A waterproof paper straw and a preparation method thereof

Abstract

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 coated 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 the PHA waterproof coating on the inner and outer walls and cross sections at both ends of the paper straw body, so that the straw is not easy to absorb water and soften, thereby ensuring the use performance; moreover, in the preparation process of the paper straw of the present invention, there is no need to use adhesives, 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 straws. The paper straw of the present invention can be directly recycled, and there is no need to separate the coating and the pulp, and no separation cost investment.

Description

Technical Field

[0001] 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

[0002] Straws are common items in our daily lives. Their main function is to drink beverages from cups. With the restriction of the use of plastic straws, paper straws are becoming more and more common.

[0003] Currently, commonly used waterproof paper straws are mainly coated with a waterproof layer or laminated. 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 pulp, it will produce microplastic hazards. The laminated layer is usually made of a PE laminated layer, which cannot be reused in pulp and pollutes the environment. The separation of the paper layer and the laminated layer consumes a lot of energy and requires a large investment. The laminated layer also uses a PLA laminated layer. Although this material can be degraded, it requires harsh industrial composting conditions, and the PLA laminated layer cannot be directly reused in pulp, resulting in waste.

[0004] Moreover, in the prior art, it is usually necessary to use an adhesive (hot melt adhesive) to bond the seams when rolling the tube, which increases the complexity of the preparation process and reduces the green safety of the waterproof paper straws. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a waterproof paper straw and a preparation method thereof.

[0006] In a 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 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.

[0007] 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, gas barrier properties, etc.

[0008] The present invention applies a PHA waterproof coating on the inner and outer walls of the paper straw body and the cross sections at both ends. On the one hand, it can be well resistant to water and oil, so that the straw is not easy to absorb water and soften, and lose 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 no separation cost investment. 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, thereby ensuring the green safety of the waterproof paper straw.

[0009] It should be noted that the coating can be applied to the target area of ​​the paper straw by common coating methods in the art, such as scraper coating, gravure printing, spraying, and dipping.

[0010] In the present invention, the waterproof paper straw may be a straight tube, a curved tube, a sleeve tube, a telescopic tube, or other straw forms available on the market.

[0011] In some embodiments of the present invention, the thickness of the PHA waterproof coating is 3-14 microns.

[0012] 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.

[0013] In other embodiments of the present invention, the PHA suspension is obtained by centrifugation of PHA fermentation broth. Preferably, the PHA fermentation broth is cell wall broken.

[0014] It is a common practice to first prepare PHA powder (usually with a particle size of 0.1-5 microns) by biological fermentation, and then disperse it in water to obtain PHA suspension. However, in order to obtain a better dispersion effect and avoid agglomeration, the present invention finds that the PHA solution obtained by treating the PHA fermentation broth can be directly used as the raw material for preparing the PHA water-based coating, and it also saves the process to a certain extent.

[0015] 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%.

[0016] In an embodiment of the present invention, the auxiliary agent includes one or more of a film former, a wetting agent, a leveling agent, and a thickener.

[0017] 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%.

[0018] 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.

[0019] In some embodiments of the present invention, the wetting agent is selected from one or more of alkyl nonylphenol ethoxylate, potassium dodecyl phosphate, sodium dodecyl polyoxyethylene ether sulfate, sodium lauroyl acid, and sodium α-olefin sulfonate.

[0020] In some embodiments of the present invention, the leveling agent is selected from one or more of polyether siloxane copolymers and modified polysiloxanes.

[0021] 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.

[0022] In a preferred embodiment of the present invention, the auxiliary agent only comprises a thickener and a leveling agent.

[0023] 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 monomer is divided into a short chain (3-5 carbons) and a medium-long chain (6-14 carbons) according to the number of carbon atoms. Specifically, the polymerized monomer includes one or more of 3-hydroxypropionic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 5-hydroxyvaleric acid, 3-hydroxycaproic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid or 3-hydroxydodecanoic acid.

