KR102465874B1 - Ceramic coating composition containing cellulose nanofibers - Google Patents

Abstract

The present invention relates to a ceramic coating composition containing cellulose nanofibers, and specifically, to prepare a ceramic coating solution containing CNF (cellulose nanofibers) without chemical modification of the surface of a substrate (aluminum, plastic, woven fiber, ceramic, etc.) Accordingly, it is directed to providing a simple method of increasing hydrophobicity by controlling surface roughness.

Description

Ceramic coating composition containing cellulose nanofibers and method for preparing the same {Ceramic coating composition containing cellulose nanofibers}

The present invention relates to a ceramic coating composition including cellulose nanofibers and a method for producing the same, and specifically, to prepare a ceramic coating composition for identifying cellulose nanofibers without additional cost and processing, and thereby controlling surface roughness to increase hydrophobicity It is to provide a ceramic coating composition.

Hydrophobic properties in various fields such as kitchen utensils and daily necessities including heating plates and glass containers, various finishing materials, piping including water pipes, semiconductors, construction, display screens, aviation and metal wiring. Demand for water repellency materials is increasing. To this end, attempts have been made to modify the surface of hydrophilic substrates to be hydrophobic, and for example, products in which hydrophilic surfaces are hydrophobic using organic polymer modifiers have been marketed. However, conventional organic polymer materials having hydrophobic properties are vulnerable to heat and deteriorate when heated to a high temperature and lose their hydrophobic properties. The poor thermal stability of these existing polymer modifiers is a major obstacle to their application to industrial fields where heat resistance is particularly required.

As a coating with high thermal stability, ceramic coating has been used for a long time in a wide range of fields such as interior and exterior materials, semiconductors, and kitchen utensils. Ceramic coatings have good hardness, heat resistance, and corrosion resistance. In particular, recently, ceramic coatings have attracted attention for their non-toxic and eco-friendly properties. Ceramic coatings are generally made by applying a coating solution to a substrate through a coating process such as spray or dip coating. Among the representative methods for preparing a ceramic coating solution, there is a sol-gel process. Through the sol-gel process, colloids form various inorganic network structures such as airgels, xerogels, and coatings. Typical precursors are silicon or metal alkoxides. The colloidal forms are hydrolyzed and then form covalent bonds with each other through a condensation reaction to form a network.

The coating surface prepared using silicon alkoxide by the sol-gel method has hydrophilicity due to exposure of hydroxyl groups. Since the surface is hydrophilic, a problem of low water repellency occurs, and many attempts have been made to make the hydrophilic surface hydrophobic.

Under this background, the present inventors determined that the hydrophobicity would be improved by implementing a texture surface without chemical modification of the ceramic coating, and as a result of diligent efforts to solve the conventional problem, when a ceramic composition was prepared by adding cellulose nanofibers, significantly hydrophobic By confirming this increase, the present invention was completed.

One object of the present invention is the first step of dispersing silica particles in water to form a silica sol in the form of a colloidal sol, putting the pulp in water, dispersing in a homogenizer, and then concentrating with a centrifuge to produce cellulose nanofibers (CNF) A second step of doing, a third step of preparing a mixture by mixing the silica sol, cellulose nanofibers and the first solvent, and a fourth step of mixing and rolling the mixture with a second solvent; manufacturing a ceramic coating composition comprising is to provide a way

Another object of the present invention is to provide a ceramic coating composition prepared by the method for preparing a ceramic coating composition of the present invention.

Another object of the present invention is to provide a water-repellent coating method, in which the ceramic coating composition of the present invention is coated on a substrate by a spray method.

A detailed description of this is as follows. Meanwhile, each description and embodiment disclosed in the present invention may also be applied to each other description and embodiment. That is, all combinations of the various elements disclosed herein fall within the scope of the present invention. In addition, it cannot be seen that the scope of the present invention is limited by the specific descriptions described below.

A first aspect of the present invention for achieving the above object is a first step of dispersing silica particles in water to form a silica sol in the form of a colloidal sol, dispersing the pulp in water with a homogenizer, and then concentrating with a centrifuge The second step of preparing cellulose nanofibers (CNF), the third step of preparing a mixture by mixing the silica sol, cellulose nanofibers and the first solvent, and the fourth step of mixing and rolling the second solvent with the mixture Including, it provides a method for producing a ceramic coating composition.

