KR102565814B1 - Process for Preparing Composite Particles of Cellulose Nanofiber and Polymer - Google Patents

Abstract

The present invention describes a method for preparing polymer composite particles containing cellulose nanofibers by Pickering emulsion. can be improved

Description

Method for preparing composite particles of cellulose nanofiber and polymer {Process for Preparing Composite Particles of Cellulose Nanofiber and Polymer}

The present invention relates to a method for preparing polymer composite particles using a Pickering emulsion.

Polymethyl methacrylate (PMMA) and polystyrene (PS), which are mainly used as glass substitutes, not only have excellent mechanical properties, but also have high visibility of 92% of visible light transmittance. It is used in a wide variety of industries, such as protective plates for bleachers and eyeglass lenses. The use of these glass substitutes can realize advantages such as reduction in automobile fuel efficiency and raw material use through lightening of materials, improvement of work environment for industrial workers, availability of flexible film materials, and the like.

In recent years, as environmental issues have emerged worldwide, interest in eco-friendly composite materials has increased. For this reason, the utilization of glass substitute materials is gradually expanding, and higher mechanical properties are required, so composite research using nano fillers is being actively conducted within the range that does not interfere with visibility.

Conventional composite material manufacturing methods have used organic solvents or pretreated the surface of nano-fillers to effectively disperse hydrophilic nano-fillers and hydrophobic polymers, but these methods require very high energy and increase production costs due to complicated processes. There are many problems such as environmental problems caused by the use of organic solvents.

As an example of various composite materials, Korean Patent Application No. 10-2015-0106317 discloses a method for preparing an emulsion having excellent dispersibility and stability using a Pickering emulsion. Specifically, a method for preparing a highly dispersed phase emulsion using an ionic water-soluble polymer and silica particles, copper particles, or polystyrene particles having an average particle diameter of 10 nm to 100 μm is disclosed. However, a method for producing a transparent composite material has not been disclosed.

In addition, Korean Patent Application No. 10-2017-7019015 discloses a method for preparing a stable emulsion by coating a plurality of hydrophobic particles on a hydrophilic core particle. The hydrophilic core particles include polysaccharides, specifically porous cellulose particles, and various acrylate polymers are used as the hydrophobic particles. However, the use of the emulsion is limited to a cosmetic composition applied to keratin, and a transparent composite material that can replace glass has not been disclosed. Accordingly, the inventors of the present application have proposed a method for producing a transparent composite material in an environmentally friendly and simpler process in Korean Patent Application No. 2018-0167773. As part of this research, the inventors of the present invention studied a method for further improving the mechanical properties and transparency of the composite material by facilitating the adsorption of cellulose during the production of the polymer composite material using Pickering emulsion.

Accordingly, the present invention is to provide a method for further improving the adsorbability of cellulose when manufacturing a composite material including cellulose and a polymer.

In addition, the present invention is to provide a composite material prepared by the above method and having better physical properties such as mechanical strength and transparency.

The technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

The technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

In order to achieve the above technical problem, the present invention is a method for producing polymer composite particles,

a) preparing an oil phase by mixing a monomer having a polymerizable functional group and a hydrophobic organic solvent;

b) preparing a suspension in which cellulose nanofibers are suspended in water;

c) preparing a dispersion by mixing the oil phase and the suspension and then stirring; and

d) adding a polymerization initiator to the dispersion and then performing a polymerization reaction while stirring to obtain an emulsion of the polymer composite particles.

According to one embodiment, the hydrophobic organic solvent may have an interfacial tension of 30 to 50 mN/m when in contact with water at 20 °C.

According to one embodiment, the oil phase in which the monomer and the hydrophobic organic solvent are mixed may have an interfacial tension of 20 to 40 mN/m when in contact with water at 20 °C.

According to one embodiment, the oil phase in which the monomer and the hydrophobic organic solvent are mixed may have an absolute value of a spreading coefficient (S) of 5 to 20 calculated by Equation 1 below.

