Biodegradable polymer dispersion, method for preparing the same, and biodegradable article using the same

Abstract

The present invention relates to a biodegradable polymer dispersion, a method for preparing the same, and a biodegradable article using the same. The method for preparing a biodegradable polymer dispersion comprises (1) a step of preparing a biodegradable suspension containing polyhydroxyalkanoate (PHA), and (2) a step of filtering the biodegradable suspension using rotor separation, wherein the solid content of the biodegradable polymer dispersion is 10 to 60% by weight, and the polyhydroxyalkanoate (PHA) contains 0.1 to 60% by weight of repeating units derived from 4-hydroxybutyric acid relative to the total weight of the polyhydroxyalkanoate (PHA).

Description

Detailed Description of the Invention

[0001] [Technical Field] The present disclosure relates to a biodegradable polymer dispersion, a method for preparing the same, and a biodegradable article using the same.

[0002] [Background Art] As environmental problems are worsening due to the abuse of synthetic plastics, interest in biodegradable polymers that have physical properties similar to those of synthetic plastics and can be naturally decomposed by microorganisms in soil or the ocean is increasing. Such biodegradable polymers are also widely used as dispersions to form coating layers for extending the lifespan of various products and improving recyclability.

[0003] However, generally, when forming a coating layer only with a dispersion containing a biodegradable polymer, since the melting point (Tm) of the material itself is high, the processability and productivity when forming the coating layer are low, and it is difficult to apply to a mass production system.

[0004] On the other hand, in order to enhance the service life and recyclability of various products such as paper, films, fibers, packaging materials, metals, various containers (for example, bottles, etc.), it is important to enhance mechanical properties such as oil resistance and water resistance. In particular, food packaging materials for packaging foods with a large amount of moisture or oil have problems such as being torn by moisture or oil from the food, contaminating the food, or shortening the service life.

[0005] In order to enhance mechanical properties, water resistance, oil resistance, etc., a process of forming a coating layer on the surface of the product is used, but there is a problem that the biodegradability and recyclability are reduced by the coating layer. For example, the biodegradability of the coating layer component that can enhance water resistance and oil resistance is low, or even if the biodegradability of the coating layer is excellent, the stability against bacteria may be low, resulting in inferior product life. And additional treatment may be required to remove the coating layer from the surface of the used product.

[0006] In addition, since it is difficult to achieve the desired concentration and viscosity of the coating solution, the coating property deteriorates, and the productivity and process efficiency decrease. As a result, it is difficult to ensure the desired physical properties, and there are still limitations in using them for various applications.

[0007] [Summary of the Invention] [Problems to be Solved by the Invention] The problem to be solved in one embodiment is to provide a biodegradable polymer dispersion and a method for preparing the same, which are environmentally friendly due to excellent biodegradability and biocompatibility, can enhance coating properties, water resistance and oil resistance, and can enhance productivity and efficiency.

[0008] Another problem according to another embodiment is to provide a biodegradable article that can improve the lifespan, quality, and recyclability in a biodegradable article using the above biodegradable polymer dispersion.

[0009] [Means for Solving the Problems] One embodiment includes (1) preparing a biodegradable suspension containing polyhydroxyalkanoate (PHA), and (2) filtering the biodegradable suspension using a centrifuge separation, wherein the solid content of the biodegradable polymer dispersion is 10% by weight to 60% by weight, and the polyhydroxyalkanoate (PHA) contains repeating units derived from 4-hydroxybutyric acid at 0.1% by weight to 60% by weight based on the total weight of the polyhydroxyalkanoate (PHA). A method for preparing a biodegradable polymer dispersion is provided.

[0010] According to another embodiment, the centrifuge separation in step (2) can be performed with a rotational force of G'-force exceeding 900 g.

[0011] According to another embodiment, the centrifuge separation in step (2) can be performed with a rotational force of G'-force exceeding 900 g and less than 35,000 g.

[0012] In another embodiment, the rotor separation in step (2) may be performed using a centrifuge.

[0013] According to another embodiment, after step (2), the filter material may be further heated at a temperature of 50-80°C for at least 10 minutes.

[0014] According to another embodiment, after the heat treatment step, a further step may be carried out in which an additive consisting of at least one selected from the group consisting of thickeners, waxes, pH adjusters, defoamers, and antibacterial agents is added.

[0015] According to another embodiment, step (1) may include mixing and dispersing polyhydroxyalkanoate (PHA) and a dispersant.

[0016] According to another embodiment, the dispersant may include at least one selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, methyl polyethylene alkyl ether, sodium dodecylbenzenesulfonate, alkylbenzenesulfonate, nonylphenol ether sulfate, sodium lauryl sulfate, lithium dodecyl sulfate, alkyl phosphoric acid, polypropylene glycol ester, cocobetaine, and lecithin.

[0017] In another embodiment, the distributed processing may be performed at a rotational speed of 500 rpm to 30,000 rpm.

[0018] According to another embodiment, the polyhydroxyalkanoate (PHA) comprises a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer, the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer may contain repeating units derived from 4-hydroxybutyrate in an amount of 18% to 60% by weight relative to the total weight of the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer.

[0019] According to another embodiment, the polyhydroxyalkanoate (PHA) can have a weight-average molecular weight of 550,000 g / mol to 1,000,000 g / mol.

[0020] Another embodiment provides a biodegradable polymer dispersion prepared by the above preparation method.

[0021] According to another embodiment, the viscosity measured by a Brookfield viscometer at 25°C can be greater than 10 cPs and less than or equal to 10,000 cPs.

[0022] According to another embodiment, 15 g / m² of a biodegradable polymer dispersion is applied to the substrate. 2 When a coating layer was formed with the specified application amount and a Cobb water absorption test was conducted in accordance with the TAPPI T441 standard, the water resistance was 3 g / m². 2 ~50g / m 2 That's fine.

[0023] According to another embodiment, 15 g / m² of the above biodegradable polymer dispersion is applied to a substrate, as evaluated according to the TAPPI T559 standard. 2 The oil-resistant kit rating when the coating layer is formed with the amount of coating applied may be 5 or higher.

[0024] According to another embodiment, a biodegradable article is provided comprising a substrate and a biodegradable coating layer formed on at least one surface of the substrate using a biodegradable polymer dispersion.

[0025] [Effects of the invention] A method for preparing a biodegradable polymer dispersion involves filtering a biodegradable suspension containing a polyhydroxyalkanoate (PHA) with a specific amount of repeating units derived from 4-hydroxybutyric acid (4-HB) using rotor separation. This allows for obtaining a dispersion with appropriate viscosity, high purity, and high concentration. When a coating layer is formed using the dispersion, the coated particles can be surface-coated with low thermal energy, enabling accelerated production speed, improved process efficiency, and enhanced dispersibility, coatability, and microbial stability.

[0026] Furthermore, the dispersion prepared according to the above-described method for preparing biodegradable polymer dispersions exhibits excellent dispersibility and coating properties. Biodegradable articles prepared using this dispersion exhibit excellent water resistance, oil resistance, and microbial stability, resulting in extended lifespan and higher quality.

