tester temperature ramp method in Example 3. [Figure 5] FIG. 5 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S5 (P(3HB-co-15.3 mol % 4HB)) obtained by the flow tester temperature ramp method in Example 4. [Figure 6] FIG. 6 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S6 (P(3HB-co-15.3 mol % 4HB)) obtained by the flow tester temperature ramp method in Example 5. [Figure 7]FIG. 7 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S7 (P(3HB-co-16.0 mol % 4HB)) obtained by the flow tester temperature ramp method in Example 6. [Figure 8] FIG. 8 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S8 (P(3HB-co-17.8 mol % 4HB)) obtained by the flow tester temperature ramp method in Example 7. [Figure 9] FIG. 9 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S9 (P(3HB-co-17.9 mol % 4HB)) obtained by the flow tester temperature ramp method in Example 8. [Figure 10] FIG. 10 shows the flow curve (solid line) and DSC curve (dashed line) of sample S10 (P(3HB-co-28.7 mol % 4HB)) obtained by the flow tester temperature ramp method. [Figure 11] FIG. 11 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S11 (P(3HB-co-32.9 mol % 4HB)) obtained by the flow tester temperature ramp method in Example 10. [Figure 12] FIG. 12 shows the flow curve (solid line) and DSC curve (dashed line) of sample S12 (P(3HB-co-74.6 mol % 4HB)) of Comparative Example 2 measured by a flow tester temperature ramp method. [Figure 13] FIG. 13 shows the flow curve (solid line) and DSC curve (dashed line) of sample S13 (P(3HB-co-8.0 mol % 3HV)) obtained by the flow tester temperature ramp method in Example 24. [Figure 14] FIG. 14 shows the flow curve (solid line) and DSC curve (dashed line) of sample S14 (P(3HB-co-12.0 mol % 3HV)) obtained by the flow tester temperature ramp method in Example 25. [Figure 15] FIG. 15 shows the flow curve (solid line) and DSC curve (dashed line) of sample S15 (P(3HB-co-35.5 mol % 3HV)) obtained by the flow tester temperature ramp method in Example 26. [Figure 16] FIG. 16 shows the flow curve (solid line) and DSC curve (dashed line) of sample S16 (P(3HB-co-48.2 mol % 3HV)) obtained by the flow tester temperature ramp method. [Figure 17]FIG. 17 shows the flow curve (solid line) and DSC curve (dashed line) of sample S17 (P(3HB-co-61.5 mol % 3HV)) obtained by the flow tester temperature ramp method in Example 28. [Figure 18] FIG. 18 shows the flow curve (solid line) and DSC curve (dashed line) of sample S18 ((P(3HB-co-73.2 mol % 3HV)) obtained by the flow tester temperature ramp method. [Figure 19] FIG. 19 shows the DSC measurement results and wide-angle X-ray diffraction diagram of Sample S7 (P(3HB-co-16 mol % 4HB)) of Reference Example 1, Examples 6, 22, and 23. [Figure 20] FIG. 20 shows the DSC measurement results and wide-angle X-ray diffraction patterns of Reference Example 2, Examples 25, 31, 32, and 33, and Sample S14 (P(3HB-co-12 mol % 3HV)) of Comparative Example 13. [Figure 21] FIG. 21 shows the flow curve (solid line) and DSC curve (dashed line) of sample S19 (PGA) of Comparative Example 14 measured by a flow tester temperature rising method. [Figure 22] FIG. 22 shows the flow curve (solid line) and DSC curve (dashed line) of sample S20 (PLLA) of Example 34 measured by a flow tester temperature rising method. [Figure 23] FIG. 23 shows the flow curve (solid line) and DSC curve (dashed line) of sample S21 (PGLA) of Example 35 measured by a flow tester temperature rising method. [Figure 24] FIG. 24 shows the flow curve (solid line) and DSC curve (dashed line) of Sample S22 (PPDO) of Example 36 measured by a flow tester temperature rising method. [Figure 25] FIG. 25 shows the flow curve (solid line) and DSC curve (dashed line) of sample S23 (PBS) of Example 37 measured by a flow tester temperature rising method. [Figure 26] FIG. 26 shows the flow curve (solid line) and DSC curve (dashed line) of sample S24 (PBSA) of Example 38 measured by a flow tester temperature rising method. [Figure 27] FIG. 27 shows the flow curve (solid line) and DSC curve (dashed line) of sample S25 (PCL) of Comparative Example 15 measured by a flow tester temperature rising method. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be described in detail below. The method for producing a polymer molded article according to the present invention comprises melt molding a polymer containing lamellar crystals having different lamellar thicknesses in a temperature range in which some of the lamellar crystals melt and become fluid, while the remaining lamellar crystals remain unmelted.

[0030] In the present invention, the processability of a thermoplastic resin that crystallizes slowly and has poor processability can be improved by melting the resin in a temperature range that is equal to or higher than the flow-out temperature measured when the fluidity of the crystalline thermoplastic resin is evaluated using a flow tester and lower than the temperature at which crystalline melting is completely completed as measured using a differential scanning calorimeter (DSC), and then molding the resin. The "temperature indicating the complete completion of crystalline melting as measured by differential scanning calorimetry (DSC)" is preferably the extrapolated melting end temperature of the melting peak. The extrapolated melting end temperature of the melting peak can be determined as described in the Examples below. That is, when the melting peak is sharp, the extrapolated melting end temperature of the melting peak is the temperature at the intersection of a tangent drawn at the point of maximum slope before the end of the peak and the baseline after the peak, in accordance with JIS-K7121 (recognized using Rigaku's Thermo plus EVO software). When multiple melting peak shapes overlap, the tangent line is manually redrawn to the higher-temperature peak, and the intersection with the baseline is determined as the extrapolated melting end temperature.

[0031] Furthermore, conventional melt molding typically involves melting a polymer at a temperature above its melting point, such as melting point +20°C, melting point +10°C, or melting point +5°C, followed by molding. In contrast, molding in a partially molten state, as in the present invention, involves partial melting at a temperature lower than the melting point. This suppresses thermal decomposition, i.e., molecular weight reduction, in polymers whose melting point and thermal decomposition point are close. This allows the polymer to maintain a high molecular weight after molding, which is beneficial in terms of physical properties. Furthermore, because the temperature for melting in a partially molten state is lower than that for complete melting, it is presumed that not only thermal decomposition of the polymer but also hydrolysis of the polymer's molecular chains, which is caused by trace amounts of water present during heating, can be reduced. Therefore, while a low moisture content in the raw material is generally desirable, there is no need to reduce or maintain a specially low moisture content. This is also expected to have the advantage of eliminating the need for special equipment to strictly maintain a dry state of the dry raw polymer, which could otherwise transfer moisture from the atmosphere to the raw polymer in spinning or molding equipment.

[0032] The present invention improves the molding processability of polyesters that have slow melt crystallization even without the addition of a crystal nucleating agent, thereby improving productivity, but does not preclude the use of a crystal nucleating agent.

[0033] In one example of the present invention, P(3HB-co-4HB) can be used as the polymer. In this case, the method of the present invention is characterized by including a step of melt-extruding P(3HB-co-4HB) at a temperature between the temperature at which crystalline and amorphous regions, including relatively thin lamellar crystals composed of 3HB segments within the polymer, begin to melt and flow, and the temperature at which relatively thicker lamellar crystals composed of 3HB segments begin to melt.

[0034] The present invention is a method for producing a biodegradable polyester molded product, characterized in that it involves melt molding while leaving behind some of the crystals, including lamellar crystals, contained in a polyester copolymer (especially a PHA copolymer), and the remaining crystals become crystal nuclei, making it possible to mold the product without waiting for the primary nucleation that occurs in conventional melt molding.

[0035] Therefore, the poor molding processability of crystalline thermoplastic polymers, which crystallize slowly, is improved, and molding is possible immediately after partial melting without waiting for primary crystalline nucleation, as is the case when the polymer is completely melted, thereby improving productivity. Some of the crystals, including lamellar crystals, already dispersed in the bulk of the crystalline thermoplastic polymer remain undissolved and act as crystal nuclei, eliminating the need for a waiting period for primary nucleation. This also reduces the stickiness caused by low crystallinity immediately after melt extrusion, making molded products such as fibers and films less likely to stick together, and allowing winding and stretching immediately after melt spinning or film formation, improving productivity.

