Polyhydroxyalkanoate aqueous dispersion and preparation method thereof

Abstract

The present invention provides a polyhydroxyalkanoate aqueous dispersion and a preparation method thereof. The preparation method comprises: (S100) treating polyhydroxyalkanoate with maleic anhydride to obtain a modified polyhydroxyalkanoate; (S200) using a high-speed mixer to mix the modified polyhydroxyalkanoate obtained in (S100), polybutylene succinate, a compatibilizer, a lubricant, a plasticizer, and sodium bicarbonate to obtain a premix; and (S300) using a screw extruder to blend and extrude the premix obtained in (S200), an inorganic filler, a biopowder, a degradation catalyst, an emulsifier, an antioxidant, polyvinyl alcohol, and water to obtain a polyhydroxyalkanoate aqueous dispersion. The preparation method of the present invention can obtain an easily degradable and environmentally friendly polyhydroxyalkanoate, and the polyhydroxyalkanoate aqueous dispersion has stable performance.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material processing and manufacturing, and in particular to a polyhydroxyalkanoate aqueous dispersion and a preparation method thereof. Background Art

[0002] By coating or applying an aqueous dispersion of a resin material to the surface of paper, it can impart hydrophobic and waterproof properties, enabling the production of disposable tableware products such as paper cups and lunch boxes. Polyhydroxyalkanoate (PHA) materials are inherently hydrophobic, biocompatible, and biodegradable, offering broad potential applications in the manufacture of disposable tableware.

[0003] Polyhydroxyalkanoates (PHA) are a type of polyester-based natural polymer material found in bacteria. They primarily serve as a storage substance for intracellular carbon and energy sources. Currently, the synthesis methods for polyhydroxyalkanoates primarily include biosynthesis (e.g., bacterial synthesis and genetic engineering) and chemical synthesis. Because polyhydroxyalkanoates have different monomer structures, they come in a wide variety. The prior art includes polyhydroxyalkanoates composed of short-chain monomers, polyhydroxyalkanoates composed of medium- and long-chain monomers, and copolymers composed of different types of monomers. The most common of these are poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV), and copolymers of PHB and PHV (PHBV). Polyhydroxyalkanoates also possess numerous excellent properties, including optical activity, piezoelectricity, and gas barrier properties. Therefore, in addition to being widely used in the biodegradable plastics industry, they may also be used in high-value-added fields such as medicine, pharmaceuticals, and electronics. Polyhydroxyalkanoates can be made into films, spun into fibers, or made into fabrics. Therefore, polyhydroxyalkanoates can not only be used as waterproof coatings for disposable tableware, but can also be widely used in many fields such as surgical sutures, personal hygiene products, and drug controlled release.

[0004] The most significant characteristic of polyhydroxyalkanoates (PHA) is their ability to be degraded by microorganisms in virtually any environment (compost, soil, seawater). Because they possess physical and chemical properties similar to those of chemical plastics and are biodegradable, PHAs can alleviate the increasingly serious problem of "white pollution," and therefore have begun to be used as biodegradable plastics.

[0005] For polyhydroxyalkanoate materials used as waterproof coatings for disposable tableware, how to improve the stability of their aqueous dispersion systems is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0006] The problem solved by the present invention is how to improve the stability of polyhydroxyalkanoate aqueous dispersion.

[0007] To solve the above problems, the present invention provides a method for preparing a polyhydroxyalkanoate aqueous dispersion, comprising:

[0008] S100, treating polyhydroxyalkanoate with maleic anhydride to obtain modified polyhydroxyalkanoate;

[0009] S200, using a high-speed mixer, mixing the modified polyhydroxyalkanoate, polybutylene succinate, compatibilizer, lubricant, plasticizer, and sodium bicarbonate obtained in S100 to obtain a premix;

[0010] S300, using a screw extruder, blending and extruding the premix obtained in S200, inorganic filler, biological powder, degradation catalyst, emulsifier, antioxidant, polyvinyl alcohol and water to obtain a polyhydroxyalkanoate aqueous dispersion.

[0011] In any of the above technical solutions, in S200, the compatibilizer includes at least one of the following or a combination thereof: poly (L-lactic acid), ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-butyl acrylate copolymer; and / or the lubricant includes at least one of the following or a combination thereof: polyethylene wax, paraffin, glycerin, white oil, stearic acid, stearamide, oleamide, erucamide; and / or the plasticizer includes at least one of the following or a combination thereof: ethylene glycol, glycerin, propylene glycol, dimethyl phthalate.