[Equation 1]

S (O/W) = γ _ow (cosθ _w -1)

In Equation 1, S (O / W) represents the spreading coefficient of a system in which solid particles are dispersed in a solvent containing oil and water, γ _ow represents the interfacial tension between oil and water (mN / m), , θ _w represents the contact angle between solid particles-water-oil.

According to one embodiment, in step a), the monomer and the organic solvent may be mixed in a volume ratio of 0.5:1 to 1:0.5.

According to one embodiment, the organic solvent may be one or more selected from the group consisting of chlorobenzene, dichlorobenzene, xylene, and d-limonene.

According to one embodiment, the content of the cellulose nanofibers in the suspension in step b) may be 0.01 to 1% by weight.

According to one embodiment, the dispersion may be prepared by mixing the oil phase and the suspension in a volume ratio of 1:1 to 1:50 in step c).

According to one embodiment, the monomer having the polymerizable functional group may include at least one selected from the group consisting of acrylic acid, methacrylic acid, and acrylic acid ester.

According to one embodiment, the polymer composite particle may be one in which the monomer having the polymerizable functional group forms a polymer core particle, and cellulose nanofibers are discontinuously coated on the surface of the polymer core particle.

According to one embodiment, the cellulose nanofibers may have one or more of a length and a diameter of 100 nm or less, and an aspect ratio of 5 to 1250.

According to one embodiment, the cellulose nanofibers may have a diameter of 4 to 100 nm and a length of 0.5 to 5 um.

According to one embodiment, the weight ratio of the polymer monomer and the cellulose nanofibers may be 100: 1 to 20.

According to one embodiment, the average size of the polymer composite particles may be 50 to 200 nm.

In addition, in the present invention, in a method for adsorbing oil by adding particles to a dispersion in which oil and water having a lower interfacial tension than water are mixed, an organic solvent having a higher interfacial tension than oil is added to increase the adsorption capacity of the particles to oil. provides a way to do it.

The present invention relates to a method for producing a composite material of cellulose and a polymer, and does not use additives such as surfactants and stabilizers, and in preparing a composite material through the formation of a Pickering emulsion using water as a solvent, adding an appropriate solvent A film manufactured using a composite material produced by improving the adsorption of cellulose through a simple process has improved permeability, mechanical properties, and thermal stability. The process according to the present invention is simple because only the solvent is added, and it does not require additional processes such as surface modification, and since the surface properties of cellulose are not changed, the original physicochemical properties of cellulose can be maintained.

1 and 2 show the stability of the emulsions prepared in Example 1 and Comparative Example 1.
3 and 4 are SEM pictures showing structures of the composite particles prepared in Example 2 and Comparative Example 2.
5 is a SEM photograph showing the structure of the composite particles prepared in Examples 3 and 4.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. The drawings are provided as examples to sufficiently convey the spirit of the present invention to those skilled in the art. Therefore, the present invention may be embodied in other forms without being limited to the drawings presented below, and the drawings presented below may be exaggerated to clarify the spirit of the present invention.

In addition, the technical terms and scientific terms used herein have meanings commonly understood by those of ordinary skill in the art to which this invention belongs, unless otherwise defined, and in the following description and accompanying drawings, the meaning of the present invention Descriptions of well-known functions and configurations that may unnecessarily obscure the gist are omitted.

The present invention relates to a method for producing composite particles in which cellulose nanofibers are continuously or discontinuously coated on the surface of polymer core particles.

Cellulose is a major component of plant cell walls and is an organic compound that exists in large quantities in nature following coal. Cellulose is a polysaccharide in which β-D-glucose forms a polymer through β-glucosidic bonds (1-4 glucosidic bonds), and its chemical formula is (C ₆ H ₁₀ O ₅ ) _n . The repeating unit is cellobiose. It has a linear structure through 1-4 glucosidic bonds in which carbon 1 and carbon 4 of β-D-glucose are bonded, and the glucose units are alternately inverted. Due to this structure, hydrogen bonds are formed between the hydroxyl groups of the 3rd and 6th carbons adjacent to the parallel cellulose molecules to exist as a linear chain.

