Waterproof paper straw and preparation method therefor

Abstract

Provided in the present invention are a waterproof paper straw and a preparation method therefor. The waterproof paper straw comprises a paper straw body and a PHA waterproof coating coated on the inner and outer walls of the paper straw body and the cross sections at both ends thereof, wherein the PHA waterproof coating is obtained by the film formation of a PHA water-based paint, and the PHA water-based paint comprises a PHA suspension and an auxiliary agent. According to the present invention, the inner and outer walls of the paper straw body and the cross sections at both ends thereof are coated with the PHA waterproof coatings, such that the straw does not easily absorb water and soften, and the service performance is guaranteed; moreover, no adhesive is needed in the preparation process of the paper straw of the present invention, the PHA coating can be used as a hot melt adhesive to bond seams, thereby ensuring the green safety of the waterproof paper straw, and the paper straw of the present invention can be directly re-pulped and recycled without separating the coating from the pulp, so there is no separation cost investment.

Description

Waterproof paper straw and preparation method thereof

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 2023112859941, filed on October 7, 2023, entitled “A Waterproof Paper Straw and Method for Preparing the Same,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to the field of paper straws, and in particular to a waterproof paper straw and a preparation method thereof. Background Art

[0004] Straws are a common item in our daily lives. Their main function is to drink from cups. With the restriction of the use of plastic straws, paper straws are becoming more and more common.

[0005] Currently, commonly used waterproof paper straws are mainly coated or laminated with a waterproof layer. The waterproof layer is usually coated with an acrylic water-based coating, which is a non-degradable material. If the paper straws are reused in the pulp, it will produce harmful microplastics. The laminated layer is often made of PE, which cannot be reused in the pulp and pollutes the environment. The separation of the paper layer and the laminated layer consumes a lot of energy and investment. PLA is also used in the laminated layer. Although this material is degradable, it requires harsh industrial composting conditions. The PLA laminated layer cannot be directly reused in the pulp, resulting in waste.

[0006] Moreover, in the existing technology, it is usually necessary to use adhesives (hot melt adhesives) to bond the seams when rolling the tubes, which increases the complexity of the preparation process and reduces the green safety of the waterproof paper straws.

[0007] Summary of the Invention

[0008] In response to the problems existing in the prior art, the present invention provides a waterproof paper straw and a preparation method thereof.

[0009] In the first aspect, the present invention provides a waterproof paper straw, comprising a paper straw body and a PHA waterproof coating coated on the inner and outer walls and cross sections of the paper straw body at both ends. The PHA waterproof coating is obtained by film formation of a PHA water-based paint, and the PHA water-based paint includes a PHA suspension and an additive.

[0010] Polyhydroxyalkanoate (PHA) is an intracellular polyester synthesized by 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.

[0011] The present invention applies a PHA waterproof coating to the inner and outer walls of the paper straw body and the cross-sections at both ends. On the one hand, it can effectively resist water and oil, making the straw less likely to absorb water and soften, thereby losing its usability. On the other hand, because PHA is a biodegradable polymer material, it can be degraded in the natural environment, and the degradation products are carbon dioxide and water, which will not produce microplastic hazards. Therefore, the paper straw of the present invention can be directly recycled, without the need to separate the coating and pulp, and without separation costs. Moreover, PHA itself has the function of hot melt adhesive, and the coating layer can be bonded to the seams by heating and pressurizing, without the need to apply adhesive, thus ensuring the green safety of the waterproof paper straw.

[0012] It should be noted that the coating can be applied to the target area of ​​the paper straw by common coating methods in the field, such as scraper coating, gravure printing, spraying, and dipping.

[0013] In the present invention, the waterproof paper straw can be a straight tube, a curved tube, a sleeve tube, a telescopic tube, or other straw forms that have appeared on the market.

[0014] In some embodiments of the present invention, the thickness of the PHA waterproof coating is 3-14 microns.

[0015] In some embodiments of the present invention, the PHA suspension is obtained by dispersing PHA powder in water, wherein the PHA powder can be prepared by chemical synthesis or microbial fermentation.

