Polyhydroxyalkanoate composition, polyhydroxyalkanoate molded article, and method for producing the same

Abstract

This invention relates to the field of biomass polymer materials technology, and more particularly to polyhydroxyalkanoate compositions, polyhydroxyalkanoate molded articles, and methods for producing the same. The polyhydroxyalkanoate composition according to the present invention comprises a polyhydroxyalkanoate and at least one selected from lactic acid and lactic acid organic derivatives. By using lactic acid or its derivatives as a nucleating agent, the crystallization rate and crystallinity during the production of polyhydroxyalkanoate molded articles can be significantly improved, and the crystallization temperature of polyhydroxyalkanoates, which have a wide melting temperature range, can be lowered, effectively shortening the solidification time of the molded articles. This provides advantages such as high nucleating agent efficiency, a simpler processing method, and reduced energy consumption.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to the Chinese patent application No. 202310621212.0, filed on 29 May 2023, with the title of the invention "Polyhydroxyalkanoate composition, polyhydroxyalkanoate molded article, and method for producing the same." The entire contents of this application are incorporated herein by reference to the extent that they are described herein in full.

[0002] The present invention relates to the field of biomass polymer materials, and more particularly to polyhydroxyalkanoate compositions, polyhydroxyalkanoate molded articles, and methods for producing the same. [Background technology]

[0003] Polyhydroxyalkanoates (PHAs) are intracellular polyesters synthesized by many microorganisms and are naturally derived polymeric biomaterials. The majority of PHA monomers are 3-hydroxy fatty acids with 3 to 14 carbon atoms, and their side chains are highly variable, ranging from saturated or unsaturated, linear or branched, and aliphatic or aromatic groups. This diverse composition and structure leads to diversified performance and offers clear advantages in applications. At the same time, PHAs are biomass-derived polymers that are biodegradable in marine environments, can help solve environmental problems caused by plastic waste, and possess excellent biocompatibility and mechanical properties, making them suitable for processing into various molded products such as films, straws, and tableware.

[0004] Controlling the crystallization rate is a crucial factor in the processing rate of polyhydroxyalkanoates. Conventional techniques improve the crystallization rate of PHA by adding additives such as nucleating agents.

[0005] Conventional nucleating agents mainly consist of inorganic substances or metal salts. However, while these can improve the crystallization rate and crystallinity of molded articles using conventional polyhydroxyalkanoates to some extent, the degree of improvement is limited. Furthermore, they cause discoloration in the molded articles, reducing their transparency and affecting their applications. In addition, polyhydroxyalkanoate materials with a wide melting temperature range have problems in the manufacturing process, such as low processing efficiency and the time required to reach the desired degree of hardening. [Overview of the project] [Problems that the invention aims to solve]

[0006] In view of the aforementioned problems in the prior art, the first object of the present invention is to provide a polyhydroxyalkanoate composition comprising lactic acid and / or an organic derivative of lactic acid that can effectively solve the problems of low crystallization rate and low processing and solidification efficiency of polyhydroxyalkanoates.

[0007] A second object of the present invention is to provide a polyhydroxyalkanoate molded article produced from the polyhydroxyalkanoate composition.

[0008] A third object of the present invention is to provide a method for producing the polyhydroxyalkanoate molded article. [Means for solving the problem]

[0009] To achieve the above objective, the present invention employs the following technical means. In the first aspect, the present invention is Polyhydroxyalkanoates and; At least one lactic acid or lactic acid organic derivative represented by the following general formula I; The present invention provides a polyhydroxyalkanoate composition containing [the specified compound]. R 2 CH2-CH(OH)-COYR 1 I Here, R 1is H or a hydrocarbon group, and R 2 is H or a hydrocarbon group, and Y is any one of C, O, N, and S.