In addition, a second aspect of the present invention provides a ceramic coating composition prepared by the method for preparing a ceramic coating composition of the present invention.

In addition, a third aspect of the present invention provides a water-repellent coating method in which the ceramic coating composition of the present invention is coated on a substrate by a spray method.

Hereinafter, the present invention will be described in more detail.

As used herein, the term "silica particles" means a material that prevents aggregation and helps in dispersion. Specifically, it may be to provide heat resistance and corrosion resistance and to provide non-toxic and environmentally friendly characteristics.

The size of the silica particles may be 40 nm to 60 nm, but is not limited thereto.

As used herein, the term "colloid sol" refers to a solution in which a solvent and a solute are completely mixed to form a single phase, in which an insoluble substance having a size of 1 to 1000 nm is dispersed in a liquid and mixed with other substances. means a mixture.

As used herein, "silica sol" means that solid silica particles are dispersed in a liquid. Specifically, the silica sol in the form of a colloidal sol may be one in which nano-sized silica particles are evenly dispersed in a liquid and evenly mixed with cellulose nanofibers.

As used herein, the term "pulp" refers to cellulose fibers mechanically or chemically extracted from wood or some species of herbaceous plants.

The pulp may include hardwood pulp, softwood pulp, dewood pulp, or non-wood pulp, but is not limited thereto.

The dispersion of the second step may be performed at 500 rpm to 2,000 rpm. If it is less than 500 rpm, the dispersing effect may be insignificant, and if it exceeds 2,000 rpm, cellulose nanofibers may be cut.

The term of the present invention, "cellulose nanofiber (CNF)" means an eco-friendly biomass material having high crystallinity, high strength, chemical stability, excellent stability to the living body, and gas barrier property. Specifically, as the amount of cellulose nanofibers added increases, the ceramic coating composition may be randomly accumulated to increase surface roughness and impart hydrophobicity.

Cellulose nanofibers of the second step may be concentrated to 1.5wt% to 5wt%. If the cellulose nanofiber is less than 1.5wt%, it may be difficult to include in the ceramic coating composition because water is excessively included, and if it exceeds 5wt%, the viscosity may increase, which may cause difficulty in spray coating.

The weight of the cellulose nanofibers compared to the silica sol may be 1 to 10% by weight. When the weight of cellulose nanofibers is less than 1% by weight, the hydrophobic effect may be insignificant, and when it exceeds 10% by weight, there may be difficulty in spray coating due to viscosity improvement.

The first solvent may include ethyl silicate, isopropyl alcohol, or a combination thereof. Specifically, the first solvent may be included as a reactant of the sol-gel reaction.

Mixing in the third step may be performed for 1 hour to 2 hours. If the mixing time is less than 1 hour, the coating layer may not be formed, and if it exceeds 2 hours, the physical properties of the coating layer may be affected due to overreaction. More specifically, the mixing may be performed by dispersing silica sol on the cellulose nanofibers so that the hydrophilic cellulose nanofibers are not directly exposed to the surface of the coating composition and only increase roughness to provide hydrophobicity.

The second solvent may include hydrochloric acid, formic acid, p-toluenesulfonic acid (PTSA), poly(dimethylsiloxane), methyltrimethoxysilane, a surfactant, isopropyl alcohol, or a combination thereof. Specifically, the second solvent may be included as a reactant of the sol-gel reaction.

The rolling of the fourth step may be performed for 0.5 to 2 hours. Specifically, it may be to use a ball mill roller, and if the rolling time is less than 0.5 hours, the mixing reaction may not react, and if it exceeds 2 hours, the reaction may be overreacted, thereby affecting the physical properties of the coating layer.

One aspect of the present invention for achieving the above object provides a ceramic coating composition prepared by the method for preparing a ceramic coating composition.

The ceramic coating composition may include silica particles and cellulose nanofibers (CNF).

The ceramic coating composition may be for spray coating.

The term "spray coating" of the present invention means that substrates of various shapes are evenly sprayed and coated with uniformity and density more simply than other coating methods. Specifically, it may further include using an air brush (GP-50, sparmax) and sintering after spray coating.

The ceramic coating composition may have a viscosity of 1 cP to 1100 cP. When the viscosity of the coating composition is less than 1 cP, a coating film may not be formed, and when it exceeds 1100 cP, it may not be suitable for spray coating that is evenly sprayed with high viscosity.