[0012] In any of the above technical solutions, in S300, the inorganic filler includes at least one of the following or a combination thereof: silicon oxide, aluminum oxide, calcium carbonate, talc, glass powder; and / or the biological powder includes at least one of the following or a combination thereof: straw powder, rice husk powder, coconut shell powder; and / or the degradation catalyst includes at least one of the following or a combination thereof: iron octadecanoate, copper octadecenoate; and / or the emulsifier includes at least one of the following or a combination thereof: monoolein, soy lecithin, Tween 60, Tween 80; and / or the antioxidant includes at least one of the following or a combination thereof: 4,4-diaminodiphenyl ether, alkylated diphenylamine, zinc dialkyl dithiophosphate.

[0013] In any of the above technical solutions, S100 specifically includes:

[0014] S110, mixing and stirring the polyhydroxyalkanoate and the organic solvent under inert gas protection at a mass ratio of polyhydroxyalkanoate:organic solvent=(10-20):100 to obtain a mixed material;

[0015] S120. Add initiator and maleic anhydride to the mixture in a mass ratio of initiator: maleic anhydride: polyhydroxyalkanoate = (1-2): (8-12): 100, heat and stir to obtain modified polyhydroxyalkanoate.

[0016] In any of the above technical solutions, in S110, the organic solvent is dichloromethane; and / or in S120, the initiator is benzoyl peroxide; and / or in S120, the temperature condition of heating and stirring is 45°C to 55°C; and / or in S120, the heating and stirring time is 5h to 6h.

[0017] In any of the above technical solutions, S200 specifically includes:

[0018] S210, adding the modified polyhydroxyalkanoate, polybutylene succinate, compatibilizer, lubricant, plasticizer and sodium bicarbonate into a high-speed mixer in a mass ratio of modified polyhydroxyalkanoate: polybutylene succinate: compatibilizer: lubricant: plasticizer: sodium bicarbonate = 100: (10-15): (2-4): (2-4): (2-4): (4-6);

[0019] S220, controlling the high-speed mixer to operate at a rotation speed of 280 r / min to 340 r / min for 20 min to 30 min to obtain a premix.

[0020] In any of the above technical solutions, S300 specifically includes:

[0021] S310, feeding the premix, inorganic filler, biopowder, and degradation catalyst into the first section of a screw extruder according to a mass ratio of premix: inorganic filler: biopowder: degradation catalyst = 100: (4-6): (4-6): (0.5-1.5), stirring uniformly, and then performing heat and pressure maintenance treatment to obtain a first mixture;

[0022] S320, feeding the first mixture into the second section of the screw extruder and adding the emulsifier and antioxidant in a mass ratio of premix:emulsifier:antioxidant=100:(4-8):(2-4), performing melt blending to obtain a second mixture;

[0023] S330. According to the mass ratio of premix: polyvinyl alcohol: water = 100: (40-80): (100-400), the second mixture is fed into the third section of the screw extruder, polyvinyl alcohol and water are added, and the mixture is stirred and emulsified to obtain a polyhydroxyalkanoate aqueous dispersion after extrusion.

[0024] In any of the above technical solutions, in S310, the inorganic filler is silicon oxide, the biological powder is straw powder, and the degradation catalyst is copper octadecenoate; in S320, the emulsifier is Tween 80, and the antioxidant is alkylated diphenylamine.

[0025] In any of the above technical solutions, in S310, the temperature condition of the heat preservation and pressure holding treatment is 50°C to 55°C, the pressure condition of the heat preservation and pressure holding treatment is 7.5MPa to 10.0MPa, and the time of the heat preservation and pressure holding treatment is 1h to 2h; in S320, in the second interval, the temperature condition of the melt blending treatment is 140°C to 160°C; in S330, in the third interval, the method of adding polyvinyl alcohol and water is: after mixing the polyvinyl alcohol and water evenly and heating them to 60°C to 80°C, add them together to the second mixture with a temperature of 70°C to 110°C.

[0026] The present invention also provides a polyhydroxyalkanoate aqueous dispersion, which is obtained by using the preparation method of any of the above technical solutions.

