A high molecular weight pha aqueous emulsion, and a preparation method and application thereof

Abstract

The application discloses a high-molecular-weight PHA aqueous emulsion, a preparation method and application thereof. The high-molecular-weight PHA aqueous emulsion comprises the following components: a PHA polymer with a weight average molecular weight of about 800,000 to about 4,000,000; 0.1-5 wt% of an emulsifier based on the weight of the PHA polymer; 0.1-5 wt% of a film-forming aid based on the weight of the PHA polymer; and water. The PHA aqueous emulsion has good stability and excellent film-forming property, can be applied to the surface of a paper-based material in a coating mode to form a barrier coating layer, significantly improves the water barrier property, water vapor barrier property and oil resistance of the coating layer, and can be widely applied to the fields of food packaging, environment-friendly coatings and the like.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer material processing technology, specifically relating to a high molecular weight polyhydroxy fatty acid ester (PHA) aqueous emulsion, its preparation method, and the application of the emulsion in biodegradable food packaging barrier coatings and water-based environmentally friendly coatings. Background Technology

[0002] Polyhydroxyalkanoates (PHA) are a class of natural high-molecular-weight polyesters synthesized by microorganisms through fermentation. They have gained wide application due to their biodegradability, biocompatibility, thermoplastic processability, and diversity of structure and varieties. One important application is to make PHA into an aqueous emulsion and use it as a barrier coating for paper to achieve the purpose of water, oil and oxygen blocking.

[0003] In paper-plastic composites, PHA coating can achieve a repulping rate of over 90-95%, making it easy to recycle paper fibers. This means that PHA-coated paper products can be recycled through conventional paper recycling processes after use, solving the problem of traditional plastic-coated paper being difficult to recycle.

[0004] PHA aqueous suspension is applied to the paper surface through various coating methods (scraper coating, roller coating, spray coating, curtain coating, dip coating, brush coating, etc.), and after being dried in an oven, it forms a barrier-resistant PHA coating.

[0005] Existing PHA coatings, due to their relatively low molecular weight, can meet the basic water resistance and oil resistance requirements of coated paper, but their barrier properties are difficult to improve to a higher level. The industry urgently needs a PHA aqueous emulsion and a corresponding preparation process that can significantly improve the barrier properties of coatings. Summary of the Invention

[0006] The inventors have discovered that increasing the molecular weight of PHA can significantly enhance molecular chain entanglement and crystal density, thereby effectively reducing water and oxygen permeation channels and achieving a leapfrog improvement in barrier performance, providing a key path for the development of high-end paper-based packaging materials.

[0007] Therefore, one aspect of the present invention provides a high molecular weight polyhydroxyalkanoate (PHA) emulsion comprising the following components: a PHA polymer (PHA dry matter) with a weight average molecular weight of about 800,000 to about 4,000,000 Daltons; 0.1 to 5 wt% of an emulsifier based on the weight of the PHA polymer; 0.1 to 5 wt% of a film-forming aid based on the weight of the PHA polymer; and 50 to 500 wt% (e.g., 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 100 wt%, 150 wt%, 200 wt%, 250 wt%, 300 wt%, 350 wt%, 400 wt%, 450 or 500 wt%) of water based on the weight of the PHA polymer.

[0008] In one specific embodiment, the weight-average molecular weight of the PHA polymer can be, for example, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350 or 4 million Daltons.

[0009] In one specific embodiment, the PHA polymer comprises at least one repeating unit (i.e., monomer) selected from 3-hydroxybutyrate (3-HB), 4-hydroxybutyrate (4-HB), 3-hydroxypropionate (3-HP), 3-hydroxyhexanoate (3-HHx), 3-hydroxyvalerate (3-HV), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV), and 6-hydroxyhexanoate (6-HH).

