Polyhydroxyalkanoate water-based coating, preparation method therefor, and use thereof

Abstract

A polyhydroxyalkanoate (PHA) water-based coating, a preparation method therefor, and a use thereof. The coating comprises a PHA suspension and an auxiliary agent, wherein the melting point of PHA is 100-120°C, and the PHA is a copolymer containing at least two polymerization monomers. By selecting the PHA meeting specific conditions, the obtained coating is environment-friendly and degradable, and the prepared coated paper can be directly pulped and recycled. The coated paper has good comprehensive performance in terms of stable standing, temperature resistance, oil resistance, environment friendliness, and coating flatness, and can meet the requirement for containing high-temperature liquids.

Description

A polyhydroxyalkanoate water-based coating and its preparation method and application

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 2023112858667, filed on October 7, 2023, entitled “A Polyhydroxyalkanoate Water-Based Coating, Its Preparation Method and Application,” all disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates to the field of biodegradable polymer materials, and in particular to a polyhydroxyalkanoate water-based coating, a preparation method and application thereof. Background Art

[0004] In daily life, people use many waterproof and impermeable products, such as paper cups, which are made by coating a base paper layer with a layer of plastic. Existing paper cups typically use PE coating, PLA coating, or acrylic water-based coating, but each has its drawbacks. PE coatings are non-degradable, polluting the environment, and separating the paper and coating layers requires significant energy and investment. PLA coatings are non-degradable, making the paper and coating layers inseparable, and the paper pulp cannot be directly recycled. Acrylic water-based coatings allow for direct reuse of the paper pulp, but acrylic cannot be degraded, resulting in microplastic pollution.

[0005] Polyhydroxyalkanoate (PHA) is an intracellular polyester synthesized by many bacteria. As a biosynthetic polymer thermoplastic material, it has physical and chemical properties similar to those of synthetic plastics and many excellent properties that synthetic plastics do not have, such as biodegradability, biocompatibility, optical activity, piezoelectricity, and gas barrier properties.

[0006] Because polyhydroxyalkanoates are biodegradable, researchers are attempting to replace existing PE, PLA, and acrylic water-based coatings with polyhydroxyalkanoate water-based coatings to achieve environmental and safety benefits. However, existing polyhydroxyalkanoate water-based coatings require drying at 160-180°C during film formation, which can cause paper deformation and yellowing.

[0007] Summary of the Invention

[0008] In response to the problems existing in the prior art, the present invention provides a polyhydroxyalkanoate water-based coating, a preparation method and an application thereof. The polyhydroxyalkanoate water-based coating can meet the processing conditions of paper to obtain a qualified and environmentally friendly waterproof and anti-penetration product.

[0009] In a first aspect, the present invention provides a polyhydroxyalkanoate water-based coating, comprising: a polyhydroxyalkanoate suspension and an additive;

[0010] The melting point of the polyhydroxyalkanoate is 100-120° C., and the polyhydroxyalkanoate comprises a copolymer of at least two polymerizable monomers.

[0011] The present invention has found that by selecting the above-mentioned specific polyhydroxyalkanoates, the water-based coating prepared can be coated on paper without using the traditional high-temperature film-forming process. Instead, the film can be formed at a temperature not exceeding 150°C. Some water-based coatings can even be dried at 60-120°C after being prepared, thus avoiding the problems of paper deformation and yellowing caused by high temperature.

[0012] The polymerizable monomers are divided into short chains (3-5 carbon atoms) and medium-long chains (6-14 carbon atoms) according to the number of carbon atoms. Specifically, the polymerizable monomers include one or more of 3-hydroxypropionic acid, 3-hydroxybutyric acid (3HB), 4-hydroxybutyric acid (4HB), 3-hydroxyvaleric acid (3HV), 5-hydroxyvaleric acid (5HV), 3-hydroxyhexanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid or 3-hydroxydodecanoic acid.

[0013] In order to form a film at a temperature not exceeding 150° C., when the polymerization monomer includes 4HB, the monomer content of 4HB is 21%-30%.

