Polyhydroxyalkanoate and synthesis method thereof

Abstract

The invention provides polyhydroxyalkanoate and a synthesis method thereof. The polyhydroxyalkanoate comprises a chain segment which is generated by carrying out ring-opening polymerization reaction on a monomer combination, the monomer combination is composed of at least two monomers selected from the group consisting of R type beta-butyrolactone, S type beta-butyrolactone, R type alpha-methyl-beta-propiolactone and S type alpha-methyl-beta-propiolactone; and the monomer combination is not a raceme of R type beta-butyrolactone and S type beta-butyrolactone or a raceme of R type alpha-methyl-beta-propiolactone and S type alpha-methyl-beta-propiolactone. The polyhydroxyalkanoate disclosed by the invention is relatively high in mechanical strength, relatively good in toughness and relatively good in appearance; the synthesis method provided by the invention is relatively low in cost, relatively mild in reaction condition and relatively short in reaction time.

Description

Technical Field

[0001] The invention belongs to the field of chemical synthesis, and in particular relates to a series of polyhydroxyalkanoates with adjustable properties and a chemical synthesis method thereof. Background Art

[0002] Polyhydroxyalkanoates (PHA) are a class of fully biodegradable materials, including a series of polymers with different structures. There are currently four mainstream PHA varieties that have been commercialized: poly 3-hydroxybutyrate (PHB), copolyester of 3-hydroxybutyric acid and 3-hydroxyvaleric acid (PHBV), copolyester of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid (PHBHHx), and copolyester of 3-hydroxybutyric acid and 4-hydroxybutyric acid (P34HB). The production method of these commercialized PHA materials is microbial fermentation. PHA is an energy storage substance for microorganisms, equivalent to human fat. The above-mentioned polymers with different structural compositions can be obtained by providing different biomass carbon sources to microorganisms. The basic process for preparing PHA by microbial fermentation is as follows. Figure 1 shown.

[0003] The process of biological production of PHA is relatively long, in which the reproduction, survival and metabolic process of microorganisms to produce polymers have very complex mechanisms, and have high requirements for environmental temperature, nutrient content, pH, oxygen content, carbon dioxide content, cleanliness, etc., and are very sensitive to environmental changes. Any slight change will affect the properties of the polymer, which is not conducive to the consistency between product batches. To maintain the stability of the microbial environment, the daily maintenance energy consumption is very high, and the production mechanism of the biological method determines its low output, so the production cost is relatively high. According to a PHA production company, the annual production cost of 1,000 tons of polymers exceeds 50,000 yuan / ton. High cost is the main bottleneck restricting the large-scale commercialization of PHA.

[0004] In addition, after the microbial cells are crushed and PHA is extracted, even after several washing and separations, a small amount of protein will still remain. During the subsequent material modification, processing and use, the protein will turn yellow due to heat, and the material or product will even appear a highly saturated yellow, limiting its use scenarios. Figure 2 In the image on the left, the spline is yellow.

[0005] From the perspective of the product molecular structure, the main chain unit structure of bio-based PHA is R configuration. The consistent configuration is conducive to the regular arrangement and crystallization of the molecular chain, providing rigidity for the molecular chain, but it also makes the material exhibit the characteristics of high melting temperature, hardness and brittleness, and poor toughness. Taking PHB as an example, the melting temperature is around 177°C, but the heat resistance of PHA materials is generally poor, and the initial decomposition temperature (defined as the temperature at which the molecular chain breaks and the molecular weight decreases) is about 180°C. The high melting temperature causes the material processing window to be too narrow, and the material will undergo thermal degradation during the modification and molding process. Although the blending modification method mentioned in patent EP723983B1 can improve the mechanical properties of the material, it still cannot improve its processing performance. Compared with PHB, PHBV, PHBHHx, and P34HB introduce different structural links, which can reduce the melting temperature and improve the toughness of the material to a certain extent, but these materials also have their own intrinsic defects. For example, PHBHHx has the disadvantages of slow crystallization rate, long molding cycle, and large shrinkage rate. The material composition and performance are regulated by changing the type and proportion of carbon sources, which involves strain selection, gene editing, and complex metabolic processes. The operation is not as direct as the chemical method, and it is impossible to achieve copolymerization with non-PHA components (such as polylactic acid, polyglycolic acid, polycaprolactone, etc.). These problems limit the application of PHA as an industrial product.