[0027] Beneficial effects

[0028] The preparation method of the polyhydroxyalkanoate aqueous dispersion provided by the present invention first uses maleic anhydride to treat the polyhydroxyalkanoate to obtain a modified polyhydroxyalkanoate. Maleic anhydride, as a grafting monomer, mainly plays a role in coupling compatibility, which can improve the compatibility and uniformity of dispersion between the polyhydroxyalkanoate and other raw materials. In particular, the present invention utilizes the grafting modification treatment of S100 to promote the uniform dispersion of biological powder and inorganic filler in the polyhydroxyalkanoate, thereby improving the uniformity and dispersion stability of the polyhydroxyalkanoate aqueous dispersion. After the modification treatment, the present invention uses S200 to mix the modified polyhydroxyalkanoate obtained in S100, polybutylene succinate, a compatibilizer, a lubricant, a plasticizer, and sodium bicarbonate to obtain a premix. Among them, polybutylene succinate is relatively easy to be decomposed and metabolized by enzymes in various microorganisms or animals and plants in nature, is environmentally friendly, and can improve the heat resistance, tensile yield strength, and processing properties of the polyhydroxyalkanoate. Finally, the present invention, through S300, blends and extrude the premix obtained in S200, the inorganic filler, the biopowder, the degradation catalyst, the emulsifier, the antioxidant, the polyvinyl alcohol, and water to obtain a polyhydroxyalkanoate aqueous dispersion. The inorganic filler is used to improve the mechanical properties of the polyhydroxyalkanoate and impart it with good thermal insulation properties. The biopowder and the degradation catalyst are used to improve the environmental friendliness of the polyhydroxyalkanoate and further reduce its decomposition difficulty. In summary, the present invention can obtain easily degradable, environmentally friendly polyhydroxyalkanoate, which is uniformly dispersed and has stable performance. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description of the specific embodiments of the present invention.

[0030] Aqueous dispersions of polyhydroxyalkanoates (PHA), used as barrier coatings for food wrappers, have become a hot topic of research in recent years due to their excellent biodegradability. To ensure uniform dispersion of PHAs in an aqueous phase, they must be mixed with various additives, such as emulsifiers, dispersants, and plasticizers, and then water is added to prepare the aqueous dispersion. Improving the uniformity and dispersion stability of PHAs in aqueous dispersions remains a pressing technical challenge for those skilled in the art.

[0031] In order to improve the dispersion uniformity and dispersion stability of a polyhydroxyalkanoate aqueous dispersion, an embodiment of the present invention provides a method for preparing a polyhydroxyalkanoate aqueous dispersion, comprising:

[0032] S100, treating polyhydroxyalkanoate with maleic anhydride to obtain modified polyhydroxyalkanoate;

[0033] S200, using a high-speed mixer, mixing the modified polyhydroxyalkanoate, polybutylene succinate, compatibilizer, lubricant, plasticizer, and sodium bicarbonate obtained in S100 to obtain a premix;

[0034] S300, using a screw extruder, blending and extruding the premix obtained in S200, inorganic filler, biological powder, degradation catalyst, emulsifier, antioxidant, polyvinyl alcohol and water to obtain a polyhydroxyalkanoate aqueous dispersion.

[0035] Maleic anhydride, also known as dehydrated malic anhydride, is used as an interfacial modifier for polymer materials modified with fillers such as glass fiber and minerals and wood powder. Grafted maleic anhydride can give polymers better polarity and compatibility. Therefore, in the embodiment of the present invention, maleic anhydride, as a grafting monomer, can play a role in promoting coupling compatibility, thereby improving the compatibility and uniformity of dispersion between polyhydroxyalkanoates and other raw materials. The embodiment of the present invention utilizes the grafting modification treatment of S100 to promote the uniform dispersion of biological powders and inorganic fillers in polyhydroxyalkanoates, thereby improving the uniformity and dispersion stability of the polyhydroxyalkanoate aqueous dispersion.

[0036] It should be noted that the raw materials used in the embodiments of the present invention can all be obtained through commercial procurement.

[0037] In some embodiments of the present invention, in S200, the compatibilizer includes at least one of the following or a combination thereof: poly(L-lactic acid), ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-butyl acrylate copolymer. The addition of the compatibilizer can improve the compatibility between the modified polyhydroxyalkanoate and polybutylene succinate.

[0038] In some embodiments of the present invention, in S200, the lubricant includes at least one of the following or a combination thereof: polyethylene wax, paraffin wax, glycerin, white oil, stearic acid, stearamide, oleamide, and erucamide. The lubricant can reduce internal friction of the polymer, increase the polymer's melting rate and melt deformation, and reduce adhesion between the polymer raw material and the equipment surface, thereby minimizing mechanical shear forces.

[0039] In some embodiments of the present invention, in S200, the plasticizer includes at least one of the following or a combination thereof: ethylene glycol, glycerin, propylene glycol, and dimethyl phthalate. The primary function of a plasticizer is to weaken the forces between polymer molecules, lower the melting temperature and melt viscosity, improve molding and processing properties, and impart flexibility to polymer products.

[0040] In some embodiments of the present invention, in S300, the inorganic filler includes at least one of the following or a combination thereof: silicon oxide, aluminum oxide, calcium carbonate, talc, and glass powder. The inorganic filler is used to improve the mechanical strength and heat-resistant and heat-insulating properties of the polyhydroxyalkanoate.