About 80 linear chains of these cellulose molecules gather to form cellulose microfibrils, which are functional units in living organisms. A large number of cellulose molecules gather to form a fiber, the smallest unit of which is a micelle, which is about 0.05 nm in diameter and about 0.6 nm in length. The micelles form a crystalline structure, and the junction between micelles and micelles is an amorphous region.

Cellulose possesses numerous hydrogen bonds, resulting in crystallinity and excellent mechanical strength. Due to strong hydrogen bonding, cellulose has no glass transition temperature or melting point, making 3D molding almost impossible. In addition, it has 6 hydroxyl groups per unit structure (cellobiose), so it has strong hydrophilicity, but it is not soluble in water due to hydrogen bonding by these groups. Therefore, there is a need for nanoization technology capable of minimizing and dispersing the size of cellulose while maintaining the mechanical properties of cellulose and compounding it.

Cellulose nanocrystals (CNC) and cellulose nanofibers (CNF) are examples of nanocellulose obtained by nanonizing cellulose.

CNF is composed of nano-sized cellulose fibrils with a high aspect ratio. Fibrils are 5 to 20 nm in width, generally several micrometers in length, exhibit thixotropy, and are characteristic of a viscous gel or liquid under normal conditions, but become less viscous when shaken or shaken. Fibrils are separated from cellulosic stocks by high-pressure, high-temperature and high-speed impact homogenization, grinding or microfluidization.

Nanocellulose can also be obtained from natural fibers by acid hydrolysis, yielding shorter (100-1000 nm), highly crystalline and hard nanoparticles than CNF obtained through homogenization, microfluidization or grinding routes, which are cellulose. They are called nanocrystals (CNC). The micelles that make up the crystalline domain are the main components of CNC.

In the present invention, nanometer-level cellulose nanofibers (CNF) were used so as not to affect the visibility of the final product, and cellulose nanofibers (CNF) and transparent polymer materials (eg, methacrylate-based ) maintained particle size control, stability, and dispersibility in the polymerization and emulsification step. In the composite of cellulose nanofibers (CNF) and transparent polymer materials, an effective method for improving the adsorbability of CNF is provided in a process in which only water is used as a reaction solvent without modifying the surface of the CNF.

Since nanocellulose has an excellent ability to emulsify hydrophobic components (oil) in water, stable oil droplets can be formed by adsorbing nanocellulose on the surface of oil droplets. An emulsion stabilized with only particles such as CNF without using a surfactant is called a Pickering emulsion, and the Pickering emulsion is used in various industries such as oil recovery, drug delivery, and composite particle manufacturing. In order to form a stable emulsion, the adsorption performance of nanocellulose at the interface between water and oil is very important.

In addition, although nanocellulose has an excellent ability to stabilize hydrophobic components in water as an emulsion, it cannot form a Pickering emulsion for all hydrophobic components. For example, it is known that it is difficult for CNF to adsorb components with low interfacial tension, such as octanol or methyl decanoate. Research has been conducted to change the wettability of the surface of nanocellulose through surface modification to enable adsorption in systems where nanocellulose is not well adsorbed. For example, a method of increasing the stability of a Pickering emulsion by changing the nanocellulose surface to a positive charge using glycidyl trimethylammonium chloride is known. It is also known to change the surface properties by surrounding the cellulose nanocrystal surface with methyl cellulose. As such, most approaches are to change the wettability by modifying the surface of nanocellulose to enable Pickering emulsion. However, these methods require an additional process because a pretreatment process for surface modification of nanocellulose is added. Since the surface properties of nanocellulose are changed, dispersibility in water may be affected, and physicochemical properties of nanocellulose may be changed due to changes in surface properties.

The present invention relates to a method for facilitating the adsorption of nanocellulose in the production of a polymer composite material by Pickering emulsion.

