KR20220121489A - Preparation method for biodegradable polymer beads - Google Patents

Abstract

Disclosed is a preparation method of biodegradable polymer beads which comprises the step of: (a) preparing a polylactic acid polymer having a molecular weight of 30,000 to 150,000 (step a); (b) dissolving the polylactic acid polymer prepared in step S-1 in at least one solvent selected from polyethylene glycol, triacetin, benzyl alcohol, and pentanol at a temperature of 160 to 190 ℃ (step b); (c) cooling the solution prepared in step b to prepare polylactic acid beads (step c); and (d) washing the polylactic acid beads prepared in step c (step d). According to the present invention, the biodegradable polymer beads can be prepared without using harmful solvents, and the amount of wastewater generated is small compared to a conventional preparation method of biodegradable polymer beads.

Description

Preparation method for biodegradable polymer beads {Preparation method for biodegradable polymer beads}

The present invention relates to a method for producing biodegradable polymer beads.

Background to the present disclosure is provided herein, which does not necessarily imply known art.

Microbeads based on polymer materials have high utility and are used for various purposes in the fields of electricity, electronics, chemistry, and biotechnology. For example, a light diffusing agent is used in a display, a roughening device, etc., and in addition, it is widely used as an additive in various industrial fields such as paints, plastic molded products, and cosmetics.

However, it has been recently reported that microplastics have a detrimental effect on the environment. Microplastic refers to a small plastic of 5mm or less, and microbeads, a type of microplastic, are sphere-shaped polymeric materials with a diameter of usually 1mm or less. It has been reported to have adverse effects on humans and marine life.

Nevertheless, about 900 to 9000 microbeads per 1mL of a scrub cosmetic that removes waste from the skin are included, and the microbeads included in the cosmetics are flowing into the sewer without being filtered.

Recently, due to public opinion urging changes in awareness and action on environmental issues, laws to ban or suppress the use of microplastics around the world have been proposed or are about to take effect. For this reason, many countries and companies are actively conducting research and development efforts to replace petrochemical-based plastics with eco-friendly and biodegradable polymers.

However, among the methods for producing biodegradable polymer beads developed so far, the method for producing microbeads by dropping a polymer solution in which a biodegradable polymer (for example, polylactic acid (PLA)) in an organic solvent is dropped into an aqueous phase is by dissolving the polymer. There is a problem of low production efficiency as well as a problem of toxicity of a solvent (eg, dichloromethane, etc.) for

In addition, the method using the spray drying method and the electrospinning method uses a harmful solvent such as trichloromethane, and a method of spraying a polymer solution to prepare microbeads. In particular, the emulsion method using a halogenated solvent such as trichloromethane generates a lot of wastewater, and it is difficult to use it as a solvent in manufacturing a material for the human body as it is regulated as a hazardous material in various countries.

Therefore, there is a need for the development of novel biodegradable polymer beads that do not generate a large amount of wastewater while using a solvent that is not harmful to the human body.

1. Korean Patent Publication No. 10-2019-0013552 2. Republic of Korea Patent Registration No. 10-1969723

In order to solve the above problems, an object of the present invention is to provide a method for preparing biodegradable polymer beads without using a solvent harmful to the human body.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

According to one embodiment of the present invention there is provided a method for producing biodegradable polymer beads comprising the steps of:

(a) preparing a polylactic acid polymer having a molecular weight of 30,000 to 150,000 (step a);

(b) dissolving the polylactic acid polymer prepared in step S-1 in at least one solvent selected from polyethylene glycol, triacetin, benzyl alcohol, and pentanol at a temperature of 160°C to 190°C (step b);

(c) cooling the solution prepared in step b to produce polylactic acid beads (step c); and

(d) washing the polylactic acid beads produced in step c (step d).