[0041] In some embodiments of the present invention, in S300, the biopowder includes at least one of the following or a combination thereof: straw powder, rice husk powder, and coconut shell powder. The biopowder is used to improve the environmental friendliness of polyhydroxyalkanoates, further reduce their decomposition difficulty, and reduce their production costs.

[0042] In some embodiments of the present invention, in S300, the degradation catalyst includes at least one of the following or a combination thereof: iron octadecanoate and copper octadecenoate. Under photon excitation, the metal ions in these degradation catalysts transfer electrons to the polymer, generating free radicals that synergistically promote and induce degradation of the polyester material. Therefore, the degradation catalyst can be used to promote the degradation of polyhydroxyalkanoates, thereby improving their degradability.

[0043] In some embodiments of the present invention, in S300, the emulsifier includes at least one of the following or a combination thereof: monoolein, soy lecithin, Tween 60, Tween 80. The emulsifier can promote the formation of a polyhydroxyalkanoate aqueous dispersion by reacting the polyhydroxyalkanoate with water.

[0044] In some embodiments of the present invention, in S300, the antioxidant includes at least one of the following or a combination thereof: 4,4-diaminodiphenyl ether, alkylated diphenylamine, and zinc dialkyldithiophosphate. The antioxidant reduces the thermal oxidative degradation of the polyhydroxyalkanoate, slowing its aging and extending its service life.

[0045] In some embodiments of the present invention, S100 specifically includes:

[0046] S110, mixing and stirring the polyhydroxyalkanoate and the organic solvent under inert gas protection at a mass ratio of polyhydroxyalkanoate:organic solvent=(10-20):100 to obtain a mixed material;

[0047] S120. Add initiator and maleic anhydride to the mixture in a mass ratio of initiator: maleic anhydride: polyhydroxyalkanoate = (1-2): (8-12): 100, heat and stir to obtain modified polyhydroxyalkanoate.

[0048] In S110, the organic solvent is dichloromethane. In S120, the initiator is benzoyl peroxide. In S120, the temperature of the heating and stirring is 45° C. to 55° C. In S120, the heating and stirring time is 5 to 6 hours.

[0049] Preferably, the mass ratio of polyhydroxyalkanoate:organic solvent is 20:100.

[0050] Preferably, the mass ratio of initiator:maleic anhydride:polyhydroxyalkanoate is 1:10:100.

[0051] Exemplarily, the specific implementation of the above S110 to S120 is as follows.

[0052] Polyhydroxyalkanoate, maleic anhydride and benzoyl peroxide were weighed in a mass ratio of 100:10:1, the polyhydroxyalkanoate was poured into a three-necked flask, and five times the mass of dichloromethane was added, while nitrogen was introduced for protection, the polyhydroxyalkanoate and dichloromethane were stirred evenly, maleic anhydride and benzoyl peroxide were added to the three-necked flask in small amounts and multiple times, and the reaction was stirred at a temperature of 50°C for 6 hours. The obtained product was extracted with acetone. After the extraction was completed, the obtained modified polyhydroxyalkanoate was dried.

[0053] In some embodiments of the present invention, S200 specifically includes:

[0054] S210, adding the modified polyhydroxyalkanoate, polybutylene succinate, compatibilizer, lubricant, plasticizer and sodium bicarbonate into a high-speed mixer in a mass ratio of modified polyhydroxyalkanoate: polybutylene succinate: compatibilizer: lubricant: plasticizer: sodium bicarbonate = 100: (10-15): (2-4): (2-4): (2-4): (4-6);

[0055] S220, controlling the high-speed mixer to operate at a rotation speed of 280 r / min to 340 r / min for 20 min to 30 min to obtain a premix.

[0056] Preferably, the mass ratio of modified polyhydroxyalkanoate:polybutylene succinate:compatibility agent:lubricant:plasticizer:sodium bicarbonate is 100:12:3:2:2:5.

[0057] Preferably, the rotation speed of the high-speed mixer is 300 r / min, and the operation time of the high-speed mixer is 30 min.

[0058] The above raw materials are mixed by a high-speed mixer, and the obtained premix is ​​subsequently melted and emulsified, which can improve the mixing uniformity of the modified polyhydroxyalkanoate and other raw materials.

[0059] In some embodiments of the present invention, S300 specifically includes:

[0060] S310, feeding the premix, inorganic filler, biopowder, and degradation catalyst into the first section of a screw extruder according to a mass ratio of premix: inorganic filler: biopowder: degradation catalyst = 100: (4-6): (4-6): (0.5-1.5), stirring uniformly, and then performing heat and pressure maintenance treatment to obtain a first mixture;

[0061] S320, feeding the first mixture into the second section of the screw extruder and adding the emulsifier and antioxidant in a mass ratio of premix:emulsifier:antioxidant=100:(4-8):(2-4), performing melt blending to obtain a second mixture;

[0062] S330. According to the mass ratio of premix: polyvinyl alcohol: water = 100: (40-80): (100-400), the second mixture is fed into the third section of the screw extruder, polyvinyl alcohol and water are added, and the mixture is stirred and emulsified to obtain a polyhydroxyalkanoate aqueous dispersion after extrusion.