An emulsion is a system in which oil droplets are dispersed in water or droplets are dispersed in oil. In particular, a high internal phase emulsion (HIPE) is a system in which the volume of dispersed droplets is 74% or more by volume of the total emulsion. refers to an emulsion system. This highly dispersed phase emulsion has a very high specific surface area to volume compared to normal emulsions, so it can be usefully used, and it is possible to manufacture various porous materials by using the highly dispersed phase emulsion as a template, so that filters, sensors, It can be used in all fields of industry, such as adsorbents and catalyst supports.

The emulsion formed by the method of the present invention is an oil-in-water type Pickering emulsion in which the oil phase (hereinafter also referred to as 'oil phase') is a dispersed phase and the water phase is a continuous phase. (Oil-in-water type pickering emulsion).

In this way, by having the oil phase as the dispersed phase, it is possible to obtain a very stable emulsion in which phase separation does not easily occur even after a long period of time. When the oil layer and the water layer are mixed to form an oil phase as a dispersed phase and an aqueous phase as a continuous phase, the polymer monomers dispersed in the water phase cause a depletion pressure so that CNF is well adsorbed on the surface (interface) of the oil droplet. This is because, by lowering the interfacial tension, phase separation due to the interfacial tension can be suppressed.

In the Pickering emulsion formation method, since the size of the emulsion formed has a specific size in a thermodynamic equilibrium state, it is possible to form a small and uniform emulsion on the order of 100 nm.

Specifically, the present invention,

a) preparing an oil phase by mixing a monomer having a polymerizable functional group and a hydrophobic organic solvent;

b) preparing a suspension in which cellulose nanofibers are suspended in water;

c) preparing a dispersion by mixing the oil phase and the suspension and then stirring; and

d) adding a polymerization initiator to the dispersion and then performing a polymerization reaction while stirring to obtain an emulsion of the polymer composite particles.

The inventors of the present invention, after mixing a monomer having a low interfacial tension with an organic solvent having an appropriate interfacial tension, found that the adsorption performance of the cellulose nanofibers was significantly improved by contacting the cellulose nanofibers suspended in water.

The degree of interfacial adsorption of cellulose nanofibers can be confirmed from the spreading coefficient (hereinafter referred to as 'S'). The spreading coefficient can be finally calculated from the experimentally measured contact angle and interfacial tension by Equation 1, and the closer it is to 0 from positive numbers, the closer to negative numbers, the easier adsorption to the interface. it means.

[Equation 1]

S (O/W) = γ _ow (cosθ _w -1)

In Equation 1, S(O/W) represents the spreading coefficient of a system in which solid particles are dispersed in a solvent containing oil and water, and γ _ow represents the interfacial tension between oil and water (mN/m), , θ _w represents the contact angle between solid particles-water-oil.

The contact angle may be measured by forming a solid particle film (eg, CNF film) on a Si wafer at room temperature and then dropping water on the solid particle film in an oil-filled environment.

Theoretically, if the value of the spreading coefficient ( S ) is positive, the solid particles can be wetted only in one phase, and if the value is negative, the solid particles can be partially wetted in both phases. That is, when the spreading coefficient is a positive number, it is difficult to form a Pickering emulsion. On the other hand, if the spreading coefficient is negative, both phases can be wetted and a Pickering emulsion is well formed. On the other hand, as the boundary value is closer to 0, it is difficult to form a Pickering emulsion because the particles are difficult to wet on both sides. That is, the larger the absolute value of the spread coefficient is, the more advantageous it is to form a Pickering emulsion.

Table 1 below shows the contact angle, interfacial tension and spread coefficient values for several oil components.

The contact angle (θ _w ) was measured using MATLAB and a CCD camera at 20 °C and is the average of values measured at three different locations. About 1 mL of the CNF suspension (1% w/w) was cast onto a Si wafer and left to dry at ambient conditions. The CNF film on the Si wafer was placed in a glass cuvette filled with the target oil to be measured, and 3 μL of water was dropped on the CNF film, and the water contact angle was measured with MATLAB and a CCD camera.