[0010] In a preferred embodiment, the PHA polymer may be selected from one or a combination of two or more of the following: poly-3-hydroxybutyrate (PHB), a copolymer of 3-hydroxybutyric acid and 4-hydroxybutyric acid (P34HB), poly-3-hydroxyvalerate (PHV), poly-3-hydroxypropionate (P3HP), a copolymer of 3-hydroxybutyric acid and 3-hydroxyvalerate (PHBV), poly-3-hydroxyoctanoate (PHO), poly-3-hydroxynonanoate (PHN), a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoate (PHBHHx), a copolymer of 3-hydroxybutyric acid, 4-hydroxybutyric acid and 3-hydroxyvalerate (P3HB4HB3HV), or a copolymer of 3-hydroxybutyric acid, 4-hydroxybutyric acid and 5-hydroxyvalerate (P3HB4HB5HV).

[0011] In a preferred embodiment, the PHA polymer may be selected from PHB, P(3HB-co-4HB), P(3HB-co-3HV), P(3HB-co-4HB-co-3HV), and combinations thereof.

[0012] In a preferred embodiment, when the high molecular weight PHA contains 3-HB repeating units, the molar percentage of the 3-HB monomer is greater than or equal to 80 mol% (e.g., greater than or equal to 85 mol%, 90 mol%, or 95 mol%) to balance the coating's softness with its mechanical strength.

[0013] In a preferred embodiment, the PHA polymer has a particle size D90 ≤ 2 μm and a purity ≥ 98 wt%.

[0014] In a preferred embodiment, the PHA polymer is a product with a dry matter content of 60-65 wt% after extraction.

[0015] In a preferred embodiment, the PHA polymer is dispersed in water (e.g., RO reverse osmosis pure water) to adjust the final dry matter content of the emulsion to 30 to 70 wt%, preferably 40 wt%.

[0016] In one specific embodiment, the emulsifier is selected from fatty alcohol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkylphenol polyoxyethylene ether, fatty acid methyl ester polyoxyethylene ether, isomeric alcohol polyoxyethylene ether, or combinations thereof.

[0017] In one specific embodiment, the film-forming aid is selected from polyvinyl alcohol, dodecyl alcohol ester, hexadecyl alcohol ester, propylene glycol methyl ether acetate, dipropylene glycol methyl ether, butyl lactate, DBE diester, or combinations thereof.

[0018] In one specific embodiment, the PHA emulsion further comprises 0.1 wt% to 0.5 wt% of a bactericide and / or 0.1 to 5 wt% of a rheology modifier based on the weight of the PHA emulsion.

[0019] In a preferred embodiment, the bactericide is selected from one or more of benzisothiazolinone, methylisothiazolinone, a mixture of methylchloroisothiazolinone and methylisothiazolinone, bromonitol, sodium pyrithione, ethylenediaminetetraacetic acid, zinc oxide, benzalkonium chloride and 2,2-dibromopropionamide.

[0020] In a preferred embodiment, the rheology modifier is selected from one or more of associative polyurethane thickeners, alkali-swellable acrylic thickeners, hydrophobically modified hydroxyethyl cellulose, bentonite, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, xanthan gum, guar gum, and sodium alginate.

[0021] Another aspect of the present invention provides a method for preparing a high molecular weight PHA emulsion according to the present invention, the method comprising the following steps: (1) Provide PHA raw materials, preferably the PHA is a product with a dry matter content of 60-65 wt% and a weight average molecular weight of 800,000 to 4,000,000; (2) Based on the dry matter content of the PHA raw material, water is added to prepare a PHA aqueous suspension with a preferred dry matter content of 40 wt%. (3) Add 0.1-5 wt% emulsifier based on the dry weight of PHA to the aqueous suspension obtained in step (2) and stir to mix; (4) The mixture obtained in step (3) is emulsified by a high-pressure homogenizer; (5) Add 0.1~5 wt% of film-forming aid based on the dry weight of PHA to the emulsion obtained in step (4), stir and mix well to obtain the high molecular weight PHA aqueous suspension.

[0022] The PHA, emulsifier, film-forming aid, etc. in the above method are consistent with those described above.