In the above embodiment, the step b of dissolving the polylactic acid polymer at a temperature of 160° C. to 190° C. includes (b-1) a temperature raising step of raising the temperature of the mixture of the polylactic acid polymer and the solvent to a temperature of 160° C. to 190° C. (b) -1) and (b-2) may include a stirring step (step b-2) of stirring the mixture of step b-1. In this case, the temperature raising step (step b-1) and the stirring step (step b-2) may be performed simultaneously. In addition, the temperature increase rate in the temperature increase step (step b-1) may be 10 ℃ / min to 20 ℃ / min. In addition, the stirring step (step b-2) may be performed in a nitrogen atmosphere at 200 RPM to 600 RPM rotation conditions.

In the embodiment, the solvent may be at least one selected from triacetin, polyethylene glycol, benzyl alcohol, benzyl benzoate, benzyl ether, and pentanol.

In the embodiment, an additive may be further included in the mixture of the solvent and polylactic acid, and the additive may be one or more selected from a polyvinyl alcohol-based dispersant, a cellulose-based dispersant, an acrylic-based dispersant, and a silicone-based dispersant.

In addition, the additive may be an acrylic dispersant represented by the following Chemical Formula 2:

(In Formula 2, m and n are the same or different integers, and R may be one or more functional groups selected from a carboxyl group, a sulfate group, a phosphonate group, a phosphate group, and an amino acid).

In another embodiment of the present invention, there is provided a biodegradable polymer bead prepared by the method for preparing the biodegradable polymer bead.

According to the present invention, it is possible to manufacture biodegradable polymer beads without using a harmful solvent, and the amount of wastewater generated is small compared to the conventional method for producing biodegradable polymer beads.

Prior to describing the present invention in detail below, it is to be understood that the terminology used herein is for the purpose of describing specific embodiments and is not intended to limit the scope of the present invention, which is limited only by the appended claims. shall.

In addition, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor may properly define the concept of the term to describe his invention in the best way. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention. However, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art, unless otherwise noted.

Throughout this specification and claims, unless stated otherwise, the term comprise, comprises, comprising is meant to include the stated object, step or group of objects, and steps, and any other object. It is not used in the sense of excluding a step or a group of objects or groups of steps.

On the other hand, various embodiments of the present invention may be combined with any other embodiments unless clearly indicated to the contrary. Any feature indicated as particularly preferred or advantageous may be combined with any other feature and features indicated as preferred or advantageous.

According to one embodiment of the present invention, there is provided a method for producing biodegradable polymer beads. The method for preparing the biodegradable polymer beads is:

(a) preparing a polylactic acid polymer having a molecular weight of 30,000 to 150,000 (step a);

(b) dissolving the polylactic acid polymer prepared in step S-1 in at least one solvent selected from polyethylene glycol, triacetin, benzyl alcohol, pentanol, and benzyl at a temperature of 160°C to 190°C (step b);

(c) cooling the solution prepared in step b to produce polylactic acid beads (step c); and

(d) washing the polylactic acid beads produced in step c (step d); includes.

Preparation of polylactic acid polymer (step a)

The raw material of the biodegradable polymer bead according to an embodiment of the present invention may be polylactic acid (which may be abbreviated as PLA) represented by the following formula (1).

PLA polymers are generally biodegradable, but it is difficult to prepare beads by dissolving them in conventional organic solvents. Accordingly, the PLA polymer may have a molecular weight of 30,000 to 150,000. If the molecular weight of the PLA polymer is less than 30,000, it may be difficult to form the bead shape. If the molecular weight of the PLA polymer exceeds 150,000, the energy required to dissolve the PLA polymer may be excessive, and the viscosity increases during cooling, resulting in improved fairness. can be inhibited, and it can be difficult to control the crystallization rate of the beads. In particular, it is preferable that the molecular weight of PLA be 40,000 or more in order to produce a perfect spherical shape with a bead flatness close to 0, and it is preferable that the molecular weight of PLA be 120,000 or less in order to secure fairness and control the crystallization rate.