[0010] In the present invention, R in the general formula I 1 , R 2 are each H or a short-chain hydrocarbon group having 1 to 16 carbon atoms, and Y is any one of C, O, N, and S. That is, the composition contains short-chain ketone-based, ester-based / acid-based, sulfur-containing, and nitrogen-containing lactic acid organic derivatives represented by the general formula I.

[0011] In the present invention, when Y in the general formula I is O and R 1 , R 2 are each H, it is lactic acid, and lactic acid can be classified into two types, L-lactic acid and D-lactic acid, depending on its chiral structure. In the present invention, the lactic acid is selected from L-lactic acid, D-lactic acid, or a combination thereof; among them, in the combination of L-lactic acid and D-lactic acid, the ratio of L-lactic acid:D-lactic acid is 0.01 to 99.9,9:99.99 to 0.01.

[0012] In the present invention, further, the lactic acid derivative can be classified into an organic ester-based derivative and an organic acid-based derivative of lactic acid.

[0013] [[ID=,26]]When Y in the general formula I is O and R 1 is a C1-C16 hydrocarbon group, the lactic acid organic-based derivative is a lactic acid ester-based derivative having the structure R 2 CH2-CH(OH)-COOR 1 , where R 2 is H or a C1-C16 hydrocarbon group; and / or When Y in the general formula I is O, R 1 is H, and R 2 is a C1-C16 hydrocarbon group, the lactic acid organic-based derivative is a lactic acid organic acid-based derivative having the structure R 2 CH2-CH(OH)-COOH.

[0014] The organic ester derivative of lactic acid according to the present invention includes a structure R formed by substituting lactic acid (including L-lactic acid, D-lactic acid or any combination thereof, preferably L-lactic acid). 2 CH2-CH(OH)-COOR 1 It includes a lactic acid ester derivative represented by the formula, where R 1 is a C1-C16 hydrocarbon group, and R 2 is H or a C1-C16 hydrocarbon group, and R 1 , R 2 is preferably a C1-C10 hydrocarbon group, a C1-C8 hydrocarbon group, or a C1-C4 hydrocarbon group, such as methyl, ethyl, propyl, butyl, isopentyl, phenyl, benzyl, tetradecyl, hexadecyl. In some specific embodiments, the lactic acid organic ester derivative may be methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isopentyl lactate, benzyl lactate, tetradecyl lactate, hexadecyl lactate, or methyl 3-phenyllactate.

[0015] In the present invention, the organic acid derivative of lactic acid includes an organic acid derivative formed by retaining the hydroxy group and carboxyl group of lactic acid in lactic acid (including L-lactic acid, D-lactic acid or any combination thereof, preferably L-lactic acid), and its structure is R 2 CH2-CH(OH)-COOH, where R 2 is a C1-C16 hydrocarbon group, more preferably a C1-C10 hydrocarbon group, a C1-C8 hydrocarbon group, or a C1-C4 hydrocarbon group, such as methyl, ethyl, propyl, butyl, phenyl, and specifically, it may be 3-phenyllactic acid.

[0016] In addition to the lactic acid organic derivatives exemplified above, when Y in the general formula I is C, N, S (carbon, nitrogen, sulfur), the organic derivatives also have the same structure as the above-exemplified (Y is O) organic derivatives, and all retain the α-hydroxy group of the lactic acid organic derivatives. Since it is presumed that the same effects can be obtained, the present invention should not be limited to the specific lactic acid organic derivatives exemplified above.

[0017] In a specific embodiment, the composition contains lactic acid.

[0018] In a specific embodiment, the composition contains a mixture of L-lactic acid, D-lactic acid, or a combination of them in any ratio. For example, the ratio of L-lactic acid:D-lactic acid is 0.01-99.99:99.99-0.01, preferably 0.1-1:1-0.1. For example, it may be 0.1:1, 1:9, 1:8, 1:5, 1:4, 0.5:1, 1:1, 1:0.5, 4:1, 5:1, 8:1, 9:1, 1:0.1.