[0016] In other embodiments of the present invention, the PHA suspension is obtained by centrifuging a PHA fermentation broth. Preferably, the PHA fermentation broth has been cell wall broken.

[0017] 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 obtain a PHA suspension. However, to achieve better dispersion and prevent agglomeration, the present inventors discovered that a PHA solution obtained by treating the PHA fermentation broth can be directly used as the raw material for preparing PHA water-based coatings, thereby significantly reducing the number of steps involved.

[0018] Furthermore, the mass fraction of PHA in the PHA suspension is 40-60%, and the amount of the additive added does not exceed 5% of the mass of the PHA suspension, preferably does not exceed 2%.

[0019] In an embodiment of the present invention, the auxiliary agent includes one or more of a film-forming agent, a wetting agent, a leveling agent, and a thickener.

[0020] Preferably, based on the mass of the PHA suspension, the added amount of the film former is 0.01-0.5%, the added amount of the wetting agent is 0.01-0.5%, the added amount of the leveling agent is 0.01-0.5%, and the added amount of the thickener is 0.01-0.5%.

[0021] 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.

[0022] 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.

[0023] In some embodiments of the present invention, the leveling agent is selected from one or more of polyether siloxane copolymers and modified polysiloxanes.

[0024] In some embodiments of the present invention, the thickener is selected from one or more of nanocellulose, sodium hydroxypropyl cellulose, gelatinized starch, 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.

[0025] In a preferred embodiment of the present invention, the auxiliary agent only comprises a thickener and a leveling agent.

[0026] The PHA involved in the PHA water-based coating of the present invention is not particularly limited and can be a homopolymer or a copolymer. Wherein the polymerized monomers are divided into short chains (3-5 carbons) and medium-long chains (6-14 carbons) according to the number of carbon atoms. Specifically, the polymerized monomers include one or more of 3-hydroxypropionic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 5-hydroxyvaleric acid, 3-hydroxyhexanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid or 3-hydroxydodecanoic acid.

[0027] In some embodiments of the present invention, PHA is one or more of PHB, PHV, P34HB, PHBV, PHBHHx, PHBHO, PHBHN, P3HB4HB3HV, and P3HB4HB5HV.

[0028] In some embodiments of the present invention, the PHA is P34HB, wherein the molar content of 4HB is any value between 1% and 50%, for example, 1%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%.

[0029] In some embodiments of the present invention, the PHA is PHBV, and the molar content of HV in the PHBV is any value between 1% and 50%, for example, 1%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.

[0030] In some specific embodiments of the present invention, the PHA is PHBHHx, and the molar content of HHx in the PHBHHx is any value between 1% and 50%, for example, 1%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.

[0031] The preparation method of the PHA water-based paint of the present invention is to mix the components uniformly.

[0032] In some embodiments of the present invention, the PHA water-based coating can be prepared by the following method: mixing the components, mechanically stirring at a speed of 1000-2000 rpm for 30-60 minutes, and removing bubbles by ultrasonication for 20-30 minutes.

[0033] In a second aspect, the present invention provides a method for preparing the waterproof paper straws. The method provided by the present invention is not exclusive, and a suitable preparation method can be selected based on the structure of the paper straw and the conditions of the equipment used.

[0034] In some embodiments of the present invention, the method for preparing the waterproof paper straw includes:

[0035] The paper is coated with PHA water-based paint on both sides and dried at 110-180°C to form a film. The double-sided coated paper is rolled into a tube, and the joints are hot-pressed using the PHA coating layer as a hot melt adhesive. After the tube is formed, the target length is cut, and the ends of the straw are immersed in PHA water-based paint for end sealing. The paper is then taken out and dried to form a film.

[0036] The above preparation method is a two-step method. First, the paper is coated and then the straw is made. Finally, the cross-sections of both ends of the straw are dip-coated with PHA coating to seal the ends, thereby obtaining paper straws with PHA coating on the inner and outer walls and both ends.

