Biodegradable polymer dispersion and method for producing the same

Abstract

The present invention relates to a biodegradable polymer dispersion and a method for producing the same. The method for producing the biodegradable polymer dispersion includes the steps of (1) mixing a biodegradable polymer and an emulsifier to produce an emulsion, (2) heating the emulsion, and (3) mixing the heated emulsion with an additive.

Description

Technical Field

[0001] The present disclosure relates to a biodegradable polymer dispersion and a method for preparing the same.

Background Art

[0002] As environmental problems are becoming more serious due to the indiscriminate use of synthetic plastics, there is an increasing 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.

[0003] Polyhydroxyalkanoate (PHA), one of the biodegradable polymers, has advantages such as excellent mechanical properties, oil resistance, and water resistance in addition to complete biodegradability. Due to these advantages, a polyhydroxyalkanoate (PHA) dispersion in which polyhydroxyalkanoate (PHA) particles are dispersed is used to form a coating layer for improving the lifespan and recyclability of various products such as films, fibers, packaging materials, and bottles.

[0004] However, a biodegradable polymer dispersion such as the above-mentioned polyhydroxyalkanoate (PHA) dispersion has a problem of being vulnerable to bacteria. That is, the biodegradable polymer particles present in the dispersion are less than several micrometers in size and have a large surface area, and the dispersion contains sufficient moisture for the growth of bacteria. Therefore, the biodegradable polymer dispersion has low resistance (stability) to bacteria.

[0005] Therefore, to increase the resistance of biodegradable polymer dispersions to bacteria, methods such as introducing antimicrobial agents into the dispersion or sterilizing the prepared dispersion at high temperatures have been attempted. However, the method of introducing antimicrobial agents has limitations in increasing resistance to bacteria to the required level due to the limited amount of antimicrobial agent that can be used. Furthermore, high-temperature sterilization is carried out at temperatures above 145°C, which is the same as that used for sterilizing synthetic plastics. While this can sterilize biodegradable polymer dispersions, it has the problem of reducing the molecular weight of heat-sensitive biodegradable polymers, and consequently degrading the physical properties of the biodegradable polymers. [Disclosure of the Invention] [Problems that the invention aims to solve]

[0006] To solve the above-mentioned conventional problems, the object of this disclosure is to provide a biodegradable polymer dispersion that maintains the basic properties of a relatively heat-sensitive biodegradable polymer while exhibiting high resistance to bacteria even with the use of a small amount of antimicrobial agent, and a method for producing the same. [Means for solving the problem]

[0007] To achieve the above objective, the present disclosure provides a method for producing a biodegradable polymer dispersion, comprising the steps of (1) mixing a biodegradable polymer with an emulsifier to produce an emulsion, (2) heat-treating (heating) the emulsion, and (3) mixing an additive into the heat-treated emulsion.

[0008] According to one embodiment of the present disclosure, the heat treatment in step (2) may be performed at 50°C to 80°C.

[0009] According to other embodiments of the present disclosure, the heat treatment in step (2) may be performed for 10 to 30 minutes.

[0010] According to other embodiments of the present disclosure, the method for producing a biodegradable polymer dispersion may further include a step of filtering the emulsion before the heat treatment of step (2).

[0011] According to other embodiments of the present disclosure, the additive in step (3) may include at least one selected from the group consisting of thickeners, waxes, defoamers, and antimicrobial agents.

[0012] In other embodiments of the present disclosure, step (3) may include (3-1) adding and mixing a first additive containing a thickener to a heat-treated emulsion; (3-2) adding and mixing a second additive containing a wax to the emulsion mixed with the first additive; and (3-3) adding and mixing a third additive containing at least one selected from the group consisting of antifoaming agents and antimicrobial agents to the emulsion mixed with the second additive.

[0013] According to other embodiments of the present disclosure, in step (3-3), the amount of antimicrobial agent added may be 0.001% to 0.5% by weight relative to the total weight of the biodegradable polymer dispersion.

[0014] According to other embodiments of the present disclosure, the biodegradable polymer of step (1) may have a particle shape with an average particle size (D50) of 0.5 μm to 5.0 μm.

[0015] According to other embodiments of the present disclosure, the biodegradable polymer of step (1) may include at least one selected from the group consisting of polyhydroxyalkanoic acid (PHA), polylactic acid (PLA), polybutylene adipate-co-terephthalate (PBAT), polybutylene succinate (PBS), and polycaprolactone (PCL).

[0016] According to other embodiments of the present disclosure, the polyhydroxyalkanoic acid may be a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer.