[0024] In some embodiments of the present invention, PHA is one or more of PHB, PHV, P34HB, PHBV, PHBHHx, PHBHO, PHBHN, P3HB4HB3HV, and P3HB4HB5HV.

[0025] In some specific 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%, 50%.

[0026] In some specific 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%.

[0027] 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%.

[0028] The preparation method of the PHA water-based coating of the present invention is to mix the components evenly.

[0029] 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 min, and removing bubbles by ultrasonication for 20-30 min.

[0030] In a second aspect, the present invention provides a method for preparing the waterproof paper straw. The method provided by the present invention is not unique, and a suitable preparation method can be selected according to the structure of the paper straw and the conditions of the equipment itself.

[0031] In some embodiments of the present invention, the method for preparing the waterproof paper straw comprises:

[0032] 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.

[0033] The above preparation method is a two-step method, first completing the coating of the paper and then making it into a straw, and finally dipping the cross sections of both ends of the straw into the PHA coating to seal the ends, thereby obtaining a paper straw with PHA coating on the inner and outer walls and both ends.

[0034] 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.

[0035] In a preferred embodiment of the present invention, the preparation method is as follows: the PHA water-based coating is applied to the surface of the straw paper by scraping, gravure printing, etc., and then dried at a temperature of 110-150°C and a drying time of 1-5min. The double-sided coated paper is rolled using a paper straw rolling machine, and the joint is preheated at a temperature of 150-170°C for 0.1-2s, and then hot-pressed and bonded. After the tube is formed, the target length is cut, and the two ends of the prepared straw are immersed in the above-mentioned PHA water-based coating for 30-60s, so that a layer of PHA water-based coating is evenly attached to the cross section of the straw, and then dried at 110-150°C for 1-5min to form a film.

[0036] In other embodiments of the present invention, the method for preparing the waterproof paper straw includes:

[0037] 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.

[0038] This method is a one-step preparation method, which has higher technical requirements than the two-step method. For example, the paper cutting is based on the target structure of the paper straw, and the cutting accuracy affects whether the subsequent tube forming can achieve the expected structure. In addition, the steps of tube rolling, bonding and drying film formation require high coordination, and all surfaces must be sealed at the same time.

[0039] 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.

[0040] 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 at both ends of the paper straw body, the straw is not easy to absorb water and soften, thereby ensuring the use performance. Moreover, there is no need to use adhesives 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 and there is no need to separate the coating and pulp, and no separation cost investment is required. DETAILED DESCRIPTION

[0041] 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 will not be substantially affected.

[0042] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0043] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "specific implementations", or "some specific implementations" etc. means 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 embodiment 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0044] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0046] In the following examples, unless otherwise specified, the “parts” are parts by weight.

[0047] The Chinese full names of the English abbreviations appearing in this article are as follows:

[0048] PHA: Polyhydroxyalkanoate

[0049] PHB: Poly-3-hydroxybutyrate

[0050] PHV: Poly-3-hydroxyvalerate

[0051] P4HB: Poly-4-hydroxybutyrate

[0052] PHBV: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

[0053] P34HB: Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

[0054] PHBHHx: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

[0055] PHBHO: Poly(3-hydroxybutyrate-co-3-hydroxyoctanoate)

[0056] PHBHN: Poly(3-hydroxybutyrate-co-3-hydroxynonanoate)

[0057] P3HB4HB3HV: poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-3-hydroxyvalerate)

[0058] P3HB4HB5HV: poly(3-hydroxybutyrate-co-4-hydroxybutyrate-co-5-hydroxyvalerate).

[0059] Example 1

[0060] The present 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 at both ends of the paper straw body, wherein the PHA waterproof coating is obtained by film formation of a PHA water-based paint.