[0006] The methods and products for synthesizing PHA using fossil raw materials and chemical means are still in the development stage, mainly reported in academia, and have not yet been commercialized. Depending on the raw materials and synthesis routes, the chemical synthesis methods of PHA include polycondensation and ring-opening polymerization.

[0007] The polycondensation method is to obtain hydroxycarboxylic acids (such as 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 3-hydroxyhexanoic acid, etc.) or corresponding esters (such as 3-hydroxybutyric acid methyl ester) through condensation polymerization. The polycondensation reaction is a reversible reaction, which mainly relies on removing small molecules produced during the reaction to achieve the forward reaction. The molecular weight of the product is related to the reaction temperature and vacuum degree, and usually requires a higher temperature and a longer reaction time. Even so, the molecular weight of the polymer product is still low, the mechanical properties of the material are poor, and the β-hydroxyl group in the reaction is prone to side reactions to form carbon-carbon double bonds.

[0008] Compared with the polycondensation method, ring-opening polymerization has a lower reaction temperature and a higher product molecular weight. The raw materials for ring-opening polymerization are cyclic lactones, such as β-butyrolactone, β-valerolactone, β-caprolactone, γ-butyrolactone, etc. These cyclic lactones and the polymer chain segments formed after ring opening have at least one chiral carbon atom. The arrangement and ratio of the R / S configuration of the chiral carbon atom will directly affect the regularity of the polymer backbone, and then affect the crystallinity, thermal properties and mechanical properties of the material. The four currently commercialized PHA products all have structures corresponding to β-butyrolactone, so the ring-opening polymerization of β-butyrolactone has high research and practical significance.

[0009] Easily available β-butyrolactone reagents or industrial raw materials are usually racemic mixtures composed of equal amounts of R-type and S-type. The melting temperature of the polymer product obtained by random copolymerization of equal amounts of two configuration monomers is only in the range of 40-70°C, and the crystallinity is low, so the texture is soft and the mechanical strength is poor. Wei Zhiyong and others from Dalian University of Technology prepared a polymer product with a molecular weight (Mw) of more than 300,000 under high vacuum conditions, proving that increasing the molecular weight of the polymer may increase the tensile strength of such polymer materials to more than 20MPa, but the 10 -3 The high vacuum condition of Pa is not industrially feasible.

[0010] Some studies are devoted to developing new catalysts that can exert stereoselectivity during polymerization. For example, the paper (Journal of the American Chemical Society 2023 145(21), 11494-11498, DOI: 10.1021 / jacs.3c02348) produced a polymer material with an isotacticity of 0.89, a melting temperature of about 140°C, and optimized mechanical properties. However, the catalyst used has a complex structure and requires precious metals or rare earth metals as catalytic active centers, which is not meaningful for amplification. Patent application CN101160342A uses a relatively common Salen chromium catalyst. The isotacticity of the polymerization product is 0.57-0.74, and the melting temperature is increased to 112-145°C. However, because the catalyst itself is dark red and considering the residual heavy metals, this type of catalyst limits the application range of polymers. According to the method described in the paper (Stereospecific polymerization of β-Methyl-β-propiolactone. Polym J1972; 3: 417–18), using alkyl-coordinated aluminum as a catalyst can obtain isotactic polymers with a melting temperature (Tm value) as high as 167-169°C, but it takes up to 7 days at 60°C to obtain a considerable polymer yield, and the reaction efficiency is low. Most of the polymerizations catalyzed by other alkyl aluminums are accompanied by a considerable proportion of low molecular weight polymers, which is not conducive to material properties.

[0011] The use of optically active lactone monomers can produce polymer products with higher isotacticity, which can improve the melting temperature and mechanical strength of the material. However, the polymer products of single-configuration lactone monomers have the same essential disadvantages as the single R-type polymers produced by biological methods, and the molecular weight of the former is even far inferior to the latter. The use of monomers with enantiomeric excess for polymerization has not been reported in the synthesis of polyhydroxyalkanoates, which is a blind spot in research and production.