[0019] In a specific embodiment, the composition contains any one selected from L-lactic acid, D-lactic acid, DL lactic acid, or a combination thereof; among which, DL lactic acid is lactic acid with a ratio of L-lactic acid:D-lactic acid of 1:1.

[0020] In a specific embodiment, the composition contains L-lactic acid.

[0021] In a specific embodiment, in the composition, lactic acid or a lactic acid derivative acts as a nucleating agent.

[0022] In a specific embodiment, the addition amount of the lactic acid and / or lactic acid derivative is 0.01%-20% based on the mass of the polyhydroxyalkanoate; preferably 0.1%-10%; more preferably 0.1%-3%, for example, 0.1%-2%, 0.1%-1.5%, 0.5%-1.5%; typically and non-limitingly, the addition amount of lactic acid and / or lactic acid derivative may be, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 1%, 1.2%, 1.5%, 2%, 2.5%, 3% based on the mass of the polyhydroxyalkanoate.

[0023] The polyhydroxyalkanoate according to the present invention may be a single polymer or a combination of two or more polymers. Here, the polymerization monomer of each polymer may be one or more kinds (that is, the structural units in the polymer may be one or more kinds).

[0024] Specifically, each polymer contains a structural unit represented by the following general formula II.

[0025] [ka]

[0026] In general formula II, R is C p H 2p+1 R represents an alkyl group, where p represents an integer from 1 to 15, preferably from 1 to 10, and more preferably from 1 to 8. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, butyl, isobutyl, tert-butyl, pentyl, and hexyl; m is 1, 2, or 3; when m=1, general formula II represents a 3-hydroxyalkanoate structural unit; when m=2, general formula II represents a 4-hydroxyalkanoate structural unit; and when m=3, general formula II represents a 5-hydroxyalkanoate structural unit; among these, the 3-hydroxyalkanoate structural unit and the 4-hydroxyalkanoate structural unit are relatively common, for example, the 3-hydroxybutyrate ester structural unit (hereinafter also referred to as 3HB) and the 4-hydroxybutyrate ester structural unit (hereinafter also referred to as 4HB).

[0027] In specific embodiments, the polyhydroxyalkanoate according to the present invention comprises at least one poly(3-hydroxyalkanoate).

[0028] Furthermore, the poly(3-hydroxyalkanoate) comprises either only 3-hydroxybutyrate ester structural units or 3-hydroxybutyrate ester structural units and other hydroxyalkanoate structural units.

[0029] Furthermore, the other hydroxyalkanoate structural units include one or more selected from 3-hydroxypropionic acid ester, 3-hydroxypentanoic acid ester, 3-hydroxyhexanoic acid ester, 3-hydroxyheptanoic acid ester, 3-hydroxyoctanoic acid ester, 3-hydroxynonanoic acid ester, 3-hydroxydecanoic acid ester, 3-hydroxyundecanoic acid ester, or 4-hydroxybutyrate ester; preferably 3-hydroxyhexanoic acid ester.

[0030] In other words, specific examples of poly(3-hydroxyalkanoate) include, for example, poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxypropionic acid), poly(3-hydroxybutyrate-co-3-hydroxypentanoate) (abbreviated as P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxypentanoate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB Examples include poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviated as P3HB4HB). Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred from the viewpoint of processability and mechanical properties.

[0031] The lactic acid or lactic acid organic derivative in the composition of the present invention can, as a whole, promote crystallization, and this does not depend on the content ratio of polyhydroxyalkanoate structural monomers in the composition. This is thought to be because certain structures contained in lactic acid or its organic derivative tend to "bond" better with polyhydroxyalkanoate and "induce" the crystallization of polyhydroxyalkanoate. The method for producing polyhydroxyalkanoate according to the present invention is not particularly limited and may be a method utilizing chemical synthesis or a method utilizing microorganisms, but polyhydroxyalkanoate produced by microorganisms is particularly preferred, and in polyhydroxyalkanoate produced by microorganisms, all 3-hydroxyalkanoate structural units are contained as (R)-isomer 3-hydroxyalkanoate structural units. Here, the poly(3-hydroxyalkanoate) includes a copolymer of 3-hydroxybutyrate ester structural units and other structural units, and the average content ratio of the 3-hydroxybutyrate ester structural units to other structural units in the poly(3-hydroxyalkanoate) is 50 / 50 to 99 / 1 (mol% / mol%), preferably 80 / 20 to 94 / 6 (mol% / mol%); if the polyhydroxyalkanoate raw material is a mixture of two or more polyhydroxyalkanoates, the average content ratio refers to the molar ratio of each monomer contained in the whole mixture.