Dissolving PLA in a solvent at a predetermined temperature condition (step b)

When two types of molecules are mixed, compatibility occurs depending on temperature or concentration to form a single phase, or is separated into two phases due to incompatibility. The temperature at the inflection point at which the polymer is separated into phases is called the upper critical solution temperature (UCST), and above this temperature, the polymer and the solvent become a homogeneous solution.

In a general UCST solute/solvent phase separation phenomenon, polymer microbeads can be prepared using a metastable region.

In one embodiment of the present invention, it comprises the step of dissolving the PLA polymer prepared in step a in a solvent to induce the phase separation of the solution described above. The solvent is polyethylene glycol (which may be abbreviated as PEG), triacetin, benzyl alcohol, benzyl benzoate, benzyl ether, and pentanol. It may be one or more selected from.

The solvent has low compatibility with PLA at room temperature, so it is difficult to substantially dissolve PLA. However, under a certain temperature, compatibility occurs and it can become a single phase.

The temperature conditions for dissolving PLA in the solvents listed above may be 160°C to 190°C. Although the temperature conditions are different from the production conditions of general polymer beads, it is preferable to dissolve PLA in a predetermined solvent in the above temperature range for the production of biodegradable polymer beads.

The content ratio of the solvent and the solute (PLA) may be 7:3 to 9:1. If the content of PLA is high and the content ratio of solvent and PLA is out of the range of 7:3, it is difficult to control the crystallization rate due to the high PLA concentration, and spherical beads may not be obtained. On the other hand, if the content of PLA is low and the content ratio of solvent and PLA is out of the range of 9:1, the productivity of the polymer beads may not be good.

In this case, the step of dissolving the polylactic acid polymer in the solvent at a temperature of 160° C. to 190° C. may include a temperature raising step (step b-1) and/or a stirring step (step b-2).

PLA may be added to the solvent that has already reached the target temperature, but in terms of stability and energy efficiency, the dissolution step may be performed by adding PLA to the solvent at room temperature and heating the mixture of the solvent and PLA at a predetermined temperature increase rate. The temperature increase rate may be in the range of 10 °C / min to 20 °C / min in terms of energy efficiency.

In the temperature raising step, it is possible to increase the dissolution efficiency by performing stirring at the same time. Stirring may be selected depending on the size and type of the reactor, but stirring may be performed using a baffle used in a general reactor.

In addition, the stirring step (step b-2) may be more specifically performed in a nitrogen atmosphere under rotation conditions of 200 RPM to 600 RPM.

In the dissolution step, the solvent may include an additive for controlling the crystallization rate in addition to PLA. The additive may include polycaprolactam, talc, titanium oxide, and the like, and may serve to assist in forming a sphere having a flatness close to 0 when PLA is crystallized.

In addition to the additives, a dispersing agent for particle stabilization may be included. In one embodiment of the present invention, polyvinyl alcohol (PVA), a cellulose-based, acrylic, or silicone-based dispersant may be used as the dispersing agent.

The functional group that imparts dispersibility to the dispersing agent for use in one embodiment of the present invention may include anionic, cationic, nonionic and zwitterionic functional groups. Examples of specific functional groups are shown in Table 1 below.

type designation rescue Anionic Carboxyl -COONa Sulfate -SO ₃ Na Phosphonate -OPO ₃ Na ₂ Phosphate -PO ₃ Na ₂ Cation Amine -N(CH ₃ ) ₃ Cl Pyridium -S(CH ₃ ) ₂ Cl,
-P(CH ₃ ) ₃ Cl,
-NH(C ₂ H ₄ NH) _m H Nonionic Polyols:
Glycerin, Glucose, Sorbitol aminoalcohol -N(C ₂ H ₄ OH) ₂ Polyethyleneglycol -(C ₂ H ₄ O) _m H Polar group:
Amineoxide
-N ⁺ (CH ₃ ) ₂ O ^- Zwitterionic amino acid -NHC ₂ H ₄ COOH Betain -N ⁺ (CH ₃ ) ₂ CH ₂ COO ^- Sulfobtain -N ⁺ (CH ₃ ) ₂ C ₂ H ₄ SO ₃ ^-

In one embodiment of the present invention, the dispersant may be an acrylic dispersant. When acrylic is used as a dispersant, it is advantageous in terms of not only high compatibility with PLA, but also control of the crystallization rate and degree of crystallization of PLA. An example of the acrylic dispersant is shown in Formula 2 below.