[0036] By melt-spinning the polymer with some remaining crystals and then stretching it immediately afterward, the remaining lamellar crystals become oriented, the amorphous polymer chains become highly oriented, and the continuous monomer unit segments that are easy to form crystals gather together, promoting crystallization. By avoiding melting at high temperatures that would cause thermal decomposition, molecular weight loss due to thermal decomposition is suppressed, which helps maintain the molecular weight of the molded product, i.e., prevents thermal degradation. Furthermore, even if the polymer contains residual moisture or is prone to absorbing moisture from the air, partial melt molding can lower the melting temperature, thereby reducing the degree of hydrolysis caused by heat and moisture compared to complete melt molding. This suppresses molecular weight loss of the polymer and helps maintain the molecular weight of the molded product.

[0037] [About polymers] The polymer is not particularly limited, but the following may be used, for example: One type of polymer may be used alone, or two or more types of polymers may be used in combination. polyester; polyamide; Polyolefin; Acid-modified polyolefins (such as maleic anhydride-grafted polyethylene and maleic anhydride-grafted polypropylene); Ethylene-vinyl compound copolymers (ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer, ethylene-(meth)acrylic acid copolymer and its ion-crosslinked products (ionomers), ethylene-methyl methacrylate copolymer, etc.) Styrene-based resins (polystyrene, acrylonitrile-styrene copolymer, α-methylstyrene-styrene copolymer, etc.); Polyvinyl compounds (polymethyl acrylate, polymethyl methacrylate, etc.); Polycarbonate; Polyether (polyethylene oxide, etc.).

[0038] Among the above, polyester, polyolefin, or polyamide is preferred. Polyester, polyolefin, or polyamide will be described below.

[0039] <Polyester> Examples of polyester include: those consisting of hydroxycarboxylic acids and their ester-forming derivatives; A composition comprising one or more selected from polycarboxylic acids including dicarboxylic acids and their ester-forming derivatives, and one or more selected from polyhydric alcohols including glycols; or those consisting of cyclic esters; etc.

[0040] As those made of hydroxycarboxylic acids and their ester-forming derivatives, aliphatic polyesters are preferred. Aliphatic polyesters are homopolymers of aliphatic hydroxycarboxylic acids (e.g., poly3-hydroxypropionic acid, poly3-hydroxybutyric acid, poly3-hydroxyvaleric acid, poly4-hydroxybutyric acid, poly3-hydroxyhexanoic acid, poly3-hydroxyoctanoic acid, poly4-hydroxyvaleric acid, poly4-hydroxyhexanoic acid, poly5-hydroxyvaleric acid, poly2-hydroxybutyric acid, poly2-hydroxyvaleric acid, poly2-hydroxyhexanoic acid, polylactic acid, polyglycolic acid, polycaprolactone, etc.), copolymers (e.g., 3-hydroxypropionic acid, Copolymer of propionic acid and 3-hydroxybutyric acid, copolymer of 3-hydroxypropionic acid and 3-hydroxyvaleric acid, copolymer of 3-hydroxypropionic acid and 4-hydroxybutyric acid, copolymer of 3-hydroxypropionic acid and 3-hydroxyhexanoic acid, copolymer of 3-hydroxypropionic acid and 3-hydroxyoctanoic acid, copolymer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid, copolymer of 3-hydroxybutyric acid and 4-hydroxybutyric acid, copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, copolymer of 3-hydroxybutyric acid and 3-hydroxy copolymer of 3-hydroxyvaleric acid and 4-hydroxybutyric acid, copolymer of 3-hydroxyvaleric acid and 3-hydroxyhexanoic acid, copolymer of 3-hydroxyvaleric acid and 3-hydroxyoctanoic acid, copolymer of lactic acid and glycolic acid, copolymer of lactic acid and ε-caprolactone, copolymer of lactic acid and 3-hydroxypropionic acid, copolymer of lactic acid and 3-hydroxybutyric acid, copolymer of lactic acid and 3-hydroxyvaleric acid, copolymer of lactic acid and 3-hydroxybutyric acid, copolymer of lactic acid and 3-hydroxyhexanoic acid, copolymer of lactic acid and 3 -hydroxyoctanoic acid copolymer, glycolic acid and ε-caprolactone copolymer, glycolic acid and 3-hydroxypropionic acid copolymer, glycolic acid and 3-hydroxybutyric acid copolymer, glycolic acid and 3-hydroxyvaleric acid copolymer, glycolic acid and 4-hydroxybutyric acid copolymer, glycolic acid and 3-hydroxyhexanoic acid copolymer, glycolic acid and 3-hydroxyoctanoic acid copolymer, ε-caprolactone and 3-hydroxypropionic acid copolymer, ε-caprolactone and 3-hydroxybutyric acid copolymer,Copolymers composed of three or more types of monomers, such as copolymers of ε-caprolactone and 3-hydroxyvaleric acid, copolymers of ε-caprolactone and 4-hydroxybutyric acid, copolymers of ε-caprolactone and 3-hydroxyhexanoic acid, and copolymers of ε-caprolactone and 3-hydroxyoctanoic acid, and terpolymers; homopolymers and copolymers of aliphatic polyhydric alcohol carboxylic acids (e.g., polybutylene succinate, etc.) (e.g., copolymers of butanediol, succinic acid, and adipic acid, etc.); copolymers of aliphatic hydroxycarboxylic acids, aliphatic polyhydric alcohols, and aliphatic polycarboxylic acids (e.g., block copolymers of polylactic acid and polybutylene succinate); polydioxanone and copolymers containing dioxanone; and mixtures thereof.

[0041] In the polymers used in the present invention, in order to form a polymer structure of crystalline segments such as lamellar crystals, fringed micellar structures, spherulites, dendrites, shish kebab structures, and extended chain crystals, it is desirable that a sufficient number of highly crystalline continuous monomer unit chains, such as lactic acid chains, glycolic acid chains, ε-caprolactone chains, 3-hydroxypropionic acid chains, 3-hydroxybutyric acid chains, 3-hydroxyvaleric acid chains, 4-hydroxybutyric acid chains, 3-hydroxyhexanoic acid chains, 3-hydroxyhexanoic acid chains, 3-hydroxyoctanoic acid chains, 4-hydroxyvaleric acid chains, 4-hydroxyhexanoic acid chains, 5-hydroxyvaleric acid chains, 2-hydroxybutyric acid chains, 2-hydroxyvaleric acid chains, 2-hydroxyhexanoic acid chains, butylene succinate chains, and butylene succinate adipate chains, be repeatedly present in the polymer chain to form a crystalline microstructure. When stereoisomers or optical isomers exist as monomer units, crystalline segments consisting of chains of the same stereoisomers are required. For example, chains of the same stereoisomers, such as L-lactic acid chains, D-lactic acid chains, R-3-hydroxybutyric acid chains, S-3-hydroxybutyric acid chains, R-3-hydroxyvaleric acid chains, S-3-hydroxyvaleric acid chains, R-3-hydroxyhexanoic acid chains, and S-3-hydroxyhexanoic acid chains, are important elements for forming a crystalline structure. Polyesters containing monomer units with stereoisomers or optical isomers have reduced crystallinity, making it difficult to obtain crystalline segments. Particularly when synthesizing polymers from these monomer units biologically, binary copolymers or ternary or higher copolymers containing R-3-hydroxybutyric acid chains and other monomer units as second components are more preferred.

[0042] Aliphatic polyesters may be produced by either chemical synthesis or biological synthesis, but in order to ensure crystalline segments due to the chain structure, if they contain monomer units with stereoisomers, it is desirable that they be copolymers consisting of one of the stereoisomers, such as copolymers of L-lactic acid and glycolic acid, copolymers of D-lactic acid and glycolic acid, copolymers of R-3-hydroxybutyric acid and 4-hydroxybutyric acid, copolymers of S-3-hydroxybutyric acid and 4-hydroxybutyric acid, copolymers of R-3-hydroxybutyric acid and ε-caprolactone, copolymers of S-3-hydroxybutyric acid and ε-caprolactone, etc.