[0027] Therefore, the biodegradable polymer dispersion according to one embodiment is useful as a coating solution and can improve the lifespan, quality, and recyclability of materials such as paper, film, fibers, packaging materials, metals, and various containers. Furthermore, it is useful as an additive to improve the properties of various formulations, making it advantageous in terms of expanding its use. [Brief explanation of the drawing]

[0028] [Figure 1] A flowchart illustrating a schematic method for preparing a biodegradable polymer dispersion according to one embodiment of the present disclosure.

[0029] [Modes for carrying out the invention] The present disclosure will be described in detail below. The present disclosure is not limited to the disclosures shown below and can be modified in various forms without departing from the spirit of the present invention.

[0030] In this specification, the term “equipped with” is used to explicitly identify specific characteristics, areas, processes, treatments, elements, and / or components. Unless explicitly stated otherwise, this does not preclude the presence or addition of other characteristics, areas, processes, treatments, components, elements, and / or components.

[0031] Unless otherwise specified, the numerical values ​​and expressions regarding component amounts, reaction conditions, etc., used herein are understood to be within a range that can be modified by the word "approximately".

[0032] In this specification, terms such as "First," "Second," etc., are used in descriptions of various components. However, these components should not be bound by these terms. These terms are simply used to distinguish one component from another.

[0033] Method for preparing a biodegradable polymer dispersion In one embodiment, the method for preparing the biodegradable polymer dispersion comprises (1) preparing a biodegradable suspension containing polyhydroxyalkanoate (PHA), and (2) filtering the biodegradable suspension using rotor separation, wherein the solid content of the biodegradable polymer dispersion is 10% to 60% by weight, and the polyhydroxyalkanoate (PHA) contains 0.1% to 60% by weight of repeating units derived from 4-hydroxybutyric acid relative to the total weight of the polyhydroxyalkanoate (PHA).

[0034] Unlike conventional methods of physical emulsification using high-temperature sterilization, homogenizers, high pressure, high shear, and colloid mills, the preparation method for biodegradable polymer dispersions utilizes rotor separation, employing sedimentation by rotational force for filtration. This allows for the production of stable biodegradable polymer dispersions with appropriate viscosity, high purity, and high concentration. Furthermore, the resulting biodegradable polymer dispersions can possess excellent dispersibility, coatability, bacterial stability, water resistance, and oil resistance. Moreover, when forming a coating layer on a substrate using the above-mentioned biodegradable polymer dispersion, the surface of the particles to be coated can be coated with low thermal energy, thus accelerating production speed and simplifying the process, which is of great technical significance.

[0035] The steps of the method for preparing a biodegradable polymer dispersion according to this embodiment (S100) will be described in detail below with reference to Figure 1.

[0036] Step (1): Preparation of a biodegradable suspension containing polyhydroxyalkanoate (PHA) (S110) One embodiment of the method for preparing a biodegradable polymer dispersion includes preparing a biodegradable suspension containing polyhydroxyalkanoate (PHA).

[0037] Polyhydroxyalkanoates (PHAs) are naturally occurring thermoplastic polyester polymers that accumulate within microbial cells. As biodegradable materials, they can be composted and ultimately broken down into carbon dioxide, water, and organic waste without producing harmful waste.

[0038] Polyhydroxyalkanoates (PHAs) possess similar physical properties to conventional petroleum-derived synthetic polymers such as polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate terephthalate (PBST), and polybutylene succinate adipate (PBSA), exhibiting complete biodegradability and excellent biocompatibility.

[0039] In particular, unlike other environmentally friendly plastic materials such as PBS, PLA, and PTT, polyhydroxyalkanoates (PHAs) can be synthesized from more than 150 monomers, and depending on the monomer used, hundreds of different PHAs can be prepared. There are hundreds of different types of PHAs depending on the monomer used, and their structures and properties are completely different.

[0040] Polyhydroxyalkanoates (PHAs) in vivo may consist of one type of monomeric repeating unit, or they may be formed by polymerizing one or more types of monomeric repeating units. Specifically, polyhydroxyalkanoates (PHAs) may be homopolyhydroxyalkanoates or polyhydroxyalkanoate copolymers, that is, copolymers in which different repeating units are randomly distributed within the polymer chain.

[0041] Polyhydroxyalkanoates (PHAs) may be obtained by mechanical or physical cell disruption during aqueous purification, or by non-mechanical or chemical cell disruption.

[0042] The weight-average molecular weight of polyhydroxyalkanoates (PHAs) ranges from 10,000 g / mol to 1,000,000 g / mol, 30,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 1,000,000 g / mol, 70,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 800,000 g / mol, 200,000 g / mol to 1,000,000 g / mol, 200,000 g / mol to 800,000 g / mol, and 300,000 g / mol. The available concentrations may be up to 1,000,000 g / mol, 300,000 g / mol to 800,000 g / mol, 400,000 g / mol to 1,000,000 g / mol, 500,000 g / mol to 1,000,000 g / mol, 500,000 g / mol to 800,000 g / mol, 550,000 g / mol to 1,000,000 g / mol, 550,000 g / mol to 800,000 g / mol, 600,000 g / mol to 1,000,000 g / mol, or 600,000 g / mol to 800,000 g / mol, but are not limited to these.

[0043] Polyhydroxyalkanoates (PHAs) may be copolymers containing repeating units derived from at least one monomer selected from the group consisting of 3-hydroxybutyric acid (3-HB), 3-hydroxypropionic acid (3-HP), 3-hydroxyvaleric acid (3-HV), 3-hydroxyhexanoic acid (3-HH), 4-hydroxybutyric acid (4-HB), 4-hydroxyvaleric acid (4-HV), 4-hydroxyhexanoic acid (4-HH), 5-hydroxyvaleric acid (5-HV), and 6-hydroxyhexanoic acid (6-HH), but are not limited thereto.

[0044] Polyhydroxyalkanoates (PHAs) may be crystalline polyhydroxyalkanoates (cPHAs), semi-crystalline polyhydroxyalkanoates (scPHAs), and amorphous polyhydroxyalkanoates (aPHAs), depending on the type of monomer and the content of their repeating units. For example, polyhydroxyalkanoates may be classified as cPHAs, scPHAs, or aPHAs by controlling their crystallinity according to the content of repeating units derived from 4-hydroxybutyric acid (4-HB).

[0045] Specifically, the polyhydroxyalkanoate (PHA) may include a poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid) copolymer comprising repeating units derived from 3-hydroxybutyric acid (3-HB) and repeating units derived from 4-hydroxybutyric acid (4-HB).