[0023] In one specific implementation, the PHA raw material mentioned in step (1) is a product with 60-65 wt% dry matter obtained by plate and frame filtration after microbial fermentation. This product is prepared by a method including cell washing, slow lysis and cell disruption, separation and purification, high-pressure homogenization and forced cell disruption, and washing steps.

[0024] In one specific implementation, the emulsification pressure of the high-pressure homogenizer in step (4) is 200-600 bar, and the number of cycles of emulsification is 2-4.

[0025] In one specific implementation, the method may further include adding, as needed, 0.1 wt% to 0.5 wt% of a bactericide and / or 0.1 to 5 wt% of a rheology modifier based on the dry matter weight of PHA to the emulsion obtained in step (4).

[0026] In another aspect, the present invention provides the application of the high molecular weight PHA emulsion described in the present invention or the high molecular weight PHA emulsion prepared by the method described in the present invention in the preparation of barrier coatings for paper-based packaging materials or water-based environmentally friendly coatings.

[0027] Specifically, the aqueous suspension is applied to the surface of a substrate by coating, and then dried to form a barrier coating. The coating method includes, but is not limited to, roller coating, blade coating, brush coating, spray coating, and dip coating. The drying temperature is 110-180℃, and the time is 30-120 seconds.

[0028] This invention selects specific high molecular weight (800,000-4,000,000) PHA and combines it with an optimized aqueous suspension formulation and preparation process, so that the final coating has significantly improved water barrier, water vapor barrier and oxygen barrier properties, while also having excellent oil resistance.

[0029] Furthermore, through the synergistic effect of high-pressure homogenization emulsification and film-forming aids, the aqueous suspension prepared by this invention exhibits good storage stability and coating film-forming properties. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise indicated, the terms used herein have their general technical meanings as understood by those skilled in the art.

[0032] In this invention, the singular articles “a” and “the” cover a plurality of indicators unless the context clearly indicates otherwise. All references cited herein are incorporated herein by reference in their entirety.

[0033] The use of "comprising" or "including" in this invention is an open-ended description that includes all specified components or steps described, as well as other specified components or steps that do not materially affect the description.

[0034] The term "and / or" as used in this invention encompasses all combinations of items connected by the term, and should be considered as if each combination had been individually listed herein. For example, "A and / or B" includes "A", "A and B", and "B". As another example, "A, B and / or C" includes "A", "B", "C", "A and B", "A and C", "B and C", and "A and B and C".

[0035] In this application, the term "about" generally refers to a variation within a range of 0.5% to 10% above or below a specified value, such as a variation within a range of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% above or below a specified value.

[0036] In one specific embodiment, the present invention provides a high molecular weight PHA aqueous emulsion.

[0037] Preferably, the molecular weight of PHA is about 800,000 to about 4 million. The higher the molecular weight of PHA, the better the crystallization, the smaller the free volume, and the more tortuous the diffusion path. The three factors work synergistically to achieve a high water and oxygen barrier index in paper-plastic composite applications.

[0038] This invention and its method are suitable for various PHA products, and the PHA can be short-chain PHA or medium- to long-chain PHA. Specifically, the PHA contains at least one repeating unit selected from 3-hydroxybutyrate (3-HB), 4-hydroxybutyrate (4-HB), 3-hydroxypropionate (3-HP), 3-hydroxyhexanoate (3-HHx), 3-hydroxyvalerate (3-HV), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV), and 6-hydroxyhexanoate (6-HH).

[0039] In the case where the PHA contains 3-hydroxybutyrate unit structures, considering the balance between flexibility and strength, the poly(3-hydroxybutyrate) composition ratio should be ≥80 mol% for the average composition ratio of repeating units (monomer structural units).

[0040] Preferably, the PHA can be a product produced by Beijing Microstructure Workshop Biotechnology Co., Ltd., with a dry matter content of 60-65 wt% after PHA extraction, a particle size D90≤2 μm, and a PHA purity ≥98%.