[0043] When the polyester contains 3-hydroxybutyric acid units and 4-hydroxybutyric acid units, the ratio of the 4-hydroxybutyric acid units to all monomer units is preferably 5 mol% or more and 40 mol% or less. The ratio of 4-hydroxybutyric acid to all monomer units may be 5 mol% or more, 6 mol% or more, 7 mol% or more, 8 mol% or more, 9 mol% or more, 10 mol% or more, 11 mol% or more, 12 mol% or more, 13 mol% or more, 14 mol% or more, 15 mol% or more, or 16 mol% or more, or may be 17 mol% or more, 18 mol% or more, 19 mol% or more, or 20 mol% or more. The ratio of 4-hydroxybutyric acid units to all monomer units may be 35 mol% or less, 34 mol% or less, 33 mol% or less, 32 mol% or less, 31 mol% or less, 30 mol% or less, 29 mol% or less, 28 mol% or less, 27 mol% or less, 26 mol% or less, 25 mol% or less, 24 mol% or less, 23 mol% or less, 22 mol% or less, or 21 mol% or less. When the polyester contains 3-hydroxybutyric acid units and 3-hydroxyvaleric acid units, the proportion of the 3-hydroxyvaleric acid units relative to all monomer units is preferably 5 mol% or more and 90 mol% or less. The proportion of the 3-hydroxyvaleric acid units relative to all monomer units may be 5 mol% or more, 6 mol% or more, 7 mol% or more, 8 mol% or more, 9 mol% or more, 10 mol% or more, 15 mol% or more, 20 mol% or more, 25 mol% or more, 30 mol% or more, 35 mol% or more, or 40 mol% or more, or may be 45 mol% or more, 50 mol% or more, 55 mol% or more, or 60 mol% or more. The proportion of the 3-hydroxyvaleric acid units relative to all monomer units may be 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, or 65 mol% or less.

[0044] The polyester may be one made from one or more selected from polycarboxylic acids including dicarboxylic acids and their ester-forming derivatives, and one or more selected from polyhydric alcohols including glycols.

[0045] Specific examples of dicarboxylic acids include saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and dimer acid, or ester-forming derivatives thereof; unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid, or ester-forming derivatives thereof; orthophthalic acid, isophthalic acid, terephthalic acid, 1,3-naphthalenedicarboxylic acid, and 1,4-naphthalenedicarboxylic acid. aromatic dicarboxylic acids or ester-forming derivatives thereof, exemplified by 5-sodium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, 5-lithium sulfoisophthalic acid, 2-lithium sulfoterephthalic acid, 5-potassium sulfoisophthalic acid, 2-potassium sulfoterephthalic acid, and the like; and lower alkyl ester derivatives thereof.

[0046] Among the above dicarboxylic acids, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acids are particularly preferred from the viewpoint of the physical properties of the resulting polyester. If necessary, other dicarboxylic acids may be copolymerized.

[0047] Specific examples of glycols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, 1,10-decamethylene glycol, 1, Examples of the glycol include aliphatic glycols such as 12-dodecanediol, polyethylene glycol, polytrimethylene glycol, and polytetramethylene glycol; and aromatic glycols such as hydroquinone, 4,4'-dihydroxybisphenol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-bis(β-hydroxyethoxyphenyl)sulfone, bis(p-hydroxyphenyl)ether, bis(p-hydroxyphenyl)sulfone, bis(p-hydroxyphenyl)methane, 1,2-bis(p-hydroxyphenyl)ethane, bisphenol A, bisphenol C, 2,5-naphthalenediol, and glycols obtained by adding ethylene oxide to these glycols.

[0048] Specific examples of polyhydric alcohols other than glycols include trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, glycerol, and hexanetriol.

[0049] Specific examples of cyclic esters include ε-caprolactone, β-propiolactone, β-methyl-β-propiolactone, δ-valerolactone, glycolide, lactide, and the like.

[0050] Specific examples of the ester-forming derivatives of polycarboxylic acids and hydroxycarboxylic acids include alkyl esters, acid chlorides, and acid anhydrides thereof.

[0051] <Polyolefin> Examples of polyolefins used in the oxygen-absorbing composition include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and linear very low-density polyethylene, olefin homopolymers such as polypropylene, polybutene-1, and poly-4-methylpentene-1; copolymers of ethylene and α-olefins such as ethylene-propylene random copolymers, ethylene-propylene block copolymers, ethylene-propylene-polybutene-1 copolymers, and ethylene-cyclic olefin copolymers; ethylene-α,β-unsaturated carboxylic acid copolymers such as ethylene-(meth)acrylic acid copolymers; ethylene-α,β-unsaturated carboxylic acid ester copolymers such as ethylene-ethyl (meth)acrylate copolymers; ion-crosslinked products of ethylene-α,β-unsaturated carboxylic acid copolymers; other ethylene copolymers such as ethylene-vinyl acetate copolymers; ring-opening polymers of cyclic olefins and hydrogenated products thereof; cyclic olefin-ethylene copolymers; and graft-modified polyolefins obtained by graft-modifying these polyolefins with acid anhydrides such as maleic anhydride.

[0052] <Polyamide> Examples of polyamides include polyamides having units derived from lactams or aminocarboxylic acids as the main structural units, aliphatic polyamides having units derived from aliphatic diamines and aliphatic dicarboxylic acids as the main structural units, partially aromatic polyamides having units derived from aliphatic diamines and aromatic dicarboxylic acids as the main structural units, partially aromatic polyamides having units derived from aromatic diamines and aliphatic dicarboxylic acids as the main structural units, etc. The polyamides referred to here may also be those in which monomer units other than the main structural units are copolymerized, if necessary.

[0053] Specific examples of lactams or aminocarboxylic acids include lactams such as ε-caprolactam and laurolactam, aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid, and aromatic aminocarboxylic acids such as para-aminomethylbenzoic acid.

[0054] Specific examples of aliphatic diamines include aliphatic diamines having 2 to 12 carbon atoms or functional derivatives thereof, and alicyclic diamines. The aliphatic diamines may be linear or branched. Specific examples of such linear aliphatic diamines include ethylenediamine, 1-methylethylenediamine, 1,3-propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, and dodecamethylenediamine. Specific examples of alicyclic diamines include cyclohexanediamine, 1,3-bis(aminomethyl)cyclohexane, and 1,4-bis(aminomethyl)cyclohexane.

[0055] Specific examples of aliphatic dicarboxylic acids include linear aliphatic dicarboxylic acids and alicyclic dicarboxylic acids. Linear aliphatic dicarboxylic acids having an alkylene group with 4 to 12 carbon atoms are particularly preferred. Examples of linear aliphatic dicarboxylic acids include adipic acid, sebacic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, undecanoic acid, undecadioic acid, dodecanedioic acid, dimer acid, and functional derivatives thereof. Examples of alicyclic dicarboxylic acids include 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid.

[0056] Specific examples of aromatic diamines include metaxylylenediamine, paraxylylenediamine, and para-bis(2-aminoethyl)benzene.

[0057] Specific examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, and functional derivatives thereof.

[0058] Specific polyamides include polyamide 4, polyamide 6, polyamide 10, polyamide 11, polyamide 12, polyamide 4,6, polyamide 6,6, polyamide 6,10, polyamide 6T, polyamide 9T, polyamide 6IT, polymetaxylylene adipamide (polyamide MXD6), isophthalic acid copolymerized polymetaxylylene adipamide (polyamide MXD6I), polymetaxylylene sebacamide (polyamide MXD10), polymetaxylylene dodecanamide (polyamide MXD12), poly 1,3-bisaminocyclohexane adipamide (polyamide BAC6), polyparaxylylene sebacamide (polyamide PXD10), etc. More preferred polyamides include polyamide 6, polyamide MXD6, and polyamide MXD6I.