[0046] The poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer may contain repeating units derived from 4-hydroxybutyrate (4-HB) in an amount of 0.1% to 60% by weight relative to the total weight of the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer. Specifically, the content of repeating units derived from 4-HB is as follows, relative to the total weight of the copolymer: 0.5% to 60% by weight, 1% to 60% by weight, 5% to 60% by weight, 10% to 60% by weight, 10% to 55% by weight, 10% to 50% by weight, 10% to 45% by weight, 10% to 40% by weight, 15% to 60% by weight, 15% to 55% by weight, 15% to 50% by weight, 15% to 45% by weight, 15% to 40% by weight, 17% to 60% by weight, 17% to 55% by weight, 17% to 50% by weight, 17% to 45% by weight, 17% to 40% by weight, 18% to 60% by weight, 18% to 55% by weight, and 18% to 50% by weight. It can be 18% to 45% by weight, 18% to 40% by weight, 20% to 60% by weight, 20% to 55% by weight, 20% to 50% by weight, 20% to 45% by weight, 20% to 40% by weight, 25% to 60% by weight, 25% to 55% by weight, 25% to 50% by weight, 25% to 45% by weight, 25% to 40% by weight, 28% to 60% by weight, 28% to 50% by weight, 28% to 45% by weight, 28% to 40% by weight, 30% to 60% by weight, 30% to 55% by weight, 30% to 50% by weight, 30% to 45% by weight, 30% to 40% by weight, 20% to 38% by weight, or 30% to 38% by weight.

[0047] For example, polyhydroxyalkanoate (PHA) includes a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer, and the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer may contain repeating units derived from 4-hydroxybutyrate (4-HB) in amounts of 18% to 60% by weight, 26% to 60% by weight, or 30% to 60% by weight, relative to the total weight of the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer.

[0048] The poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid) copolymer may be amorphous PHA (aPHA) as long as the content of repeating units derived from 4-HB is within the above range. A biodegradable polymer dispersion according to one embodiment, in which such amorphous PHA is dispersed, can form a coating layer having excellent mechanical properties, oil resistance, water resistance, and heat resistance.

[0049] Polyhydroxyalkanoates (PHAs) may have a particle shape controlled to a predetermined size. Specifically, the polyhydroxyalkanoate (PHA) particles are biodegradable polymer particles with an average particle diameter (D 50 The average particle size (D) may be 0.5 μm to 5 μm. Specifically, polyhydroxyalkanoate (PHA) has an average particle size (D 50 The average particle size (D) of polyhydroxyalkanoate (PHA) particles can be 0.6 μm or larger, 0.8 μm or larger, or 1.0 μm or larger, and 5 μm or smaller, 4.5 μm or smaller, 4 μm or smaller, 3.5 μm or smaller, 3 μm or smaller, 2.5 μm or smaller, or 2 μm or smaller. 50 As long as the above range is met, a biodegradable polymer dispersion with excellent dispersibility can be obtained. When used to form a coating layer on a substrate (e.g., paper, fiber, metal, etc.), a coating layer with excellent mechanical properties, oil resistance, water resistance, heat resistance, etc. can be formed.

[0050] According to one embodiment, step (1) may include mixing polyhydroxyalkanoate (PHA) and a dispersant and performing a dispersion treatment.

[0051] Specifically, step (1) may include preparing a crude dispersion containing polyhydroxyalkanoate (PHA), mixing the crude dispersion containing polyhydroxyalkanoate (PHA) with a dispersant, and performing a dispersion treatment.

[0052] In other words, polyhydroxyalkanoate (PHA), in the form of a crude dispersion containing polyhydroxyalkanoate (PHA), may be mixed with a dispersant. In such cases, the crude dispersion containing polyhydroxyalkanoate (PHA) may contain polyhydroxyalkanoate (PHA) as a solid content of 20% by weight or less, 15% by weight or less, or 10% by weight or less, relative to the total weight of the crude dispersion. Specifically, the crude dispersion containing polyhydroxyalkanoate (PHA) may be a crude dispersion containing polyhydroxyalkanoate (PHA) with a solid content of 1% to 20% by weight, 1% to 15% by weight, 1% to 10% by weight, 3% to 15% by weight, 3% to 10% by weight, 5% to 15% by weight, or 5% to 10% by weight. Furthermore, the crude dispersion containing polyhydroxyalkanoate (PHA) may also be a solution in which polyhydroxyalkanoate (PHA) is dispersed in an aqueous solvent (e.g., water).

[0053] According to one embodiment, the crude dispersion containing polyhydroxyalkanoate (PHA) may be a crude dispersion of low-concentration amorphous PHA, having a solid content of 5 to 15% by weight, for example, 5 to 10% by weight.

[0054] On the other hand, the dispersant is not particularly limited as long as it is a material that can uniformly disperse polyhydroxyalkanoates (PHAs). Specifically, the dispersant may include at least one selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, methyl polyethylene alkyl ether, sodium dodecylbenzenesulfonate, alkylbenzenesulfonate, nonylphenol ether sulfate, sodium lauryl sulfate, lithium dodecyl sulfate, alkyl phosphoric acid, polypropylene glycol ester, cocobetaine, and lecithin. Specifically, the dispersant may be used dispersed in a solvent. More specifically, the dispersant may be a PVA dispersant in which polyvinyl alcohol (PVA) is dispersed in an aqueous solvent (e.g., water). By using a PVA dispersant, a suspension in which polyhydroxyalkanoates (PHAs) are uniformly dispersed can be obtained.

[0055] The polyvinyl alcohol (PVA) content in the PVA dispersant may be, but is not limited to, 1% to 50% by weight, 1% to 40% by weight, 2% to 30% by weight, 3% to 20% by weight, or 3% to 10% by weight, relative to the total weight of the PVA dispersant.

[0056] Polyvinyl alcohol (PVA) can have a saponification value (degree of hydrolysis) of 1 mol% to 99 mol%, 5 mol% to 99 mol%, 10 mol% to 99 mol%, 20 mol% to 99 mol%, 30 mol% to 99 mol%, 40 mol% to 99 mol%, 45 mol% to 99 mol%, 48 mol% to 99 mol%, 50 mol% to 99 mol%, 60 mol% to 99 mol%, or 70 mol% to 98 mol%, but is not limited to these.

[0057] The dispersant content may range from 0.01% to 30% by weight, based on the solid content of the PHA. For example, the solid content of the dispersant may be, but is not limited to, 0.01% to 20% by weight, 0.01% to 15% by weight, 0.01% to 12% by weight, 0.02% to 8% by weight, 0.05% to 6% by weight, 0.1% to 5% by weight, 0.2% to 7% by weight, 0.3% to 7% by weight, 0.5% to 7% by weight, or 1% to 7% by weight.

[0058] According to one embodiment, the distributed processing may be performed at a rotational speed of 500 rpm to 30,000 rpm.

[0059] The mixing of polyhydroxyalkanoate (PHA) and dispersant can be carried out using a known mixer (e.g., a homomixer). When mixing (stirring) the polyhydroxyalkanoate (PHA) and dispersant through the mixer, the rotation speed of the mixer may be 500 rpm to 30,000 rpm, 1,000 rpm to 30,000 rpm, 1,500 rpm to 30,000 rpm, 2,000 rpm to 30,000 rpm, 2,000 rpm to 25,000 rpm, 2,000 rpm to 20,000 rpm, 2,000 rpm to 15,000 rpm, 3,000 rpm to 15,000 rpm, 4,000 rpm to 10,000 rpm, 5,000 rpm to 8,500 rpm, 5,300 rpm to 8,300 rpm, or 5,500 rpm to 8,200 rpm. The rotational speed can be adjusted according to the type and size of the equipment, but is not limited to this. For example, the rotational speed may be selected according to the impeller diameter size of the device, within the range of 150 cm / s to 2,000 cm / s based on the linear speed of the homomixer.