[0041] Preferably, the present invention provides a high molecular weight PHA aqueous emulsion, wherein high molecular weight PHA is the main resin, supplemented with emulsifiers and film-forming aids, and optionally bactericides and rheology modifiers are added; based on 100 parts of dry PHA: the high molecular weight PHA has a weight-average molecular weight of 800,000-4,000,000 Da, a dry matter content of 60-65 wt%, a PHA purity ≥98 wt%, and a particle size D90 ≤2 μm; the amount of emulsifier added is 0.1-5 wt%, and the amount of film-forming aid added is 0.1-5 wt%; the final dry matter content of the emulsion is 40 wt%; the high molecular weight PHA contains at least one repeating unit selected from 3-hydroxybutyrate, 4-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxyhexanoate, 3-hydroxyvalerate, 4-hydroxyvalerate, 5-hydroxyvalerate, and 6-hydroxyhexanoate.

[0042] In one embodiment, the emulsifier is selected from fatty alcohol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkylphenol polyoxyethylene ether, fatty acid methyl ester polyoxyethylene ether, isomeric alcohol polyoxyethylene ether, or combinations thereof.

[0043] Fatty alcohol polyoxyethylene ether (AEO) is a nonionic surfactant that is polymerized from fatty alcohols (R-OH) and ethylene oxide (EO), with the general formula RO-(CH2CH2O).n -H, R is usually C 12 -C 18 Hydrocarbon group. Typical AEOs include the AEO series (such as AEO-3, AEO-7, AEO-9) commercially available from BASF or McLean.

[0044] Alkylphenol polyoxyethylene ethers are nonionic surfactants that typically include: the TX series (such as TX-4, TX-7, TX-10), corresponding to nonylphenol polyoxyethylene ether (NPEO); and the OP series (such as OP-4, OP-7, OP-10), corresponding to octylphenol polyoxyethylene ether (OPEO).

[0045] Fatty acid methyl ester polyoxyethylene ether (FMEE) is a nonionic surfactant with both ester-ether and alcohol-ether structures. It is prepared by the direct addition of fatty acid methyl ester and ethylene oxide under the action of a catalyst (CAS No.: 65218-33-7).

[0046] Isomeric alcohol polyoxyethylene ethers are a class of nonionic surfactants with branched isomeric alcohols as lipophilic groups, polymerized from isomeric alcohols (such as isodecanool and isotridecanool) and ethylene oxide. Typical isomeric alcohol polyoxyethylene ethers are mainly based on isodecanool (XP series) and isotridecanool (TO / E series).

[0047] In one specific embodiment, the film-forming aid is selected from polyvinyl alcohol, dodecyl alcohol ester, hexadecyl alcohol ester, propylene glycol methyl ether acetate, dipropylene glycol methyl ether, butyl lactate, DBE diester, or combinations thereof.

[0048] Dodecyl alcohol ester (also known as dodecyl alcohol ester) is one of the film-forming aids in water-based coatings. Its chemical name is 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate. Typical products include TEXANOL™ from Eastman Chemical Company in the United States.

[0049] Hexadecyl alcohol ester (also known as hexadecyl alcohol ester) is a film-forming aid that is homologous to but structurally different from hexadecyl alcohol ester. Its chemical name is 2,2,4-trimethyl-1,3-pentanediol diisobutyrate.

[0050] DBE diester is a mixture of dimethyl succinate, dimethyl glutarate and dimethyl adipate (CAS No.: 95481-62-2), commercially available from DuPont.

[0051] Preferably, the emulsifier is fatty alcohol polyoxyethylene ether; and / or the film-forming aid is polyvinyl alcohol.

[0052] Preferably, the bactericide is selected from one or more of ethylenediaminetetraacetic acid, benzisothiazolinone, zinc oxide, benzalkonium chloride, methylisothiazolinone, methylchloroisothiazolinone, and 2,2-dibromopropionamide; the rheology modifier is selected from one or more of carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, alkali-swellable acrylic thickener, xanthan gum, guar gum, sodium alginate, bentonite, and polyurethane rheology modifier.