[0014] When the polymerization monomer includes 3HV, the monomer content of 3HV is 5% to 20%.

[0015] When the polymerized monomer includes 5HV, the monomer content of 5HV is 5% to 20%.

[0016] In some embodiments of the present invention, the polyhydroxyalkanoate comprises a copolymer of two polymerizable monomers, that is, the PHA comprises a dimer, and the dimer is selected from one or more of P34HB, PHBV, PHBHHx, PHBHO, and PHBHN.

[0017] The monomer content of 4HB in P34HB is any value between 21% and 30%, for example, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%.

[0018] The monomer content of 3HV in PHBV is any value between 5% and 20%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0019] The monomer content of 3HHx in PHBHHx is any value between 1% and 99%, for example, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, and 99%.

[0020] The monomer content of 3HO in PHBHO is any value between 1% and 99%, for example, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, and 99%.

[0021] The monomer content of 3HN in PHBHN is any value between 1% and 99%, for example, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, and 99%.

[0022] In other embodiments of the present invention, the polyhydroxyalkanoate comprises a copolymer of three polymerizable monomers, that is, the PHA comprises a trimer, and the trimer is selected from one or more of P3HB4HB3HV and P3HB4HB5HV.

[0023] Among them, the monomer content of 4HB in P3HB4HB3HV is any value between 21% and 30%, for example, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%; the monomer content of 3HV is any value between 5% and 20%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0024] The monomer content of 4HB in P3HB4HB5HV is any value between 21% and 30%, for example, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%; the monomer content of 5HV is any value between 5% and 20%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0025] The polyhydroxyalkanoate water-based coating of the present invention is suitable for coating paper, and the processing tolerance temperature of the paper is above the melting point of the polyhydroxyalkanoate and below 150°C.

[0026] It should be noted that the processing temperature tolerance refers to the temperature at which the paper can be processed without causing deformation or yellowing due to heat, which would otherwise affect its appearance and performance. Specifically, the paper described herein includes conventional paper with a processing temperature tolerance between the melting point of polyhydroxyalkanoates and 150°C, such as white cardboard, gray board, coated paper, offset paper, corrugated paper, writing paper, kraft paper, and newsprint. It does not include specialty paper with a processing temperature tolerance exceeding 150°C.

[0027] In some embodiments of the present invention, the paper used is white cardboard.

[0028] In some embodiments of the present invention, the polyhydroxyalkanoate suspension is obtained by dispersing PHA powder in water.

[0029] In other embodiments of the present invention, the polyhydroxyalkanoate suspension is a PHA solution obtained by centrifugal extraction of PHA fermentation broth; preferably, the centrifugal extraction includes a cell wall breaking treatment; further preferably, the particle size of PHA in the PHA solution is less than 1 micron.

[0030] Conventional methods involve first preparing PHA powder (typically with a particle size of 0.1-5 microns) through biofermentation and then dispersing it in water to produce a PHA aqueous solution. However, to achieve better dispersion and prevent agglomeration, the present inventors discovered that the PHA solution obtained by centrifugation of the PHA fermentation broth can be directly used as a raw material for preparing water-based coatings.

[0031] Furthermore, in a specific embodiment of the present invention, the mass fraction of polyhydroxyalkanoate in the polyhydroxyalkanoate suspension is 30-70%, and the amount of the additive added does not exceed 5% of the mass of the polyhydroxyalkanoate suspension.

[0032] The polyhydroxyalkanoate water-based coating of the present invention minimizes the need for additives, with the additive amount not exceeding 5% of the mass of the polyhydroxyalkanoate suspension, surpassing existing standards. Because polyhydroxyalkanoates are hydrophobic, they are traditionally dispersed using toxic and hazardous organic solvents. Later aqueous systems also typically incorporate large amounts of additives to ensure stability. However, the present invention utilizes PHA, which has a smaller particle size, better dispersibility in water, and exhibits excellent film-forming and leveling properties, thus reducing the amount of additives required.