Specifically, the ceramic coating composition may be prepared without chemical modification to provide a hydrophobic effect by controlling surface roughness.

Another aspect of the present invention for achieving the above object provides a water-repellent coating method, which uses a ceramic coating composition to coat a substrate by spraying.

The substrate may include aluminum, plastic, ceramic or woven fabric. Specifically, “substrate” means a polymeric organic material substrate as well as inorganic materials such as ceramics and metals such as glass and silicon wafer fibers. Specifically, the substrate includes polyolefin (PO), polyethylene (PE), polypropylene (PP), polyester, or biaxially oriented polypropylene (BOPP). It may be, but is not limited thereto.

In a specific embodiment, the ceramic coating composition of the present invention containing CNF does not lose hydrophobicity by coating ceramic particles on CNF even if it contains hydrophilic CNF, and the surface roughness (Ra) increases as the CNF content increases. confirmed that

Therefore, through the above specific embodiment, it was confirmed that the ceramic coating composition of the present invention was prepared without chemical change and had a hydrophobic effect, which means that the ceramic coating composition of the present invention is resistant to moisture and oxygen such as chemicals, electronic members, and electronic devices. This suggests that it can be used as a hydrophobic coating composition, etc.

It is to control the surface roughness and hydrophobicity and provide a water repellent effect by including cellulose nanofibers in the ceramic coating composition of the present invention in an environmentally friendly manner without chemical modification.

1 is a 3D laser scanning micrograph of the surface of the ceramic coating composition of the present invention.
Figure 2 is a graph showing the roughness according to the cellulose nanofiber content of the ceramic coating composition of the present invention.
Figure 3 is a SEM picture of the composition surface according to the cellulose nano content included in the ceramic coating composition of the present invention.
4 is a photograph showing the surface of the ceramic coating composition of the present invention by SEM-EDX analysis.
5 is a graph showing the water contact angle of the composition surface according to the cellulose nano content included in the ceramic coating composition of the present invention.
6 is a graph showing the roughness and water contact angle of the surface of the composition according to the cellulose nano content included in the ceramic coating composition of the present invention.
7 is a graph showing the contact angle change over time of the surface coated with the ceramic coating composition of the present invention.
8 is a photograph showing a change in the shape of a surface droplet over time of a surface coated with the ceramic coating composition of the present invention.
9 is a photograph of polyester coated with the ceramic coating composition of the present invention.

Hereinafter, the present invention will be described in more detail through examples. These examples are intended to explain the present invention in more detail, and the scope of the present invention is not limited by these examples.

ingredient

A colloidal sol was used by dispersing silica particles (50%) with a size of 50 nm in 50% water. Tetraethyl orthosilicate (TEOS), methyltrimethoxysilane (MTMS), isopropyl alcohol, ethyl alcohol, hydrochloric acid, formic acid, p-toluenesulfonic acid (PTSA), poly(dimethylsiloxane) (PDMS) and eucalyptus hardwood bleached kraft Pulp was purchased from Sigma-Aldrich and used.

Preparation Example 1: Preparation of cellulose nanofibers (CNF)

10 g of hardwood pulp was put into 100 g of water and firstly mixed for 5 minutes at 15,000 rpm using a homogenizer. The solution was further stirred at 1,000 rpm using basket milling to prepare a 1 wt% CNF dispersion. Since the 1 wt% CNF dispersion contains excessive water for use as a solvent, it is difficult to include it in the ceramic coating composition, so 10,000 g RCF (Relative centrifugal force) was used to increase the CNF content of the dispersion using a centrifuge (Gyrozen 2336 HR) It was concentrated by centrifugation for 15 minutes to prepare CNF at 2wt% to 4wt%.

Preparation Example 2: Preparation of ceramic coating composition

Using a ball-less ball mill roller, 15.27 g of colloidal silica sol, 15.27 g of water, 5.47 g of ethyl silicate (Tetraethyl orthosilicate, TEOS), 5.47 g of isopropyl alcohol (IPA) and Preparation Example 1 A mixture was prepared by adding CNF prepared as shown in Table 1 below and mixing for 1.5 hours. To the mixture was added 0.5g HCl, formic acid and p-toluenesulfonic acid (PTSA). Thereafter, 10 g of poly(dimethylsiloxane) (PDMS) and 26.94 g of methyltrimethoxysilane (MTMS) were added and reacted for 1 hour using a ball mill roller. Finally, after adding 10.08 g of methyltrimethoxysilane (MTMS) and 10 g of isopropyl alcohol (IPA), the mixture was reacted by rolling for 0.5 hour.