[Formula 2]

(In Formula 2, m and n are the same or different integers, and R may be one or more functional groups selected from a carboxyl group, a sulfate group, a phosphonate group, a phosphate group, and an amino acid)

Cooling the PLA solution to generate PLA beads (step c)

If the temperature is lowered to take advantage of the phase separation of the UCST solute/solvent by confirming the UCST point after the generation of a single-phase solution, particle formation is possible as a domain in the metastable phase separation region.

The cooling may proceed to natural cooling gradually at the elevated temperature, and the temperature at the time when the cooling is completed may be at a level of about 50°C to 75°C. The temperature is the temperature at which the PLA crystals pass the crystallization temperature and the crystals grow, and thus the temperature in the section where the particles are generated.

Preferably, a homogenizer may be used to uniform the state of the formed polylactic acid beads and to prepare particles having a diameter of a micro unit.

washing step (step d)

The polylactic acid beads prepared in the cooling process of step c are separated from the solution and washed with acetone, methanol, and distilled water to remove the organic solvent.

Biodegradable polymer beads (PLA beads)

According to another embodiment of the present invention, there is provided a biodegradable polymer bead prepared by the method for preparing the biodegradable polymer bead comprising the steps a to d. The biodegradable polymer beads are decomposed in 2 days when dissolved in a 1 mol% solution of NaOH, but it was found that the biodegradable polymer beads are not decomposed when stored at room temperature in air.

Example 1

800 g of triacetin as a solvent was added to a round glass reactor of 2 liter capacity, and 200 g of PLA having an Mw of 60,000 was additionally added. In addition, a condenser was installed, and the temperature was raised to 180° C. while stirring at 400 RPM in a nitrogen atmosphere. The temperature increase rate was 15 °C/min, and after reaching the target 180 °C, the PLA was sufficiently dissolved by stirring for 20 minutes while maintaining the solution at 180 °C.

After confirming the dissolution state, natural cooling was performed. When the PLA-dissolved triacetin solution was cooled to 70°C, 1 liter of acetone was added and the PLA particles, the solvent, and acetone were separated using a separatory funnel connected to a reduced pressure flask, and washed 2-3 times. It was dried to prepare PLA microbeads.

Examples 2 to 6

PLA microbeads were prepared in the same manner as in Example 1, except that the type or content of the solvent and biodegradable polymer (PLA) was changed as described in Table 2 below.

Comparative Example 1

PLA microbeads were prepared in the same manner as in Example 1, except that the reaction temperature was changed to 210°C.

ingredient content Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 menstruum triacetin 80 75 85 80 80 PEG - - - 80 - benzyl ancol - - - 80 - biodegradable
polymer PLA
(Mw 60,000) 20 25 15 20 20 20 PLA
(Mw 120,000) - - - 20 additive acrylic dispersant 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Reaction temperature (℃) 180 180 180 180 180 180 210 Average particle size (μm) 49.2 31.6 82.0 152.8 30.2 73.2 19.1 particle size distribution 1.24 1.92 1.32 4.2 2.12 1.51 2.47

In Table 2, the content of the solvent and the biodegradable polymer is wt%, and the acrylic dispersant means the amount of phr (part per hundred resin) externally added based on the solvent and PLA formulation 100.

Experimental example

The biodegradability evaluation, particle size and stability evaluation were performed on the PLA microbeads obtained by the manufacturing method of Example 1, and the results are shown in Table 3.