[0053] In one specific embodiment, the present invention provides a method for preparing a high molecular weight PHA aqueous emulsion, characterized by comprising the following steps: S1 Preparation of high molecular weight PHA wet material: Take high molecular weight PHA fermentation broth, wash the cells, slowly lyse and break the cell walls, purify, homogenize under high pressure for secondary cell wall breaking, and wash with water to obtain virgin PHA emulsion; dehydrate the virgin emulsion by plate and frame filter press to obtain high molecular weight PHA wet material with 60~65wt% dry matter. S2 Pre-dispersion slurry preparation: The wet PHA material obtained in S1 is diluted with RO pure water to prepare a PHA initial suspension with 40 wt% dry matter. Emulsifier is added and stirred at room temperature for 20 min. S3 High-pressure homogenization emulsification: Pass the pre-dispersed slurry into a high-pressure homogenizer and homogenize it 2-4 times at 200-600 bar; S4 Additive Mixing: Add pre-dissolved polyvinyl alcohol film-forming aid and stir at room temperature for 30 min; add bactericide and rheology modifier as needed and mix evenly to obtain high molecular weight PHA aqueous emulsion.

[0054] Preferably, the purification process of PHA fermentation broth in step S1 is carried out in accordance with patent CN118440308A.

[0055] In one specific embodiment, the present invention provides the application of the high molecular weight PHA emulsion according to the present invention or the high molecular weight PHA emulsion prepared by the method according to the present invention in the preparation of barrier coatings for paper-based packaging materials or water-based environmentally friendly coatings.

[0056] Preferably, the aqueous emulsion is coated onto the paper substrate by any one of the following methods: roller coating, blade coating, brush coating, spray coating, dip coating, or curtain coating, with the dry coating amount controlled at 15 g / m². 2 After coating, dry and cure in an oven at a temperature of 110~180℃ for 30~120 seconds.

[0057] Preferably, the high-barrier coated paper prepared by the high molecular weight PHA emulsion of the present invention is characterized by having a Cobb 1800 water absorption value of 3.3~6.7 as measured by GB / T 1540, and a water vapor transmission rate (WVTR) of 4.9~8.2 g / m³ under 38℃ / 90%RH conditions as measured by ASTM F1249-20. 2 • After 24 hours, the oil resistance Kit rating was measured to be 12 according to TAPPI T559 cm-22.

[0058] The present invention is further illustrated in the following embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the reagents, materials, etc., used in the embodiments are commercially available. All quantitative experiments were performed in triplicate, and the results were averaged.

[0059] Preparation of high molecular weight PHA: Using the high molecular weight PHA fermentation broth from Microstructure Factory, pure PHA emulsion was prepared according to the method disclosed in patent CN118440308A or Chinese patent application number 202511934156.1. The pure PHA emulsion was then subjected to plate and frame filter press to obtain high molecular weight PHA with 60-65% dry matter.

[0060] Core process: After washing the bacterial cells, a slow lysis and cell-wall disruption method is used for further separation and purification. After purification, the cells are then subjected to forced cell-wall disruption using a high-pressure homogenizer followed by washing to obtain a high-purity PHA emulsion. This method avoids the problem of difficult re-emulsification of dried PHA.

[0061] Barrier test: The water absorption of the coated paper was tested according to GB / T1540, and the Cobb value (Cobb1800) was calculated after 30 minutes.

[0062] Water vapor transmission rate (WVTR): ASTM F1249-20.

[0063] Oxygen Transmission Rate (OTR): ASTM D3985-24.

[0064] Oil resistance rating (Kit): TAPPI T559 cm-22.