[0032] Furthermore, the weight-average molecular weight of the polyhydroxyalkanoate is 100,000 to 1,000,000 Da; preferably 200,000 to 900,000 Da; and more preferably 300,000 to 800,000 Da or 600,000 to 800,000 Da. If the weight-average molecular weight is less than 100,000 Da, the mechanical properties of the resulting polyhydroxyalkanoate resin molded article tend to decrease. On the other hand, if the weight-average molecular weight exceeds 1,000,000 Da, the load on the machinery during melt processing increases, and productivity tends to decrease.

[0033] The polyhydroxyalkanoate composition of the present invention can be prepared using conventional techniques and equipment known in the art, for example, by directly mixing in a kneading facility to obtain a powder, or by further kneading at room temperature using, for example, a high-speed mixer.

[0034] To facilitate the processing of the polyhydroxyalkanoate composition of the present invention into a molded article, the polyhydroxyalkanoate composition may further contain certain additives to increase the fluidity of the material and facilitate molding. Furthermore, the auxiliary agent may be an auxiliary agent that promotes fluidity, such as a dispersant, plasticizer, internal lubricant, external lubricant, or mold release agent; for example, it may be one or more selected from amides such as ethylenebis-stearamide (EBS), erukaamide, oleamide, linoleamide, palmitamide, and stearamide, polyethylene wax, rice bran wax, 8024 (amide wax-based rheological auxiliary agent), silicone oil-based auxiliary agents, stearic acid, stearates, epoxidized soybean oil, and other auxiliary agents having dispersion and lubrication effects. Furthermore, the amount of the aforementioned additive is approximately 2% to 5% relative to the mass of polyhydroxyalkanoate.

[0035] In a second aspect, the present invention provides a polyhydroxyalkanoate molded article produced from the polyhydroxyalkanoate composition of the present invention. The polyhydroxyalkanoate molded articles according to the present invention may include multiple forms such as pellets, films, fibers, nonwoven fabrics, straws, sheets, paper-plastic composites, and films.

[0036] The polyhydroxyalkanoate molded articles of the present invention can be manufactured by a thermoforming method or by a non-thermal forming method such as a solution casting method. Therefore, in a third aspect, the present invention further provides a method for manufacturing the polyhydroxyalkanoate molded articles.

[0037] In a specific embodiment, the method for producing the polyhydroxyalkanoate molded article is as follows: (1) A step of melting the uniformly mixed polyhydroxyalkanoate composition at a temperature above the melting point of the polyhydroxyalkanoate to form a molten body, (2) A step of crystallizing and molding the molten material from step (1) at a temperature of 65°C or lower, Includes. In a specific embodiment, the molten body temperature in step (1) of the manufacturing method is 140 to 180°C. In a specific embodiment, in step (2) of the manufacturing method, the molten body is crystallized and molded at a temperature of 40°C or lower, for example, 20 to 40°C.

[0038] In specific embodiments, the polyhydroxyalkanoate molded articles of the present invention can be manufactured by various thermal processing molding methods such as extrusion molding, injection molding, calendering, casting, blow molding, and biaxial stretching.