[0033] In some embodiments of the present invention, the auxiliary agent includes one or more of a film former, a wetting agent, a leveling agent, and a thickener.

[0034] Preferably, the above four additives are all added to the polyhydroxyalkanoate water-based coating.

[0035] More preferably, based on the mass of the polyhydroxyalkanoate suspension, the added amount of the film-forming agent is 0.1-1%, the added amount of the wetting agent is 0.1-1%, the added amount of the leveling agent is 0.1-1%, and the added amount of the thickener is 0.1-1%.

[0036] In some embodiments of the present invention, the film-forming agent is selected from one or more of diethanol ether, propylene glycol ether, and N-methylpyrrolidone.

[0037] In some embodiments of the present invention, the wetting agent is selected from one or more of alkyl nonylphenol ethoxylate, lauryl phosphate potassium salt, sodium lauryl polyoxyethylene ether sulfate, sodium lauroyl acid, and sodium α-olefin sulfonate.

[0038] In some embodiments of the present invention, the leveling agent is selected from one or more of Digo 432, modified polysiloxane, and cellulose.

[0039] In some embodiments of the present invention, the thickener is selected from one or more of gelatinized starch, polyacrylonitrile, sodium dodecylbenzene sulfonate, sodium polyacrylate, sodium alginate, and polypyrrolidone; preferably, the gelatinized starch is selected from one or more of corn starch, potato starch, sweet potato starch, and cassava starch.

[0040] In a second aspect, the present invention provides a method for preparing the above-mentioned polyhydroxyalkanoate water-based coating.

[0041] The preparation method provided by the present invention comprises: dispersing an auxiliary agent into the polyhydroxyalkanoate suspension to form a colloidal dispersed solution.

[0042] The preparation method of the present invention has low cost, simple production process and is easy to industrialize.

[0043] The dispersion can be performed by mechanical stirring or ultrasonic dispersion, which are commonly used in the art. Further preferably, when mechanical stirring is used, the rotation speed is controlled at about 2000 rpm. When ultrasonic dispersion is used, the dispersion time is controlled at about 30 min.

[0044] In a third aspect, the present invention provides the use of the above-mentioned polyhydroxyalkanoate water-based coating in the preparation of an anti-penetration material.

[0045] Specifically, the present invention provides an anti-permeation paper, comprising paper and a coating coated on the paper, wherein the coating is made of the above-mentioned polyhydroxyalkanoate water-based coating.

[0046] In some embodiments of the present invention, the paper is white cardboard.

[0047] In some embodiments of the present invention, the coating has a thickness of 3-14 microns.

[0048] In some embodiments of the present invention, the method for preparing the anti-permeation paper includes: applying the polyhydroxyalkanoate water-based coating on paper, controlling the coating wet material thickness to 10-20 microns, drying at 60-65°C for 1-1.5 hours after coating, and then drying at 120-150°C for no more than 1 minute to obtain an anti-permeation paper with a coating dry thickness of 3-14 microns.

[0049] Among them, common equipment such as a wire rod coater, a smooth plate coating roller, or a gravure coating roller can be used to apply the water-based paint.

[0050] In addition, it should be noted that the anti-penetration paper of the present invention is not only waterproof but also oil-proof, and has temperature resistance and permeation resistance. After being made into paper cups, it can be used to hold high-temperature liquids.

[0051] The present invention provides a polyhydroxyalkanoate water-based coating, a preparation method and application thereof. By selecting polyhydroxyalkanoate that meets specific conditions, the water-based coating prepared can be used for coating paper, etc. The water-based coating is environmentally friendly and degradable. The prepared coated paper can be directly pulped and reused without the need to separate the coating and pulp, and no separation cost investment is required.

[0052] Furthermore, the coated paper obtained by the present invention has good comprehensive properties such as static stability, temperature resistance, oil resistance, environmental protection, and coating smoothness. It does not require adhesives to glue the coating to a substrate such as base paper, and can meet the requirements of containing high-temperature liquids. DETAILED DESCRIPTION

[0053] The term "include" or "comprising" in the present invention is an open description containing the specified components or steps described, as well as other specified components or steps that do not substantially affect them.