[0065] Example 1 Formulation composition: PHB with a molecular weight of 3.9 million and a dry matter content of 65 wt% is prepared into a PHB aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. 0.8 wt% of fatty alcohol polyoxyethylene ether (Maclean, model AEO-9) emulsifier with dry matter of PHA is added. After stirring at room temperature for 20 min, emulsification is carried out by a high pressure homogenizer (ATS homogenizer, model AH-P1LOT) for 2-4 times at 200-600 bar. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to PHB aqueous emulsion) to PHB dry matter, and stir thoroughly for 30 min at room temperature to mix well; Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 180℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0066] Example 2 Formulation composition: P(3HB-co-4HB) (4HB mol%: 5.2), with a molecular weight of 2.6 million and a dry matter content of 65 wt%, is prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. Sodium dodecyl sulfate (Maclean, analytical grade) emulsifier with a dry matter content of 0.5% is added. After stirring at room temperature for 20 min, emulsification is carried out by a high pressure homogenizer (ATS homogenizer, model AH-P1LOT) at 200-600 bar for 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-4HB) aqueous emulsion) to P(3HB-co-4HB) dry matter, and stir thoroughly at room temperature for 30 min to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 140℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0067] Example 3 Formulation composition: P(3HB-co-4HB) (4HB mol% : 15.4) with a molecular weight of 1.2 million and a dry matter content of 65 wt% is prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. 1 wt% of fatty acid methyl ester polyoxyethylene ether emulsifier (Maclean, content ≥70%) is added to the PHA dry matter. After stirring at room temperature for 20 min, emulsification is carried out by a high-pressure homogenizer (ATS homogenizer, model AH-P1LOT) at 200-600 bar for 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-4HB) aqueous emulsion) to P(3HB-co-4HB) dry matter, and stir thoroughly at room temperature for 30 min to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 110℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0068] Example 4 Formulation composition: P(3HB-co-4HB-co-3HV) with a molecular weight of 2.17 million and a dry matter content of 65 wt% (4HB mol%: 7.4; 3HV mol%: 3.0) was prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. 1 wt% of isomeric alcohol polyoxyethylene ether emulsifier (Aladdin, E-1006) was added to the PHA dry matter. After stirring at room temperature for 20 min, emulsification was carried out using a high-pressure homogenizer (ATS homogenizer, model AH-P1LOT) at 200-600 bar for 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-4HB-co-3HV) aqueous emulsion) to P(3HB-co-4HB-co-3HV) dry matter and stir thoroughly at room temperature for 30 min to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 130℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0069] Example 5 Formulation composition: P(3HB-co-3HV) (3HV mol% : 9.3) with a molecular weight of 2 million and a dry matter content of 65 wt% is prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. Add 1 wt% of PHA dry matter isomeric alcohol polyoxyethylene ether emulsifier (Maclean, E-1306), stir at room temperature for 20 min, and then emulsify using a high pressure homogenizer (ATS homogenizer, model AH-P1LOT) at 200-600 bar for 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-3HV) aqueous emulsion) to P(3HB-co-3HV) dry matter, and stir thoroughly at room temperature for 30 min to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 130℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0070] Comparative Example 1 Formulation composition: PHB with a molecular weight of 700,000 and a dry matter content of 65 wt% is prepared into a PHB aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. 