[0059] <Molecular weight of polymer> For aliphatic hydroxycarboxylic acid polymers such as polyhydroxyalkanoates, the weight-average molecular weight as measured by gel permeation chromatography relative to polystyrene standards is preferably 100,000 or more, more preferably 200,000 or more, and may even be 300,000 or more, 400,000 or more, or 500,000 or more. The weight-average molecular weight as measured by gel permeation chromatography relative to polystyrene standards may be 600,000 or more, 700,000 or more, 800,000 or more, 900,000 or more, 1,000,000 or more, 1,100,000 or more, 1,200,000 or more, 1,300,000 or more, 1,400,000 or more, 1,500,000 or more, 2,000,000 or more, 3,000,000 or more, or 4,000,000 or more. The upper limit of the weight-average molecular weight as measured by gel permeation chromatography relative to polystyrene standards is not particularly limited, but is generally 20,000,000 or less, and may be 10,000,000 or less, 8,000,000 or less, 7,000,000 or less, 6,000,000 or less, 5,000,000 or less, 4,000,000 or less, or 3,000,000 or less. However, when melt molding is performed, taking into consideration the reduction in molecular weight due to thermal decomposition and the viscosity during melting to be not too high, the weight average molecular weight as measured by gel permeation chromatography in terms of polystyrene is desirably 400,000 or more and 2,500,000 or less, more preferably 500,000 or more and 2,200,000 or less, and even more preferably 600,000 or more and 2,000,000 or less. Regarding the molecular weight of the polymer other than the aliphatic hydroxycarboxylic acid polymer, an appropriate molecular weight can be used depending on the type of the polymer.

[0060] <Preferred embodiment of polymer> The polymer of the present invention may be a random polymer, a block polymer, an alternating polymer, or a graft polymer, but is preferably a random polymer.

[0061] The polymer preferably comprises a thermoplastic resin. The polymer is more preferably a biodegradable polymer, and even more preferably a bioabsorbable polymer. Biodegradable means that it can be decomposed by microorganisms or enzymes in the natural environment (e.g., soil, compost, lakes, marshes, seawater, etc.) or can be decomposed into non-toxic components in the living body. Bioabsorbable means that it can be metabolized by the living body, such as a human or animal.

[0062] The melting point of the polymer is not particularly limited, but is preferably 180°C or lower, more preferably 175°C or lower, and even more preferably lower than 175°C. The melting point of the polymer may be 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, or 130°C or lower. The lower limit of the melting point of the polymer is not particularly limited, but is generally 40°C or higher, and may be 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, or 100°C or higher. When the polymer has multiple melting points, it is sufficient that the melting point of the main component is within the above range.

[0063] [About melt molding] In the present invention, the polymer described above is melt-molded. When the polymer is melt-molded, additives may be added as long as the effects of the present invention are not impaired. Examples of additives include one or more selected from antioxidants, heat stabilizers (e.g., hindered phenols, hydroquinone, phosphites, and substituted derivatives thereof), ultraviolet absorbers (e.g., resorcinol, salicylate), color inhibitors (phosphites, hypophosphites, etc.), lubricants, mold release agents (montanic acid and its metal salts, its esters, its half esters, stearyl alcohol, stearamide, polyethylene wax, etc.), colorants (dyes or pigments, etc.), conductive agents or carbon black as a colorant, plasticizers, flame retardants (bromine-based flame retardants, phosphorus-based flame retardants, red phosphorus, silicone-based flame retardants, etc.), flame retardant assistants, and antistatic agents.

[0064] The method for blending the additives with the polymer is not particularly limited, and examples thereof include dry blending, solution blending, and addition during polymer polymerization.

[0065] The polymer can be subjected to known melt molding methods such as injection molding, injection compression molding, compression molding, extrusion molding (melt extrusion molding), blow molding, press molding, and spinning (melt extrusion spinning). The number of times of melt molding is not particularly limited, but it is preferably carried out only once.

[0066] In the present invention, the solidification step after molding can be carried out in a molding die, in a gas (e.g., air, nitrogen, etc.), or in a liquid (e.g., water, alcohol, glycerin, or a mixture thereof, etc.). That is, the polymer partially melted by the method of the present invention can be solidified by cooling it in a molding die, in a gas, or in a liquid. Preferably, the partially melted polymer can be cooled in a molding die, in air, or in water. More preferably, the partially melted polymer can be cooled in a molding die or in air.

[0067] Examples of polymer molded articles produced by the method of the present invention include injection molded articles, extrusion molded articles, press molded articles, sheets, pipes, various films such as unstretched films, uniaxially stretched films, and biaxially stretched films, various fibers such as unstretched yarns and ultrastretched yarns, etc. The polymer molded articles produced by the method of the present invention may be tubular or may have shapes other than tubular.

[0068] The present invention will be described in detail below with reference to Examples, Comparative Examples, and Reference Examples. Note that the descriptions of Examples, Comparative Examples, Reference Examples, and aspects in the specification of this application are provided to aid in understanding the contents of the present invention, and are not intended to provide a basis for narrowly interpreting the technical scope of the present invention. Note that the following thermoplastic polymers were used in the following Examples and Comparative Examples. [Example]

[0069] <Polymer used> The poly-3-hydroxybutyrate (P(3HB)) used was "Biogreen (registered trademark) (MW 940,000)" manufactured by Mitsubishi Gas Chemical. P(3HB-co-4HB) copolymer was produced by the culture method described in WO2019 / 044837. P(3HB-co-4HB) copolymers with various 4HB ratios were produced by appropriately changing the type and supply ratio of the carbon source used. The P(3HB-co-3HV) copolymers used were Biopol (8.0 mol% 3HV and 12.0 mol% 3HV) from ICI, and the 3HV-rich P(3HB-co-3HV) copolymers were produced by the culture method described in JP-A-04-084890 and JP-A-01-069622. Polyglycolic acid (PGA) was BMG Corporation's "PGA (MFR (240,10) = 0.5-5.0 g / 10 min)", poly-L-lactic acid (PLLA) was BMG Corporation's "PLLA (Mw 470,000)", polycaprolactone (PCL) was Ingevity's "Capa 6800 (Mw 80,000)", The copolymer of glycolic acid and L-lactic acid used was "PGLA (90:10) (glycolic acid 88.5 mol %: L-lactic acid 11.5 mol %, MFR (240,10) = 2.75)" manufactured by BMG Corporation. Poly-p-dioxanone (PPDO) used was "PPDO" from BMG Corporation. The polybutylene succinate (PBS) used was "BioPBS (registered trademark) FZ91PB (MFR 190,10) = 5 g / 10 min)" manufactured by Mitsubishi Chemical Corporation, and the polybutylene succinate adipate used was "BioPBS (registered trademark) FD92PB (MFR 190,10) = 4 g / 10 min)" manufactured by Mitsubishi Chemical Corporation. As a method for extracting PHA from bacterial cells, which is already known, a solvent extraction method may be used, in which PHA is extracted using a halogenated hydrocarbon solvent such as chloroform and then precipitated with a poor solvent such as hexane or methanol, or an aqueous extraction method may be used, as described in JP-B 04-061638, JP-A 07-177894, and WO2004 / 029266.

[0070] This paper describes various evaluation methods and melt extrusion methods for analyzing thermoplastic polymers. (1) Molecular weight measurement of thermoplastic polymers [PHA molecular weight measurement (gel permeation chromatography (GPC) method)] The molecular weight of PHA was measured by gel permeation chromatography as follows. Chloroform was added to the solution so that the PHA concentration was approximately 0.5 mg / ml, and the solution was dissolved at 60°C for 4 hours. After that, the solution was returned to room temperature and filtered through a PTFE filter with a pore size of 0.2 μm to remove insoluble matter, and the measurement sample was obtained. The GPC conditions were as follows:

[0071] Equipment: Shimadzu HPLC Prominence system Column: Showa Denko Shodex K-806L (two columns in series) Column temperature: 40℃ Mobile phase: chloroform (1 ml / min) Detector: RI (40℃) Standard: Shodex polystyrene molecular weight standard (6.87 million to 1270) Injection volume: 60μl Analysis time: 30 minutes

[0072] (2) Measurement of the flow start temperature of thermoplastic polymers [Measurement of flow start temperature of thermoplastic polymers using a flow tester] Thermoplastic polymers are measured using a flow tester (Capillary Rheometer Flowtester, Shimadzu Corporation) or CFT-500EX (Shimadzu Corporation). The sample amount used for measurement is approximately 1.2 g of thermoplastic polymer in pellet, powder, or film form, which is filled into a cylinder. Powdered polymers can be formed using an appropriate granulator or press and then filled into a cylinder. A die (nozzle) with a diameter of 1.0 mm and a thickness of 1.0 mm is used. A 5 kg extrusion load is applied. After preheating for 240 seconds at an initial temperature of 30°C to 140°C (selected appropriately depending on the type of polymer and its melting point), the temperature is increased at a constant rate of 3°C / min from 130°C to 260°C (selected appropriately depending on the type of polymer and its melting point). The stroke length (mm) vs. temperature curve is obtained. As the temperature increases, the thermoplastic polymer heats up and begins to flow out of the die. This temperature is the flow initiation temperature.