[0017] According to other embodiments of the present disclosure, the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer may contain repeating units derived from 4-hydroxybutyrate in an amount of 6% to 20% by weight relative to the total weight of the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer.

[0018] According to other embodiments of the present disclosure, the emulsifier in step (1) may include at least one selected from the group consisting of polyvinyl alcohol (PVA), sodium dodecylsulfonate (SDS), cocobetaine, and lecithin.

[0019] On the other hand, in order to achieve the above objective, this disclosure provides a biodegradable polymer dispersion prepared by the manufacturing process described above.

[0020] According to one embodiment of the present disclosure, the biodegradable polymer dispersion may have a viscosity of 10 cP to 3,000 cP as measured by a Brookfield viscometer at 25°C. [Effects of the Invention]

[0021] In this disclosure, a biodegradable polymer is emulsified, the resulting emulsion is heat-treated at a temperature much lower than that of conventional high-temperature sterilization, and then an additive is added to prepare a biodegradable polymer dispersion. As a result, a biodegradable polymer dispersion can be provided that maintains the heat-sensitive properties of the biodegradable polymer while significantly improving its resistance (stability) to bacteria.

[0022] Therefore, the biodegradable polymer dispersion according to this disclosure has excellent long-term storage stability due to its high resistance (stability) to bacteria, and thus can extend the storage period of the dispersion compared to conventional dispersions.

[0023] Furthermore, because the biodegradable polymer contained in the biodegradable polymer dispersion relating to this disclosure has excellent physical properties, it can be advantageously used as a coating solution to enhance the lifespan and recyclability of various products such as films, fibers, packaging materials, and bottles.

Brief Description of Drawings

[0024] [Figure 1] FIG. 1 is a flowchart schematically showing a method for producing a biodegradable polymer dispersion according to an embodiment of the present invention. [Figure 2] FIG. 2 is an image showing the results of the bacterial contamination test in Test Example 1.

Modes for Carrying Out the Invention

[0025] Hereinafter, the present disclosure will be described in detail. Although the present disclosure is not limited to what is described below, it can be modified in various forms as long as the gist of the present disclosure is not changed.

[0026] In this specification, the term "comprising" is intended to identify a particular characteristic, region, step, process, element, and / or component. Unless otherwise stated, it does not exclude the presence or addition of any other characteristic, region, step, process, element, and / or component.

[0027] Numerical values and expressions related to the amounts of components, reaction conditions, etc. used herein are understood to be modified by "about" unless otherwise indicated.

[0028] Terms such as first, second, etc. in this specification are used to describe various components. However, the components should not be limited by these terms. These terms are used only for the purpose of distinguishing one component from another.

[0029] Unlike the method of sterilizing at a high temperature after preparing a conventional biodegradable polymer dispersion, the present disclosure completes the preparation of a biodegradable polymer dispersion by performing a heat treatment at a relatively low temperature during the production process of the biodegradable polymer dispersion. As a result, a biodegradable polymer dispersion with significantly improved resistance (stability) to bacteria can be provided. Hereinafter, the present disclosure will be described in detail.

[0030] [Method for producing a biodegradable polymer dispersion] The method for producing a biodegradable polymer dispersion according to this disclosure includes (1) a step of mixing a biodegradable polymer and an emulsifier to produce an emulsion, (2) a step of heat-treating the emulsion, and (3) a step of mixing an additive into the heat-treated emulsion.

[0031] The following steps will be explained with reference to Figure 1. Step (1): Emulsion preparation According to this disclosure, step (1) is a step of mixing a biodegradable polymer and an emulsifier to produce an emulsion. Specifically, step (1) is a step of emulsifying the biodegradable polymer.

[0032] Biodegradable polymers are not particularly limited, as long as they are polymers that can be naturally decomposed by microorganisms in soil or the ocean. Specifically, biodegradable polymers may include at least one selected from the group consisting of polyhydroxyalkanoic acid (PHA), polylactic acid (PLA), polybutylene adipate-co-terephthalate (PBAT), polybutylene succinate (PBS), and polycaprolactone (PCL). Preferably, the biodegradable polymer may be polyhydroxyalkanoic acid (PHA), which, in addition to being completely biodegradable, has excellent mechanical properties, oil resistance, water resistance, etc.

[0033] Polyhydroxyalkanoates (PHAs) may be obtained by mechanical or physical cell disruption of microorganisms, or by non-mechanical or chemical cell disruption of microorganisms.