[0061] The PHA water-based coating is composed of: 100 parts of a P34HB (wherein the 4HB molar content is 10%) aqueous solution with a solid content of 40%, 0.2 parts of a thickener nanocellulose and 0.01 parts of a leveling agent modified polysiloxane.

[0062] 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 ultrasound for 20 minutes.

[0063] This embodiment also provides a method for preparing the waterproof paper straw:

[0064] Coating: Use a scraper to apply the PHA water-based coating to the surface of the paper, and then dry it at a temperature of 150°C for 1 minute.

[0065] Pipe making: 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 0.5MPa. The two ends of the prepared straws are then immersed in PHA water-based paint for 30s, so that a layer of PHA water-based paint is evenly attached to the cross section of the straws, and then dried at 150°C for 1min to form a film, resulting in waterproof paper straws with waterproof coatings (about 3 microns thick) on the inner and outer walls and the cross sections at both ends.

[0066] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 1.

[0067] Table 1

[0068] Test items result Stability at room temperature for 24 hours Unstratified Stability after immersion in water at 25℃ for 24h No blistering, no peeling Stability after immersion in water at 100℃ for 24h No blistering, no peeling Stability after immersion in oil-water mixture at 50℃ for 24h No blistering, no peeling Is the food safe? yes Is it recyclable and degradable? yes Can it be re-pulped? yes

[0069] Example 2

[0070] The present 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 at both ends of the paper straw body, wherein the PHA waterproof coating is obtained by film formation of a PHA water-based paint.

[0071] 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.

[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 ultrasound for 20 minutes.

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

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

[0075] Pipe making: 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 0.5MPa. The two ends of the prepared straws are then immersed in the above-mentioned PHA water-based coating for 30s so that a layer of PHA water-based coating is evenly attached to the cross-section of the straw, and then dried at 150°C for 1min to form a film. Prepare paper straws with a waterproof coating (about 5 microns thick) on the inner and outer walls and both ends.

[0076] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 2.

[0077] Table 2

[0078] Test items result Stability at room temperature for 24 hours Unstratified Stability after immersion in water at 25℃ for 24h No blistering, no peeling Stability after immersion in water at 100℃ for 24h No blistering, no peeling Stability after immersion in oil-water mixture at 50℃ for 24h No blistering, no peeling Is the food safe? yes Is it recyclable and degradable? yes Can it be re-pulped? yes

[0079] Example 3

[0080] The present 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 at both ends of the paper straw body, wherein the PHA waterproof coating is obtained by film formation of a PHA water-based paint.

[0081] 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.

[0082] 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 ultrasound for 20 minutes.

[0083] This embodiment also provides a method for preparing the waterproof paper straw:

[0084] Coating: Use a scraper to apply the PHA water-based coating to the surface of the paper, and then dry it at a temperature of 150°C for 1 minute.

[0085] Pipe making: 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 0.5MPa. The two ends of the prepared straws are then immersed in PHA water-based paint for 30s, so that a layer of PHA water-based paint is evenly attached to the cross section of the straws. The straws are then dried at 150°C for 1min to form a film, resulting in waterproof paper straws with waterproof coatings (about 4 microns thick) on the inner and outer walls and the cross sections at both ends.

[0086] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 3.

[0087] Table 3

[0088] Test items result Stability at room temperature for 24 hours Unstratified Stability after immersion in water at 25℃ for 24h No blistering, no peeling Stability after immersion in water at 100℃ for 24h No blistering, no peeling Stability after immersion in oil-water mixture at 50℃ for 24h No blistering, no peeling Is the food safe? yes Is it recyclable and degradable? yes Can it be re-pulped? yes

[0089] Example 4

[0090] The present 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 at both ends of the paper straw body, wherein the PHA waterproof coating is obtained by film formation of a PHA water-based paint.

[0091] 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.

[0092] 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 ultrasound for 20 minutes.

[0093] This embodiment also provides a method for preparing the waterproof paper straw:

[0094] Coating: Use a scraper to apply the PHA water-based coating to the surface of the paper, and then dry it at a temperature of 150°C for 1 minute.