[0073] (3) Melting behavior measurement of thermoplastic polymers [Measurement of thermal properties using a differential scanning calorimeter (DSC)] The melting behavior of thermoplastic polymers, including polyhydroxyalkanoates, was measured using a differential scanning calorimeter (Rigaku, Thermo plus EVO DSC8230). The measurement atmosphere was nitrogen (30 ml / min), and the temperature was raised from 30°C to 130-260°C (appropriately selected depending on the type of polymer and its melting point) at a rate of 20°C / min. The sample was approximately 1 mg, and an aluminum sample pan was used. Indium was used for temperature calibration.

[0074] When the melting peak is sharp, the extrapolated melting end temperature of the melting peak is determined in accordance with JIS-K7121 as the temperature at the intersection of a tangent drawn at the point of maximum slope before the end of the peak and the baseline after the peak (recognized by Rigaku Thermo plus EVO software). However, when multiple melting peak shapes overlap, a tangent line is manually redrawn to the higher-temperature peak, and the intersection with the baseline is taken as the extrapolated melting end temperature.

[0075] (4) Partial melt extrusion and melt extrusion of thermoplastic polymers [Constant temperature melt spinning using a flow tester] Melt extrusion spinning was performed using a flow tester CFT-500D (Shimadzu Corporation) or CFT-500EX (Shimadzu Corporation).

[0076] <Various analysis results> The results of DSC and CFT (Capillary Flow Tester) measurements of the 4HB-containing PHA copolymer are shown in Table 1 below.

[0077] [Table 1]

[0078] <Comparative Example 1> Sample S1 P(3HB) (sample S1) with a molecular weight of 940,000 was analyzed using a flow tester (CFT) and DSC. The CFT flow onset temperature was 181.0°C, and the DSC crystalline melting peak range was approximately 140-189°C. The crystalline melting peak ...

[0079] Example 1: Sample S2 P(3HB-co-11.8 mol% 4HB) (sample S2) with a molecular weight of 1.16 million was analyzed by CFT and DSC. The CFT flow onset temperature was 131.3°C, and the DSC crystalline melting peak range was approximately 80-167°C. The crystalline melting peak peak peaks were 95.2°C and 141.8°C, the DSC extrapolated melting end temperature was 158.7°C, and the melting peak baseline temperature was 167.0°C. The DSC extrapolated melting end temperature was higher than the CFT flow onset temperature, indicating that partial melt extrusion was possible in the range of 131.3°C to 158.7°C. Figure 2 shows the CFT and DSC measurement results. Melt spinning was carried out at temperatures of 135°C (Example 11) and 150°C (Example 12) where partial melting was possible, and at temperatures of 170°C (Comparative Example 3) and 180°C (Comparative Example 4) where almost melting was achieved. The Mw before melt spinning was 1.16 million, while the Mw after partial melt spinning at 135°C was 1.1 million, the Mw after partial melt spinning at 150°C was 1.08 million, the Mw after melt spinning at 170°C was 720,000, and the Mw after melt spinning at 180°C was 460,000. The residual molecular weight Mw after melt spinning at each temperature was 95% at 135°C and 93% at 150°C, compared with 62% at 170°C and 39% at 180°C, assuming the molecular weight Mw of 1.16 million before melt spinning as 100%, demonstrating that spinning at lower temperatures is effective in suppressing molecular weight reduction. The suppression of molecular weight reduction was particularly significant when partial melt spinning at 135°C and 150°C, which are not in a fully molten state. The results are shown in Table 2. Furthermore, partial melt extrusion spinning at 135°C and 150°C suppressed the tackiness of the polymer immediately after spinning, as seen in melt extrusion spinning at 170°C and 180°C, and the polymer could be taken up and drawn without requiring a crystallization time of 30 minutes to 1 hour at room temperature. In other words, partial melt extrusion spinning shortened the crystallization time, improved the melt processability of the polymer, and increased productivity.

[0080] [Table 2]

[0081] Example 2: Sample S3 P(3HB-co-13.1 mol% 4HB) with a molecular weight of 1 million (sample S3) was analyzed by CFT and DSC. The CFT flow onset temperature was 125.1°C, and the DSC crystalline melting peak range was approximately 49-144°C. The crystalline melting peak peak peaks were 63.7°C and 114.8°C. The DSC extrapolated melting end temperature was 135.1°C, and the melting peak baseline temperature was 155.0°C. The DSC extrapolated melting end temperature was higher than the CFT flow onset temperature, indicating that partial melt extrusion was possible in the range of 125.1°C to 135.1°C. Figure 3 shows the CFT and DSC measurement results.

[0082] Melt spinning was performed at temperatures of 126°C (Example 13), 130°C (Example 14), and 135°C (Example 15) where partial melting was possible, and at temperatures of 150°C (Comparative Example 5), 160°C (Comparative Example 6), and 170°C (Comparative Example 7) where almost melting was possible. The Mw before melt spinning was 1 million, whereas the Mw after partial melt spinning at 126°C was 950,000, the Mw after partial melt spinning at 130°C was 970,000, the Mw after partial melt spinning at 135°C was 970,000, the Mw after partial melt spinning at 140°C was 920,000, the Mw after melt spinning at 150°C was 820,000, the Mw after melt spinning at 160°C was 650,000, and the Mw after melt spinning at 170°C was 540,000. The residual molecular weight Mw after melt spinning at each temperature was 95% at 126°C, 97% at 130°C, 97% at 135°C, 82% at 150°C, 65% at 160°C, and 53% at 170°C, assuming that the molecular weight Mw of 1 million before melt spinning was 100%. This demonstrates that spinning at lower temperatures, especially at low temperatures where a partial melt state is possible, is effective in suppressing molecular weight reduction. Partial melt spinning at 135°C or below, where it is clear that the state is not completely melted, significantly suppressed molecular weight reduction. The results are shown in Table 3. When melt-spun at 170°C, the extruded polymer was highly tacky and stuck together, and the polymer solidified after winding, making it impossible to unwind. On the other hand, yarns partially extruded at 135°C or below showed almost no stickiness, and could be wound and drawn immediately after spinning without sticking. This shows that partial-melt extrusion spinning can shorten crystallization time, improve the melt processability of polymers, and increase productivity.

[0083] [Table 3]

[0084] Example 3: Sample S4 P(3HB-co-14.7 mol% 4HB) with a molecular weight of 900,000 (sample S4) was analyzed by CFT and DSC. The CFT flow-initiating temperature was 113.9°C, and the DSC crystalline melting peak range was approximately 88-145°C. The crystalline melting peak ... Melt spinning was carried out at temperatures of 115°C (Example 16), 130°C (Example 17), and 140°C (Example 18) where partial melting was possible, and at 170°C (Comparative Example 8) where almost melting was achieved. The Mw before melt spinning was 900,000, whereas the Mw after partial melt spinning at 115°C was 890,000, the Mw after partial melt spinning at 130°C was 840,000, the Mw after melt spinning at 140°C was 870,000, the Mw after melt spinning at 150°C was 870,000, and the Mw after melt spinning at 170°C was 550,000. The residual molecular weight Mw after melt spinning at each temperature was 99% at 115°C, 94% at 130°C, and 97% at 140°C, assuming the molecular weight Mw of 900,000 before melt spinning as 100%, while it was 61% at 170°C. This demonstrates that spinning at lower temperatures is effective in suppressing molecular weight reduction. Low-temperature partial melt spinning in a partially molten state at temperatures below 140°C significantly suppressed molecular weight reduction. The results are shown in Table 4. When melt-spun at 170°C, the extruded polymer was highly viscous and stuck together, and the polymer solidified after winding, making it impossible to unwind. On the other hand, yarns partially extruded at 140°C or below showed almost no stickiness, and could be wound and drawn immediately after spinning without sticking. This shows that partial-melt extrusion spinning can shorten the crystallization time, improve the melt processability of polymers, and increase productivity.