[0054] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0055] In the description of this specification, the reference terms "one embodiment", "some embodiments", "specific implementation methods", or "some specific implementation methods" and the like mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0056] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0057] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0058] The English abbreviations that appear in this article correspond to the following Chinese full names:

[0059] PHA: polyhydroxyalkanoate

[0060] P4HB: Poly-4-hydroxybutyrate

[0061] PHBV: poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

[0062] P3HB4HB or P34HB: poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

[0063] PHBHHx: poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

[0064] PHBHO: poly(3-hydroxybutyrate-co-3-hydroxyoctanoate)

[0065] PHBHN: poly(3-hydroxybutyrate-co-3-hydroxynonanoate)

[0066] P3HB4HB3HV: poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-3-hydroxyvalerate)

[0067] P3HB4HB5HV: poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-5-hydroxyvalerate).

[0068] In the following examples, the heat resistance test method is as follows: a certain mass of water at a specified temperature (100°C) is added to heat-sealed paper cups, reaching a height of approximately 6 mm from the cup rim. The cups are then placed on a flat glass plate and allowed to stand for 1 hour. The cups are then observed for bubbling, peeling, or other signs of coating flaking. Five cups are tested for each sample; if any one exhibits bubbling or peeling, the cup is deemed unqualified.

[0069] The corn oil resistance test method involves adding a certain amount of corn oil at a specified temperature (23°C or 100°C) to a heat-sealed paper cup, filling it to approximately 6mm from the cup's rim. The cup is then placed on a flat glass plate and left to stand for 1 hour before being inspected for signs of leakage. Five cups are tested for each sample; if even one shows leakage, the cup is deemed unqualified.

[0070] Example 1

[0071] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0072] Weigh 30 parts by mass of P34HB (melting point 112° C., 4-hydroxybutyric acid content 21%) powder (particle size 1 micron), add it to 70 parts by mass of water, use 2000 rpm stirring, dispersion time 30 minutes, so that the polyhydroxyalkanoate is evenly dispersed in the water, then add 0.1 parts by mass of diethanol ether, 0.1 parts by mass of alkyl nonylphenol ethoxylate, 0.1 parts by mass of Digo 432 and 0.1 parts by mass of sodium alginate, stir at 2000 rpm, dispersion time 30 minutes, so that the additives are evenly dispersed to form a colloidal, uniformly dispersed dilute solution, and obtain a water-based coating of polyhydroxyalkanoate.

[0073] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 20 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 150°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 6 μm.

[0074] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 1.

[0075] Table 1

[0076] Example 2

[0077] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0078] Weigh 70 parts by mass of P34HB (melting point 105° C., 4-hydroxybutyric acid content 25%) powder (particle size 3 μm), add it to 30 parts by mass of water, use ultrasound for ultrasonic dispersion, and disperse for 30 minutes to uniformly disperse the polyhydroxyalkanoate in the water. Then, add 0.5 parts by mass of propylene glycol ether, 0.5 parts by mass of potassium lauryl phosphate, 0.5 parts by mass of modified polysiloxane and 0.5 parts by mass of polypyrrolidone, stir at a speed of 2000 rpm, and disperse for 30 minutes to uniformly disperse the additives to form a colloidally uniformly dispersed dilute solution to obtain a water-based coating of polyhydroxyalkanoate.

[0079] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 10 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 110°C for 0.5 minutes to obtain an anti-penetration paper with a dry coating thickness of 7 μm.

[0080] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 2.