[0063] It is understood that in S320 or S330, those skilled in the art may further add other additives, such as film-forming agents, protective carriers, leveling agents, rheological agents, pH adjusters, and defoaming agents, as needed. The specific types and amounts of these additives may be selected and adjusted by those skilled in the art as needed.

[0064] Preferably, in S310, the inorganic filler is silicon oxide, the biological powder is straw powder, and the degradation catalyst is copper octadecenoate.

[0065] Preferably, in S320, the emulsifier is Tween 80, and the antioxidant is alkylated diphenylamine.

[0066] Preferably, in S310, the temperature condition of the heat preservation and pressure holding treatment is 50° C. to 55° C., the pressure condition of the heat preservation and pressure holding treatment is 7.5 MPa to 10.0 MPa, and the time of the heat preservation and pressure holding treatment is 1 hour to 2 hours.

[0067] Preferably, in S320, in the second interval, the temperature condition of the melt blending process is 140°C to 160°C.

[0068] Preferably, in S330, in the third interval, the polyvinyl alcohol and water are added by uniformly mixing the polyvinyl alcohol and water, heating them to 60°C to 80°C, and then adding them to the second mixture at a temperature of 70°C to 110°C.

[0069] Preferably, the mass ratio of premix: inorganic filler: biological powder: degradation catalyst is 100:6:6:1.

[0070] Preferably, the mass ratio of premix:emulsifier:antioxidant is 100:8:2.

[0071] Preferably, the mass ratio of premix:polyvinyl alcohol:water is 100:40:200.

[0072] As mentioned above, inorganic fillers, biopowders, and degradation catalysts can respectively improve the mechanical strength and heat-insulating properties of polyhydroxyalkanoates, reduce their decomposition difficulty, and further promote and induce their degradation. Therefore, the addition of these raw materials is very necessary.

[0073] However, the process of adding these raw materials to polyhydroxyalkanoates (PHA) presents the following challenges: the physical properties of inorganic fillers, biopowders, and degradation catalysts, particularly their polarity and surface activity, differ significantly from those of the PHA. This makes uniform dispersion of these materials difficult, leading to stratification and agglomeration.

[0074] To this end, in the first section of the screw extruder, the embodiment of the present invention heats, pressurizes, and insulates the premix, including the polyhydroxyalkanoate, inorganic filler, biopowder, and degradation catalyst, at a temperature of 50°C to 55°C, a pressure of 7.5 MPa to 10.0 MPa, and a duration of 1 to 2 hours.

[0075] It can be understood that sodium bicarbonate is added in the premix preparation process of S200, and the thermal decomposition temperature of sodium bicarbonate is 50°C. Therefore, in S310, the temperature condition of 50°C to 55°C causes the sodium bicarbonate in the premix to be heated and decomposed to form carbon dioxide. The temperature condition of 50°C to 55°C and the pressure condition of 7.5MPa to 10.0MPa cause the carbon dioxide uniformly distributed in the premix, inorganic filler, biological powder and degradation catalyst to reach a supercritical state. The supercritical carbon dioxide helps to promote the compatibility between the modified polyhydroxyalkanoate, polybutylene succinate, compatibilizer, lubricant and plasticizer, and improves the mixing uniformity and dispersion uniformity between the modified polyhydroxyalkanoate and the inorganic filler, biological powder and degradation catalyst.

[0076] It is understood that the first section of the screw extruder provides a sealed environment. A shielding gas delivery pipeline is connected to the inner cavity of the first section, and a valve is provided between the shielding gas delivery pipeline and the inner cavity of the first section. The shielding gas delivery pipeline is used to deliver shielding gas to the inner cavity of the first section to regulate the gas pressure within the inner cavity.

[0077] It can be understood that an exhaust valve is provided in the first section of the screw extruder, and the exhaust valve is used to discharge gas so as to regulate the air pressure in the inner cavity when the air pressure is too high.

[0078] After obtaining the first mixture through S310, the embodiment of the present invention performs melt blending treatment on the raw materials in the second zone of the screw extruder through S320. According to the physical properties of polyhydroxyalkanoate, the embodiment of the present invention controls the temperature of the second zone to 140° C. to 160° C.