The oil-water interfacial tension ( γ _ow ) was measured by the pendant drop method and has a unit of mN/m. The shape of the oil droplet hanging at the end of a needle (22 gauge, Hamilton) was photographed at 20 °C using a CCD camera (WAT-902H Ultimate, Watec). The shape of the droplet was traced using MATLAB and analyzed to calculate the interfacial tension. Each value is the average of values measured at three different locations on the sample.

The unit of the spreading coefficient (S) is mN/m, and was calculated by Equation 1 above.

According to the results of Table 1, the spread coefficient of MMA (methyl methacrylate) is -2.2 mN/m, which is considerably smaller than other oils known to adsorb cellulose relatively well. Through this, it can be seen that cellulose adsorption is not good in the system using MMA.

In this way, in order to improve the adsorption performance for monomer components that are not well adsorbed to cellulose (absolute value of spreading coefficient is small), a hydrophobic organic solvent having a somewhat high interfacial tension is mixed with an oil in which a monomer and a hydrophobic organic solvent are mixed The phase may make the absolute value of the spreading coefficient (mN / m) calculated by Equation 1 be 5 to 20.

In this case, the monomer having a polymerizable functional group may have an interfacial tension of 10 mN/m or more and 20 mN/m or less, or 15 mN/m or less when in contact with water at 20 °C. The absolute value of the spreading coefficient of the monomer may be less than 5.

In addition, the hydrophobic organic solvent may have an interfacial tension of 30 to 50 mN/m or 30 to 40 mN/m when in contact with water at 20 °C. In addition, the absolute value of the spreading coefficient may be 20 to 30.

The oil phase in which the monomer and the hydrophobic organic solvent are mixed has an interfacial tension of 20 to 40 mN/m or 20 to 30 mN/m when in contact with water at 20° C., and an absolute value of the spreading coefficient of 5 to 20 or 10 to 15 days. there is.

Table 2 below shows the contact angle, interfacial tension and spreading coefficient when the components listed in Table 1 were mixed with MMA in a volume ratio of 1: 1.

From the results of Tables 1 and 2, it can be seen that the absolute value of the spreading coefficient increased rapidly when chlorobenzene having interfacial tension and spreading coefficient within a predetermined range was mixed with the monomer. As will be described in the following examples, the present inventors confirmed through experiments that cellulose was effectively adsorbed when the absolute value of the spread coefficient was large.

According to a preferred embodiment of the present invention, the monomer having a polymerizable functional group may include at least one selected from the group consisting of acrylic acid, methacrylic acid, and acrylic acid ester. For example, it may be methacrylate-based. The monomer capable of forming the methacrylate-based polymer may be methyl methacrylate, ethyl methacrylate, phenyl methacrylate, 2-hydropropyl methacrylate, etc., but is not limited thereto.

In addition, the organic solvent may be one or more selected from the group consisting of chlorobenzene, dichlorobenzene, xylene, and d-limonene.

According to a preferred embodiment of the present invention, in step a), the volume ratio of the monomer and the organic solvent is 0.5: 1 to 1: 0.5, or 0.8: 1 to 1: 0.8. Most preferably, it may be mixed in a volume ratio of 1:1. If the content of any one of the monomer and the organic solvent is too large or small, the effect of improving the adsorption performance of the cellulose nanofibers may be insignificant.

In addition, in step b), the content of the cellulose nanofibers in the suspension may be 0.01 to 1% by weight or 0.05 to 0.5% by weight. If the content of cellulose nanofibers is too small, the effect of improving the physical properties of the composite material by adding cellulose nanofibers is insignificant.

In addition, in step c), the dispersion may be prepared by mixing the oil phase and the suspension in a volume ratio of 1:1 to 1:50. It is preferred that the volume ratio of the oil phase to the suspension is greater than the volume of the oil phase. For example, the volume ratio of the oil phase to the suspension may be greater than 1:5, greater than 1:10, greater than 1:15 or greater than 1:20.