[0037] Furthermore, in the heat-compression bonding step, the heating temperature is 110-180° C., the heating time is 0.1-2 s, and the pressure is 0.1-0.5 MPa.

[0038] In a preferred embodiment of the present invention, the preparation method comprises applying a PHA water-based coating to the surface of a paper straw using a scraper, gravure printing, or other methods, followed by drying at a temperature of 110-150°C for 1-5 minutes. The double-sided coated paper is rolled using a paper straw reel, and the joints are preheated at 150-170°C for 0.1-2 seconds before being hot-pressed and bonded. After the tube is formed, the target length is cut. The ends of the prepared straw are then immersed in the PHA water-based coating for 30-60 seconds to evenly coat the cross-section of the straw. The straw is then dried again at 110-150°C for 1-5 minutes to form a film.

[0039] In other embodiments of the present invention, the method for preparing the waterproof paper straw includes:

[0040] Immerse the cut paper in PHA water-based coating, take out the coated paper, roll it into a tube, glue it, and dry it to form a film.

[0041] This one-step process requires more technical expertise than the two-step method. For example, paper cutting is dictated by the target structure of the paper straw, and cutting accuracy impacts whether the subsequent tube formation will achieve the desired structure. Furthermore, the winding, gluing, and drying steps require high coordination, and all surfaces must be sealed simultaneously.

[0042] The paper of the present invention can be conventional paper in the art, such as white cardboard, grey board, coated paper, offset paper, corrugated paper, writing paper, kraft paper, newsprint, etc. In the embodiment of the present invention, the paper used is white cardboard.

[0043] The present invention provides a waterproof paper straw and a preparation method thereof. By applying a PHA waterproof coating on the inner and outer walls and cross sections of the paper straw body, the straw is prevented from absorbing water and softening, thereby ensuring its performance. Moreover, no adhesive is required during the preparation process of the paper straw of the present invention. The PHA coating layer can be used as a hot melt adhesive to bond the seams, thereby ensuring the green safety of the waterproof paper straw. The paper straw of the present invention can be directly recycled and there is no need to separate the coating and pulp, and no separation cost investment is required. DETAILED DESCRIPTION

[0044] The term "include" or "comprising" in the present invention is an open description containing the specified components or steps described, and other specified components or steps that do not substantially affect them.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] In the following examples, unless otherwise specified, "parts" are parts by weight.

[0050] The Chinese full names of the English abbreviations appearing in this article are as follows: PHA: polyhydroxyalkanoate PHB: poly-3-hydroxybutyrate PHV: poly-3-hydroxyvalerate P4HB: poly-4-hydroxybutyrate PHBV: poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P34HB: poly(3-hydroxybutyrate-co-4-hydroxybutyrate) PHBHHx: poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) PHBHO: poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) PHBHN: poly(3-hydroxybutyrate-co-3-hydroxynonanoate) P3HB4HB3HV: poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-3-hydroxyvalerate) P3HB4HB5HV: poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-5-hydroxyvalerate).

[0051] Example 1

[0052] This embodiment provides a waterproof paper straw, which consists of a paper straw body and a PHA waterproof coating coated on the inner and outer walls and cross sections of the paper straw body. The PHA waterproof coating is obtained by film formation of PHA water-based paint.

[0053] The PHA water-based coating is composed of: 100 parts of a P34HB aqueous solution with a solid content of 40% (wherein the 4HB molar content is 10%), 0.2 parts of a thickener, nanocellulose, and 0.01 parts of a leveling agent, modified polysiloxane.

[0054] Preparation steps of PHA water-based coating: weigh each component according to the mass ratio, stir mechanically at a speed of 1000 rpm for 30 minutes, and remove bubbles by ultrasonication for 20 minutes.

[0055] This embodiment also provides a method for preparing the waterproof paper straw:

[0056] Coating: Use a scraper to apply the PHA water-based coating to the paper surface, and then dry it at a temperature of 150°C for 1 minute.