[0085] [Table 4]

[0086] Example 4: Sample S5 P(3HB-co-15.3 mol% 4HB) with a molecular weight of 750,000 (sample S5) was analyzed by CFT and DSC. The CFT flow onset temperature was 109.4°C, and the DSC crystalline melting peak range was approximately 58-170°C. The crystalline melting peak apex was 65.5, 92.7, 110.0, and 164.3°C. The DSC extrapolated melting end temperatures were 80.0, 109.0, 130.2, and 168.9°C, and the melting peak reached the baseline at 172.6°C. The DSC extrapolated melting end temperature was higher than the CFT flow onset temperature, indicating that partial melt extrusion was possible in the range of 109.4°C to 168.9°C. Figure 5 shows the CFT and DSC measurement results. Melt spinning was carried out at temperatures at which partial melting was possible, 115°C (Example 19), 120°C (Example 20), and 125°C (Example 21). The Mw before melt spinning was 750,000, while the Mw after partial melt spinning at 115°C, 120°C, and 125°C was 750,000 in all cases. It became clear that being able to spin in a partially molten state at temperatures significantly below 150°C is effective in suppressing molecular weight reduction. The results are shown in Table 5. The yarns partially extruded at temperatures below 125°C showed almost no tackiness and could be wound and drawn immediately after spinning without sticking. This indicates that partial melt extrusion spinning can shorten the crystallization time, improve the melt processability of the polymer, and increase productivity.

[0087] [Table 5]

[0088] Example 5: Sample S6 P(3HB-co-15.3 mol% 4HB) (sample S6) with a molecular weight of 710,000 was analyzed by CFT and DSC. The CFT flow-initiating temperature was 113.8°C, and the DSC crystalline melting peak range was approximately 81-155°C. The crystalline melting peak ... Melt spinning was carried out at a temperature of 160°C (Comparative Example 9) or 170°C (Comparative Example 10) so that the mixture was almost melted. The Mw before melt spinning was 710,000, whereas the Mw after melt spinning at 160°C was 480,000 and the Mw after melt spinning at 170°C was 310,000, demonstrating that a decrease in molecular weight is unavoidable when melt spinning at high temperatures such as 160°C and 170°C, which are not in a partially molten state. The results are shown in Table 6. The polymer extruded by melt spinning at 160℃ and 170℃ was very sticky, and required 30 minutes to 1 hour of crystallization and solidification time at room temperature before it could be stretched.

[0089] [Table 6]

[0090] Example 6: Sample S7 P(3HB-co-16.0 mol% 4HB) (sample S7) with a molecular weight of 620,000 was analyzed by CFT and DSC. The CFT flow onset temperature was 94.0°C, and the DSC crystalline melting peak range was approximately 57-178°C. The crystalline melting peak ... Melt spinning was carried out at a temperature of 130°C (Example 22) and 160°C (Example 23), which are temperatures that allow partial melting. The Mw before melt spinning was 620,000, while the Mw after partial melt spinning at 130°C was 610,000, the Mw after partial melt spinning at 160°C was 500,000, and the Mw after melt spinning at 170°C was 440,000. The residual molecular weight Mw after melt spinning at each temperature was 98% at 130°C, 81% at 160°C, and 71% at 170°C, assuming the molecular weight Mw of 620,000 before melt spinning as 100%. In the case of sample S7, which contains some crystals that melt at high temperatures (around 172°C) in DSC, it is thought that some crystals remain unmelted even at 160 and 170°C, resulting in a partial melt state. However, because these are relatively high temperatures for the melting point of PHA, a decrease in molecular weight was observed. It was clear that the molecular weight decrease was suppressed when melt spinning at a low temperature of 130°C, confirming that being able to spin at a lower temperature is effective in suppressing molecular weight decrease.

[0091] [Table 7]

[0092] Example 7: Sample S8 P(3HB-co-17.8 mol% 4HB) (sample S8) with a molecular weight of 580,000 was analyzed by CFT and DSC. The CFT flow onset temperature was 96.2°C, and the DSC crystalline melting peak ranged from approximately 43 to 177°C. The crystalline melting peak apices were 47.5°C and 100.6°C, with a small melting peak at 166.6°C likely derived from 3HB-rich crystals. The DSC extrapolated melting end temperature of the main melting peak was 107.3°C, the DSC extrapolated melting end temperature of the gentle melting peak following the main melting peak was 142.1°C, the DSC extrapolated melting end temperature of the higher melting peak was 175.6°C, and the melting peak baseline temperature was 177.6°C. The DSC extrapolated melting end temperature was higher than the CFT flow onset temperature, demonstrating that partial melt extrusion was possible in the range of 96.2 to 175.6°C. Figure 8 shows the results of CFT and DSC measurements.

[0093] Example 8: Sample S9 P(3HB-co-17.9 mol% 4HB) (sample S9) with a molecular weight of 630,000 was analyzed by CFT and DSC. The CFT flow initiation temperature was 131.3°C, and the DSC crystalline melting peak range was approximately 90-149°C. The crystalline melting peak peak peaks were 116.9°C and 131.7°C. The DSC extrapolated melting end temperature was 146.0°C, and the melting point peak reached the baseline at 151.7°C. The DSC extrapolated melting end temperature was higher than the CFT flow initiation temperature, indicating that partial melt extrusion was possible in the range of 131.3°C to 146.0°C. Figure 9 shows the CFT and DSC measurement results.

[0094] Example 9: Sample S10 P(3HB-co-28.7 mol% 4HB) (sample S10) with a molecular weight of 1.05 million was analyzed by CFT and DSC. The CFT flow onset temperature was 109.5°C, and the DSC crystalline melting peak range was approximately 39–167°C. The crystalline melting peak apexes were 47.0°C and 164.0°C, and the DSC extrapolated melting end temperatures were 55.9°C and 166.7°C, respectively. The melting peak reached the baseline at 170.3°C. The higher-temperature melting peaks may be the result of a small amount of 3HB-rich PHA being blended into the polymer. However, the DSC extrapolated melting end temperature was higher than the CFT flow onset temperature, suggesting that crystalline components remained in the range of 109.5°C to 166.7°C. This range indicated that partial melt extrusion was possible. Figure 10 shows the CFT and DSC measurement results.

[0095] Example 10: Sample S11 P(3HB-co-32.9 mol% 4HB) (sample S11) with a molecular weight of 1.04 million was analyzed by CFT and DSC. The CFT flow onset temperature was 123.1°C, and the DSC crystalline melting peak range was approximately 40 to 148°C. The crystalline melting peak peak apexes were 44.8°C, 79.1°C, and 123.8°C. The DSC extrapolated melting end temperatures were 55.9°C, 88.1°C, and 144.7°C, and the melting peak baseline temperature was 151.4°C. The DSC extrapolated melting end temperature was higher than the CFT flow onset temperature, indicating that partial melt extrusion was possible in the range of 123.1°C to 144.7°C. Figure 11 shows the CFT and DSC measurement results.

[0096] <Comparative Example 2> Sample S12 P(3HB-co-74.6 mol% 4HB) (sample S12) with a molecular weight of 1.11 million was analyzed by CFT and DSC. The CFT flow-out onset temperature was 94.6°C, and the DSC crystalline melting peak width was approximately 39-72°C. The crystalline melting peak peak peak apex was 58.7°C, the DSC extrapolated melting end temperature was 64.1°C, and the melting point peak reached the baseline at 72.1°C. The DSC extrapolated melting end temperature was lower than the CFT flow-out onset temperature, indicating that the material would not flow unless it was in a completely molten state at 94.6°C or higher. Figure 12 shows the CFT and DSC measurement results.