[0060] Step (2): Filtration of the biodegradable suspension using rotor separation (S120) The method for preparing a biodegradable polymer dispersion according to this embodiment includes filtering the biodegradable suspension obtained in step (1) using rotor separation.

[0061] By incorporating a method for preparing the above-mentioned biodegradable polymer dispersion, including filtration using rotor separation, it is possible to obtain a dispersion with high viscosity, concentration, and purity, in which fine-particle-sized polyhydroxyalkanoates (PHAs) are uniformly dispersed. In particular, the occurrence of aggregation or precipitation can be minimized, thereby increasing the production rate and ensuring process simplification and process efficiency.

[0062] Specifically, step (2) is a filtration method using rotor separation and sedimentation by rotational force. For example, this can be done using a centrifuge, preferably a high-speed centrifuge.

[0063] For example, a biodegradable suspension is placed in the container (drum) of a high-speed centrifuge, and rotated at high speed. This separates the substances in the biodegradable suspension uniformly and finely according to their density and size, and then filters them out.

[0064] When using rotor separation, the degree of aggregation, particulate matter size, solid content, viscosity, application rate, bacterial stability, water resistance, and oil resistance of the final biodegradable polymer dispersion may vary depending on the relative centrifugal force (RCF).

[0065] Relative centrifugal force refers to the ratio of gravity to centrifugal force acting on particles in a biodegradable suspension, and can be denoted as G'-force.

[0066] According to one embodiment, the rotational force of the rotor separation minimizes the occurrence of aggregation or precipitation, further increasing productivity and enabling the acquisition of a dispersion with optimal purity, concentration, and viscosity.

[0067] This can be an important factor in improving stability against bacteria, oil resistance, and water resistance.

[0068] Specifically, the rotor separation in process (2) may be performed with a rotational force that results in a G'-force of over 900g. For example, the rotational force in the G'-force for rotor separation in process (2) can be 1,000g or more, 1,500g or more, 2,000g or more, 3,000g or more, 4,000g or more, 5,000g or more, 7,000g or more, 8,000g or more, 10,000g or more, 12,000g or more, 15,000g or more, 17,000g or more, 18,000g or more, or 20,000g or more, less than 35,000g, 30,000g or less, 29,000g or less, 28,000g or less, 25,000g or less, 23,000g or less, 22,000g or less, or 21,000g or less. For example, rotor separation in step (2) may be performed with a rotational force of G'-force in the following ranges: over 900g and under 35,000g, 1,000g to 30,000g, 3,000g to 30,000g, 5,000g to 30,000g, 7,000g to 30,000g, 10,000g to 30,000g, 15,000g to 30,000g, 15,000g to 25,000g, 18,000g to 30,000g, 18,000g to 25,000g, or 18,000g to 22,000g. By using a rotational force within the above range for rotor separation, aggregation can be minimized, a dispersion with high viscosity, concentration, and purity can be obtained, improving coatability, bacterial stability, water resistance, and oil resistance, thereby increasing productivity and process efficiency.

[0069] Specifically, by rotating a cylindrical drum with a diameter of approximately 45 cm in a high-speed centrifuge at speeds of approximately 2,000 to 15,000 rpm, over 3,000 to less than 15,000 rpm, 3,500 to 14,000 rpm, and 5,000 to 13,000 rpm, a rotational force of over 900 g of G'-force can be generated. The G'-force may vary depending on the rotation speed and the diameter of the centrifuge, such as a high-speed centrifuge.

[0070] On the other hand, according to one embodiment, an additive may be added to the biodegradable suspension before rotor separation. The additive is not particularly limited as long as it is a known additive. Specifically, the additive may include at least one selected from the group consisting of thickeners, waxes, pH adjusters, defoamers, and antimicrobial agents. More specifically, the additive may include a defoamer.

[0071] The defoaming agent is not particularly limited as long as it is a known substance. Specifically, the defoaming agent may include at least one selected from the group consisting of inorganic particulate defoaming agents, oil-based defoaming agents, and polymer-based defoaming agents. More specifically, the defoaming agent may include at least one selected from the group consisting of silicone-based defoaming agents, mineral oil-based defoaming agents, and polysiloxane-based defoaming agents.

[0072] pH adjusters, thickeners, waxes, and antimicrobial agents are not particularly limited as long as they are commonly known substances. For example, they may include the additives listed in step (3).

[0073] According to one embodiment, a PHA suspension with high viscosity, concentration, and purity (e.g., amorphous PHA suspension) is obtained by first adding an antifoaming agent to the above suspension, then performing a high-speed dispersion treatment, and then filtering using rotor separation. In this case, the high-speed dispersion treatment is the same as that described in step (1) (dispersion treatment in step (1)).

[0074] Step (3): The filtered product is subjected to heat treatment (S130). Furthermore, the method for preparing a biodegradable polymer dispersion according to one embodiment may further include subjecting the filtered result obtained in step (2) to a heat treatment.

[0075] Specifically, step (3) is a step in which the suspension is heated and sterilized at a temperature significantly lower than the conventional high-temperature sterilization temperature (for example, 145°C or higher).

[0076] More specifically, after step (2), a further step may be performed in which the filtered result is subjected to heat treatment at 50-80°C for 10 minutes or more. For example, the heat treatment may be carried out at 50-75°C, 50-70°C, or 60-70°C for 15-60 minutes, 15-50 minutes, 15-40 minutes, 20-60 minutes, 20-50 minutes, or 20-40 minutes.

[0077] By heat-treating the above suspension, sterilization can be efficiently performed while minimizing changes in the physical properties of the biodegradable polymer (e.g., polyhydroxyalkanoate (PHA)) contained in the suspension. By preparing the biodegradable polymer dispersion according to the above embodiment using the heat-treated suspension, a biodegradable polymer dispersion with excellent stability against bacteria and dispersion stability can be provided.

[0078] Alternatively, after the heat treatment step, a step of adding an additive to the heat-treated suspension may be performed. The additive is not particularly limited as long as it is a known additive.

[0079] Specifically, the additives to be added may be mixed into the above-mentioned suspension that has been subjected to heat treatment.

[0080] More specifically, after the heat treatment step, a further step may be performed to add an additive containing at least one selected from the group consisting of thickeners, waxes, pH adjusters, defoamers, and antimicrobial agents. The additive may contain two or more selected from the group consisting of thickeners, waxes, pH adjusters, defoamers, and antimicrobial agents. The additives should be selected according to the desired physical properties and application.

[0081] Furthermore, the additives may be added simultaneously or in stages.

[0082] According to one embodiment, the additive may be added at the same time.

[0083] According to another embodiment, the additives may be added in stages. By adding the additives in stages, a biodegradable polymer dispersion can be efficiently prepared from the suspension.

[0084] The thickening agent is not particularly limited as long as it is a substance that can control the viscosity of the above suspension. Specifically, the thickening agent may include at least one selected from the group consisting of starch, xanthan gum, guar gum, carboxymethylcellulose (CMC), and carrageenan gum.