[0057] Tube Making: Double-sided coated paper is rolled using a paper straw reel. The joints are preheated at 150°C for 0.5 seconds and then hot-pressed at 0.5 MPa. Both ends of the prepared straw are then soaked in a PHA water-based coating for 30 seconds to coat the cross-section evenly. The paper is then dried again at 150°C for 1 minute to form a film. The resulting paper straws have a waterproof coating (approximately 3 microns thick) on both the inner and outer walls and on both ends.

[0058] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 1.

[0059] Table 1

[0060] Example 2

[0061] This embodiment provides a waterproof paper straw, which consists of a paper straw body and a PHA waterproof coating coated on the inner and outer walls and cross sections of the paper straw body. The PHA waterproof coating is obtained by film formation of PHA water-based paint.

[0062] The PHA water-based coating is composed of: 100 parts of a PHBV aqueous solution with a solid content of 60% (wherein the HV molar content is 5%), 0.2 parts of a thickener, nanocellulose, and 0.01 parts of a leveling agent, modified polysiloxane.

[0063] Preparation steps of PHA water-based coating: weigh each component according to the mass ratio, stir mechanically at a speed of 1000 rpm for 30 minutes, and remove bubbles by ultrasonication for 20 minutes.

[0064] This embodiment also provides a method for preparing the waterproof paper straw:

[0065] Coating: Use spray to apply the PHA water-based coating to the paper surface, and then dry it at a drying temperature of 150°C and a drying time of 1 minute.

[0066] Tube Making: Double-sided coated paper is rolled using a paper straw rolling machine. The joints are preheated at 150°C for 0.5 seconds and then hot-pressed at 0.5 MPa. The ends of the prepared straws are then soaked in the aforementioned PHA water-based coating for 30 seconds to evenly coat the cross-section. The paper is then dried again at 150°C for 1 minute to form a film. This results in a paper straw with a waterproof coating (approximately 5 microns thick) on both the inner and outer walls and both ends.

[0067] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 2.

[0068] Table 2

[0069] Example 3

[0070] This embodiment provides a waterproof paper straw, which consists of a paper straw body and a PHA waterproof coating coated on the inner and outer walls and cross sections of the paper straw body. The PHA waterproof coating is obtained by film formation of PHA water-based paint.

[0071] The PHA water-based coating is composed of: 100 parts of a PHBHHx aqueous solution with a solid content of 55% (wherein the HHx molar content is 3%), 0.2 parts of a thickener, nanocellulose, and 0.01 parts of a leveling agent, modified polysiloxane.

[0072] Preparation steps of PHA water-based coating: weigh each component according to the mass ratio, stir mechanically at a speed of 1000 rpm for 30 minutes, and remove bubbles by ultrasonication for 20 minutes.

[0073] This embodiment also provides a method for preparing the waterproof paper straw:

[0074] Coating: Use a scraper to apply the PHA water-based coating to the paper surface, and then dry it at a temperature of 150°C for 1 minute.

[0075] Tube Making: Double-sided coated paper is rolled using a paper straw reel. The joints are preheated at 150°C for 0.5 seconds and then hot-pressed at 0.5 MPa. Both ends of the prepared straw are then soaked in a PHA water-based coating for 30 seconds to coat the cross-section evenly. The paper is then dried again at 150°C for 1 minute to form a film. The resulting paper straws have a waterproof coating (approximately 4 microns thick) on both the inner and outer walls and on both ends.

[0076] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 3.

[0077] Table 3

[0078] Example 4

[0079] This embodiment provides a waterproof paper straw, which consists of a paper straw body and a PHA waterproof coating coated on the inner and outer walls and cross sections of the paper straw body. The PHA waterproof coating is obtained by film formation of PHA water-based paint.

[0080] The PHA water-based coating is composed of: 40 parts of P34HB (wherein the molar content of 4HB is 10%) powder, 60 parts of deionized water, 0.2 parts of thickener nanocellulose and 0.01 parts of leveling agent modified polysiloxane.