[0097] The DSC and CFT measurement results of the 3HV-containing PHA copolymer are shown in Table 8 below.

[0098] [Table 8]

[0099] Example 24: Sample S13 P(3HB-co-8.0 mol% 3HV) (sample S13) with a molecular weight of 460,000 was analyzed by CFT and DSC. The CFT flow-initiating temperature was 151.6°C, and the DSC crystalline melting peak range was approximately 125-174°C. The crystalline melting peak ... Melt spinning was carried out at 160°C (Example 30) as the temperature at which partial melting was possible, and at 175°C (Comparative Example 11) and 185°C (Comparative Example 12) as the temperature at which the material was almost melted. The Mw before melt spinning was 460,000, whereas the Mw after melt spinning at 160°C was 450,000, the Mw after melt spinning at 175°C was 390,000, and the Mw after melt spinning at 185°C was 360,000. If the molecular weight Mw of 460,000 before melt spinning is taken as 100%, the residual rate of the molecular weight Mw after melt spinning at each temperature was 97% at 160°C, 86% at 175°C, and 79% at 185°C. Not only P(3HB-co-4HB) copolymer, but also P(3HB-co-3HV) copolymers composed of other monomer units showed a significant effect of suppressing molecular weight reduction when melt-spun at lower temperatures. The results are shown in Table 9. When melt-spun at 185°C, the extruded polymer was highly viscous and stuck together, and the polymer solidified after winding, making it impossible to unwind. On the other hand, yarns partially extruded at 160°C showed almost no stickiness, and could be wound and drawn immediately after spinning without sticking. This shows that partial-melt extrusion spinning can shorten the crystallization time, improve the melt processability of polymers, and increase productivity.

[0100] [Table 9]

[0101] Example 25: Sample S14 P(3HB-co-12.0 mol% 3HV) (sample S14) with a molecular weight of 190,000 was analyzed by CFT and DSC. The CFT flow-initiating temperature was 140.4°C, and the DSC crystalline melting peak width was approximately 124-166°C. The crystalline melting peak peak peak peak apex was 144.9°C, the DSC extrapolated melting end temperature was 156.7°C, and the melting point peak baseline temperature was 165.7°C. The DSC extrapolated melting end temperature was higher than the CFT flow-initiating temperature, indicating that partial melt extrusion was possible in the range of 140.4°C to 156.7°C. Figure 14 shows the CFT and DSC measurement results.

[0102] Melt spinning was carried out at temperatures of 145°C (Example 31), 150°C (Example 32), and 155°C (Example 33) where partial melting was possible, and at 170°C (Comparative Example 13) where almost melting was achieved. The Mw before melt spinning was 190,000, whereas the Mw after melt spinning at 145°C, 150°C, and 155°C was 190,000, and the Mw after melt spinning at 170°C was 160,000. If the molecular weight Mw of 190,000 before melt spinning is taken as 100%, the residual rate of the molecular weight Mw after melt spinning at each temperature was 98% at 145°C, 98% at 150°C, and 98% at 155°C, while it was 83% at 170°C. Not only the P(3HB-co-4HB) copolymer but also the P(3HB-co-3HV) copolymer showed a remarkable effect of suppressing the molecular weight reduction when melt-spun at a lower temperature. The results are shown in Table 10. When melt-spun at 170°C, the extruded polymer was highly viscous and stuck together, and the polymer solidified after winding, making it impossible to unwind. On the other hand, yarns partially extruded at 150°C or below showed almost no stickiness, and could be wound and drawn immediately after spinning without sticking. This shows that partial-melt extrusion spinning can shorten the crystallization time, improve the melt processability of polymers, and increase productivity.

[0103] [Table 10]

[0104] Example 26: Sample S15 P(3HB-co-35.5 mol% 3HV) (sample S15) with a molecular weight of 330,000 was analyzed by CFT and DSC. The CFT flow onset temperature was 85.1°C, and the DSC crystalline melting peak range was approximately 45 to 173°C. The crystalline melting peak ... Even if we assume that no components exhibiting a small melting peak on the high-temperature side, which is thought to be derived from 3HB-rich crystals, are mixed in, the extrapolated melting end temperature of the melting peak on the low-temperature side is 106.0°C, and in this case, partial melt extrusion is possible in the range of 85.1°C to less than 106.0°C. Figure 15 shows the results of CFT and DSC measurements.

[0105] Example 27: Sample S16 P(3HB-co-48.2 mol% 3HV) (sample S16) with a molecular weight of 830,000 was analyzed by CFT and DSC. The CFT flow onset temperature was 83.8°C, and the DSC crystalline melting peak range was approximately 50 to 178°C. The crystalline melting peak peak apexes were at 75.0°C and 88.7°C, with a small melting peak at 165.7°C likely derived from 3HB-rich crystals. The DSC extrapolated melting end temperature of the main melting peak was 94.8°C, the DSC extrapolated melting end temperature of the higher melting peak was 173.7°C, and the melting peak baseline temperature was 177.7°C. The DSC extrapolated melting end temperature was higher than the CFT flow onset temperature, indicating that partial melt extrusion was possible in the range of 83.8 to 173.7°C. Even if we assume that no components exhibiting a small melting peak on the high-temperature side, which is thought to be derived from 3HB-rich crystals, are mixed in, the extrapolated melting end temperature of the melting peak on the low-temperature side is 94.8°C, and in this case, partial melt extrusion is possible in the range of 83.8 to 94.8°C. Figure 16 shows the results of CFT and DSC measurements.

[0106] Example 28: Sample S17 P(3HB-co-61.5 mol% 3HV) (sample S17) with a molecular weight of 730,000 was analyzed by CFT and DSC. The CFT flow onset temperature was 84.5°C, and the DSC crystalline melting peak range was approximately 56–178°C. The crystalline melting peak ... Even if we assume that no components exhibiting a small melting peak on the high-temperature side, which is thought to be derived from 3HB-rich crystals, are mixed in, the extrapolated melting end temperature of the melting peak on the low-temperature side is 97.5°C, and in this case, partial melt extrusion is possible in the range of 84.5 to 97.5°C. Figure 17 shows the results of CFT and DSC measurements.

[0107] Example 29: Sample S18 P(3HB-co-73.2 mol% 3HV) (sample S18) with a molecular weight of 730,000 was analyzed by CFT and DSC. The CFT flow onset temperature was 91.1°C, and the DSC crystalline melting peak range was approximately 64-179°C. The crystalline melting peak ... Even if we assume that no components exhibiting a small melting peak on the high-temperature side, which is thought to be derived from 3HB-rich crystals, are mixed in, the extrapolated melting end temperature of the melting peak on the low-temperature side is 101.3°C, and in this case, partial melt extrusion is possible in the range of 91.1°C to less than 101.3°C. Figure 18 shows the results of CFT and DSC measurements.

[0108] <Analysis of partially melted state> From the shape of the melting peak of thermoplastic polymers observed during the heating process of DSC, it is thought that the crystalline structure remains during melt processing in the region below the extrapolated melting end temperature, and when the flow tester heating method's outflow start temperature is lower than the DSC extrapolated melting end temperature, it is thought that the melt processing is performed in a partially molten state between the CFT outflow start temperature and the DSC extrapolated melting end temperature. The change in the crystalline structure of the polymer during the heating process of DSC was analyzed using wide-angle X-ray diffraction (WAXD).