[0085] The wax is not particularly limited as long as it is a known substance. Specifically, it may include at least one selected from the group consisting of beeswax, soy wax, and carnauba wax.

[0086] The defoaming agent is not particularly limited as long as it is a known substance. Specifically, it may include at least one selected from the group consisting of inorganic particulate defoaming agents, oil-based defoaming agents, and polymer-based defoaming agents. For example, the defoaming agent may include at least one selected from the group consisting of silicone-based defoaming agents, mineral oil-based defoaming agents, and polysiloxane-based defoaming agents.

[0087] The antibacterial agent is not particularly limited as long as it is a commonly known substance. Specifically, the antibacterial agent may include at least one selected from the group consisting of alcohol, salicylic acid, benzoic acid, licorice extract, yucca extract, chito-oligosaccharide, chitosan, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), octylisothiazolon (OIT), and benzisothiazolon (BIT).

[0088] A pH adjuster is a substance added to a solution to adjust its pH. A pH adjuster may include both a pH lowering agent and a pH raising agent. Specifically, the pH lowering agent may be a strongly acidic substance such as sulfuric acid or hydrochloric acid, or an aqueous solution of an ammonium salt. The pH raising agent may be a basic substance such as ammonia water, sodium hydroxide, lithium hydroxide, potassium hydroxide, or an aqueous solution of an acetate, but is not limited to these. For example, the pH adjuster may be at least one selected from the group consisting of acetic acid, lactic acid, hydrochloric acid, phosphoric acid, sodium hydroxide, citric acid, malic acid, fumaric acid, potassium phosphate, sodium bicarbonate, and sodium phosphate.

[0089] The amounts added (used) of thickeners, waxes, pH adjusters, defoamers, and antibacterial agents can be 0.001% to 20% by weight, 0.005% to 20% by weight, 0.01% to 15% by weight, 0.01% to 12% by weight, 0.01% to 10% by weight, 0.01% to 8% by weight, 0.01% to 5% by weight, 0.2% to 4.5% by weight, 0.2% to 4% by weight, or 0.5% to 3% by weight, respectively, based on the total weight of the solid content of the biodegradable polymer dispersion.

[0090] The solid content of the biodegradable polymer dispersion prepared by the above preparation method may be 10% to 60% by weight. Specifically, the solid content of the biodegradable polymer dispersion may be 20% to 60% by weight, 20% to 50% by weight, 30% to 60% by weight, 30% to 50% by weight, or 35% to 45% by weight.

[0091] For example, according to one embodiment, an amorphous biodegradable polymer dispersion with a solid content of, for example, 20% to 50% by weight may be obtained using a crude dispersion of amorphous PHA with a solid content of, for example, 10% by weight or less.

[0092] Specifically, for example, an optimal amorphous biodegradable polymer dispersion with a solid content of, for example, 20-50% by weight and a viscosity of 20-10,000 cPs can be obtained using a crude dispersion of amorphous PHA with a solid content of 10% by weight or less.

[0093] As described above, the method for preparing a biodegradable polymer dispersion of the present invention is characterized by filtering a biodegradable suspension containing a polyhydroxyalkanoate (PHA) containing repeating units derived from a specific amount of 4-hydroxybutyric acid (4-HB) using rotor separation and sedimentation by rotational force. This makes it possible to obtain a stable dispersion with appropriate viscosity, high purity, and high concentration. Furthermore, when forming a coating layer using the dispersion, the coating particles can be surface-coated with low thermal energy, thus enabling high-speed production and process simplification.

[0094] Biodegradable polymer dispersion According to one embodiment, the biodegradable polymer dispersion prepared by the above preparation method is provided. Specifically, it is prepared by the above preparation method for biodegradable polymer dispersions and has a solid content of 10% to 60% by weight. The solid content of the biodegradable polymer dispersion is as described above.

[0095] The biodegradable polymer dispersion prepared by the method for preparing biodegradable polymer dispersions has high viscosity, high concentration, and high purity.

[0096] Because of its excellent dispersibility and applicability, it can be used as a coating solution to enhance the durability and recyclability of various papers, films, fibers, packaging materials, metals, and various containers, making it advantageous for use in these products. Furthermore, the above biodegradable polymer dispersion exhibits excellent bacterial stability, improving the lifespan and quality of biodegradable products. Coating layers formed using the same material can exhibit excellent water and oil resistance. The biodegradable polymer dispersion possessing the above characteristics can be advantageously used as an additive to various formulations and as a physical property improver, thus offering advantages in terms of expanding its applications.

[0097] A biodegradable polymer dispersion according to one embodiment comprises polyhydroxyalkanoate (PHA) particles, which are biodegradable polymer particles as described above, the dispersant as described above, the additive as described above, and a dispersion solvent (for example, water).

[0098] Furthermore, the above-mentioned biodegradable polymer dispersion may contain an additive comprising at least one selected from the group consisting of thickeners, waxes, pH adjusters, defoamers, and antibacterial agents.

[0099] There are no particular restrictions on the additives used; the specific types are as described above.

[0100] A biodegradable polymer dispersion according to one embodiment may have a viscosity necessary to ensure applicability and workability. Specifically, a biodegradable polymer dispersion according to one embodiment may have a viscosity measured by a Brookfield viscometer at 25°C that is greater than 10 cPs and greater than 10,000 cPs. Specifically, the viscosity of the biodegradable polymer dispersion at 25°C may be 20 cPs to 10,000 cPs, 30 cPs to 10,000 cPs, 50 cPs to 10,000 cPs, 100 cPs to 10,000 cPs, 200 cPs to 10,000 cPs, 300 cPs to 10,000 cPs, 400 cPs to 10,000 cPs, 500 cPs to 10,000 cPs, and 300 cPs. The cPs can range from s to 8,000 cPs, 300 cPs to 6,000 cPs, 300 cPs to 5,000 cPs, 300 cPs to 4,000 cPs, 300 cPs to 3,000 cPs, 300 cPs to 2,000 cPs, 300 cPs to 1,000 cPs, 200 cPs to 2,000 cPs, 300 cPs to 1,500 cPs, 350 cPs to 1,200 cPs, 400 cPs to 1,000 cPs, 400 cPs to 900 cPs, 400 cPs to 800 cPs, 400 cPs to 700 cPs, 500 cPs to 700 cPs, and 500 cPs to 600 cPs. If the biodegradable polymer dispersion has a viscosity within the above range, it may be advantageous in terms of obtaining the desired effect.

[0101] The biodegradable polymer dispersion according to one embodiment may have a pH in order to ensure long-term storage stability and the like. Specifically, the biodegradable polymer dispersion according to one embodiment can have a pH of 5 to 11, and more specifically, it can be 6 to 11, 6 to 10, or 8 to 10, but is not limited thereto.

[0102] On the other hand, when a coating layer is formed on a substrate with an application amount of 15 g / m 2 from the above biodegradable polymer dispersion, and a Cobb water absorption test conforming to the TAPPI T441 standard is performed, the water resistance may be 3 g / m 2 to 50 g / m 2 .