[0039] In a specific embodiment, the polyhydroxyalkanoate molded article of the present invention is manufactured by an extrusion pelletization method comprising the following steps: (1) Melt extrusion: A process in which the uniformly mixed polyhydroxyalkanoate composition is melt-extruded in an extrusion pelletizer, with the temperature of the extrusion pelletizer set to 50-180°C; (2) Pelletization: A process of crystallizing the molten extruded material into pellets at a temperature of 65°C or lower.

[0040] In the extrusion pelletizing method described above, in step (1), the extrusion pelletizing apparatus can be selected from granulation apparatus commonly used in the field, for example, parallel co-screw extruders with different aspect ratios, parallel anomalous twin-screw extruders, tapered twin-screw extruders, and single-screw extruders can be used. The temperature of the extrusion pelletizing apparatus is set in the range of 50°C to 180°C, the main engine speed is set to 50 to 500 r / min, and the feed rate or production rate is adjusted according to the actual production conditions.

[0041] In a specific embodiment, a crystallization temperature with lower energy consumption can be adopted while maintaining crystallization efficiency and processing effect, and in step (2), the molten extruded material is crystallized into pellets at a temperature of 40°C or lower, for example, 20°C to 40°C.

[0042] In a specific embodiment, step (2) can be performed by a pelletizing method such as air-cooled strand cutting, water bath strand cutting, hot die face cutting, water ring cutting, or underwater cutting.

[0043] In specific embodiments, the process further includes drying the manufactured pellets after step (2). Specifically, the manufactured pellets are dried using a forced-air dryer to eliminate the influence of moisture on the pellet properties and to ensure complete crystallization of the pellets. [Effects of the Invention]

[0044] Beneficial effects (1) Research based on the present invention has shown that by using lactic acid or its organic derivative as a nucleating agent, the crystallization rate and crystallinity during the production of molded polyhydroxyalkanoates can be significantly improved. (2) Normally, the crystallization temperature required to produce polyhydroxyalkanoate molded articles is about 40 to 65°C. However, in the present invention, lactic acid or its organic derivative lowers the crystallization temperature (20 to 40°C) of polyhydroxyalkanoates, which have a wide melting temperature range, and effectively shortens the solidification time of the molded article. This results in high nucleating agent efficiency, and at the same time, by employing a lower crystallization temperature, it is possible to obtain a molded article with good crystallization without requiring continuous heating, simplifying the processing method and effectively reducing energy consumption. [Modes for carrying out the invention]

[0045] In the field of thermoplastic processing, the crystallization of polymer materials is a microscopic process in which a portion of the polymer chain aligns, and in this process the polymer chain folds to form ordered regions. Such regions become lamellar crystals, and lamellar crystals form larger spherical structures called spherulites, which constitute macroscopic crystalline molded bodies. Polyhydroxyalkanoate (PHA) in this invention is a polymer raw material with excellent complete biodegradability, and its physical properties such as glass transition temperature, crystallization temperature, melting point, and melting temperature range differ significantly from those of other materials such as polyglycolic acid (PGA), polylactic acid (PLA), and poly-ε-caprolactone (PCL). In normal processing processes, materials such as PLA crystallize and mold easily and quickly, but PHA has a relatively low glass transition temperature (Tg of PHA is about 0°C, Tg of PLA is about 60°C), so it is often not possible to crystallize and mold quickly during processing.

[0046] Considering the unique characteristics of polymer material crystallization, the inventors have conducted a specialized study on the effects of crystallization nucleating agents commonly used in the field of thermoplastic processing on PHA, such as inorganic nucleating agents (e.g., nanocalcium carbonate, nanosilicon dioxide, terephthalic acid, titanium dioxide, talc, boron nitride, etc.), organic nucleating agents (e.g., nucleating agents specifically for polylactic acid (PLA) (TMC-306, TMC-200, etc.)), and lactic acid or its derivatives used in the present invention, on the crystallization effect of PHA, and have found a more suitable method for promoting PHA crystallization.