[0012] In summary, the bio-fermentation method for synthesizing PHA and its products has the following disadvantages: (1) long process flow, (2) high energy consumption, low yield, high cost, (3) poor quality control, (4) residual impurities causing product discoloration, (5) narrow product processing window, (6) poor material toughness, and (7) inconvenient product performance control. The polycondensation method for synthesizing PHA and its products has the following disadvantages: complex process conditions, low product molecular weight, and easy side reactions. The existing ring-opening polymerization method for synthesizing PHA and its products has the following disadvantages: (1) the random polymerization products using conventional raw materials (racemic monomers) under ordinary catalysts have either poor mechanical strength or harsh reaction conditions; (2) the configuration selectivity / configuration change catalysts used in the polymerization of conventional raw materials (racemic monomers) have either complex catalyst structures and high costs, or affect the product appearance, or the polymerization reaction time is too long; (3) the polymerization products of single-configuration monomers have the same disadvantages as the biological method products: narrow product processing window and poor material toughness.

[0013] Therefore, there is a need in the art for a PHA with high mechanical strength, good toughness and good appearance and a synthesis method thereof with low cost, mild reaction conditions and short reaction time. Summary of the invention

[0014] In view of the problems existing in the prior art, the present invention provides a polyhydroxyalkanoate and a synthesis method thereof. The polymer contained in the polyhydroxyalkanoate of the present invention is prepared by a ring-opening polymerization reaction of a specific monomer combination. The polyhydroxyalkanoate of the present invention has high mechanical strength, good toughness and good appearance. The synthesis method provided by the present invention has low cost, mild reaction conditions and short reaction time.

[0015] Specifically, one aspect of the present invention provides a polyhydroxyalkanoate, which comprises a chain segment generated by a monomer combination through a ring-opening polymerization reaction, wherein the monomer combination is composed of at least two monomers selected from R-type β-butyrolactone, S-type β-butyrolactone, R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone, and the monomer combination is not a racemate of R-type β-butyrolactone and S-type β-butyrolactone or a racemate of R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone.

[0016] In one or more embodiments, the monomer combination includes a first monomer, the mass of the first monomer accounts for 55% to 99%, preferably 75% to 98% of the total mass of the monomer combination, and the first monomer is R-type β-butyrolactone, S-type β-butyrolactone, R-type α-methyl-β-propiolactone or S-type α-methyl-β-propiolactone.

[0017] In one or more embodiments, the first monomer is R-type β-butyrolactone or S-type β-butyrolactone, preferably R-type β-butyrolactone.

[0018] In one or more embodiments, the polyhydroxyalkanoate has a melting temperature of 100 to 165° C., a tensile strength of ≥15 MPa, a tensile modulus of ≥400 MPa, and an elongation at break of ≥2%.

[0019] Another aspect of the present invention provides a polyhydroxyalkanoate composition, comprising the polyhydroxyalkanoate according to any one of the embodiments herein and an additive.

[0020] In one or more embodiments, the additive includes one or more selected from the group consisting of a thermal stabilizer, an antioxidant, and an anti-hydrolysis agent.

[0021] In one or more embodiments, in the polyhydroxyalkanoate composition, the mass ratio of the additive to the polyhydroxyalkanoate is (0.01-1):100.

[0022] In one or more embodiments, the polyhydroxyalkanoate composition has a melting temperature of 100 to 165° C., a tensile strength of ≥15 MPa, a tensile modulus of ≥400 MPa, and an elongation at break of ≥2%.

[0023] The present invention also provides a method for synthesizing the polyhydroxyalkanoate described in any embodiment herein or the polyhydroxyalkanoate composition described in any embodiment herein, the method comprising subjecting the monomer combination to a ring-opening polymerization reaction in the presence of a catalyst.

[0024] In one or more embodiments, the catalyst is a tin catalyst, and the tin catalyst is selected from one or more of dibutyltin oxide, dioctyltin oxide, dioctoate tin, dibutyltin laurate, distannoxane and cycloalkoxy tin, and the cycloalkoxy tin is a compound shown in Formula I or Formula II:

[0025]

[0026] Among them, R 1 and R 2 Each independently is an alkyl or alkoxy group containing 1 to 10 carbon atoms, R 3 , R 4 and R 5 Each is independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

[0027] In one or more embodiments, the cycloalkoxytin is selected from the following compounds:

[0028]

[0029]

[0030] In one or more embodiments, the amount of the catalyst used is 0.1 wt% to 5 wt%, preferably 0.2 wt% to 2 wt%, based on the total weight of the monomer combination.

[0031] In one or more embodiments, the ring-opening polymerization reaction is carried out in a one-pot manner.

[0032] In one or more embodiments, the temperature of the ring-opening polymerization reaction is 60 to 130°C, preferably 80 to 115°C.

[0033] In one or more embodiments, the ring-opening polymerization reaction time is 2 to 24 hours, preferably 4 to 20 hours.