[0034] Polyhydroxyalkanoic acid may have a weight-average molecular weight (Mw) of 100,000 g / mole to 800,000 g / mole, 125,000 g / mole to 775,000 g / mole, 150,000 g / mole to 750,000 g / mole, 175,000 g / mole to 725,000 g / mole, or 200,000 g / mole to 700,000 g / mole, but is not limited to these ranges.

[0035] The polyhydroxyalkanoic acid may be a copolymer containing repeating units derived from at least one monomer selected from the group consisting of 3-hydroxybutyrate (3-HB), 3-hydroxypropionic acid (3-HP), 3-hydroxyvaleric acid (3-HV), 3-hydroxycaproic acid (3-HH), 4-hydroxybutyrate (4-HB), 4-hydroxyvaleric acid (4-HV), 4-hydroxycaproic acid (4-HH), 5-hydroxyvaleric acid (5-HV), and 6-hydroxycaproic acid (6-HH), but is not limited thereto.

[0036] Polyhydroxyalkanoic acids may be crystalline polyhydroxyalkanoic acids (cPHA), semi-crystalline polyhydroxyalkanoic acids (scPHA), or amorphous polyhydroxyalkanoic acids (aPHA), depending on the type of monomer and the content of repeating units derived therefrom. For example, polyhydroxyalkanoic acids can be classified as cPHA, scPHA, or aPHA by controlling the degree of crystallinity according to the content of repeating units derived from 4-hydroxybutyrate (4-HB).

[0037] Specifically, the polyhydroxyalkanoic acid may be a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer containing repeating units derived from 3-hydroxybutyrate (3-HB) and repeating units derived from 4-hydroxybutyrate (4-HB).

[0038] The poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer may contain, but is not limited to, 6% to 20% by weight of repeating units (4-HB repeating units) derived from 4-hydroxybutyrate (4-HB) based on the total weight of the polymer. Specifically, the content of 4-HB repeating units may be 6.5% to 19% by weight, 7% to 18% by weight, 7.5% to 17% by weight, 8% to 16% by weight, 8% to 15% by weight, 8.5% to 15% by weight, 9% to 14% by weight, or 9.5% to 13% by weight based on the total weight of the polymer. By having a 4-HB repeating unit content within the above range, the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer can be semi-crystalline PHA (scPHA) or amorphous PHA (aPHA). A biodegradable polymer dispersion of the present disclosure, in which such PHA is dispersed as a biodegradable polymer, can form a coating layer having excellent mechanical properties, oil resistance, water resistance, heat resistance, etc.

[0039] The biodegradable polymer may have a particle shape controlled to a predetermined size. Specifically, the biodegradable polymer may have an average particle size (D50) of 0.5 μm to 5.0 μm as biodegradable polymer particles, but is not limited to this. For example, the average particle size (D50) of the biodegradable polymer particles may be 0.6 μm to 4.9 μm, 0.7 μm to 4.8 μm, 0.8 μm to 4.7 μm, 0.9 μm to 4.6 μm, 1 μm to 4.5 μm, 1.1 μm to 4.4 μm, 1.2 μm to 4.3 μm, or 1.2 μm to 4.2 μm. By having the average particle size (D50) of the biodegradable polymer particles within the above range, a biodegradable polymer dispersion with excellent dispersibility can be obtained. When this is used to form a coating layer on a substrate (e.g., a film), a coating layer with excellent mechanical properties, oil resistance, water resistance, heat resistance, etc. can be formed.

[0040] The biodegradable polymer may be mixed with the emulsifier in the form of a crude solution containing the biodegradable polymer. In this case, the crude solution containing the biodegradable polymer may contain, but is not limited to, a biodegradable polymer solids content of 10% to 70% by weight relative to the total weight of the crude solution. Specifically, the crude solution containing the biodegradable polymer may contain a biodegradable polymer solids content of 20% to 70% by weight, 20% to 60% by weight, or 30% to 50% by weight. Alternatively, the crude solution containing the biodegradable polymer may be a solution in which the biodegradable polymer (biodegradable polymer particles) is dispersed in an aqueous solvent (e.g., water).

[0041] The emulsifier is not particularly limited as long as it is a substance that can uniformly disperse the biodegradable polymer. Specifically, the emulsifier may include at least one selected from the group consisting of polyvinyl alcohol (PVA), sodium dodecyl sulfonate (SDS), cocobetaine, and lecithin. More specifically, the emulsifier may be a PVA emulsifier in which polyvinyl alcohol (PVA) is dispersed in an aqueous solvent (e.g., water). By using a PVA emulsifier, an emulsion in which the biodegradable polymer is uniformly and evenly dispersed can be obtained.