[0047] The following describes specific embodiments of the present invention in detail. It should be understood that the specific embodiments described herein are for the purpose of illustrating and understanding the present invention, and do not limit it. The present invention will now be described in detail with reference to the following examples. In the following examples, unless otherwise specified, all materials used can be obtained by purchasing commercially available products, and unless otherwise specified, the methods used are conventional methods in the art.

[0048] The endpoints of the ranges and any values ​​disclosed herein are not limited to their exact ranges or values, and these ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, one or more new numerical ranges can be obtained by combining the endpoints of each range, the endpoints of each range with individual point values, and individual point values ​​with each other, and these numerical ranges should be considered as specifically disclosed herein.

[0049] The present invention will be described in more detail by the following examples, but none of these examples limit the present invention. Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products.

[0050] Raw materials used and their sources: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), Product No.: BP350, Shanghai Lanjing Microbial Technology Co., Ltd., 3HB (3-hydroxybutyrate unit) content: 89%, Weight-average molecular weight: approximately 600,000-800,000 L-Lactic acid ((S)-2-hydroxypropionic acid), Product No.: L118493, Aladdin, Purity >98.0%(T), Refractive index 1.4260~1.4310, Specific rotation -10.0~-15.0 deg (C=2.5, 1.5 mol / L NaOH aqueous solution) D-Lactic acid ((R)-2-hydroxypropionic acid), Product No.: S161106, Aladdin, Purity >90.0%(T), Refractive index 1.43, Specific rotation 13° (C=2.5, 1.5 mol / L NaOH aqueous solution) Methyl lactate (methyl DL-lactate), product number: M158854, Aladdin, purity >98.0% (GC), refractive index 1.413 Ethyl lactate (alpha-hydroxypropionate ethyl), product number: E108230, Aradain, purity 98.0% (GC), refractive index 1.4125 Butyl lactate (butyl α-hydroxypropionate), product number: B111190, Aradain, purity 98.0% (GC), refractive index 1.421, specific rotation -10.0 to -13.0 degrees (neat)

[0051] Device: High-speed mixer: Zhangjiagang Zhengde Machinery Factory, model: SHR-50L Twin-screw extrusion granulator: Nanjing Keya Chemical Technology Equipment Co., Ltd., model: HK36

[0052] Methods for producing polyhydroxyalkanoate pellet molded articles in Experimental Examples 1-35: Preparation of Pellet Molded Bodies: Pellet bodies were manufactured using a twin-screw extruder. The formulations of the polyhydroxyalkanoate compositions used in Experimental Examples 1-35 (components in the formulation are expressed in parts by mass) are shown in Tables 1-4. The specific manufacturing procedure is as follows: (1) Mixing: The polyhydroxyalkanoate powder and nucleating agent were placed in a high-speed mixer and mixed at room temperature. The mixing speed was 200 r / min and the mixing time was 5 minutes. After mixing, the mixture was fed into the feed hopper of a twin-screw extruder. (2) Melt extrusion: The conditions of the extrusion granulation apparatus were set, and melt extrusion was performed under conditions of a molten body temperature of 150°C. (3) Granulation: Granulation was performed using a cut granulation method with an underwater cut system, and the water bath heating temperature was set as shown in Tables 1 to 4.

[0053] Performance evaluation method for polyhydroxyalkanoate pellet molded products in Experimental Examples 1-35:

[0054] Crystallinity: A differential scanning calorimeter (DSC) (TA Instruments DSC25 model) was used to weigh 2 to 10 mg of polyhydroxyalkanoate molded bodies. The DSC curve obtained by heating the bodies once from -50°C to 180°C at a heating rate of 10°C / min was used. From the obtained DSC curves, data such as the glass transition temperature, melting temperature, melting peak area, and cold crystallization peak area were determined. Crystallinity (%) = 100% × (Enthalpy of Melting) / (Enthalpy of Melting for 100% Crystalline) Here, 100% crystalline enthalpy of melting refers to the theoretical enthalpy of melting of a 100% crystalline material. A higher degree of crystallinity indicates higher crystallinity of the molded product, which is preferable for subsequent processing and molding.