[0103] Specifically, the water resistance of the coating layer is 3 g / m 2 to 40 g / m 2 , 3 g / m 2 to 30 g / m 2 , 3 g / m 2 to 30 g / m 2 less than, 3 g / m 2 to 25 g / m 2 , 3 g / m 2 to 20 g / m 2 , 3 g / m 2 to 15 g / m 2 , 5 g / m 2 to 18 g / m 2 , or 5 g / m 2 to 15 g / m 2 .

[0104] The water resistance may be measured by a Cobb water absorption test (test conditions: 25 ml, 10 minutes) conforming to the TAPPI T441 standard.

[0105] Also, when a coating layer is formed on a substrate evaluated according to the TAPPI T559 standard with an application amount of 15 g / m 2 from the above biodegradable polymer dispersion, the oil resistance kit rating may be 5 or more.

[0106] Specifically, the kit evaluation reagent is dropped from a specific height onto the surface of a biodegradable article (5 cm wide, 15 cm long) made from a biodegradable polymer dispersion, specifically onto a coating layer formed on one side of the biodegradable article. After a certain period of time (e.g., about 15 seconds), any excess kit evaluation reagent is wiped off with a clean tissue or cotton swab, and the surface is immediately visually inspected to perform the oil resistance kit rating.

[0107] In this test, if the surface becomes significantly darker compared to the surface where the test reagent was not applied, it is considered a failure; otherwise, it is considered a pass. The above test is repeated in order of the kit rating reagents, starting with those with the highest evaluation, until a kit rating reagent is observed to be a failure. Alternatively, the oil resistance kit rating may be the average of the highest-passing kit rating reagents.

[0108] Oil resistance kit ratings are classified on a scale from 1 to 12. A higher number indicates better oil resistance.

[0109] A biodegradable polymer dispersion according to one embodiment exhibits excellent stability against bacteria, thus providing superior long-term storage stability. Due to its excellent applicability, it can be used as a coating solution to enhance the durability and recyclability of various papers, films, fibers, packaging materials, metals, and various containers, making it advantageously applicable to these products.

[0110] biodegradable articles According to one embodiment, a biodegradable article is provided comprising a substrate and a biodegradable coating layer formed on at least one surface of the substrate using a biodegradable polymer dispersion.

[0111] The substrate is not particularly limited as long as it can form a biodegradable coating layer on its surface from a biodegradable polymer dispersion. The substrate may be at least one selected from the group consisting of, for example, paper, kraft paper, woven fabric, knitted fabric, nonwoven fabric, polyester films such as polyethylene terephthalate (PET), polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate terephthalate (PBST), and polyimide (PI) films.

[0112] Specifically, the base material may be preferably a single-material base material from the viewpoint of improving the coating properties of the base material. The base material may be, but is not limited to, paper, kraft paper, woven fabric, or nonwoven fabric. Furthermore, if the base material is paper or kraft paper, it may be more advantageous in providing environmentally friendly packaging materials because it has better biodegradability than other plastic materials.

[0113] The substrate may have a thickness of 15 μm or more. For example, the thickness of the substrate may be 15 μm or more, 20 μm or more, 50 μm or more, 70 μm or more, 100 μm or more, 130 μm or more, 150 μm or more, 200 μm or more, 300 μm or more, or 500 μm or more.

[0114] Furthermore, the base weight per unit area of ​​the substrate is 30g / m². 2 ~500g / m 2 This may also be the case. For example, if the base material is paper, kraft paper, woven fabric, knitted fabric, or nonwoven fabric, the base weight of the base material is 30 g / m². 2 ~500g / m 2 30g / m 2 ~350g / m 2 30g / m 2 ~200g / m 2 50g / m 2 ~200g / m 2 80g / m 2 ~200g / m 2 100g / m 2 ~200g / m 2 130g / m2 ~190g / m 2 150g / m 2 ~185g / m 2 , or 120g / m 2 ~320g / m 2 That's fine.

[0115] On the other hand, a barrier layer may be provided on at least one surface of the substrate. The surface of the substrate may be coated with an environmentally friendly barrier film to provide moisture and / or oxygen barrier properties, and a functional coating layer having antistatic or adhesive properties may also be formed. The functional coating layer may include a primer coating layer and / or an adhesive coating layer to the extent that the desired effect is not impaired, and these layers may have commonly used materials and properties.

[0116] For example, the substrate may comprise a barrier layer or a functional coating layer, and the barrier layer or functional coating layer may be located on one side of the substrate or on one side of the biodegradable coating layer.

[0117] Furthermore, the biodegradable coating layer may have a thickness of 5 μm to 50 μm, 5 μm to 40 μm, or 6 μm to 30 μm.

[0118] Biodegradable articles equipped with a biodegradable coating layer may include, but are not limited to, packaging materials, cardboard boxes, shopping bags, disposable tableware, packaging containers, paper straws, etc.

[0119] The above-mentioned biodegradable articles offer excellent biodegradability and recyclability, as well as superior water resistance, oil resistance, and antibacterial resistance, enabling extended lifespan and higher quality.

[0120] The water resistance, oil resistance, and antibacterial properties of the above-mentioned biodegradable articles are as described in the above-mentioned biodegradable polymer dispersion.

[0121] Method for preparing biodegradable articles According to one embodiment, a method for preparing the above-mentioned biodegradable article is provided.

[0122] The above method for preparing a biodegradable article includes the steps of preparing a biodegradable polymer dispersion and forming a biodegradable coating layer on at least one surface of a substrate using the biodegradable polymer dispersion. For example, a film-like biodegradable article having a biodegradable coating layer may be obtained by the above preparation method.

[0123] The method for preparing the biodegradable polymer dispersion is as described above, and the base material is also as described above.

[0124] This may also be a step of forming a biodegradable coating layer by applying a biodegradable polymer dispersion to at least one surface of a substrate and drying it.

[0125] Specifically, the amount of the biodegradable polymer dispersion applied to at least one surface of the substrate is 5 g / m². 2 ~100g / m 2 5g / m 2 ~85g / m 2 5g / m 2 ~70g / m 2 , 8g / m 2 ~60g / m 2 9g / m 2 ~50g / m 2 5g / m 2 ~50g / m 2 , 6g / m 2 ~40g / m 2 7g / m 2 ~30g / m 2 10g / m 2 ~40g / m 2 , or 10g / m 2 ~30g / m 2 This is also acceptable. By ensuring that the coating amount meets the above range, coating performance, productivity, and processability can be further improved.

[0126] Furthermore, the coating may be performed only once to form a single layer, or it may be performed two or more times to form multiple coating layers. The amount of coating can be adjusted within the above range according to the desired number of coating layers. Specifically, the amount of coating may be the total amount applied to multiple coating layers.

[0127] After applying the biodegradable polymer dispersion onto the substrate, it may be dried at 50°C to 200°C for 5 seconds to 30 minutes. For example, it may be done at 60°C to 200°C, 80°C to 185°C, 80°C to 150°C, or 80°C to 130°C for 5 seconds to 30 minutes, 10 seconds to 20 minutes, 10 seconds to 10 minutes, 10 seconds to 5 minutes, 10 seconds to 3 minutes, 10 seconds to 1 minute, 10 seconds to 50 seconds, or 10 seconds to 30 minutes.