[0109] <Reference example 1> 2 mg of Sample S7, P(3HB-co-16.0 mol % 4HB) used in Examples 6, 22, and 23, was placed in an X-ray capillary and placed in a heating apparatus capable of DSC measurement. Wide-angle X-ray images were taken while heating at a rate of 10°C / min. Wide-angle X-ray images were taken in 2°C increments with a 1-second exposure time. DSC measurements were performed from approximately 50°C to 200°C. The DSC curve and wide-angle X-ray diffraction pattern are shown in Figure 19. Two endothermic (melting) peaks were observed in the DSC curve. The endothermic peak on the low-temperature side is thought to be the melting peak of thin lamellar crystals. The endothermic peak on the high-temperature side is thought to be the melting peak of thick lamellar crystals. Two ring patterns were observed in the wide-angle X-ray diagram, clearly indicating the presence of crystals. Even after passing the endothermic peak on the low-temperature side, the peaks derived from the two crystals did not disappear, indicating that thick crystals remained. As shown in Example 6, this sample could be partially melt extruded in the temperature range of 94.0°C or higher and lower than 175.9°C, and in fact, melt extrusion spinning was possible even at 130°C, which is within that range (Example 22). From the wide-angle X-ray diagram, a peak (ring pattern) derived from crystals was confirmed even at 130°C. Therefore, it was proven that melt spinning at 130°C using this sample was possible in a state where not all crystals were melted, i.e., in a partially melted state.

[0110] <Reference example 2> 2 mg of Sample S14, P(3HB-co-12.0 mol% 3HV) used in Examples 25, 31, 32, and 33 and Comparative Example 13 was placed in an X-ray capillary, placed in a heating apparatus capable of DSC measurement, and subjected to wide-angle X-ray imaging while heating at a rate of 10°C / min. Wide-angle X-ray imaging was performed at 2°C intervals for a 1-second imaging time. DSC measurements were performed from approximately 50°C to 200°C. The DSC curve and wide-angle X-ray diffraction pattern are shown in Figure 20. This DSC curve showed only one endothermic peak. Two clear crystal-derived diffraction patterns were observed in the wide-angle X-ray diagram. As shown in Example 25, this sample was capable of partial melt extrusion in the temperature range of 140.4 to 156.7°C. In fact, partial melt extrusion spinning was also possible at temperatures within this range, 145°C, 150°C, and 155°C (Examples 31, 32, and 33). The diffraction pattern at 150°C, shown as 4 in the wide-angle X-ray diagram in Figure 21, shows a crystalline pattern even at the melt spinning temperature of 150°C, proving that spinning is possible in a partially molten state, where not all the crystals are melted. A faint ring pattern derived from the crystals was also observed in the wide-angle X-ray diffraction diagram at 160°C (5 in Figure 20), which is between the extrapolated melting end temperature of 156.7°C and the temperature at which the melting peak reaches the baseline of 165.7°C. This suggests that most of the crystals are melted even at 160°C, but a small amount of crystals remain.

[0111] The DSC and CFT measurement results for other biodegradable polymers are shown in Table 11 below.

[0112] [Table 11]

[0113] <Comparative Example 14> Sample S19 (PGA) Polyglycolic acid (PGA) from BMG Corporation (referred to as sample S19) was analyzed using a flow tester (CFT) and DSC. The CFT flow onset temperature was 233.9°C, and the DSC crystalline melting peak width was approximately 195-240°C. The crystalline melting peak peak peak peak was 228.0°C, the DSC extrapolated melting end temperature was 232.7°C, and the temperature at which the melting point peak reached the baseline was 240.0°C. The DSC extrapolated melting end temperature was lower than the CFT flow onset temperature, indicating that PGA would not flow unless it was completely molten. Figure 21 shows the CFT and DSC measurement results.

[0114] Example 34: Sample S20 (PLLA) PLLA (sample S20) with a molecular weight of 470,000 from BMG Corporation was analyzed by CFT and DSC. The CFT flow initiation temperature was 193.6°C, and the DSC crystalline melting peak width was approximately 155-204°C. The crystalline melting peak peak peak peak peak height was 193.6°C, the DSC extrapolated melting end temperature was 198.4°C, and the melting point peak baseline temperature was 204.4°C. The DSC extrapolated melting end temperature was higher than the CFT flow initiation temperature, and partial melt extrusion was possible in the range of 193.6°C to 198.4°C. Figure 22 shows the CFT and DSC measurement results.

[0115] Example 35: Sample S21 (PGLA) PGLA (sample S21) from BMG Corporation was analyzed by CFT and DSC. The CFT flow initiation temperature was 203.5°C, and the DSC crystalline melting peak on the higher temperature side was approximately 190-221°C. The crystalline melting peak peak peak peak apex was 207.3°C, the DSC extrapolated melting end temperature was 212.6°C, and the temperature at which the melting point peak reached the baseline was 220.8°C. The DSC extrapolated melting end temperature was higher than the CFT flow initiation temperature, and it was found that partial melt extrusion was possible in the range of 203.5°C to 212.6°C. Figure 23 shows the CFT and DSC measurement results.

[0116] Example 36: Sample S22 (PPDO) BMG PPDO (sample S22) was analyzed by CFT and DSC. The CFT flow initiation temperature was 108.4°C, and the DSC crystalline melting peak range on the higher side was approximately 77-124°C. The crystalline melting peak peak peaks were 104.2°C and 113.1°C. The DSC extrapolated melting end temperature was 117.3°C, and the melting peak baseline temperature was 123.6°C. The DSC extrapolated melting end temperature was higher than the CFT flow initiation temperature, demonstrating that partial melt extrusion was possible in the range of 108.4°C to 117.3°C. Figure 24 shows the CFT and DSC measurement results.

[0117] Example 37: Sample S23 (PBS) Mitsubishi Chemical Corporation's PBS (referred to as sample S23) was analyzed by CFT and DSC. The CFT flow initiation temperature was 117.7°C, and the DSC crystalline melting peak width was approximately 80 to 124°C. The crystalline melting peak peak peak peak apex was 115.0°C, the DSC extrapolated melting end temperature was 119.5°C, and the temperature at which the melting point peak reached the baseline was 124.4°C. The DSC extrapolated melting end temperature was higher than the CFT flow initiation temperature, and it was found that partial melt extrusion was possible in the range of 117.7 to 119.5°C. Figure 25 shows the CFT and DSC measurement results.

[0118] Example 38: Sample S24 (PBSA) Mitsubishi Chemical Corporation's PBSA (sample S24) was analyzed by CFT and DSC. The CFT flow initiation temperature was 87.3°C, and the DSC crystalline melting peak width was approximately 55-98°C. The crystalline melting peak peak peak peak apex was 90.1°C, the DSC extrapolated melting end temperature was 94.5°C, and the temperature at which the melting point peak reached the baseline was 98.4°C. The DSC extrapolated melting end temperature was higher than the CFT flow initiation temperature, and it was found that partial melt extrusion was possible in the range of 87.3 to 94.5°C. Figure 26 shows the CFT and DSC measurement results.

[0119] <Comparative Example 15> Sample S25 (PCL) Polycaprolactone (PCL) from Ingevity (Sample S25) was analyzed using a flow tester (CFT) and DSC. The CFT flow onset temperature was 69.3°C, and the DSC crystalline melting peak width was approximately 35-70°C. The crystalline melting peak peak peak peak height was 59.3°C, the DSC extrapolated melting end temperature was 63.7°C, and the temperature at which the melting point peak reached the baseline was 70.4°C. The DSC extrapolated melting end temperature was lower than the CFT flow onset temperature, indicating that the sample would not flow unless it was completely molten. Figure 27 shows the CFT and DSC measurement results.

Claims

1. A method for producing a polymer molded product, comprising melt molding a polymer containing lamellar crystals having different lamellar thicknesses in a temperature range in which some of the lamellar crystals melt and become fluid, while the remaining lamellar crystals remain unmelted, the temperature range is higher than the outflow initiation temperature determined by a flow tester heating method and lower than the extrapolated melting end temperature, the polymer is a copolymer containing 3-hydroxybutyric acid and 4-hydroxybutyric acid as monomer units, and the proportion of 4-hydroxybutyric acid is 5 mol % or more and 40 mol % or less.

2. 2. The method of claim 1, comprising cooling the molten polymer in air in a temperature range in which some lamellar crystals melt and become fluid, while the remaining lamellar crystals remain unmelted.

3. The method according to claim 1 or 2, wherein the melt-forming is by melt-extrusion.

4. The method according to any one of claims 1 to 3, wherein the melt-forming is by melt-extrusion spinning.

5. 5. The method according to claim 1, wherein the melt-forming is carried out once.

6. A method described in any one of claims 1 to 5, wherein the residual molecular weight of the polymer after melt molding is greater than 86%.

Images