[0081] Table 2

[0082] Example 3

[0083] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0084] Weigh 35 parts by mass of P34HB (melting point 101° C., 4-hydroxybutyric acid content 30%) powder (particle size 5 μm), add it to 65 parts by mass of water, use ultrasound for ultrasonic dispersion, and disperse for 30 minutes to uniformly disperse the polyhydroxyalkanoate in water. Then, add 1 part by mass of N-methylpyrrolidone, 1 part by mass of sodium lauroyl acid, 1 part by mass of cellulose, and 1 part by mass of corn starch. Stir at a speed of 2000 rpm for 30 minutes to uniformly disperse the additives to form a colloidal, uniformly dispersed dilute solution to obtain a water-based coating of polyhydroxyalkanoate.

[0085] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 15 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 130°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 6 μm.

[0086] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 3.

[0087] Table 3

[0088] Example 4

[0089] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0090] 70 parts by mass of PHBV (melting point 110° C., 3-hydroxyvaleric acid content 20%) powder (particle size 0.2 μm) was weighed and added to 30 parts by mass of water. Ultrasonic dispersion was performed using ultrasound for a dispersion time of 30 min to uniformly disperse the polyhydroxyalkanoate in the water. Subsequently, 0.5 parts by mass of propylene glycol ether, 0.5 parts by mass of potassium lauryl phosphate, 0.5 parts by mass of modified polysiloxane, and 0.5 parts by mass of polypyrrolidone were added. The mixture was stirred at a speed of 2000 rpm for a dispersion time of 30 min to uniformly disperse the additives to form a colloidal, uniformly dispersed dilute solution to obtain a water-based coating of polyhydroxyalkanoate.

[0091] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 10 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 110°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 7 μm.

[0092] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 4.

[0093] Table 4

[0094] Example 5

[0095] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0096] Weigh 70 parts by mass of PHBHHx (melting point 108° C., 3-hydroxyhexanoic acid content 40%) powder (particle size 0.5 μm), add it to 30 parts by mass of water, use ultrasound for ultrasonic dispersion, and disperse for 30 minutes to uniformly disperse the polyhydroxyalkanoate in the water. Then, add 0.5 parts by mass of propylene glycol ether, 0.5 parts by mass of potassium lauryl phosphate, 0.5 parts by mass of modified polysiloxane and 0.5 parts by mass of polypyrrolidone, stir at a speed of 2000 rpm, and disperse for 30 minutes to uniformly disperse the additives to form a colloidal, uniformly dispersed dilute solution to obtain a water-based coating of polyhydroxyalkanoate.

[0097] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 10 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 110°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 7 μm.

[0098] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 5.

[0099] Table 5

[0100] Example 6

[0101] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0102] Weigh 40 parts by mass of PHBHHx (melting point 108° C., 3-hydroxyhexanoic acid content 10%) and 30 parts by mass of P34HB (melting point 112° C., 4-hydroxybutyric acid content 21%) powder (particle size 0.5 μm), add them to 30 parts by mass of water, use ultrasound for ultrasonic dispersion, and disperse for 30 minutes to uniformly disperse the polyhydroxyalkanoate in water. Then, add 0.5 parts by mass of propylene glycol ether, 0.5 parts by mass of potassium lauryl phosphate, 0.5 parts by mass of modified polysiloxane and 0.5 parts by mass of polypyrrolidone, stir at a speed of 2000 rpm, and disperse for 30 minutes to uniformly disperse the additives to form a colloidally uniformly dispersed dilute solution to obtain a water-based coating of polyhydroxyalkanoate.

[0103] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 10 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 110°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 7 μm.

[0104] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 6.

[0105] Table 6

[0106] Example 7

[0107] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0108] Weigh 70 parts by mass of P3HB4HB3HV (4-hydroxybutyric acid content 22%, 3-hydroxyvaleric acid content 10%) powder (particle size 0.5 micron), add it to 30 parts by mass of water, use ultrasound for ultrasonic dispersion, and disperse for 30 minutes to uniformly disperse the polyhydroxyalkanoate in the water. Then, add 0.5 parts by mass of propylene glycol ether, 0.5 parts by mass of potassium lauryl phosphate, 0.5 parts by mass of modified polysiloxane and 0.5 parts by mass of polypyrrolidone, stir at a speed of 2000 rpm, and disperse for 30 minutes to uniformly disperse the additives to form a colloidally uniformly dispersed dilute solution to obtain a water-based coating of polyhydroxyalkanoate.