[0128] The formation of the biodegradable coating layer is not particularly limited as long as it is a commonly used coating process. For example, the biodegradable coating layer may be formed by gravure coating, slot coating, doctor blade coating, spray coating, bar coating, spin coating, or in-line coating, but is not limited to these.

[0129] When producing biodegradable articles using a biodegradable polymer dispersion, coating can be performed with low thermal energy, thus ensuring high speed and process simplification, and easily achieving desired physical properties.

[0130] Mode of the invention The present disclosure will be further described below with reference to examples, but the scope of the present disclosure is not limited to these examples.

[0131] [Examples] Example 1 [Preparation of biodegradable polymer dispersion] Step (1): Preparation of a biodegradable suspension containing polyhydroxyalkanoate (PHA) Distilled water was added to polyhydroxyalkanoate (PHA) particles (Mw: 600,000 g / mol, 4-HB-derived repeating unit content: 34% by weight, manufacturer: CJ CheilJedang) obtained by physical crushing to obtain a crude dispersion of low-concentration amorphous PHA with a solid content of 8% by weight.

[0132] 50 liters of crude PHA dispersion and 5 parts by weight of polyvinyl alcohol (PVA, degree of saponification 80 mol%, average degree of polymerization 13,000, manufacturer: KURARAY) were added to a homomixer (product name: Homomixer Mark2, manufacturer: PRIMIX) per 100 parts by weight of solids of PHA. High-speed dispersion treatment was performed at a linear speed of 1,250 cm / s to prepare a biodegradable suspension containing a low concentration of amorphous PHA.

[0133] Step (2): Filtration of the biodegradable suspension using rotor separation. To the biodegradable suspension obtained in step (1) above, 0.5% by weight of a polysiloxane-based antifoaming agent was added, and the mixture was rapidly stirred under the same conditions as above. The mixture was filtered using a high-speed centrifuge (product name: Clara20, manufacturer: Alfa Laval, cylindrical drum diameter approximately 45 cm) with a rotational force of approximately 20,500 g under G'-force to obtain an amorphous suspension with a solid content of 40% by weight.

[0134] Step (3): Heat treatment of the filtered suspension The highly concentrated amorphous suspension obtained in step (2) was heated at approximately 60°C for about 20 minutes while being stirred at a low speed, and then cooled to room temperature.

[0135] Subsequently, additives such as 0.7% by weight of carrageenan gum as a thickening agent and 0.01% by weight of polysiloxane as an antifoaming agent were added to the solid content of the high-concentration amorphous suspension to obtain a biodegradable polymer dispersion (PHA dispersion).

[0136] [Production of biodegradable materials (films)] A biodegradable polymer dispersion was applied to the substrate using a bar coater (Meyer bar coater, manufacturer: RDS) at a rate of 15 g / m². 2 A biodegradable article (film) was prepared by applying a coating to a certain extent and drying it at approximately 100°C for approximately 20 seconds to form a biodegradable coating layer. Here, the base material was uncoated kraft paper with a basis weight of 180 g / m². 2 That is the case.

[0137] Example 2 In step (1), the PHA dispersion and membrane were prepared using the same procedure as in Example 1, except that the type of PHA (solid content 9% by weight, repeating unit content derived from 4-HB: 50% by weight, Mw: 800,000 g / mol, manufacturer: CJ CheilJedang) was changed when preparing the crude PHA dispersion.

[0138] Example 3 In step (1), the PHA dispersion and membrane were prepared using the same procedure as in Example 1, except that the type of PHA (solid content 8% by weight, repeating unit content derived from 4-HB: 25% by weight, Mw: 700,000 g / mol, manufacturer: CJ CheilJedang) was changed when preparing the crude PHA dispersion.

[0139] Comparative Example 1 In step (1), the PHA dispersion and membrane were prepared using the same procedure as in Example 1, except that the type of PHA (solid content 8% by weight, repeating unit content derived from 4-HB: 17% by weight, Mw: 700,000 g / mol, manufacturer: CJ CheilJedang) was changed when preparing the crude PHA dispersion.

[0140] Comparative Example 2 In step (1), the PHA dispersion and membrane were prepared using the same procedure as in Example 1, except that the type of PHA (solid content 8% by weight, repeating unit content derived from 4-HB: 25% by weight, Mw: 500,000 g / mol, manufacturer: CJ CheilJedang) was changed when preparing the crude PHA dispersion.

[0141] Comparative Example 3 The PHA dispersion and film were prepared using the same procedure as in Example 1, except that the biodegradable suspension was filtered using a high-speed centrifuge with a G'-force of approximately 900 g.

[0142] Comparative Example 4 PHA dispersions and films were prepared using the same procedure as in Example 1, except that the biodegradable suspension was filtered using a high-speed centrifuge with a G'-force of approximately 35,000 g.

[0143] Comparative Example 5 In step (2), the PHA dispersion and film were prepared using the same procedure as in Example 1, except that filtration was performed using a filter press (product name: F-SA-1000-40, manufacturer: APK) instead of a high-speed centrifuge.

[0144] For each of the examples and comparative examples, the biodegradable polymer dispersion (PHA dispersion) and film were evaluated as follows. Test example Test Example 1: Preparation of Emulsified Substances The preparation of emulsions from biodegradable polymer dispersions was evaluated from the perspective of solid content and aggregation, as shown in Table 1 below. Aggregation was observed with the naked eye.

[0145] ◎: When the solid content of the biodegradable polymer dispersion was 30% by weight or more, there was no aggregation and emulsification was good.

[0146] ○: When the solid content of the biodegradable polymer dispersion was 8% by weight or more and less than 30% by weight, slight aggregation occurred.

[0147] △: When the solid content of the biodegradable polymer dispersion was 5% by weight or more and less than 8% by weight, preparation was possible, but aggregation occurred.

[0148] ×: If the solid content of the biodegradable polymer dispersion was less than 5% by weight, preparation by aggregation or recovery of fine particles was impossible.

[0149] Test Example 2: Solid Content The biodegradable polymer dispersion was dried at 170°C for 10 minutes, and then the amount of water evaporated was measured. The results are shown in Table 1 below.

[0150] Test Example 3: Viscosity Measurements were taken using a DV-1 VISCOMETER (BROOKFIELD) instrument at spindle number 63 and 12 rpm. The results are shown in Table 1 below.

[0151] Test Example 4: Evaluation of Stability Against Bacteria Three types of dry media (3M Petrifilm) were prepared for general bacteria, fungi, and E. coli. A diluent was prepared by diluting 1 ml of PHA dispersion 10-fold in 9 ml of sterile water. After vortexing for 1 minute, 1 ml was taken and evenly dispensed into each dry media. The general bacteria dry media were then incubated at 35°C for 48 hours, the fungal dry media at 25°C for 48 hours, and the E. coli dry media at 35°C for 24 hours. At the end of incubation, the number of colonies was measured and evaluated as follows.