Samples CNFs (g) Silica (g) CNF/Silica
Ratio (%) Total solid
(g) Total solution
(g) Solution concentration
(%) Viscosity
(cP) CS0 0 15.27 0 15.27 100 15.27 28 CS1 0.15 15.27 One 15.24 104 14.86 108 CS3 0.46 15.27 3 15.73 111 14.11 284 CS5 0.76 15.27 5 16.03 119 13.46 880 CS10 1.53 15.27 10 16.80 176 9.52 1080

As shown in Table 1, the amount of CNF was prepared at a ratio of 0% (CS0), 1% (CS1), 3% (CS3), 5% (CS5), and 10% (CS10) relative to the added silica. The viscosity increased as the CNF content increased, and showed a suitable viscosity (cP) for the spray coating process.

Preparation Example 3: Coating layer formation

5 ml of the ceramic coating composition (CS0) without CNF and the ceramic coating composition (CS1, CS3, CS5, and CS10 in Table 1 above) to which CNF was added were applied using an airbrush (GP-50, sparmax) to a 9 cm x 5 cm It was applied to the surface of a polypropylene (PP) plate of the same size. After coating, it was sintered at 60° C. for 3 hours.

Example 1: Roughness (Ra) analysis of coating surface

In order to confirm the roughness of the surface of the ceramic coating composition of the present invention, it was analyzed with a 3D laser scanning microscope (3D LSM) and the roughness (Ra) value was calculated using a formula based on this analysis.

As shown in FIG. 1, the surface of the CSO coating layer coated with the ceramic coating composition to which CNF was not added in FIGS. 1 (a) and (f) showed a unique texture when the ceramic was cured. On the other hand, the surface of CS1 to which 1% CNF was added in FIGS. 1 (b) and (g) was observed to have a fibrous shape. In addition, it was confirmed that aggregation occurred due to strong attraction between the fibers of the CNF and the fibers appearing on the surface of the coating layer. As a result, unlike the surface of CS0, it was confirmed that the surface roughness of CS1 increased. In addition, it was confirmed that the size of the pores was larger than that of the surface of CS0 and the number of pores was large. On the other hand, CS3 of FIGS. 1 (c) and (h), CS5 of FIGS. 1 (d) and (i), and CS10 of FIG. 1 (e) and (i) find a CS0 ceramic texture as the CNF content increases. It was confirmed that the number and size of pores increased due to aggregation of fibers, resulting in an increase in roughness.

Next, as shown in FIG. 2, the roughness was analyzed by analyzing the photograph of FIG. 1, and the roughness (Ra) was specifically calculated using the following formula.

As a result, it was confirmed that the Ra of CS0 without CNF was 3.1368 ± 0.1036 μm, and that of CS1 with CNF was 6.1149 ± 0.3552 μm, which was twice as high as that of CSO. CS3 showed Ra values of 7.4420 ± 1.4270 μm, CS5 15.6329 ± 1.9977 μm, and CS10 46.3399 ± 2.7129 μm, and it was confirmed that the roughness increased as the CNF content increased.

In addition, as shown in FIG. 3, (a), (f) and (k) of FIG. 3 indicate CS0, (b), (g) and (l) indicate CS1, (c), (h) and (m) shows CS3, (d) (i) and (n) show CS5, and (e), (j) and (o) show the surface of CS10. As the CNF content increases, the surface It was confirmed that the aggregated CNF was exposed and covered with silica particles to further increase the surface roughness.

Example 2: Hydrophobicity analysis

Hydrophobicity was confirmed by analyzing elements on the surface of the coating layer coated with the silica coating composition of the present invention using SEM-EDX.

As a result, as shown in FIG. 4, SEM-EDX analysis showed that Si elements were mainly distributed on the surface of CS5 and O and C elements were present. Through this, it was confirmed that the hydrophilic CNF component was not directly exposed, but was covered with silica particles on the CNF to maintain hydrophobicity.

Example 3: Analysis of the water contact angle of the coating surface

The water contact angle of the surface of the polyester fabric and the coating layer (CS0, CS1, CS3, CS5, CS10) coated with the silica coating composition of the present invention was analyzed.