[0034] In one or more embodiments, it is characterized in that the ring-opening polymerization reaction comprises first a liquid phase polymerization reaction and then a solid phase polymerization reaction; preferably, the temperature of the liquid phase polymerization reaction is 60 to 130°C, preferably 80 to 115°C, the temperature of the solid phase polymerization reaction is 80 to 120°C, preferably 90 to 110°C, and the total time of the ring-opening polymerization reaction is 2 to 24 hours, preferably 4 to 20 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Flowchart for the production of PHA by microbial fermentation.

[0036] Figure 2 The appearance of the injection-molded specimens of PHB synthesized by biological methods (left) and the appearance of the injection-molded specimens of the product synthesized in Example 3 (right).

[0037] Figure 3 The appearance of the product after the polymerization of Comparative Example 1-1 (above) and the appearance of the product after the polymerization of Example 2 (below). DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0039] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0040] Herein, “comprising”, “including”, “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of”. For example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to be disclosed herein.

[0041] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0042] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0043] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0044] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0045] The invention provides a method for synthesizing polyhydroxyalkanoate (PHA) by a chemical method, and also provides a PHA material synthesized by the method.

[0046] The present invention uses monomers of the same structure but different configurations and / or isomers of similar structures as monomer combinations for copolymerization. By changing the ratio of each monomer, the melting temperature, crystallization temperature, crystallinity, mechanical strength, mechanical toughness and other properties of the material can be flexibly regulated to improve the processing window and mechanical properties of the material, especially toughness. The method of the present invention has mild reaction conditions. Compared with the commercialized biological synthesis of polyhydroxyalkanoates, it has the advantages of short process flow, controllable energy consumption, easy access to raw materials, stable product quality, easy regulation of product composition and properties, relatively low cost, and stable and beautiful appearance. Compared with other existing chemical synthesis methods, it has more optimized monomer composition and reaction conditions, and the catalyst used is more conventional and easier to prepare. Compared with the improved materials obtained by copolymerization of multiple monomers, the reaction process of the present invention is easier to control and more conducive to closed-loop chemical recovery.

[0047] In the present invention, the monomer combination used as the raw material of polyhydroxyalkanoate is composed of at least two monomers selected from R-type β-butyrolactone, S-type β-butyrolactone, R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone, and the monomer combination is not a racemic body of R-type β-butyrolactone and S-type β-butyrolactone, nor is it a racemic body of R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone.

[0048] The structural formula of R-type β-butyrolactone (R-BBL for short) is: The structural formula of S-β-butyrolactone (S-BBL for short) is: The racemic body of R-type β-butyrolactone and S-type β-butyrolactone is referred to as rac-BBL, which is composed of R-type β-butyrolactone and S-type β-butyrolactone in an equal mass ratio.

[0049] The structural formula of R-α-methyl-β-propiolactone (R-AMBP for short) is The structural formula of S-α-methyl-β-propiolactone (abbreviated as S-AMBP) is The racemic form of R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone is referred to as rac-AMBP, which is composed of R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone in an equal mass ratio.

[0050] In the present invention, the monomers participating in the polymerization reaction may be two, three or four of R-type β-butyrolactone, S-type β-butyrolactone, R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone.

[0051] In a preferred embodiment, the monomer combination includes a first monomer as a main monomer, and the first monomer accounts for 55% to 99%, preferably 75% to 98%, and more preferably 80% to 98%, for example 82%, 84%, 85%, 88%, 90%, 92%, 94%, 95% of the total mass of the monomer combination, which is conducive to obtaining a material with high tensile strength and tensile modulus and good toughness.

[0052] The first monomer may be any one of R-type β-butyrolactone, S-type β-butyrolactone, R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone. The first monomer is preferably R-BBL or S-BBL, particularly preferably R-BBL, which is conducive to obtaining a material with better comprehensive properties including tensile strength, tensile modulus and toughness.

[0053] The polyhydroxyalkanoate of the present invention comprises a segment generated by the aforementioned monomer combination through a ring-opening polymerization reaction. In some embodiments, the polyhydroxyalkanoate of the present invention comprises a segment generated by the aforementioned monomer combination through a ring-opening polymerization reaction and a capping group converted from a capping agent. In some embodiments, the polyhydroxyalkanoate of the present invention only comprises a segment generated by the aforementioned monomer combination through a ring-opening polymerization reaction, that is, the polyhydroxyalkanoate of the present invention is prepared by the aforementioned monomer combination through a ring-opening polymerization reaction.