[0109] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 10 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 100°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 7 μm.

[0110] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 7.

[0111] Table 7

[0112] Example 8

[0113] This embodiment provides a polyhydroxyalkanoate water-based coating, the preparation method of which is as follows:

[0114] The fermentation cell liquid of P34HB is subjected to enzymatic hydrolysis and cell wall disruption to obtain an aqueous solution containing 70% P34HB, wherein the P34HB has a particle size of 0.5 micron, a melting point of 105°C, and a 4-hydroxybutyric acid content of 25%. To 100 parts by mass of the aqueous solution, 0.5 parts by mass of propylene glycol ether, 0.5 parts by mass of potassium lauryl phosphate, 0.5 parts by mass of modified polysiloxane, and 0.5 parts by mass of polypyrrolidone are added. The mixture is stirred at 2000 rpm for 30 minutes to uniformly disperse the additives, forming a colloidal, uniformly dispersed dilute solution, thereby obtaining a water-based coating of polyhydroxyalkanoate.

[0115] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 10 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 110°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 7 μm.

[0116] The viscosity and static stability of the obtained polyhydroxyalkanoate water-based coating were tested, and the heat resistance and corn oil resistance of the obtained waterproof paper were tested. The results are shown in Table 8.

[0117] Table 8

[0118] Comparative Example 1

[0119] In this comparative example, PHA powder (same as in Example 3) was directly dissolved in water to prepare a dispersion system with a dry weight of 35%, and the mixture was stirred at a speed of 2000 rpm for a dispersion time of 30 minutes to obtain a water-based coating.

[0120] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 15 μm. After coating, the coating was dried at 60° C. for 1 hour and then dried at 150° C. for 1 minute to obtain a composite paper with a dry coating thickness of 6 μm.

[0121] The obtained materials were tested and the results are shown in Table 9.

[0122] This comparative example does not contain any additives, has poor stability, and is prone to stratification when left standing.

[0123] Table 9

[0124] Comparative Example 2

[0125] In this comparative example, PHA powder (same as in Example 3) was directly dissolved in chloroform to prepare a 5% dry weight solution, and the solution was stirred at 2000 rpm for 30 minutes to obtain a coating.

[0126] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 20 μm. After coating, the coating was dried at 60° C. for 1 hour and then dried at 150° C. for 1 minute to obtain a composite material with a dry coating thickness of 1 μm.

[0127] The obtained materials were tested and the results are shown in Table 10.

[0128] This comparative example uses an organic solvent to prepare the solution, which has low solubility, large amount of organic solvent used, and high pollution.

[0129] Table 10

[0130] Comparative Example 3

[0131] Weigh 35 parts by mass of P34HB (melting point 165° C., 4-hydroxybutyric acid content 8%) powder (particle size 5 μm), add it to 65 parts by mass of water, use ultrasound for ultrasonic dispersion, and disperse for 30 minutes to uniformly disperse the polyhydroxyalkanoate in the water. Then, add 1 part by mass of N-methylpyrrolidone, 1 part by mass of sodium lauroyl acid, 1 part by mass of cellulose, and 1 part by mass of corn starch. Stir at a speed of 2000 rpm for 30 minutes to uniformly disperse the additives to form a colloidal, uniformly dispersed dilute solution to obtain a water-based coating of polyhydroxyalkanoate.

[0132] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 15 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 160°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 6 μm.

[0133] The obtained materials were tested and the results are shown in Table 11.

[0134] The P34HB used in this comparative example has a high melting point and a high drying and film-forming temperature, which can easily cause the paper to bend, deform, and yellow, and the coating is also prone to yellowing.