[0079] It is understood that the purpose of S330 is to add water and polyvinyl alcohol to the melt-blended polymer containing polyhydroxyalkanoate to prepare a stable polyhydroxyalkanoate aqueous dispersion. The polyvinyl alcohol and water can be mixed and preheated in advance to improve the mixing effect.

[0080] It is understood that in order to achieve mixing and emulsification, the temperature of the third zone is lower than that of the second zone. In other words, after the material from the second zone enters the third zone, it can be stirred first, and then the preheated polyvinyl alcohol and water mixture can be added after the temperature drops to 70°C to 110°C.

[0081] It is understood that the materials are continuously stirred and mixed in each section of the screw extruder. In particular, continuous stirring in S330 is key to promoting the emulsification of the polyhydroxyalkanoate and forming an aqueous dispersion. Those skilled in the art will select and adjust the speed of the screw extruder based on actual needs.

[0082] Preferably, pullulan is also added in S330. Pullulan is an extracellular water-soluble mucosal polysaccharide similar to glucan and xanthan gum, produced by fermentation of Aureobasidium pullulans. Pullulan can improve the film-forming properties of polyhydroxyalkanoates and further promote their biodegradation rate, thereby increasing their degradability.

[0083] Exemplarily, S330 specifically includes: feeding the second mixture into the third section of the screw extruder and adding pullulan, polyvinyl alcohol and water according to the mass ratio of premix: pullulan: polyvinyl alcohol: water = 100: (4-10): (40-80): (100-400), stirring and emulsifying, and obtaining a polyhydroxyalkanoate aqueous dispersion after extrusion.

[0084] Example 1

[0085] This embodiment prepares a polyhydroxyalkanoate aqueous dispersion, and its preparation process includes the following steps:

[0086] S1. Mixing polyhydroxyalkanoate and dichloromethane at a mass ratio of polyhydroxyalkanoate to dichloromethane = 20:100 under nitrogen protection to obtain a mixed material;

[0087] S2. Add benzoyl peroxide initiator and maleic anhydride to the mixture in a mass ratio of benzoyl peroxide: maleic anhydride: polyhydroxyalkanoate = 1:10:100, and heat and stir at 50° C. for 6 hours to obtain modified polyhydroxyalkanoate;

[0088] S3. Add modified polyhydroxyalkanoate, polybutylene succinate, poly(L-lactic acid) compatibilizer, polyethylene wax lubricant, propylene glycol plasticizer, and sodium bicarbonate into a high-speed mixer in a mass ratio of modified polyhydroxyalkanoate: polybutylene succinate: poly(L-lactic acid): polyethylene wax: propylene glycol: sodium bicarbonate = 100:12:3:2:2:5;

[0089] S4, controlling the high-speed mixer to operate at a speed of 300 r / min for 30 min to obtain a premix;

[0090] S5. According to the mass ratio of premix: silicon oxide: straw powder: copper octadecenoate = 100:6:6:1, the premix, the silicon oxide inorganic filler, the straw powder and the copper octadecenoate degradation catalyst are fed into the first section of the screw extruder, stirred evenly, and then subjected to heat and pressure treatment at 52° C. and 7.8 MPa for 2 h to obtain a first mixture;

[0091] S6. Feed the first mixture into the second section of the screw extruder at a mass ratio of premix: Tween 80: alkylated diphenylamine = 100:8:2, add Tween 80 emulsifier and alkylated diphenylamine antioxidant, and melt blend at 150° C. to obtain a second mixture;

[0092] S7. Feed the second mixture into the third section of the screw extruder at a mass ratio of premix: polyvinyl alcohol: water = 100:40:200. After the polyvinyl alcohol and water are mixed evenly and heated to 70° C., they are added to the third section containing the second mixture at 90° C., stirred and emulsified, and extruded to obtain a polyhydroxyalkanoate aqueous dispersion.

[0093] Example 2

[0094] This embodiment prepares a polyhydroxyalkanoate aqueous dispersion, and its preparation process includes the following steps:

[0095] S1. Mixing polyhydroxyalkanoate and dichloromethane at a mass ratio of polyhydroxyalkanoate to dichloromethane = 15:100 under nitrogen protection to obtain a mixed material;

[0096] S2. Add benzoyl peroxide initiator and maleic anhydride to the mixture in a mass ratio of benzoyl peroxide: maleic anhydride: polyhydroxyalkanoate = 2:10:100, and heat and stir at 50° C. for 6 hours to obtain modified polyhydroxyalkanoate;

[0097] S3. Add modified polyhydroxyalkanoate, polybutylene succinate, poly(L-lactic acid) compatibilizer, polyethylene wax lubricant, propylene glycol plasticizer, and sodium bicarbonate into a high-speed mixer in a mass ratio of modified polyhydroxyalkanoate: polybutylene succinate: poly(L-lactic acid): polyethylene wax: propylene glycol: sodium bicarbonate = 100:10:4:4:4:6;