[0081] Preparation steps of PHA water-based coating: weigh each component according to the mass ratio, stir mechanically at a speed of 1000 rpm for 30 minutes, and remove bubbles by ultrasonication for 20 minutes.

[0082] This embodiment also provides a method for preparing the waterproof paper straw:

[0083] Coating: Use a scraper to apply the PHA water-based coating to the paper surface, and then dry it at a temperature of 150°C for 1 minute.

[0084] Tube Making: Double-sided coated paper is rolled using a paper straw reel. The joints are preheated at 150°C for 0.5 seconds and then hot-pressed at 0.5 MPa. Both ends of the prepared straw are then soaked in a PHA water-based coating for 30 seconds to coat the cross-section evenly. The paper is then dried again at 150°C for 1 minute to form a film. The resulting paper straws have a waterproof coating (approximately 3 microns thick) on both the inner and outer walls and on both ends.

[0085] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 4.

[0086] Table 4

[0087] Example 5

[0088] This embodiment provides a waterproof paper straw, which consists of a paper straw body and a PHA waterproof coating coated on the inner and outer walls and cross sections of the paper straw body. The PHA waterproof coating is obtained by film formation of PHA water-based paint.

[0089] The PHA water-based coating is composed of: 100 parts of a P34HB aqueous solution with a solid content of 40% (wherein the 4HB molar content is 10%), 0.2 parts of a thickener, nanocellulose, and 0.01 parts of a leveling agent, modified polysiloxane.

[0090] Preparation steps of PHA water-based coating: weigh each component according to the mass ratio, stir mechanically at a speed of 1000 rpm for 30 minutes, and remove bubbles by ultrasonication for 20 minutes.

[0091] This embodiment also provides a method for preparing the waterproof paper straw:

[0092] The cut paper is immersed in PHA water-based coating, the coated paper is taken out, rolled into a tube and bonded, and then dried to form a film at a drying temperature of 150°C to obtain waterproof paper straws with a waterproof coating (thickness of about 3 microns) on the inner and outer walls and cross sections at both ends.

[0093] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 5.

[0094] Table 5

[0095] Comparative Example 1

[0096] This comparative example uses water-soluble acrylic resin waterproof coating paper straws, uses a large amount of additives, and the resin is a non-degradable polymer, and the re-slurry utilization will produce microplastic hazards.

[0097] Comparative Example 2

[0098] This comparative example uses PE waterproof coated paper straws, in which PE is a non-degradable polymer that produces harmful microplastics and cannot be recycled.

[0099] Comparative Example 3

[0100] This comparative example uses PLA waterproof coated paper straws, where PLA is a degradable polymer, but it requires industrial composting for degradation, which has harsh conditions and cannot be recycled.

[0101] Comparative Example 4

[0102] This comparative example provides paper straws whose cross sections at both ends are not waterproofed. As a result, both ends easily absorb water and soften, affecting their usability.

[0103] Comparative Example 5

[0104] In this comparative example, PHA powder (same as Example 4) was directly dissolved in chloroform to prepare a 5% dry weight solution, and the mixture was stirred at 2000 rpm for 30 minutes to obtain a PHA coating.

[0105] The coating is applied to the surface of the paper using a wire rod coater and then dried. The double-sided coated paper is rolled using a paper straw rolling machine, and the joints are preheated at 150°C for 0.5s, followed by hot pressing at 0.5MP. The two ends of the prepared straws are then immersed in the PHA coating for 30s to evenly adhere a layer of PHA coating to the cross section of the straws, which is then dried and film-formed again to obtain paper straws with a waterproof coating (about 3 microns thick) on the inner and outer walls and the cross sections of both ends.

[0106] The obtained paper straws were tested and the results are shown in Table 6.

[0107] Table 6

[0108] It can be seen from the above results that the paper straws provided in the embodiments of the present invention are not easy to absorb water and soften, thereby ensuring the performance of use; and no adhesive is required in the preparation process of the paper straws of the present invention. The PHA coating layer can be used as a hot melt adhesive to bond the seams, thereby ensuring the green safety of the waterproof paper straws. The paper straws of the present invention can be directly recycled, without the need to separate the coating and pulp, and no separation cost investment is required.