[0042] The PVA emulsifier may have a viscosity of 10 cps to 1,000 cps, 20 cps to 700 cps, 30 cps to 500 cps, or 40 cps to 300 cps, but is not limited thereto.

[0043] The polyvinyl alcohol (PVA) content in the PVA emulsifier may be, but is not limited to, 1% to 50% by weight, 2% to 40% by weight, 3% to 30% by weight, or 4% to 20% by weight, based on the total weight of the PVA emulsifier.

[0044] Polyvinyl alcohol (PVA) may have a degree of saponification of 1 mol% to 99 mol%, 2 mol% to 97 mol%, 3 mol% to 95 mol%, or 4 mol% to 93 mol%, but is not limited thereto.

[0045] When mixing a biodegradable polymer (A) and an emulsifier (B), the mixing ratio (A:B) (based on solid content) may be, but is not limited to, 1:99 to 10:90, 2:98 to 9:91, or 3:97 to 8:92.

[0046] The mixing of the biodegradable polymer and the emulsifier may be carried out using a known mixer (e.g., a homomixer). When mixing (stirring) the biodegradable polymer and the emulsifier with a mixer, the rotation speed of the mixer may be, but is not limited to, 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 mixing (stirring) time in the mixer may be, but is not limited to, 15 minutes to 60 minutes, 20 minutes to 50 minutes, 20 minutes to 40 minutes, or 25 minutes to 35 minutes.

[0047] On the other hand, the method for producing a biodegradable polymer dispersion according to this disclosure may further include a step of filtering the emulsion obtained by mixing with an emulsifier before the heat treatment described later. By filtering the emulsion, large particles of the biodegradable polymer that were not dispersed in the mixing step with the emulsifier can be removed. As a result, an emulsion in which biodegradable polymers of fine particle size are uniformly dispersed can be obtained.

[0048] The emulsion may be filtered using known filters. Specifically, the filtration step may consist of primary filtration or secondary or higher filtration. More specifically, the filtration step may include a step of primary filtration of the emulsion using a filter with a pore size of 100 μm to 150 μm (e.g., 120 μm to 145 μm, 125 μm to 140 μm, or 125 μm to 135 μm) (e.g., a filter capable of filtering biodegradable polymers with an average particle size of 120 μm to 150 μm), and a step of secondary filtration of the primary filtered emulsion using a filter with a pore size of 90 μm to less than 300 μm (e.g., 95 μm to 280 μm, 100 μm to 270 μm, or 100 μm to 250 μm) (e.g., a filter capable of filtering biodegradable polymers with an average particle size of 90 μm to less than 120 μm).

[0049] Step (2): Heat treatment of the emulsion According to this disclosure, step (2) is a step of heat-treating the emulsion (for example, an emulsion that has been optionally filtered as described above). Specifically, step (2) is a step of sterilizing the emulsion by heat-treating it at a temperature significantly lower than the conventional high-temperature sterilization temperature (for example, 145°C or higher).

[0050] The temperature at which the emulsion is heat-treated may be, but is not limited to, 50°C to 80°C. Specifically, the temperature at which the emulsion is heat-treated may be 51°C to 78°C, 52°C to 78°C, 53°C to 75°C, 54°C to 75°C, 55°C to 73°C, 56°C to 73°C, 57°C to 70°C, 58°C to 70°C, 59°C to 68°C, or 60°C to 65°C.

[0051] Furthermore, the time the emulsion is heated may be between 10 and 30 minutes, but is not limited to this. Specifically, the time the emulsion is heated may be between 11 and 30 minutes, 12 and 29 minutes, 13 and 29 minutes, 14 and 28 minutes, 15 and 28 minutes, 16 and 27 minutes, 17 and 27 minutes, 18 and 26 minutes, 18 and 25 minutes, 19 and 23 minutes, 19 and 22 minutes, or 20 and 21 minutes.

[0052] By heat-treating the emulsion within the above temperature range for the above time, sterilization can be efficiently performed while minimizing changes in the physical properties (e.g., decrease in molecular weight) of the biodegradable polymer contained in the emulsion. Therefore, by preparing the dispersion according to this disclosure using a heat-treated emulsion, it is possible to provide a biodegradable polymer dispersion containing a biodegradable polymer with maintained physical properties and excellent resistance (stability) to bacteria.

[0053] Furthermore, the emulsion may be heat-treated until its viscosity reaches 100 cPs to 3,000 cPs. Specifically, the viscosity of the emulsion heat-treated in step (2) may be 200 cPs to 2,000 cPs, 300 cPs to 1,500 cPs, or 350 cPs to 1,200 cPs, but is not limited to these values.