[0098] S4, controlling the high-speed mixer to operate at a speed of 300 r / min for 30 min to obtain a premix;

[0099] S5. According to the mass ratio of premix: silicon oxide: straw powder: copper octadecenoate = 100:4:4:1.5, the premix, the silicon oxide inorganic filler, the straw powder and the copper octadecenoate degradation catalyst are fed into the first section of the screw extruder, stirred evenly, and then subjected to heat and pressure holding treatment at 55° C. and 9.0 MPa for 1 hour to obtain a first mixture;

[0100] S6. Feed the first mixture into the second section of the screw extruder according to a mass ratio of premix: Tween 80: alkylated diphenylamine = 100:6:4, add Tween 80 emulsifier and alkylated diphenylamine antioxidant, and melt blend at a temperature of 150° C. to obtain a second mixture;

[0101] S7. Feed the second mixture into the third section of the screw extruder at a mass ratio of premix: polyvinyl alcohol: water = 100:60:400. After the polyvinyl alcohol and water are mixed evenly and heated to 60° C., they are added to the third section containing the second mixture at a temperature of 80° C., stirred and emulsified, and extruded to obtain a polyhydroxyalkanoate aqueous dispersion.

[0102] Example 3

[0103] This embodiment prepares a polyhydroxyalkanoate aqueous dispersion, and its preparation process includes the following steps:

[0104] S1. Mixing polyhydroxyalkanoate and dichloromethane at a mass ratio of polyhydroxyalkanoate to dichloromethane = 20:100 under nitrogen protection to obtain a mixed material;

[0105] S2. Add benzoyl peroxide initiator and maleic anhydride to the mixture in a mass ratio of benzoyl peroxide: maleic anhydride: polyhydroxyalkanoate = 1:10:100, and heat and stir at 50° C. for 6 hours to obtain modified polyhydroxyalkanoate;

[0106] S3. Add modified polyhydroxyalkanoate, polybutylene succinate, poly(L-lactic acid) compatibilizer, polyethylene wax lubricant, propylene glycol plasticizer, and sodium bicarbonate into a high-speed mixer in a mass ratio of modified polyhydroxyalkanoate: polybutylene succinate: poly(L-lactic acid): polyethylene wax: propylene glycol: sodium bicarbonate = 100:12:3:2:2:5;

[0107] S4, controlling the high-speed mixer to operate at a speed of 300 r / min for 30 min to obtain a premix;

[0108] S5. According to the mass ratio of premix: silicon oxide: straw powder: copper octadecenoate = 100:6:6:1, the premix, the silicon oxide inorganic filler, the straw powder and the copper octadecenoate degradation catalyst are fed into the first section of the screw extruder, stirred evenly, and then subjected to heat and pressure treatment at 52° C. and 7.8 MPa for 2 h to obtain a first mixture;

[0109] S6. Feed the first mixture into the second section of the screw extruder at a mass ratio of premix: Tween 80: alkylated diphenylamine = 100:8:2, add Tween 80 emulsifier and alkylated diphenylamine antioxidant, and melt blend at 150° C. to obtain a second mixture;

[0110] S7. Feed the second mixture into the third section of the screw extruder at a mass ratio of premix: pullulan: polyvinyl alcohol: water = 100:5:40:200. After uniformly mixing the pullulan, polyvinyl alcohol, and water and heating them to 60° C., add them together to the third section containing the second mixture at 70° C., stir and emulsify, and extrude to obtain a polyhydroxyalkanoate aqueous dispersion.

[0111] Performance Testing

[0112] The polyhydroxyalkanoate aqueous dispersions prepared in Examples 1 to 3 were stored at 25°C and 50°C for 16 weeks. After the expiration date, no slurry formation or sedimentation occurred in the samples. The viscosity change of the samples after expiration (30 rpm) was measured, and the results are listed in Table 1. Here, viscosity change rate = (viscosity after 16 weeks - initial viscosity) / initial viscosity.