[0054] In some embodiments, the polyhydroxyalkanoate of the present invention does not contain a structure formed by reacting other monomers other than the aforementioned monomer combination.

[0055] In the present invention, both polyhydroxyalkanoate and polyhydroxyalkanoate composition can be used as polyhydroxyalkanoate materials. The polyhydroxyalkanoate composition of the present invention comprises the polyhydroxyalkanoate of the present invention and an additive. The additive can be an additive commonly added to polyhydroxyalkanoate, including but not limited to a heat stabilizer, an antioxidant, an anti-hydrolysis agent, acetic anhydride, and the like. Examples of heat stabilizers include cuprous iodide and potassium iodide compositions (CuI+KI), calcium stearate, zinc stearate, alkyl phosphates, hypophosphites, phosphites, hypophosphites, phosphites, and the like. Examples of antioxidants include antioxidant 1098, antioxidant 168, antioxidant 1010, antioxidant 1076, antioxidant PEPQ, antioxidant S9228, and the like. Examples of anti-hydrolysis agents include carbodiimide, isocyanate, oxazoline compounds, epoxy compounds, and the like. The main function of acetic anhydride is to remove trace water in the system and to act as a capping agent at the same time. In the polyhydroxyalkanoate composition, the mass ratio of the additive to the polyhydroxyalkanoate may be (0.01-1):100, for example, 0.02:100, 0.05:100, 0.1:100, 0.2:100, or 0.5:100.

[0056] In some preferred embodiments, by controlling the type and amount of the first monomer in the monomer combination, the polyhydroxyalkanoate and polyhydroxyalkanoate composition of the present invention have one, more or all of the following properties:

[0057] The melting temperature is 100 to 165°C, for example, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C;

[0058] Tensile strength ≥15MPa, such as ≥20MPa, ≥25MPa, ≥30MPa;

[0059] Tensile modulus ≥ 400 MPa, e.g. ≥ 500 MPa, ≥ 1000 MPa, ≥ 2000 MPa, ≥ 3000 MPa;

[0060] The elongation at break is ≥2%, for example ≥3%, ≥5%, ≥10%, ≥15%, ≥20%.

[0061] The polyhydroxyalkanoate and polyhydroxyalkanoate composition of the present invention are prepared by ring-opening polymerization of the monomer combination described herein in the presence of a catalyst. For the polyhydroxyalkanoate composition, the additive can be added to the reaction system before the ring-opening polymerization reaction begins. In the present invention, the ring-opening polymerization reaction is preferably carried out in a "one-pot method", that is, the reaction product is always retained in the same reactor during the reaction process, and there is no separation or purification step of the intermediate product.

[0062] The catalyst suitable for the present invention can be a known catalyst that can be used to catalyze the ring-opening polymerization reaction. Preferably, the catalyst is a tin catalyst. Examples of tin catalysts include, but are not limited to, dibutyltin oxide, dioctyltin oxide, dioctoate tin, dibutyltin laurate, distannoxane, cycloalkoxy tin, etc. In some preferred embodiments, the catalyst used in the present invention is cycloalkoxy tin, which is conducive to improving the reaction efficiency and making the reaction conditions milder.

[0063] The cycloalkoxytin compound suitable for the present invention may be a compound represented by Formula I or Formula II:

[0064]

[0065] Among them, R 1 and R 2 Each independently is an alkyl or alkoxy group containing 1 to 10 carbon atoms, R 3 , R 4 and R 5 Each R is independently a hydrogen atom or an alkyl group containing 1 to 10 carbon atoms. 1 and R 2 Can be the same or different. In some embodiments, R 1 and R 2 Each is independently an alkyl or alkoxy group containing 4 to 8 carbon atoms. 3 , R 4 and R 5 Can be the same or different. In some embodiments, R 3 , R 4 and R 5 Each is independently a hydrogen atom or a methyl group.

[0066] In some embodiments, the cycloalkoxytin used in the present invention is selected from the following compounds:

[0067]

[0068] The preparation method of the cycloalkoxytin used in the present invention is known.

[0069] In the present invention, the amount of the catalyst used can be 0.1-5 wt% of the total weight of the monomer combination, preferably 0.2-2 wt%, such as 0.5 wt%, 1 wt%, 1.5 wt%.