[0055] Difficulty of thermoplastic processing of pelletized molded bodies: ○: Continuous and stable processing is possible, and the solidification time of the molded product is short. △: Extrusion is stable during thermoplastic processing, but the solidification time of the molded product is relatively long. ×: Extrusion by the extruder is unstable, resulting in a long solidification time for the molded product.

[0056] Weight average molecular weight: The molecular weight was measured using a gel permeation chromatography (GPC) system (HPLC GPC system, Shimadzu Corporation) with chloroform solution, and the measurement was performed in polystyrene equivalent. The column used in this GPC system was one suitable for measuring weight-average molecular weight.

[0057] Tables 1-4 show the performance evaluation results of the polyhydroxyalkanoate pellet molded bodies in the above experimental examples 1-35.

[0058] Example 1: Effects of molded bodies of lactic acid, organic lactic acid derivatives, and similar substances on nucleation

[0059] [Table 1]

[0060] As can be seen from Experimental Examples 1-8, compared to Experimental Example 8, which was a blank control, the addition of lactic acid (Experimental Example 1-3) and its organic derivatives (Experimental Examples 4-7) can both improve the crystal nucleation ability of PHA. In comparison, lactic acid has superior crystal nucleation ability, and its crystal nucleation effect far surpasses that of lactic acid organic ester derivatives. Furthermore, research has shown that six-membered cyclic lactides formed as lactic acid dimers actually decrease the crystallinity of PHA (Experimental Example 4). This indicates that adding six-membered cyclic lactides without an α-hydroxyl group to PHA did not improve crystallinity, demonstrating that retaining the α-hydroxyl group in the lactic acid organic derivative is important to obtain a similar crystal-promoting effect. Therefore, the present invention is not limited to the specific lactic acid organic derivatives containing the α-hydroxyl group exemplified above.

[0061] Example 2: Effects of lactic acid and other existing nucleating agents on the molding effect of molded articles

[0062] [Table 2]

[0063] Comparing Experimental Example 1 with Experimental Examples 9-19, it can be seen that the lactic acid nucleating agent exhibits significantly improved crystallinity compared to other types of nucleating agents, and its nucleation efficiency surpasses that of other existing types of nucleating agents. Furthermore, compared to other existing nucleating agents, the raw material for lactic acid is more readily available, lactic acid has excellent applicability, and the molded products produced have good environmental and biocompatibility.

[0064] Example 3: Effects of different amounts of lactic acid on the nucleation effect and performance of molded products

[0065] [Table 3]

[0066] Regarding crystallinity, higher crystallinity indicates better nucleation efficiency. From Examples 1 and 20-30, compared to Experimental Example 8, which served as a blank control, the addition of lactic acid resulted in a significant improvement in crystallinity relative to the raw material. In the aforementioned experiments where the addition amount was in the range of 0.1 to 3 parts, lactic acid was found to have a crystal-promoting effect, improving the crystallization effect and also improving the processability of the molded articles produced. Research in these examples revealed that the effect was unclear when the amount of lactic acid added was less than 0.01%, and when the amount of lactic acid added exceeded 20%, it often caused resin decomposition and generated an unpleasant odor. Therefore, the range of the amount of lactic acid added can be 0.01% to 20%.

[0067] Example 4: Effects of lactic acid and other additives on the processing of molded articles

[0068] [Table 4]

[0069] Here, the meaning of the symbols is as follows: ○: Continuous and stable processing is possible, and the solidification time of the molded product is short. △: Extrusion is stable during thermoplastic processing, but the solidification time of the molded product is relatively long. ×: Extrusion by the extruder is unstable, resulting in a long solidification time for the molded product.