[0054] Step (3): Mixing of emulsion and additives According to this disclosure, step (3) is a step of mixing additives into a heat-treated emulsion. Specifically, step (3) is a step of mixing two or more additives into a heat-treated emulsion in order to prepare an emulsion.

[0055] The additives are not particularly limited, as long as they are known additives. Specifically, the additive may include at least one selected from the group consisting of thickeners, waxes, defoamers, and antimicrobial agents. More specifically, the additive may include at least two selected from the group consisting of thickeners, waxes, defoamers, and antimicrobial agents.

[0056] The additives may be mixed in stages. As a result, a biodegradable polymer dispersion can be efficiently prepared from the emulsion. Specifically, the additive mixing step may include (3-1) adding and mixing a first additive containing a thickener to a heat-treated emulsion, (3-2) adding and mixing a second additive containing wax to the emulsion mixed with the first additive, and (3-3) adding and mixing a third additive containing at least one selected from the group consisting of antifoaming agents and antibacterial agents to the emulsion mixed with the second additive.

[0057] Step (3-1) is a step of adding a first additive containing a thickening agent to a heat-treated emulsion and mixing it. This allows the viscosity of the biodegradable polymer dispersion to be adjusted to a desired level. The thickening agent is not particularly limited as long as it is a substance that can adjust the viscosity of the emulsion. Specifically, the thickening agent may include at least one selected from the group consisting of starch, xanthan gum, guar gum, carboxymethylcellulose (CMC), and carrageenan.

[0058] The mixing of the emulsion and the first additive containing a thickener may be carried out using a known mixer (e.g., a homomixer). When mixing (stirring) the emulsion and the first additive with the mixer, the rotation speed of the mixer may be, but is not limited to, 4,500 rpm to 9,000 rpm, 5,000 rpm to 8,500 rpm, 5,300 rpm to 8,300 rpm, or 5,500 rpm to 8,200 rpm. The mixing (stirring) time in the mixer may be, but is not limited to, 10 minutes to 30 minutes, 15 minutes to 30 minutes, or 20 minutes to 25 minutes.

[0059] Step (3-2) is a step of adding and mixing a second additive containing wax to an emulsion mixed with the first additive. This can improve the water resistance and coating properties of the biodegradable polymer dispersion. The wax is not particularly limited as long as it is a known substance. Specifically, the wax may include at least one selected from the group consisting of beeswax, soybean wax, and carnauba wax.

[0060] The mixing of the emulsion mixed with the first additive and the second additive containing wax may be carried out using a known mixer (e.g., a homomixer). When mixing (stirring) the emulsion and the second additive with the mixer, the rotation speed of the mixer may be, but is not limited to, 4,500 rpm to 9,000 rpm, 5,000 rpm to 8,500 rpm, 5,300 rpm to 8,300 rpm, or 5,500 rpm to 8,200 rpm. The mixing (stirring) time in the mixer may be, but is not limited to, 10 minutes to 30 minutes, 15 minutes to 30 minutes, or 20 minutes to 25 minutes.

[0061] Step (3-3) is a step of adding and mixing a third additive, which contains at least one selected from the group consisting of defoamers and antibacterial agents, to the emulsion mixed with the second additive. This improves the antibacterial performance and coating properties of the biodegradable polymer dispersion. The defoamer is not particularly limited as long as it is a known substance. Specifically, the defoamer may contain at least one selected from the group consisting of silicone-based defoamers, mineral oil-based defoamers, and polymer-based defoamers. The antibacterial agent is also not particularly limited as long as it is a known substance. Specifically, the antibacterial agent may contain 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 benzoisothiazolon (BIT).

[0062] On the other hand, in step (3-3), the amount of antimicrobial agent added to (used) in the emulsion may be 0.001% to 0.5% by weight relative to the total weight of the biodegradable polymer dispersion, but is not limited thereto. Specifically, the amount of antimicrobial agent added may be 0.005% to 0.5% by weight, 0.005% to 0.4% by weight, 0.01% to 0.4% by weight, 0.01% to 0.3% by weight, 0.02% to 0.3% by weight, or 0.03% to 0.2% by weight relative to the total weight of the biodegradable polymer dispersion. By keeping the amount of antimicrobial agent added within the above range, it is possible to provide a biodegradable polymer dispersion with excellent antimicrobial performance while applying a dosage that complies with international regulations (e.g., the US FDA).