[0070] In some embodiments, the ring-opening polymerization process of the present invention is as follows: the raw materials are added into the reactor together, the atmosphere in the reactor is replaced with a protective gas (such as nitrogen), the reactor is sealed and no material exchange occurs, the polymerization reaction is carried out while stirring and heating, and the polymerization product is taken out after the reaction is completed. The ring-opening polymerization reaction first performs liquid phase polymerization, and then solid phase polymerization can be performed, or solid phase polymerization can be omitted.

[0071] In the present invention, the polymerization temperature is preferably 60 to 130°C, more preferably 80 to 115°C, such as 90°C, 100°C, 110°C. If the temperature is too low, the reaction rate is low and the reaction time is too long; if the temperature is too high, the monomer is prone to decomposition reaction to produce gas, which increases the system pressure. In the present invention, the solid phase polymerization temperature is preferably 80 to 120°C, more preferably 90 to 110°C.

[0072] In the present invention, the total solid phase polymerization reaction time is preferably 2 to 24 hours, more preferably 4 to 20 hours, such as 5 hours, 8 hours, 10 hours, 12 hours, 15 hours. If the time is too short, the reaction is incomplete, and if the time is too long, the energy consumption increases and side reactions are likely to occur.

[0073] Compared with the block copolymerization method described in EP723983A2 and EP686656A2 and block polymer (composition), " one pot method " of the present invention is simpler and more direct, and the main monomer participating in the reaction has a similar structure, so that the reactivity of the copolymerization component is consistent, and the link structure of the polymerized product is also similar, and there is no need to carry out complex changes to the conditions such as reaction time, temperature, pressure because of different reaction components, so that the control of the reaction is more conducive to production, the reaction is made to be more fully complete, and the utilization rate of raw materials is improved. Even if the product performance is to be adjusted, it is only necessary to change the adding ratio of the isomer, and there is no need to adjust the reaction process parameters. From the perspective of recovery after use and green chemistry, because the link structure is identical (in the case of no isomers) or similar, not only physical recovery can be carried out, but also the development and application of chemical recovery method can be conducive to.

[0074] The present invention will be described below in the form of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents and materials used in the examples are, unless otherwise stated, conventional methods, reagents and materials in the art. The raw material compounds in the examples can all be purchased through commercial routes.

[0075] In the present invention, the testing method of polymer performance is as follows:

[0076] (1) Melting temperature, cold crystallization temperature and crystallinity: DSC test was performed according to the national standard GB / T19466 "Plastic Differential Scanning Calorimetry (DSC)", with a heating / cooling rate of 10K / min and a test temperature range of -60°C to 180°C. The melting temperature and cold crystallization temperature were read on the test curve. The ratio between the integrated area of ​​the sample melting peak (unit: J / g) and the 100% crystallization melting enthalpy of PHB is the crystallinity.

[0077] (2) Tensile strength, tensile modulus and elongation at break: Test specimens were prepared according to the national standard GB / T 17037 “Preparation of injection molding specimens of thermoplastic materials”, and tensile tests were performed according to GB / T 1040 “Test methods for tensile properties of plastics”. The tensile speed was 2 mm / min.

[0078] (3) Weight average molecular weight: The weight average molecular weight was measured on a gel permeation chromatograph, the liquid solvent was tetrahydrofuran, and the standard sample was polystyrene.

[0079] Example 1

[0080] 144.7g of R-BBL, 27.3g of S-BBL and 1.152g of catalyst SnA were added to a polymerization reactor, heated to 90°C for 12h, and then cooled to obtain a white solid product. Product properties: melting temperature 120°C, cold crystallization temperature 60°C, crystallinity 25.8%, tensile strength 25MPa, tensile modulus 689MPa, elongation at break 19.5%.

[0081] Comparative Example 1-1

[0082] 172 g of rac-BBL and 1.152 g of catalyst SnA were added to the polymerization reactor, heated to 90°C for 12 h, and then cooled to obtain a colorless, transparent, soft and elastic product. The product has an appearance of Figure 3 As shown in the figure above. Product properties: melting temperature 50℃, 62℃, 85℃, no cold crystallization peak, about 14 days after synthesis, the appearance transparency tends to be stable, showing a frosted glass-like opaque state, crystallinity 8%, tensile strength 1MPa, tensile modulus 20MPa, elongation at break 1576%.