[0152] The results are shown in Table 1 below. Contamination: If the number of colonies measured is 10 or more. Path: If the number of measured colonies is less than 10.

[0153] Test Example 5: Application Amount When preparing films by coating the biodegradable polymer dispersions prepared in the examples and comparative examples onto a substrate, a Meyer bar coater #18 was used. The coated layer was dried at approximately 100°C for 20 seconds, and the coating amount was measured. The results are shown in Table 1 below.

[0154] Test Example 6: Measurement of Water Resistance Each biodegradable article prepared in the examples and comparative examples was subjected to the Cobb water absorption test (test conditions: 25 ml, 10 minutes) in accordance with the TAPPI T441 standard. The results are shown in Table 1 below.

[0155] Test Example 7: Measurement of Oil Resistance The oil-resistant kit rating of each biodegradable article prepared in the examples and comparative examples was evaluated according to the TAPPI T559 standard.

[0156] Specifically, five drops of the kit evaluation reagent were dropped from a height of 2.54 cm onto the surface of biodegradable articles (5 cm wide, 15 cm long) prepared from the biodegradable polymer dispersions of the examples and comparative examples, specifically onto the coating layer formed on one side of the biodegradable article. After 15 seconds, any excess kit evaluation reagent was wiped off with a clean tissue or cotton swab, and the surface was immediately inspected visually.

[0157] The coating surface was judged as failing if it became significantly darker compared to a surface where the test reagent was not applied; otherwise, it passed. The above test was repeated for high-rated kit rating test reagents until one of them failed. The oil resistance kit rating was calculated as the average of the highest-passing kit rating reagents.

[0158] Oil resistance kit ratings are classified on a scale from 1 to 12. A higher number indicates better oil resistance. The results are shown in Table 1 below.

[0159] [Table 1]

[0160] Table 1 above shows that the biodegradable polymer dispersions prepared in the examples are all highly concentrated dispersions and exhibit excellent viscosity, stability against bacteria (bacterial stability), application rate, water resistance, and oil resistance.

[0161] Specifically, the biodegradable polymer dispersions prepared in Examples 1-3 all had a solid content of 40% by weight or more and a viscosity of 500-600 cPs. These dispersions (emulsifies) were highly viscous and concentrated, free from bacterial contamination, and exhibited excellent stability (resistance) to bacteria. Furthermore, they had a water resistance of 8-15 g / m². 2 Furthermore, all of them had an oil resistance kit rating of 5 or higher, indicating excellent performance in all cases.

[0162] In contrast, the biodegradable polymer dispersions prepared in Comparative Examples 1, 2, and 4 could not be emulsified by aggregation. The biodegradable polymer dispersion prepared in Comparative Example 3 could be prepared as an emulsion, but its solid content was 9% by weight and its viscosity was 20 cPs, which was significantly lower than that of the biodegradable polymer dispersions prepared in Examples 1-3. The oil-resistant kit rating was 1.

[0163] On the other hand, the biodegradable polymer dispersion prepared in Comparative Example 5 had a low concentration and low viscosity, making it impossible to recover the fine particles. From the above results, it can be seen that the method for preparing biodegradable polymer dispersions according to the examples is excellent in productivity and process efficiency, and can easily produce biodegradable polymer dispersions with high viscosity, concentration, and purity. Furthermore, the biodegradable polymer dispersions prepared by the above method have significantly improved water and oil resistance when applied to a substrate, in addition to their stability against bacteria, and can be advantageously used as coatings to improve the lifespan, quality, and recyclability of various products.

Claims

1. (1) Prepare a biodegradable suspension containing polyhydroxyalkanoate (PHA), (2) Filtering the biodegradable suspension using rotor separation, A method for preparing a biodegradable polymer dispersion, wherein the solid content of the biodegradable polymer dispersion is 10% to 60% by weight, and the polyhydroxyalkanoate (PHA) contains 0.1% to 60% by weight of repeating units derived from 4-hydroxybutyric acid relative to the total weight of the polyhydroxyalkanoate (PHA).

2. The method for preparing a biodegradable polymer dispersion according to claim 1, wherein the rotor separation in step (2) is performed with a rotational force of G'-force exceeding 900 g.

3. The method for preparing a biodegradable polymer dispersion according to claim 2, wherein the rotor separation in step (2) is performed with a rotational force of G'-force greater than 900 g and less than 35,000 g.

4. The method for preparing a biodegradable polymer dispersion according to claim 1, wherein the rotor separation in step (2) is performed using a centrifuge.

5. A method for preparing a biodegradable polymer dispersion according to claim 1, further comprising heating the filtrate at a temperature of 50°C to 80°C for at least 10 minutes after step (2).

6. The method for preparing a biodegradable polymer dispersion according to claim 5, further comprising adding, after the heat treatment step, an additive comprising at least one selected from the group consisting of a thickener, a wax, a pH adjuster, an antifoaming agent, and an antibacterial agent.

7. The method for preparing a biodegradable polymer dispersion according to claim 1, wherein step (1) includes mixing the polyhydroxyalkanoate (PHA) and a dispersant and performing a dispersion treatment.

8. A method for preparing a biodegradable polymer dispersion according to claim 7, wherein the dispersant comprises at least one selected from the group consisting of polyvinyl alcohol, polyvinylpyrrolidone, methyl polyethylene alkyl ether, sodium dodecylbenzenesulfonate, alkylbenzenesulfonate, nonylphenol ether sulfate, sodium lauryl sulfate, lithium dodecyl sulfate, alkyl phosphoric acid, polypropylene glycol ester, cocobetaine, and lecithin.

9. A method for preparing a biodegradable polymer dispersion according to claim 1, wherein the polyhydroxyalkanoate (PHA) comprises a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer, and the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer contains repeating units derived from 4-hydroxybutyrate in an amount of 18% to 60% by weight relative to the total weight of the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer.

10. A method for preparing a biodegradable polymer dispersion according to claim 1, wherein the weight-average molecular weight of the polyhydroxyalkanoate (PHA) is 550,000 g / mol to 1,000,000 g / mol.

11. A biodegradable polymer dispersion prepared by the preparation method described in any one of claims 1 to 10.

12. The biodegradable polymer dispersion according to claim 11, wherein the viscosity measured by a Brookfield viscometer at 25°C is greater than 10 cPs and less than or equal to 10,000 cPs.

13. Distribute 15 g / m² of the biodegradable polymer dispersion onto the substrate. ２ When a coating layer was formed with the specified application amount and a Cobb water absorption test was conducted in accordance with the TAPPI T441 standard, the water resistance was 3 g / m². ２ ~50g / m ２ The biodegradable polymer dispersion according to claim 11.

14. Evaluated according to the TAPPI T559 standard, 15 g / m² of the biodegradable polymer dispersion is applied to the substrate. ２ The biodegradable polymer dispersion according to claim 11, wherein the oil-resistant kit rating when a coating layer is formed with the amount of coating applied is 5 or higher.

15. A biodegradable article comprising a substrate and a biodegradable coating layer formed on at least one surface of the substrate using the biodegradable polymer dispersion described in claim 11.

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