[0135] Table 11

[0136] Comparative Example 4

[0137] 35 parts by mass of P34HB (melting point 148° C., 4-hydroxybutyric acid content 18%) powder (particle size 5 μm) was weighed and added to 65 parts by mass of water. Ultrasonic dispersion was performed using ultrasound for a dispersion time of 30 minutes to uniformly disperse the polyhydroxyalkanoate in the water. Subsequently, 1 part by mass of N-methylpyrrolidone, 1 part by mass of sodium lauroyl acid, 1 part by mass of cellulose, and 1 part by mass of corn starch were added. The mixture was stirred at a speed of 2000 rpm for a dispersion time of 30 minutes to uniformly disperse the additives to form a colloidal, uniformly dispersed dilute solution, thereby obtaining a water-based coating of polyhydroxyalkanoate.

[0138] The coating was applied to the base paper using a wire rod coater, with the wet coating thickness controlled at 15 μm. After coating, the coating was dried at 60°C for 1 hour and then dried at 160°C for 1 minute to obtain an anti-penetration paper with a dry coating thickness of 6 μm.

[0139] The obtained materials were tested and the results are shown in Table 12.

[0140] The P34HB used in this comparative example has a high melting point and a high drying and film-forming temperature, which can easily cause the paper to bend, deform, and yellow, and the coating is also prone to yellowing.

[0141] Table 12

[0142] Comparative Example 4

[0143] This comparative example uses a PE laminated layer composite paper layer.

[0144] The obtained material was tested and the results are shown in Table 13.

[0145] This comparative example uses a PE coating, which is non-degradable and has a high investment cost for separating the coating layer from the paper layer.

[0146] Table 13

[0147] Comparative Example 5

[0148] This comparative example uses a PLA laminated paper layer.

[0149] The obtained materials were tested and the results are shown in Table 14.

[0150] This comparative example uses PLA coating, which requires composting to degrade, resulting in high costs, and the coating composite material cannot be directly re-pulped and reused.

[0151] Table 14

[0152] Comparative Example 6

[0153] This comparative example uses acrylic acid water-based paint to composite the paper layer.

[0154] The obtained materials were tested and the results are shown in Table 15.

[0155] This comparative example uses acrylic water-based coating. Although it can be re-pulped, acrylic acid cannot be degraded and produces microplastic hazards.

[0156] Table 15

[0157] It can be seen from the above results that the polyhydroxyalkanoate water-based coatings prepared in Examples 1-8 of the present invention have good system stability, excellent oil and water penetration resistance, can be degraded in the natural environment, and can be directly re-pulped and reused without pollution. In addition, the present invention has low cost, simple production process, and is easy to industrialize.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention. Industrial Applicability

[0159] The present invention provides a polyhydroxyalkanoate water-based coating, a preparation method and application thereof, wherein the polyhydroxyalkanoate water-based coating comprises a polyhydroxyalkanoate suspension and an additive; wherein the polyhydroxyalkanoate has a melting point of 100-120°C, and the polyhydroxyalkanoate comprises a copolymer of at least two polymerized monomers. The present invention selects polyhydroxyalkanoates that meet specific conditions, thereby preparing a water-based coating that can be used for coating paper, etc. The water-based coating is environmentally friendly and degradable, and the prepared coated paper can be directly pulped and reused without the need to separate the coating and the pulp, and there is no separation cost investment. The coated paper obtained by the present invention has good comprehensive properties such as static stability, temperature resistance, oil resistance, environmental protection, and coating smoothness. It does not require adhesives to glue the coating to a substrate such as base paper, can meet the requirements of containing high-temperature liquids, and has good economic value and application prospects.

Claims

1. A polyhydroxyalkanoate water-based coating, characterized in that: Includes polyhydroxyalkanoate suspension and adjuvant; The melting point of the polyhydroxyalkanoate is 100-120° C., and the polyhydroxyalkanoate comprises a copolymer of at least two polymerizable monomers.