[0109] 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

[0110] The present invention provides a waterproof paper straw and a preparation method thereof, wherein the waterproof paper straw comprises a paper straw body and a PHA waterproof coating applied on the inner and outer walls and cross sections at both ends of the paper straw body, wherein the PHA waterproof coating is obtained by film formation of a PHA water-based coating, and the PHA water-based coating comprises a PHA suspension and an additive. The present invention applies a PHA waterproof coating on the inner and outer walls and cross sections at both ends of the paper straw body, thereby making the straw less likely to absorb water and soften, thereby ensuring performance. Moreover, in the preparation process of the paper straw of the present invention, no adhesive is required, and the PHA coating layer can be used as a hot melt adhesive to bond the seams, thereby ensuring the green safety of the waterproof paper straw. The paper straw of the present invention can be directly recycled, without the need to separate the coating and the pulp, and without separation cost investment, and has good economic value and application prospects.

Claims

1. A waterproof paper straw, characterized in that: It includes a paper straw body and a PHA waterproof coating coated on the inner and outer walls and cross sections at both ends of the paper straw body. The PHA waterproof coating is obtained by film formation of a PHA water-based coating, and the PHA water-based coating includes a PHA suspension and an additive.

2. The waterproof paper straw according to claim 1, characterized in that: The waterproof paper straw is a straight tube, a curved tube, a sleeve tube or a telescopic tube; And / or, the thickness of the PHA waterproof coating is 3-14 microns.

3. The waterproof paper straw according to claim 1 or 2, characterized in that: The PHA suspension is obtained by dispersing PHA powder in water; Alternatively, the PHA suspension is obtained by centrifugation extraction of PHA fermentation broth.

4. The waterproof paper straw according to claim 3, characterized in that: The mass fraction of PHA in the PHA suspension is 40-60%, and the amount of the additive added does not exceed 5% of the mass of the PHA suspension, preferably does not exceed 2%.

5. The waterproof paper straw according to claim 4, 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 PHA suspension, the added amount of the film former is 0.01-0.5%, the added amount of the wetting agent is 0.01-0.5%, the added amount of the leveling agent is 0.01-0.5%, and the added amount of the thickener is 0.01-0.5%.

6. The waterproof paper straw according to claim 5, characterized in that: The film-forming agent is selected from one or more of diethanol ether, propylene glycol ether, and N-methyl pyrrolidone; 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 polyether siloxane copolymers and modified polysiloxanes; And / or, the thickener is selected from one or more of nanocellulose, sodium hydroxypropyl cellulose, gelatinized starch, sodium alginate, polypyrrolidone; preferably, the gelatinized starch is selected from corn starch. One or more of flour, potato starch, sweet potato starch, and tapioca starch.

7. The waterproof paper straw according to any one of claims 1 to 6, characterized in that: PHA is one or more of PHB, PHV, P34HB, PHBV, PHBHHx, PHBHO, PHBHN, P3HB4HB3HV, and P3HB4HB5HV.

8. The method for preparing the waterproof paper straw according to any one of claims 1 to 7, characterized in that: include: Coat the paper with PHA water-based coating on both sides, dry it at 110-180℃ to form a film, roll the double-sided coated paper into a tube, use the PHA coating layer as a hot melt adhesive to hot-press and bond the joints, cut the target length after the tube is formed, immerse both ends of the straw in PHA water-based coating for end sealing, and take out and dry to form a film.

9. The preparation method according to claim 8, characterized in that: In the heat-compression bonding step, the heating temperature is 110-180° C., the heating time is 0.1-2 s, and the pressure is 0.1-0.5 MPa.

10. The method for preparing the waterproof paper straw according to any one of claims 1 to 7, characterized in that: include: The cut paper is immersed in the PHA water-based coating, the dipped paper is taken out, rolled and bonded, and then dried to form a film.

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