0.8 wt% of fatty alcohol polyoxyethylene ether emulsifier (Maclean, model AEO-9) with dry matter of PHA is added. After stirring at room temperature for 20 min, emulsification is carried out by a high pressure homogenizer (ATS homogenizer, model AH-P1LOT) for 2-4 times at 200-600 bar. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to PHB aqueous emulsion) to PHB dry matter, and stir thoroughly for 30 min at room temperature to mix well; Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 180℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0071] Comparative Example 2 Formulation composition: P(3HB-co-4HB) (4HB mol% : 5.2) with a molecular weight of 570,000 and a dry matter content of 65 wt% was prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. Sodium dodecyl sulfate (Maclean, analytical grade) emulsifier with a dry matter content of 0.5% was added. After stirring at room temperature for 20 min, it was emulsified by a high pressure homogenizer (ATS homogenizer, model AH-P1LOT) at 200-600 bar 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-4HB) aqueous emulsion) to P(3HB-co-4HB) dry matter, and stir thoroughly at room temperature for 30 min to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 140℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0072] Comparative Example 3 P(3HB-co-4HB) (4HB mol% : 15.4) with a molecular weight of 320,000 and a dry matter content of 65 wt% was prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water. 1 wt% of fatty acid methyl ester polyoxyethylene ether emulsifier (Maclean, content ≥70%) was added to the PHA dry matter. After stirring at room temperature for 20 min, the mixture was emulsified using an ATS homogenizer (model AH-P1LOT) at 200-600 bar for 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-4HB) aqueous emulsion) to P(3HB-co-4HB) dry matter, and stir thoroughly for 30 min at room temperature to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 110℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0073] Comparative Example 4 Formulation composition: P(3HB-co-4HB-co-3HV) with a molecular weight of 480,000 and a dry matter content of 65 wt% (4HB mol%: 7.4; 3HV mol%: 3.0) was prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. 1 wt% of isomeric alcohol polyoxyethylene ether emulsifier (Aladdin, E-1006) was added to the PHA dry matter. After stirring at room temperature for 20 min, emulsification was carried out using a high-pressure homogenizer (ATS homogenizer, model AH-P1LOT) at 200-600 bar for 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-4HB-co-3HV) aqueous emulsion) to P(3HB-co-4HB-co-3HV) dry matter and stir thoroughly at room temperature for 30 min to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 130℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0074] Comparative Example 5 Formulation composition: P(3HB-co-3HV) (3HV mol% : 9.3) with a molecular weight of 500,000 and a dry matter content of 65 wt% was prepared into an aqueous suspension with a dry matter content of 40 wt% by adding RO water according to the dry matter content. 1 wt% of isomeric alcohol polyoxyethylene ether emulsifier (Maclean, E-1306) was added to the PHA dry matter. After stirring at room temperature for 20 min, emulsification was carried out using a high-pressure homogenizer (ATS homogenizer, model AH-P1LOT) at 200-600 bar for 2-4 times. Add 1 wt% of polyvinyl alcohol (Maclean, model 1788) film-forming aid (polyvinyl alcohol dissolved in water and added to P(3HB-co-3HV) aqueous emulsion) to P(3HB-co-3HV) dry matter and stir thoroughly for 30 min at room temperature to mix well. Application: Paper coating using an automatic coating machine (BEVS1811 / 2), controlling the coating amount to 15 g / m². 2 Then, it is dried at 130℃ for 120 seconds. Barrier test: The coated paper is tested for water absorption, water vapor transmission rate and oil resistance according to the standard.