2. The polyhydroxyalkanoate water-based coating according to claim 1, characterized in that: When the polymerized monomer includes 4HB, the monomer content of 4HB is 21%-30%; and / or, when the polymerized monomer includes 3HV, the monomer content of 3HV is 5%-20%; And / or, when the polymerized monomer includes 5HV, the monomer content of 5HV is 5%-20%.

3. The polyhydroxyalkanoate water-based coating according to claim 1 or 2, characterized in that: The polyhydroxyalkanoate comprises a copolymer of two polymerized monomers; Preferably, the copolymer of the two polymerizable monomers is selected from one or more of P34HB, PHBV, PHBHHx, PHBHO, and PHBHN.

4. The polyhydroxyalkanoate water-based coating according to claim 1 or 2, characterized in that: The polyhydroxyalkanoate comprises a copolymer of three polymerized monomers; Preferably, the copolymer of the three polymerized monomers is selected from one or more of P3HB4HB3HV and P3HB4HB5HV.

5. The polyhydroxyalkanoate water-based coating according to any one of claims 1 to 4, characterized in that: The polyhydroxyalkanoate water-based coating is suitable for processing paper with a tolerance temperature of more than the melting point of the polyhydroxyalkanoate and less than 150°C.

6. The polyhydroxyalkanoate water-based coating according to any one of claims 1 to 4, characterized in that: The polyhydroxyalkanoate suspension is obtained by dispersing PHA powder into water; Alternatively, the polyhydroxyalkanoate suspension is obtained by centrifugation extraction of PHA fermentation broth.

7. The polyhydroxyalkanoate water-based coating according to claim 6, characterized in that: In the polyhydroxyalkanoate suspension, the mass fraction of polyhydroxyalkanoate is 30-70%, and the added amount of the auxiliary agent does not exceed 5% of the mass of the polyhydroxyalkanoate suspension.

8. The polyhydroxyalkanoate water-based coating according to claim 7, characterized in that: The auxiliary agent includes one or more of a film former, a wetting agent, a leveling agent, and a thickener; Preferably, based on the mass of the polyhydroxyalkanoate suspension, the added amount of the film former is 0.1-1%, the added amount of the wetting agent is 0.1-1%, the added amount of the leveling agent is 0.1-1%, and the added amount of the thickener is 0.1-1%; Further preferably, the film-forming agent is selected from one or more of diethanol ether, propylene glycol ether, and N-methylpyrrolidone; And / or, the wetting agent is selected from one or more of alkyl nonylphenol ethoxylate, potassium dodecyl phosphate, sodium dodecyl polyoxyethylene ether sulfate, sodium lauroyl acid, sodium α-olefin sulfonate; And / or, the leveling agent is selected from one or more of Digo 432, modified polysiloxane, and cellulose; And / or, the thickener is selected from one or more of gelatinized starch, polyacrylonitrile, sodium dodecylbenzene sulfonate, sodium polyacrylate, sodium alginate, and polypyrrolidone; preferably, the gelatinized starch is selected from one or more of corn starch, potato starch, sweet potato starch, and cassava starch.

9. The method for preparing the polyhydroxyalkanoate water-based coating according to any one of claims 1 to 8, characterized in that: include: The auxiliary agent is dispersed in the polyhydroxyalkanoate suspension to form a colloidal dispersion solution.

10. Use of the polyhydroxyalkanoate water-based coating according to any one of claims 1 to 8 in the preparation of anti-penetration materials.

11. An anti-permeation paper, characterized in that: The invention comprises paper and a coating applied on the paper, wherein the coating is made of the polyhydroxyalkanoate water-based coating according to any one of claims 1 to 8; and the paper is preferably white cardboard.

12. The anti-permeation paper according to claim 11, characterized in that: The thickness of the coating is 3-14 microns; Preferably, the method for preparing the anti-permeation paper comprises: applying the polyhydroxyalkanoate water-based coating on paper, controlling the coating wet material thickness to 10-20 microns, drying at 60-65°C for 1-1.5h after coating, and then drying at 120-150°C for no more than 1min, to obtain an anti-permeation paper with a coating dry thickness of 3-14 microns.

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