According to one aspect of the present invention, the step of obtaining the polymer composite particle by drying the emulsion of the polymer composite particle may be further included.

The polymer composite material prepared by the method according to the present invention may be in the form of particles in which monomers having polymerizable functional groups form polymer core particles, and cellulose nanofibers are discontinuously coated on the surface of the polymer core particles.

According to one embodiment, the mass ratio of the polymer core particles and the cellulose nanofibers may be 100: 1 to 20, preferably 100: 5 to 15. If the mass ratio of the cellulose nanofibers is too high, the overall stirring is not performed smoothly due to the increase in the viscosity of the dispersion itself, making it difficult for the CNF particles to be adsorbed to the polymer core particles, and also the optical properties are deteriorated due to overlap between the CNF particles. On the other hand, if it is too low, the effect of improving mechanical properties may be insignificant. Therefore, it may be important to increase the input amount by adjusting the aspect ratio of CNF in order to obtain the maximum effect of improving mechanical properties within the range in which the optical properties are maintained.

According to a preferred embodiment, the cellulose nanofibers have at least one of a length and a diameter of 100 nm or less.

According to a preferred embodiment, the cellulose nanofibers have a diameter of 4 to 100 nm and a length of 0.5 to 5 um. It may preferably have a diameter of 4 to 50 nm, a length of 0.5 to 3 um, or a diameter of 5 to 20 nm and a length of 0.5 to 2 um. The aspect ratio of the cellulose nanofibers may be adjusted in the range of 5 to 1250, preferably 25 to 400.

The average size of the composite particles prepared by the method according to the present invention may be 50 to 200 nm, preferably 80 nm or more or 90 nm or more, and may be 150 nm or less or 120 nm or less.

In addition, the composite particles may have a glass transition temperature of 120 °C or higher or 125 °C or higher, and may be 180 °C or lower or 150 °C or lower. The glass transition temperature of the composite particles can be said to be a measure of mechanical properties, and the higher the glass transition temperature, the better the mechanical properties, but there may be a problem in formability, and if it is too low, the physical properties may be poor.

In order to manufacture a cellulose-reinforced polymer composite material using Pickering emulsion, the reinforcing material should be easily adsorbed at the interface between water and monomers. An organic solvent having a predetermined interfacial tension and spreading coefficient characteristics was mixed with the monomer. In this way, since cellulose is more easily adsorbed, when the polymer composite particles produced as a result are thermally compressed with a hot press, etc., the composite film produced has the same characteristics as a composite film in which reinforcing materials are individually dispersed, thereby reducing stress when an external force is applied. By smoothly dispersing, excellent mechanical properties can be maintained. In addition, since a polymer composite material with excellent visible light transmittance can be manufactured depending on the type of polymer monomer, it is expected that it can be used in various fields requiring transmittance and mechanical strength.

The manufacturing method according to the present invention will be described in more detail through the following examples. However, the following examples are only one reference for explaining the present invention in detail, but the present invention is not limited thereto, and may be implemented in various forms. In addition, the unit of additives not specifically described in the specification may be % by weight.

<Example 1>

An oil phase was prepared by mixing methyl methacrylate and chlorobenzene at a ratio of 1:1 v/v. After diluting cellulose nanofibers (diameter of about 13 nm, length of about 445 nm) in water to a concentration of 1 g/L, ultrasonic waves were applied to prepare a dispersion. All water used in this example was deionized (Milli-Q, Merck-Millipore, 18.2 MΩ·cm). The oil phase and the cellulose nanofiber suspension were mixed at a ratio of 1:25 v/v (CNF input amount: 2.5% w/w) and then emulsified using a homogenizer to prepare an emulsion.

<Comparative Example 1>

An emulsion was prepared in the same manner as in Example 1, except that chlorobenzene was not mixed.