[0083] Comparative Example 1-2

[0084] 172g of R-BBL and 1.152g of catalyst SnA were added to the polymerization reactor, heated to 90°C for 12h, and then cooled to obtain a hard white solid product. Product properties: melting temperature 172°C, cold crystallization temperature 98°C, crystallinity 47.3%, tensile strength 37MPa, tensile modulus 4544MPa, elongation at break 1.6%.

[0085] Comparative Examples 1-3

[0086] 120g of R-BBL, 52g of S-BBL and 1.152g of catalyst SnA were added to the polymerization reactor, heated to 90°C for 12h, and then cooled to obtain a colorless, transparent, soft product, which was softer than the product of Comparative Example 1-1. In the DSC test, no melting peak or cold crystallization peak appeared, and only Tg was 3°C.

[0087] Example 2

[0088] 168 g of R-BBL, 3 g of R-AMBP and 0.576 g of catalyst SnB were added to the polymerization reactor, heated to 110°C for 6 h, and then solid phase polycondensed at 98°C for 12 h. The product was cooled to obtain a white solid product. Figure 3 As shown in the figure below. Product properties: weight average molecular weight 149465g / mol, melting temperature 158℃, 163℃, cold crystallization temperature 95℃, crystallinity 46.2%, tensile strength 36MPa, tensile modulus 3693MPa, elongation at break 3.9%.

[0089] Comparative Example 2

[0090] Add 206g of R-3-hydroxybutyric acid methyl ester and 0.576g of catalyst SnB into the polymerization reactor, stir and heat to 110℃, distill methanol at normal pressure for 3h until no more distillate; heat to 160℃, continue reaction and distillation for 3h, and pass nitrogen appropriately according to the distillation speed; cool to 155℃, continue distillation, slowly reduce pressure to 2kPa, and continue for 6h; cool to obtain a slightly yellow solid product, which is brittle and easy to crush. Product properties: weight average molecular weight 6387g / mol, melting temperature 156℃, cold crystallization temperature 75℃, crystallinity 46.5%.

[0091] Example 3

[0092] 161.4g of R-BBL, 8.9g of S-BBL, 1.7g of rac-AMBP, 2.15g of catalyst SnC and 0.195g of acetic anhydride were added to the polymerization reactor, heated to 100°C for 6h, and then cooled to obtain a white solid product. Product properties: melting temperature 135°C, 149°C, cold crystallization temperature 90°C, crystallinity 37.4%, tensile strength 34MPa, tensile modulus 1675MPa, elongation at break 6.7%. The appearance of the tensile specimen obtained by injection molding is as follows: Figure 2 In the image on the right, the spline appears white.

[0093] Example 4

[0094] 155.2g of S-BBL, 17.2g of R-BBL, 0.384g of catalyst SnD and 0.172g of antioxidant sodium hypophosphite were added to the polymerization reactor, heated to 80°C for 20h, and then cooled to obtain a white solid product. Product properties: melting temperature 121°C, 132°C, cold crystallization temperature 69°C, crystallinity 34.2%, tensile strength 32MPa, tensile modulus 1338MPa, elongation at break 13.3%.

[0095] Example 5

[0096] 138g of S-BBL, 27g of R-AMBP, 7g of S-AMBP and 1.535g of catalyst SnC were added to a polymerization reactor, heated to 100°C for 20h, and then cooled to obtain a white solid product. Product properties: melting temperature 108°C, 115°C, crystallinity 14.1%, cold crystallization temperature not shown in DSC test, tensile strength 21MPa, tensile modulus 437MPa, elongation at break 23.3%.

[0097] Comparative Example 3

[0098] 138g of γ-butyrolactone, 34.4g of R-BBL and 1.535g of catalyst SnC were added to the polymerization reactor, heated to 100°C for 20h, cooled and dissolved in dichloromethane, and then precipitated with n-hexane. According to H-NMR spectrum, only 32wt% of the product was the ring segments of γ-butyrolactone after ring opening, which was far lower than the feed ratio of 80wt%.

[0099] Comparative Example 4

[0100] 138g of rac-BBL, 34.4g of ε-caprolactone and 1.535g of catalyst SnC were added to the polymerization reactor, heated to 100°C and reacted for 20h, and then cooled to obtain a colorless, transparent, soft solid product with a texture similar to that of plasticine. Product performance: No melting peak or crystallization peak was shown in the DSC test.