+ 0 days + 45 days Average particle size (μm) 49.2 49.5 particle size distribution 1.24 1.23

From the above table, it can be seen that the PLA microbeads prepared by the manufacturing method of Example 1 according to an embodiment of the present invention maintain the average particle size and particle size distribution even after 45 days, so that the stability of the particles is maintained. . In addition, it was confirmed that decomposition in 2 days in 1 mol% NaOH solution, biodegradability was confirmed.

The evaluation method for each physical property is described below:

(1) Biodegradability evaluation

- Relevant standard: KS M ISO 14855-1 (Measurement of aerobic biodegradability of plastic materials under composting conditions - Method by analysis of released carbon dioxide - Part 1: General method)

- Method to measure the biodegradability and disintegration degree of test substances in the virtual aerobic composting process

- As an inoculum, fully mature and stabilized compost made from composting of municipal solid waste is used.

- After mixing the test substance with the inoculum and immobilizing it, put the composting container in it and allow composting to occur under the condition that moisture content, temperature, and oxygen are controlled during the test period of 6 months or less.

- The degree of biodegradation is determined by the ratio of the theoretical amount of carbon dioxide generated from the test material to the amount of carbon dioxide generated from the actual test material.

(2) Particle size and stability evaluation

- The average particle size and particle size distribution of the crosslinked polymer particles prepared in Examples and Comparative Examples were measured using a Mastersizer 2000S instrument from Melbourne.

- The average particle size and distribution were measured by leaving it to stand for 45 days under the conditions of 30°C and 50% humidity in a constant temperature and humidity chamber.

Although preferred embodiments of the present invention have been described above, it is clear that the present invention can use various changes and equivalents, and can be equally applied by appropriately modifying the above embodiments. Accordingly, the above description is not intended to limit the scope of the present invention, which is defined by the limits of the following claims.

Since the biodegradable polymer bead prepared by the method for manufacturing the biodegradable polymer bead according to the embodiment of the present invention uses a solvent that is not harmful to the human body, it can be appropriately used as a microbead used for medical or cosmetic purposes.

Claims (10)

(a) preparing a polylactic acid polymer having a molecular weight of 30,000 to 150,000 (step a);
(b) dissolving the polylactic acid polymer prepared in step S-1 in at least one solvent selected from polyethylene glycol, triacetin, benzyl alcohol, and pentanol at a temperature of 160° C. to 190° C. (step b);
(c) cooling the solution prepared in step b to produce polylactic acid beads (step c); and
(d) washing the polylactic acid beads produced in step c (step d); comprising, a method for producing biodegradable polymer beads. According to claim 1, wherein the step b of dissolving the polylactic acid polymer at a temperature of 160 °C to 190 °C:
(b-1) a temperature raising step (step b-1) of raising the temperature of the mixture of the polylactic acid polymer and the solvent to a temperature of 160°C to 190°C; and
(b-2) a stirring step of stirring the mixture of step b-1 (step b-2); which will include, a method for producing a biodegradable polymer bead. The method of claim 2, wherein the temperature raising step (step b-1) and the stirring step (step b-2) are simultaneously performed. The method of claim 2, wherein the temperature increase rate in the temperature increase step (step b-1) is 10° C./min to 20° C./min. The method of claim 2, wherein the stirring step (step b-2) is carried out in a nitrogen atmosphere at 200 RPM to 600 RPM rotation conditions. The method of claim 1, wherein the solvent is at least one selected from triacetin, polyethylene glycol, benzyl alcohol, benzyl benzoate, benzyl ether and pentanol. The method of claim 1, wherein an additive is further included in the mixture of the solvent and polylactic acid. The method of claim 7, wherein the additive is at least one selected from a polyvinyl alcohol-based dispersant, a cellulose-based dispersant, an acrylic-based dispersant, and a silicone-based dispersant. The method according to claim 7, wherein the additive is an acryl-based dispersant represented by the following formula (2):

(In Formula 2, m and n are the same or different integers, and R is at least one functional group selected from a carboxyl group, a sulfate group, a phosphonate group, a phosphate group, and an amino acid) 10. The biodegradable polymer beads prepared by the method of any one of claims 1 to 9.