The results of comparing the stability of the emulsions of Example 1 and Comparative Example 1 are shown in FIGS. 1 and 2. The stability of the emulsion was observed by the change in emulsion size over time. The emulsion of Example 1 with the addition of chlorobenzene showed high stability up to 7 days, but in the case of Comparative Example 1 without the addition of chlorobenzene, 1 day showed the stability of

<Example 2>

Potassium persulfate (KPS) was added as an initiator to the emulsion prepared in Example 1 (1% w/w based on MMA), and polymerization was performed in a water bath at 70° C. for 8 hours. After completion of the reaction, it was centrifuged and washed with water and methanol to remove remaining monomers and initiators. The resulting PMMA/CNF composite particles were dried at 25° C. for 12 hours in a vacuum condition to obtain polymer composite particles having a particle diameter of about 100 nm.

<Comparative Example 2>

Polymer composite particles were prepared in the same manner as in Example 2, except that the emulsion of Comparative Example 1 was used.

3 and 4 are scanning electron microscope (SEM) pictures of the PMMA/CNF composite particles prepared in Example 2 and Comparative Example 2 (S-4800, Hitachi at 10 kV). Figure 3 is a photograph of the particles obtained 5 hours after the start of polymerization and Figure 4 is 8 hours. Compared to the particles (a) of Comparative Example 2, it can be observed that the particles (b) of Example 2 are adsorbed more reliably to the cellulose nanofibers.

<Example 3>

Polymer composite particles were prepared by reacting for 5 hours in the same manner as in Example 2, except that 1,2-dichlorobenzene was used as the organic solvent mixed with MMA.

<Example 4>

Polymer composite particles were prepared by reacting for 5 hours in the same manner as in Example 2, except that xylene was used as the organic solvent mixed with MMA.

5 is a SEM photograph of the composite particles obtained in Examples 3 and 4. 5, a is the composite particle of Example 3, and b is the composite particle of Example 4. In both examples, it can be confirmed that the cellulose nanofibers are well adsorbed on the surface.

<Example 5>

Polymer composite particles were prepared in the same manner as in Example 2, except that the amount of CNF was changed to 7% w/w.

<Comparative Example 3>

Polymer composite particles were prepared in the same manner as in Comparative Example 2, except that the amount of CNF was changed to 7% w/w.

<Comparative Example 4>

Commercially purchased PMMA (Sigma Aldrich, product name -445746, molecular weight (Mw) 350,000 g/mol) was used.

<Example 6>

The polymer composite particles obtained in Examples 2 and 5 and Comparative Examples 2 to 4 were compressed at 160° C. and 20 MPa for 1 minute to prepare a composite film (thickness of 200 μm). The results of measuring the mechanical properties (Young's modulus) of the composite film are shown in Table 3.

CNF input chlorobenzene multiparticles Young's modulus (GPa) initial input
(% w/w) adsorption amount
(% w/w) 2.5 2.4 O Example 2 1.70±0.14 1.2 X Comparative Example 2 1.51±0.06 7 6.2 O Example 5 2.04±0.10 1.2 X Comparative Example 3 1.52±0.10 0 0 X Comparative Example 4 1.22±0.06

Young's modulus was measured with a Universal Tensile Machine (UTM) (DBCM-20, BONSHIN) equipped with a 200N load cell. A specimen of 3 Х 30 mm (width Х length) was measured at a strain rate of 0.01 min ^-1 through a motor (RKE543AC, Oriental motor) controlled by a software program. A minimum of 5 specimens were measured for each sample.

As shown in the above results, the strength of the composite film using the composite particles prepared by the method according to the present invention was improved by about 70% compared to the composite film of Comparative Example 3 in which cellulose nanofibers were not used at all, and chlorobenzene It can be seen that the composite film of Comparative Example 2, which is not used, exhibits significantly superior strength.