As a result, as shown in FIGS. 5 and 6, it was confirmed that the contact angle increased as the CNF content increased, and it was confirmed that the water-repellent and hydrophobic effect was exhibited as the CNF content increased.

In addition, as shown in FIGS. 7 to 8, as a result of comparing the ceramic composition CS0 without CNF on the polyester fabric and the ceramic composition C10 including CNF on the polyester raw sugar, the polyester fabric The contact angle was 126.1 and the time taken for the water droplet to permeate the fabric was 225.4 seconds, and the contact angle of CS0 was 128.0, and the time required for the water droplet to permeate the fabric was 463.5 seconds, which doubled. . Through this, the contact angle of CS10 coated with the ceramic coating composition of the present invention increased to 131.6, and the time required for water droplets to permeate into the fabric increased more than 10 times to 2455.3 seconds, providing a woven fabric with improved hydrophobicity. I was able to confirm that it could be done.

In addition, as shown in FIG. 9, it was confirmed that flexibility was still maintained even when the hydrophobic coating composition CS10 of the present invention was coated on the polyester fabric.

In summary of Examples 1 to 3 of the present invention, the ceramic coating composition of the present invention containing CNF does not lose hydrophobicity as the ceramic particles are coated on CNF even if it contains hydrophilic CNF, and as the CNF content increases, It was confirmed that the surface roughness (Ra) increased and the water repellent and hydrophobic effect increased.

From the above description, those skilled in the art to which the present invention pertains will be able to understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential characteristics thereof. In this regard, it should be understood that the embodiments described above are illustrative in all respects and not limiting. The scope of the present invention should be construed as including all changes or modifications derived from the meaning and scope of the claims to be described later and equivalent concepts rather than the detailed description above are included in the scope of the present invention.

Claims (18)

A first step of dispersing silica particles in water to form a silica sol in the form of a colloidal sol;
A second step of preparing cellulose nanofibers (CNF) by dispersing the pulp in water with a homogenizer and then concentrating the pulp with a centrifuge;
A third step of preparing a mixture by mixing the silica sol, cellulose nanofibers and the first solvent; and
A method for producing a ceramic coating composition comprising a; fourth step of mixing and rolling a second solvent in the mixture,
The size of the silica particles is 40nm to 60nm, ceramic coating composition manufacturing method.
delete According to claim 1,
The method of producing a ceramic coating composition, wherein the pulp comprises hardwood pulp, softwood pulp, dewood pulp, or non-wood pulp.
According to claim 1,
The dispersion of the second step is a ceramic coating composition manufacturing method that is performed at 500 rpm to 2,000 rpm.
According to claim 1,
The cellulose nanofibers of the second step are concentrated to 1.5wt% to 5wt%, a ceramic coating composition manufacturing method.
According to claim 1,
The weight of the cellulose nanofibers compared to the silica sol is to include 1 to 10% by weight, a ceramic coating composition manufacturing method.
According to claim 1,
The method of claim 1, wherein the first solvent includes ethyl silicate, isopropyl alcohol, or a combination thereof.
According to claim 1,
The mixing of the third step is performed for 1 hour to 2 hours, a method for producing a ceramic coating composition.
According to claim 1,
The second solvent includes hydrochloric acid, formic acid, p-toluenesulfonic acid (PTSA), poly(dimethylsiloxane), methyltrimethoxysilane, a surfactant, isopropyl alcohol, or a combination thereof, Ceramic Coating Composition Preparation Way.
According to claim 1,
The method of producing a ceramic coating composition, wherein the rolling of the fourth step is performed for 0.5 to 2 hours.
A ceramic coating composition prepared by the method of claim 1.
According to claim 11,
The ceramic coating composition may include silica particles; and
A ceramic coating composition comprising cellulose nanofibers (CNF).
According to claim 12,
The weight of the cellulose nanofibers compared to the silica particles is to include 1 to 10% by weight, the ceramic coating composition.
According to claim 12,
The silica particles are in the form of a colloidal sol, a ceramic coating composition.
According to claim 12,
The ceramic coating composition is for spray coating, the ceramic coating composition.
According to claim 12,
The viscosity of the ceramic coating composition is 1cP to 1100cP, the ceramic coating composition.
A water-repellent coating method, wherein the ceramic coating composition according to any one of claims 11 to 16 is coated on a substrate by a spray method.
According to claim 17,
The substrate is a water-repellent coating method comprising plastic or fiber.

Images