[0101] Comparative Example 5

[0102] 138g of R-BBL, 34.4g of lactide and 1.535g of catalyst SnC were added to the polymerization reactor, heated to 110°C for 20h, and cooled to obtain a white solid product, which was crisp. After washing by the dissolution-precipitation method, it was found that lactide did not form a continuous polymer chain. It is easy to learn from the literature that the polymerization of lactide can usually be achieved at above 130°C, preferably 150-180°C. This is far beyond the thermal decomposition temperature of β-butyrolactone, and the polymerization conditions of the two do not match.

[0103] Table 1 summarizes the main monomers and their proportions as well as the product properties of the examples and comparative examples. Table 1: Main monomers, mass fractions of main monomers in the total amount of monomers and product properties of the examples and comparative examples

[0104]

[0105]

Claims

1. A polyhydroxyalkanoate, It is characterized in that The polyhydroxyalkanoate comprises a chain segment generated by a monomer combination through a ring-opening polymerization reaction, wherein the monomer combination is composed of at least two monomers selected from R-type β-butyrolactone, S-type β-butyrolactone, R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone, and the monomer combination is not a racemate of R-type β-butyrolactone and S-type β-butyrolactone or a racemate of R-type α-methyl-β-propiolactone and S-type α-methyl-β-propiolactone.

2. The polyhydroxyalkanoate according to claim 1, It is characterized in that The monomer combination includes a first monomer, the mass of the first monomer accounts for 55% to 99%, preferably 75% to 98% of the total mass of the monomer combination, and the first monomer is R-type β-butyrolactone, S-type β-butyrolactone, R-type α-methyl-β-propiolactone or S-type α-methyl-β-propiolactone.

3. The polyhydroxyalkanoate according to claim 2, It is characterized in that The first monomer is R-type β-butyrolactone or S-type β-butyrolactone, preferably R-type β-butyrolactone.

4. The polyhydroxyalkanoate according to claim 1, It is characterized in that The polyhydroxyalkanoate has a melting temperature of 100-165° C., a tensile strength of ≥15 MPa, a tensile modulus of ≥400 MPa, and an elongation at break of ≥2%.

5. A polyhydroxyalkanoate composition, It is characterized in that The polyhydroxyalkanoate composition comprises the polyhydroxyalkanoate according to any one of claims 1 to 4 and an additive; Preferably, in the polyhydroxyalkanoate composition, the mass ratio of the additive to the polyhydroxyalkanoate is (0.01-1):100; Preferably, the additive comprises one or more selected from the group consisting of a heat stabilizer, an antioxidant and an anti-hydrolysis agent.

6. The polyhydroxyalkanoate composition according to claim 5, It is characterized in that The polyhydroxyalkanoate composition has a melting temperature of 100-165° C., a tensile strength of ≥15 MPa, a tensile modulus of ≥400 MPa, and an elongation at break of ≥2%.

7. A method for synthesizing the polyhydroxyalkanoate according to any one of claims 1 to 4 or the polyhydroxyalkanoate composition according to claim 5 or 6, It is characterized in that The method includes subjecting the monomer combination to a ring-opening polymerization reaction in the presence of a catalyst.

8. The method according to claim 7, It is characterized in that The catalyst is a tin catalyst, and the tin catalyst is selected from one or more of dibutyltin oxide, dioctyltin oxide, dioctoate tin, dibutyltin laurate, distannoxane and cycloalkoxy tin, and the cycloalkoxy tin is a compound shown in Formula I or Formula II: Among them, R 1 and R 2 Each independently is an alkyl or alkoxy group containing 1 to 10 carbon atoms, R 3 , R 4 and R 5 Each is independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Preferably, the cycloalkoxytin is selected from the following compounds:

9. The method according to claim 7, It is characterized in that The method has one or more of the following features: The amount of the catalyst is 0.1wt% to 5wt% of the total mass of the monomer combination, preferably 0.2wt% to 2wt%; The ring-opening polymerization reaction is carried out in a one-pot manner; The temperature of the ring-opening polymerization reaction is 60 to 130° C., preferably 80 to 115° C.; The ring-opening polymerization reaction time is 2 to 24 hours, preferably 4 to 20 hours.

10. The method according to claim 7, It is characterized in that The ring-opening polymerization reaction comprises first a liquid phase polymerization reaction and then a solid phase polymerization reaction, wherein the temperature of the liquid phase polymerization reaction is 60 to 130° C., preferably 80 to 115° C., the temperature of the solid phase polymerization reaction is 80 to 120° C., preferably 90 to 110° C., and the total time of the ring-opening polymerization reaction is 2 to 24 hours, preferably 4 to 20 hours.

Images