From the above, the composite particles prepared according to the present invention are products that can be used only when transparency and mechanical properties are secured, that is, glass windows, sunroofs, aquarium partitions, ice hockey rink bleachers, lenses, etc., as substitutes for glass or existing transparent plastic materials. , for example, it is expected to be widely used in transparent electrodes, films, coating materials, adhesives, headlamps, and electronic parts materials.

In addition, the method according to the present invention is used not only in the case of forming a composite material, but also in the case where a system requiring adsorption of particles such as oil recovery or encapsulation is required, the interfacial tension is adjusted through a solvent mixing method to remove a system that is not well adsorbed. Adsorption can be made easy.

Claims (15)

a) preparing an oil phase by mixing a monomer having a polymerizable functional group and a hydrophobic organic solvent;
b) preparing a suspension in which cellulose nanofibers are suspended in water;
c) preparing a dispersion by mixing the oil phase and the suspension and then stirring; and
d) adding a polymerization initiator to the dispersion and then proceeding with a polymerization reaction while stirring to obtain an emulsion of the polymer composite particles,
The monomer having the polymerizable functional group includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and acrylic acid ester, and the hydrophobic organic solvent is chlorobenzene, dichlorobenzene, or a mixture thereof,
The oil phase in which the monomer having the polymerizable functional group and the hydrophobic organic solvent are mixed has an interfacial tension of 20 to 40 mN/m when in contact with water at 20 ° C,
Method for producing polymeric composite particles, wherein the oil phase obtained by mixing the monomer having the polymerizable functional group and the hydrophobic organic solvent has an absolute value of a spreading coefficient ( S ) of 5 to 20 calculated by Equation 1 below:
[Equation 1]
S (O/W) = γ _ow (cosθ _w -1)
In Equation 1, S(O/W) represents the spreading coefficient of a system in which cellulose nanofibers are dispersed in a solvent containing oil and water, and γ _ow represents the interfacial tension between oil and water (mN/m) and _θw represents the contact angle between cellulose nanofibers-water-oil. delete delete delete According to claim 1,
In step a), the monomer and the organic solvent are mixed in a volume ratio of 0.5: 1 to 1: 0.5. delete According to claim 1,
In step b), the content of the cellulose nanofibers in the suspension is 0.01 to 1% by weight. According to claim 1,
In step c), the dispersion is prepared by mixing the oil phase and the suspension in a volume ratio of 1:1 to 1:50. delete According to claim 1,
The polymer composite particle is a method of manufacturing a polymer composite particle in which the monomer having the polymerizable functional group forms a polymer core particle, and cellulose nanofibers are discontinuously coated on the surface of the polymer core particle. According to claim 1,
Wherein the cellulose nanofibers have at least one of a length and a diameter of 100 nm or less, and an aspect ratio of 5 to 1250. According to claim 1,
The cellulose nanofiber is a method for producing a polymer composite particle having a diameter of 4 to 100 nm and a length of 0.5 to 5 um. According to claim 1,
The weight ratio of the monomer and cellulose nanofibers is 100: 1 to 20, the method of producing a polymer composite particle. According to claim 1,
A method for producing a polymer composite particle having an average size of 50 to 200 nm. A method of adsorbing oil by adding particles to a dispersion in which oil and water having a lower interfacial tension than water are mixed, wherein an organic solvent having a higher interfacial tension than oil is added to increase the adsorption capacity of the particles to oil, The oil includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and acrylic acid ester, and the organic solvent is chlorobenzene, dichlorobenzene, or a mixture thereof,
The mixture of the oil and the organic solvent has an interfacial tension of 20 to 40 mN / m when in contact with water at 20 ° C,
The method in which the mixed solution of the oil and the organic solvent has an absolute value of 5 to 20 of the spreading coefficient ( S ) calculated by Equation 1 below:
[Equation 1]
S (O/W) = γ _ow (cosθ _w -1)
In Equation 1, S(O/W) represents the spreading coefficient of a system in which particles are dispersed in a solvent containing oil and water, γ _ow represents the interfacial tension between oil and water (mN/m), θ _w represents the contact angle between particles-water-oil.