[0063] In this disclosure, a biodegradable polymer dispersion is prepared by emulsifying a biodegradable polymer, heat-treating the resulting emulsion at a relatively low temperature of 50°C to 80°C, and then adding additives stepwise to prepare the emulsion. As a result, it is possible to provide a biodegradable polymer dispersion that exhibits excellent resistance (stability) to bacteria while minimizing changes in the physical properties of the heat-sensitive biodegradable polymer.

[0064] [Biodegradable polymer dispersion] This disclosure provides a biodegradable polymer dispersion prepared by the manufacturing process described above. The biodegradable polymer dispersion according to this disclosure comprises the biodegradable polymer (biodegradable polymer particles), the emulsifier, the additive, and a dispersion solvent (e.g., water).

[0065] The biodegradable polymer dispersion relating to this disclosure may have excellent long-term storage stability due to its high resistance (stability) to bacteria.

[0066] Furthermore, the biodegradable polymer dispersion according to this disclosure may have a viscosity that ensures coating properties, workability, etc. Specifically, the biodegradable polymer dispersion according to this disclosure may have a viscosity of 10 cP to 3,000 cP, more specifically 20 cP to 2,500 cP, 30 cP to 2,000 cP, 40 cP to 1,500 cP, or 50 cP to 1,000 cP, as measured by a Brookfield viscometer at 25°C, but is not limited thereto.

[0067] The biodegradable polymer dispersion relating to this disclosure may have a pH that ensures long-term storage stability, etc. Specifically, the biodegradable polymer dispersion relating to this disclosure may have a pH of 5 to 9, more specifically 5.5 to 8.8, but is not limited thereto.

[0068] The biodegradable polymer dispersion relating to this disclosure has excellent long-term storage stability and coating properties on substrates, and can therefore be advantageously used as a coating solution to enhance the lifespan and recyclability of various products such as films, fibers, packaging materials, and bottles.

[0069] [Embodiments of the Invention] The present disclosure will be described in detail below with reference to examples, but the scope of the present disclosure is not limited to examples.

[0070] [Example 1] Distilled water was added to dried polyhydroxyalkanoic acid (PHA) particles (powder) (MW: 340,000 g / mole, 4-HB repeating unit content: 10% by weight, manufacturer: CJ CheilJedang) to obtain a crude solution with a solid content of 40% by weight. Next, the crude solution and a 10% PVA emulsifier were added to a disper (product name: homogenizing disper, manufacturer: PRIMIX) so that the solid content was 1.5 parts by weight relative to the crude solution, and the mixture was stirred at 1,000 rpm to 2,000 rpm for 5 minutes to obtain a suspension. Subsequently, the obtained suspension was subjected to an emulsification process using a homomixer (product name: homogenizing mixer, manufacturer: PRIMIX) and stirred at 6,000 rpm to 8,000 rpm for 30 minutes to prepare a PHA emulsion.

[0071] The PHA emulsion obtained after the emulsification procedure was subjected to primary filtration through a 130 μm filter, followed by secondary filtration through a 110 μm filter to remove large, unemulsified particles.

[0072] The PHA emulsion, after primary and secondary filtration, was sterilized by heat treatment at 60°C for 20 minutes.

[0073] First preparation was performed by adding 0.3% by weight of a thickening agent (relative to the total weight of the PHA dispersion) to a heat-sterilized PHA emulsion and stirring in a homomixer at 6,000 rpm to 8,000 rpm for 20 minutes. Next, second preparation was performed by adding 0.9% by weight of wax (relative to the total weight of the PHA dispersion) to the PHA product prepared in the first preparation and stirring in a homomixer at 6,000 rpm to 8,000 rpm for 20 minutes. Next, third preparation was performed by adding 0.05% by weight each of an antifoaming agent and an antibacterial agent (relative to the total weight of the PHA dispersion) to the PHA product prepared in the second preparation and stirring in a homomixer at 6,000 rpm to 8,000 rpm for 20 minutes. After that, the PHA product prepared in the third preparation was finally filtered through a 245 μm filter to prepare a PHA dispersion.

[0074] [Example 2] A PHA dispersion was prepared using the same procedure as in Example 1, except that the PHA emulsion, which had undergone primary and secondary filtration in Example 1, was heat-treated for 30 minutes.

[0075] [Example 3] A PHA dispersion was prepared using the same procedure as in Example 1, except that instead of the dried polyhydroxyalkanoic acid (powder) used in Example 1, dried polyhydroxyalkanoic acid (PHA) particles (powder) (MW: 450,000 g / mole, 4-HB repeating unit content: 12.6% by weight, manufacturer: CJ IeilJedang) were used.