[0075] Table 1 below shows the test results of Examples 1 to 5 and Comparative Examples 1 to 5.

[0076]

[0077] Test results show that the Cobb 1800 values ​​of the coated papers in Examples 1-5 using the technical solution of this invention are all significantly lower than those in the comparative examples, and the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) are also significantly lower than those in the corresponding low molecular weight comparative examples. Simultaneously, the oil resistance grade reaches the highest level (>12), demonstrating comprehensive and excellent barrier performance, fully proving the significant advantages of high molecular weight PHA in improving barrier performance. Furthermore, the copolymer systems in Examples 2-5 also show the same trend, indicating that the effect of this technology is universally applicable to different copolymer systems of PHA.

[0078] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0079] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A high molecular weight polyhydroxyalkanoate (PHA) emulsion, comprising the following components: PHA polymers with a weight-average molecular weight of approximately 800,000 to approximately 4 million; 0.1 to 5 wt% emulsifier based on the weight of the PHA polymer; Film-forming aids of 0.1-5 wt% based on the weight of the PHA polymer; and 50-500 wt% water based on the weight of the PHA polymer.

2. The PHA emulsion according to claim 1, wherein: 1) The PHA polymer comprises at least one repeating unit selected from 3-hydroxybutyrate (3-HB), 4-hydroxybutyrate (4-HB), 3-hydroxypropionate (3-HP), 3-hydroxyhexanoate (3-HHx), 3-hydroxyvalerate (3-HV), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV), and 6-hydroxyhexanoate (6-HH), preferably selected from poly-3-hydroxybutyrate (PHB), a copolymer of 3-hydroxybutyric acid and 4-hydroxybutyric acid (P34HB), poly-3-hydroxyvalerate (PHV), poly-3-hydroxypropionate (P3HP), a copolymer of 3-hydroxybutyric acid and 3-hydroxyvalerate (PHBV), poly-3-hydroxyoctanoate (PHO), poly- One or more of the following: 3-hydroxynonanoate (PHN), a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid (PHBHHx), a copolymer of 3-hydroxybutyric acid, 4-hydroxybutyric acid and 3-hydroxyvalerate (P3HB4HB3HV), or a copolymer of 3-hydroxybutyric acid, 4-hydroxybutyric acid and 5-hydroxyvalerate (P3HB4HB5HV), wherein preferably, when the high molecular weight PHA contains a 3-HB repeating unit, the molar percentage of 3-HB is greater than or equal to 80 mol%; and / or 2) The particle size D90 of the PHA polymer is ≤2 μm and the purity is ≥98 wt%.

3. The PHA emulsion according to claim 1 or 2, wherein the emulsifier is selected from fatty alcohol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkylphenol polyoxyethylene ether, fatty acid methyl ester polyoxyethylene ether, isomeric alcohol polyoxyethylene ether, or a combination thereof.

4. The PHA emulsion according to any one of claims 1 to 3, wherein the film-forming aid is selected from polyvinyl alcohol, dodecyl alcohol ester, hexadecyl alcohol ester, propylene glycol methyl ether acetate, dipropylene glycol methyl ether, butyl lactate, DBE diester or a combination thereof.

5. The PHA emulsion according to any one of claims 1 to 4, further comprising 0.1 wt% to 0.5 wt% of a bactericide and / or 0.1 to 5 wt% of a rheology modifier based on the weight of the PHA emulsion.

6. The PHA emulsion according to claim 5, wherein the bactericide is selected from one or more of benzisothiazolinone, methylisothiazolinone, a mixture of methylchloroisothiazolinone and methylisothiazolinone, bromonitol, sodium pyrithione, ethylenediaminetetraacetic acid, zinc oxide, benzalkonium chloride and 2,2-dibromopropionamide.

7. The PHA emulsion according to claim 5 or 6, wherein the rheology modifier is selected from one or more of associative polyurethane thickeners, alkali-swellable acrylic thickeners, hydrophobically modified hydroxyethyl cellulose, bentonite, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, xanthan gum, guar gum, and sodium alginate.

8. A method for preparing a high molecular weight PHA emulsion according to any one of claims 1 to 7, the method comprising the following steps: (1) Provide PHA raw materials, preferably the PHA is a product with a dry matter content of 60-65 wt% and a weight average molecular weight of 800,000 to 4,000,000; (2) Based on the dry matter content of the PHA raw material, water is added to prepare a PHA aqueous suspension with a preferred dry matter content of 40 wt%. (3) Add 0.1-5 wt% emulsifier based on the dry weight of PHA to the aqueous suspension obtained in step (2) and stir to mix; (4) The mixture obtained in step (3) is emulsified by a high-pressure homogenizer; (5) Add 0.1~5 wt% of film-forming aid based on the dry weight of PHA to the emulsion obtained in step (4), stir and mix well to obtain the high molecular weight PHA aqueous suspension.

9. The method according to claim 8, wherein: 1) The PHA raw material mentioned in step (1) is a product with 60-65 wt% dry matter obtained by plate and frame filtration after microbial fermentation, extraction, and purification; and / or 2) The emulsification pressure of the high-pressure homogenizer in step (4) is 200-600 bar, and the number of cycles of emulsification is 2-4.

10. The application of the high molecular weight PHA emulsion according to any one of claims 1 to 7 or the high molecular weight PHA emulsion prepared according to the method of claim 8 in the preparation of barrier coatings for paper-based packaging materials or water-based environmentally friendly coatings.

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