[0070] As can be seen by comparing the data in Table 4, when the crystallization temperature is lowered, that is, under conditions where the water bath temperature is set to 20°C to 40°C (38°C), adding lactic acid (Experimental Example 31) allows for effective solidification of PHA in a shorter time, improving processing efficiency and reducing processing difficulty, compared to adding auxiliary agents such as behenic acid, boron nitride, 16-hydroxyhexadecanoic acid, and TMC-200 (Experimental Examples 32-35). This indicates that adding lactic acid makes it possible to adopt a lower crystallization temperature, guaranteeing the crystal quality of the molded product, shortening the solidification time and improving efficiency, as well as reducing energy consumption in actual production.

[0071] Although the present invention has been described in detail above through a general description and specific embodiments, it will be apparent to those skilled in the art that several modifications or improvements can be made based on the present invention. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope for which the present invention seeks protection.

Claims

1. Polyhydroxyalkanoates and; At least one of the lactic acid or lactic acid organic derivatives represented by the following general formula I, Includes, R ２ CH ２ -CH(OH)-COYR １ I Here, R １ is H or a hydrocarbon group, R ２ is H or a hydrocarbon group, and Y is one of C, O, N, or S. Polyhydroxyalkanoate composition.

2. In general formula I, Y is O, and R １ , R ２ Each of these is H, that is, the composition contains lactic acid, and the lactic acid is selected from L-lactic acid, D-lactic acid, or a combination thereof; The polyhydroxyalkanoate composition according to claim 1, characterized in that, in the combination of L-lactic acid and D-lactic acid, the ratio of L-lactic acid to D-lactic acid is 0.01 to 99.99:99.99 to 0.

01.

3. In general formula I, Y is O, and R １ is a C1-C16 hydrocarbon group, and R ２ is H or a C1-C16 hydrocarbon group; alternatively, In general formula I, Y is O, and R １ H is R ２ The polyhydroxyalkanoate composition according to claim 1, characterized in that is a C1-C16 hydrocarbon group.

4. The polyhydroxyalkanoate composition according to claim 3, characterized in that the lactic acid organic derivative comprises methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isopentyl lactate, benzyl lactate, tetradecyl lactate, hexadecyl lactate, methyl 3-phenyllactic acid, and 3-phenyllactic acid.

5. The polyhydroxyalkanoate composition according to any one of claims 1 to 4, characterized in that the amount of lactic acid and / or lactic acid organic derivative added is 0.01% to 20% relative to the mass of the polyhydroxyalkanoate.

6. The aforementioned polyhydroxyalkanoate contains a structural unit represented by the following general formula II, 【Chemistry 1】 Here, R is C ｐ H ２ｐ＋１ The alkyl group is represented by , where p is an integer from 1 to 15, preferably an integer from 1 to 10, more preferably an integer from 1 to 8; and m is 1, 2, or 3. The polyhydroxyalkanoate composition according to claim 1, characterized in that...

7. A polyhydroxyalkanoate molded article produced from the polyhydroxyalkanoate composition according to any one of claims 1 to 6.

8. A method for producing a polyhydroxyalkanoate molded article according to claim 7, comprising: (1) melting a uniformly mixed polyhydroxyalkanoate composition according to any one of claims 1 to 6 at a temperature above the melting point of the polyhydroxyalkanoate to form a molten body; (2) A step of crystallizing and molding the molten material from step (1) at a temperature of 65°C or lower, A manufacturing method characterized by including

9. A method for producing a polyhydroxyalkanoate molded article according to claim 8, characterized in that in step (2), the molten material is crystallized and molded at a temperature of 40°C or lower.

10. The polyhydroxyalkanoate molded article is (1) Melt extrusion: A step of melt extruding a uniformly mixed polyhydroxyalkanoate composition according to any one of claims 1 to 6 in an extrusion pelletizer, and setting the temperature of the extrusion pelletizer to 50 to 180°C, (2) Pelletization: A process of crystallizing the molten extruded material into pellets at a temperature of 20 to 40°C, The manufacturing method according to claim 8 or 9, characterized in that a pelletized body is produced by an extrusion pelletization method, which includes the above.

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