[0076] [Comparative Example 1] Distilled water was added to dried polyhydroxyalkanoic acid (PHA) particles (powder) (MW: 340,000 g / mole, 4-HB repeating unit content: 10% by weight, manufacturer: CJ CheilJedang) to obtain a crude solution with a solid content of 40% by weight. Next, the crude solution and a 10% PVA emulsifier were added to a disperser (product name: homogenizing disperser, manufacturer: PRIMIX) so that the solid content was 1.5 parts by weight relative to the crude solution, and the mixture was stirred at 1,000 rpm to 2,000 rpm for 5 minutes to obtain a suspension. Subsequently, the suspension thus obtained was subjected to an emulsification process by stirring at 6,000 rpm to 8,000 rpm for 30 minutes using a homomixer (product name: homogenizing mixer, manufacturer: PRIMIX) to prepare a PHA emulsion.

[0077] First preparation was performed by adding a thickener at a rate of 0.3% by weight (relative to the total weight of the PHA dispersion) to the PHA emulsion and stirring in a homomixer at 6,000 rpm to 8,000 rpm for 20 minutes. Next, second preparation was performed by adding wax at a rate of 0.9% by weight (relative to the total weight of the PHA dispersion) to the PHA product prepared in the first preparation and stirring in a homomixer at 6,000 rpm to 8,000 rpm for 20 minutes. Next, third preparation was performed by adding an antifoaming agent and an antibacterial agent at a rate of 0.05% by weight each (relative to the total weight of the PHA dispersion) to the PHA product prepared in the second preparation and stirring in a homomixer at 6,000 rpm to 8,000 rpm for 20 minutes. After that, the PHA product prepared in the third preparation was subjected to primary filtration through a 130 μm filter and then secondary filtration through a 110 μm filter to prepare a PHA dispersion.

[0078] [Comparative Example 2] The PHA dispersion prepared in Comparative Example 1 was heat-treated at 70°C for 10 minutes.

[0079] [Comparative Example 3] The PHA dispersion was prepared using the same procedure as in Comparative Example 1, except that 0.1% by weight of the antibacterial agent (relative to the total weight of the PHA dispersion) was added during the second preparation of Comparative Example 1.

[0080] The PHA dispersions of the examples and comparative examples were evaluated as follows.

[0081] [Test Example 1] Bacterial Contamination Test Three types of dry media (MC-Media Pad, JNC CORPORATION) were prepared for general bacteria, fungi, and Escherichia coli. Dilutions were prepared by diluting 1 mL of each PHA dispersion 10-fold with 9 mL of sterile water. These dilutions were vortexed for 1 minute, 1 mL was taken, and evenly dispensed into each dry media. Next, the dry media for general bacteria were incubated at 35°C for 48 hours, the dry media for fungi at 25°C for 48 hours, and the dry media for Escherichia coli at 35°C for 24 hours. After incubation was complete, the number of colonies was measured. If the measured number of colonies was less than 10, it was evaluated as no bacterial contamination (pass). If the number was 10 or more, it was evaluated as bacterial contamination (contaminated).

[0082] Figure 2 shows the results of the bacterial contamination test. The PHA dispersions of Examples 1 and 2 according to this disclosure were prepared by mixing additives after heat treatment of the emulsion. As a result, they showed excellent stability (resistance) to bacteria. In particular, when an antimicrobial agent was added after heat treatment at approximately 60°C for 20 to 30 minutes, all common bacteria, Escherichia coli, and fungi were sterilized, and no bacterial contamination occurred.

[0083] In contrast, Comparative Example 1, which did not undergo heat treatment, resulted in serious bacterial contamination. In Comparative Example 2, where heat treatment was performed after the preparation of the PHA dispersion, the dispersion was stable against E. coli and fungi, but contamination by general bacteria occurred. This may indicate that heat treatment is desirable to perform between the preparation of the PHA emulsion and the addition of additives.

[0084] On the other hand, in Comparative Example 3, which contained a larger amount of antimicrobial agent than Comparative Example 1, the number of bacteria decreased compared to Comparative Example 1, but bacterial contamination could not be prevented. This may mean that even if the amount of antimicrobial agent is increased, bacterial contamination cannot be effectively prevented without heat treatment. In contrast, this disclosure shows that bacterial contamination can be prevented by heat treatment, even when using a relatively small amount of antimicrobial agent.

[0085] [Test Example 2] Viscosity Measurements were performed using a DV-1 VISCOMETER (BROOKFIELD) device with spindle #63 and 12 rpm. The results are shown in Table 1 below.