[0113] Table 1

[0114]

[0115] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A method for preparing a polyhydroxyalkanoate aqueous dispersion, characterized in that: include: S100, treating polyhydroxyalkanoate with maleic anhydride to obtain modified polyhydroxyalkanoate; S200, using a high-speed mixer, mixing the modified polyhydroxyalkanoate, polybutylene succinate, compatibilizer, lubricant, plasticizer, and sodium bicarbonate obtained in S100 to obtain a premix; S300, using a screw extruder, blending and extruding the premix obtained in S200, an inorganic filler, a biological powder, a degradation catalyst, an emulsifier, an antioxidant, polyvinyl alcohol, and water to obtain the polyhydroxyalkanoate aqueous dispersion; S100 specifically includes: S110, mixing and stirring the polyhydroxyalkanoate and the organic solvent under inert gas protection at a mass ratio of polyhydroxyalkanoate:organic solvent=(10-20):100 to obtain a mixed material; S120, adding the initiator and the maleic anhydride to the mixture in a mass ratio of initiator: maleic anhydride: polyhydroxyalkanoate = (1-2): (8-12): 100, heating and stirring, to obtain the modified polyhydroxyalkanoate; S200 specifically includes: S210, adding the modified polyhydroxyalkanoate, the polybutylene succinate, the compatibilizer, the lubricant, the plasticizer, and the sodium bicarbonate into the high-speed mixer in a mass ratio of modified polyhydroxyalkanoate: polybutylene succinate: compatibilizer: lubricant: plasticizer: sodium bicarbonate = 100: (10-15): (2-4): (2-4): (2-4): (4-6); S300 specifically includes: S310, feeding the premix, the inorganic filler, the biopowder, and the degradation catalyst into the first section of the screw extruder at a mass ratio of premix: inorganic filler: biopowder: degradation catalyst = 100: (4-6): (4-6): (0.5-1.5), stirring them uniformly, and then performing heat and pressure maintenance treatment to obtain a first mixture; S320, feeding the first mixture into the second section of the screw extruder and adding the emulsifier and the antioxidant in a mass ratio of premix:emulsifier:antioxidant=100:(4-8):(2-4), performing melt blending to obtain a second mixture; S330, feeding the second mixture into the third section of the screw extruder according to a mass ratio of premix: polyvinyl alcohol: water = 100: (40-80): (100-400), adding the polyvinyl alcohol and the water, stirring and emulsifying, and obtaining the polyhydroxyalkanoate aqueous dispersion after extrusion; In S330, in the third interval, the polyvinyl alcohol and the water are added by uniformly mixing the polyvinyl alcohol and the water, heating them to 60° C. to 80° C., and then adding them to the second mixture at a temperature of 70° C. to 110° C.

2. The preparation method according to claim 1, characterized in that In S200, The compatibilizer comprises at least one of the following or a combination thereof: poly (L-lactic acid), ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-butyl acrylate copolymer; and / or The lubricant comprises at least one of the following or a combination thereof: polyethylene wax, paraffin, glycerol, white oil, stearic acid, stearamide, oleamide, erucamide; and / or The plasticizer includes at least one of the following or a combination thereof: ethylene glycol, glycerol, propylene glycol, and dimethyl phthalate.

3. The preparation method according to claim 1, characterized in that In S300, The inorganic filler comprises at least one of the following or a combination thereof: silicon oxide, aluminum oxide, calcium carbonate, talc, glass powder; and / or The biological powder includes at least one of the following or a combination thereof: straw powder, rice husk powder, coconut shell powder; and / or The degradation catalyst comprises at least one of the following or a combination thereof: iron octadecanoate, copper octadecenoate; and / or The emulsifier comprises at least one of the following or a combination thereof: monoolein, soy lecithin, Tween 60, Tween 80; and / or The antioxidant comprises at least one of the following or a combination thereof: 4,4-diaminodiphenyl ether, alkylated diphenylamine, and zinc dialkyl dithiophosphate.

4. The preparation method according to claim 1, characterized in that In S110, the organic solvent is dichloromethane; and / or In S120, the initiator is benzoyl peroxide; and / or In S120, the temperature condition of the heating and stirring is 45° C. to 55° C.; and / or In S120, the heating and stirring time is 5 hours to 6 hours.

5. The preparation method according to claim 1, characterized in that S200 specifically includes: S220, controlling the high-speed mixer to operate at a rotation speed of 280 r / min to 340 r / min for 20 min to 30 min to obtain the premix.

6. The preparation method according to claim 1, characterized in that In S310, the inorganic filler is silicon oxide, the biological powder is straw powder, and the degradation catalyst is copper octadecenoate; In S320, the emulsifier is Tween 80, and the antioxidant is alkylated diphenylamine.

7. The preparation method according to claim 6, characterized in that In S310, the temperature condition of the heat preservation and pressure holding treatment is 50° C. to 55° C., the pressure condition of the heat preservation and pressure holding treatment is 7.5 MPa to 10.0 MPa, and the time of the heat preservation and pressure holding treatment is 1 hour to 2 hours; In S320, in the second interval, the temperature condition of the melt blending process is 140°C to 160°C.

8. A polyhydroxyalkanoate aqueous dispersion, characterized in that: The polyhydroxyalkanoate aqueous dispersion is obtained by the preparation method according to any one of claims 1 to 7.

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