[0095] Pipe making: 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 0.5MPa. The two ends of the prepared straws are then immersed in PHA water-based paint for 30s, so that a layer of PHA water-based paint is evenly attached to the cross section of the straws, and then dried at 150°C for 1min to form a film, resulting in waterproof paper straws with waterproof coatings (about 3 microns thick) on the inner and outer walls and the cross sections at both ends.

[0096] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 4.

[0097] Table 4

[0098] Test items result Stability at room temperature for 24 hours Unstratified Stability after immersion in water at 25℃ for 24h No blistering, no peeling Stability after immersion in water at 100℃ for 24h No blistering, no peeling Stability after immersion in oil-water mixture at 50℃ for 24h No blistering, no peeling Is the food safe? yes Is it recyclable and degradable? yes Can it be re-pulped? yes

[0099] Example 5

[0100] The present 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 at both ends of the paper straw body, wherein the PHA waterproof coating is obtained by film formation of a PHA water-based paint.

[0101] The PHA water-based coating is composed of: 100 parts of a P34HB (wherein the 4HB molar content is 10%) aqueous solution with a solid content of 40%, 0.2 parts of a thickener nanocellulose and 0.01 parts of a leveling agent modified polysiloxane.

[0102] 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 ultrasound for 20 minutes.

[0103] This embodiment also provides a method for preparing the waterproof paper straw:

[0104] Immerse the cut paper in PHA water-based coating, take out the coated paper, roll it into a tube, bond it, and dry it to form a film at a drying temperature of 150°C to obtain waterproof paper straws with waterproof coating (thickness of about 3 microns) on the inner and outer walls and cross sections at both ends.

[0105] The paper straws obtained in this example were subjected to performance testing, and the results are shown in Table 5.

[0106] Table 5

[0107]

[0108]

[0109] Comparative Example 1

[0110] 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 the harm of microplastics.

[0111] Comparative Example 2

[0112] This comparative example uses PE waterproof coated paper straws, wherein PE is a non-degradable polymer that produces harmful microplastics and cannot be recycled into pulp.

[0113] Comparative Example 3

[0114] This comparative example uses PLA waterproof coated paper straws, wherein PLA is a degradable polymer, but it requires industrial composting for degradation, which has harsh conditions and cannot be recycled.

[0115] Comparative Example 4

[0116] This comparative example provides paper straws whose cross sections at both ends are not waterproofed, and as a result, both ends easily absorb water and soften, affecting their usability.

[0117] Comparative Example 5

[0118] In this comparative example, PHA powder (same as Example 4) was directly dissolved in chloroform to prepare a 5% dry weight solution, and the solution was stirred at a speed of 2000 rpm for a dispersion time of 30 minutes to obtain a PHA coating.

[0119] 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 soaked in the PHA coating for 30s so that a layer of PHA coating is evenly attached to the cross section of the straw, and 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 at both ends.

[0120] The obtained paper straws were tested and the results are shown in Table 6.

[0121] Table 6

[0122] Test items result Stability at room temperature for 24 hours Unstratified Stability after immersion in water at 25℃ for 24h No blistering, no peeling Stability after immersion in water at 100℃ for 24h No blistering, no peeling Stability after immersion in oil-water mixture at 50℃ for 24h No blistering, no peeling Is the food safe? no Is it recyclable and degradable? yes Can it be re-pulped? yes

[0123] From the above results, it can be seen that the paper straws provided in the embodiments of the present invention are not easy to absorb water and soften, thereby ensuring the use performance; and there is no need to use adhesives 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 and there is no need to separate the coating and pulp, and no separation cost investment is required.

[0124] 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 embodiments of the present invention.

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, and polypyrrolidone; preferably, the gelatinized starch is selected from one or more of corn starch, potato starch, sweet potato starch, and cassava 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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