[0086] [Test Example 3] Particle Size (Average Particle Size, D50) The measurements were performed using a particle size analyzer (LS13320 laser particle size analyzer). The results are shown in Table 1 below. In this case, a PHA dispersion diluted 100-fold with ultrapure water was used as the measurement sample.

[0087] [Table 1]

[0088] As shown in Table 1 above, Examples 1 and 2 and Comparative Examples 1 and 2 have the same or similar pH and particle size, indicating that the pH of the PHA dispersion and the particle size of the PHA particles hardly change even when heat treatment is performed. On the other hand, in Example 2, where the heat treatment time was increased by 10 minutes compared to Example 1, the viscosity of the PHA dispersion increased, indicating that the heat treatment time needs to be controlled when considering the coating properties of the PHA dispersion.

[0089] [Test Example 4] Storage Stability The PHA dispersion prepared in Example 3 was stored in a constant temperature and humidity chamber at 35°C and 80% humidity for 12 weeks, and its storage stability was evaluated. The results are shown in Table 2 below. Specifically, after redispersing each PHA dispersion by vortexing for 1 minute, the degree of aggregation of particles contained in the PHA dispersion was checked using a spoon. If no aggregation was observed after redispersion, storage stability was considered to have been ensured.

[0090] Meanwhile, the PHA dispersion prepared in Example 3 was also evaluated in Test Examples 1 and 3. The results are shown in Table 2 below.

[0091] [Table 2]

[0092] As shown in Table 2 above, the PHA dispersion of Example 3 according to this disclosure was prepared by mixing additives after heat treatment of the emulsion. As a result, it was redispersible for up to 12 weeks and showed excellent storage stability. Furthermore, since no bacterial contamination occurred, it also exhibited excellent stability (resistance) to bacteria.

Claims

1. (1) Mixing a biodegradable polymer with an emulsifier to prepare an emulsion. (2) Heat treatment of the emulsion, and (3) A step of mixing an additive into the heat-treated emulsion, A method for producing a biodegradable polymer dispersion containing [the specified substance].

2. The method for producing a biodegradable polymer dispersion according to claim 1, wherein the heat treatment in step (2) is performed at 50°C to 80°C.

3. The method for producing a biodegradable polymer dispersion according to claim 1, wherein the heat treatment in step (2) is performed for 10 to 30 minutes.

4. A method for producing a biodegradable polymer dispersion according to claim 1, further comprising filtering the emulsion before the heat treatment in step (2).

5. The method for producing a biodegradable polymer dispersion according to claim 1, wherein the additive in step (3) comprises at least one selected from the group consisting of thickeners, waxes, defoamers, and antibacterial agents.

6. Step (3) is, (3-1) Adding a first additive containing a thickening agent to the heat-treated emulsion and mixing it, (3-2) Adding a second additive containing wax to the emulsion mixed with the first additive and mixing it, (3-3) Adding and mixing a third additive, which includes at least one selected from the group consisting of an antifoaming agent and an antibacterial agent, to the emulsion mixed with the second additive. A method for producing a biodegradable polymer dispersion according to claim 1, comprising the above.

7. The method for producing a biodegradable polymer dispersion according to claim 6, wherein in step (3-3), the amount of the antimicrobial agent added is 0.001% to 0.5% by weight relative to the total weight of the biodegradable polymer dispersion.

8. A method for producing a biodegradable polymer dispersion according to claim 1, wherein the biodegradable polymer in step (1) has a particle shape with an average particle size (D50) of 0.5 μm to 5.0 μm.

9. A method for producing a biodegradable polymer dispersion according to claim 1, wherein the biodegradable polymer in step (1) comprises at least one selected from the group consisting of polyhydroxyalkanoic acid (PHA), polylactic acid (PLA), polybutylene adipate-co-terephthalate (PBAT), polybutylene succinate (PBS), and polycaprolactone (PCL).

10. The method for producing a biodegradable polymer dispersion according to claim 9, wherein the polyhydroxyalkanoic acid is a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer.

11. The method for producing a biodegradable polymer dispersion according to claim 10, wherein the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer contains 6% to 20% by weight of repeating units derived from 4-hydroxybutyrate based on the total weight of the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer.

12. A method for producing a biodegradable polymer dispersion according to claim 1, wherein the emulsifier in step (1) comprises at least one selected from the group consisting of polyvinyl alcohol (PVA), sodium dodecylsulfonate (SDS), cocobetaine, and lecithin.

13. A biodegradable polymer dispersion prepared by the manufacturing method described in any one of claims 1 to 12.

14. The biodegradable polymer dispersion according to claim 13, having a viscosity of 10 cP to 3,000 cP as measured by a Brookfield viscometer at 25°C.

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