JP2011026390A - Coating composition and film comprising the coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition from which films having excellent transparency, high strengths and high elastic moduli can more certainly be obtained, and to provide a film comprising the coating composition and having excellent transparency, high strength and high elastic modulus. <P>SOLUTION: There is provided the coating composition wherein a small amount of nano diamond particles is dispersed in polyvinyl alcohol to obtain the coating composition from which films having excellent transparency, high strengths and high elastic moduli can more certainly be obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coating composition comprising polyvinyl alcohol and nanodiamond particles, and a film comprising the coating composition.

  Conventionally, so-called nanocarbon materials represented by carbon nanotubes and fullerenes have excellent strength and elastic modulus, and it is expected that excellent composite materials can be obtained by combining with polymers. Research and development is in progress.

  However, when carbon nanotubes and a polymer are mixed, the obtained mixture cannot sufficiently bring out the characteristics of the carbon nanotubes, and specifically, the strength and elastic modulus do not increase as expected. . In addition, the polymer is blackened due to the carbon nanotubes, and its use is limited because it is inferior in transparency. In particular, it is difficult to use the coating composition and a film made of the coating composition.

  On the other hand, as one of the nanocarbon materials, a technique using nanodiamonds (particles) has been studied. For example, Patent Document 1 hardly exhibits a color and sufficiently suppresses a change in color over time. The deodorizing antibacterial agent includes a nanodiamond aggregate in which nanodiamonds are aggregated with the intention of providing a deodorizing antibacterial agent having excellent deodorizing properties and antibacterial properties. A deodorizing antibacterial agent having a content of 1% by mass or less is disclosed, and it is disclosed that polyvinyl alcohol is added as a binder (see, for example, Patent Document 1, paragraph [0036]).

  Moreover, in patent document 2, the thermoplastic resin (A) and the single-piece | unit thermal conductivity are 1 in order to provide the inorganic substance containing thermoplastic resin composition excellent in electrical insulation and heat conductivity. Contains at least 5 W / m · K or more and a high thermal conductivity inorganic compound (B) having a volume resistivity of 0.1 Ω · cm or more, and an electrically insulating low-melting-point inorganic substance (C) having a softening point temperature of 350 ° C. or less. In addition, an electrically insulating high thermal conductive thermoplastic resin composition characterized by having a thermal conductivity of 1.5 W / m · K or more is disclosed, and diamond is used as the high thermal conductive inorganic compound (B). For example, see Patent Document 2 and paragraph number [0034].

  However, the deodorizing antibacterial agent described in Patent Document 1 is not used for a coating composition or a film made of the coating composition, and a film having excellent transparency, high strength, and high elastic modulus can be obtained. It was not a thing. Further, in the electrically insulating high thermal conductive thermoplastic resin composition described in Patent Document 2, the content of the high thermal conductive inorganic compound (B) is large (see, for example, Patent Document 2, paragraph [0039]), A film having excellent transparency, high strength and high elastic modulus could not be obtained.

  On the other hand, Patent Document 3 discloses a polymer composite material in which nanodiamonds are dispersed in a polymer in an attempt to provide a polymer composite material having excellent heat resistance and elastic modulus and a method for producing the polymer composite material. Polyvinyl alcohol is exemplified as the polymer (see, for example, Patent Document 3, paragraph [0009]).

JP 2009-45287 A JP 2008-169265 A JP 2004-51937 A

  However, in the above-mentioned Patent Document 3, with respect to the polymer composite material, it is preferable to add 1 to 20 parts by weight of nanodiamond with respect to 100 parts by weight of the polymer (the same document, paragraph [0011]). Although described, only an organic soluble acrylic resin is used as the polymer, and the effect of increasing the elastic modulus is not sufficient. Moreover, although polyvinyl alcohol is illustrated as a polymer, it does not describe at all about the effect by the Example using polyvinyl alcohol, or employ | adopting polyvinyl alcohol. That is, there is still room for improvement from the viewpoint of obtaining a film having excellent transparency, high strength and high elastic modulus and a coating composition from which such a film can be obtained.

  Accordingly, the present invention has been made in view of the above-described problems of the prior art, and a coating composition that can more reliably obtain a film having excellent transparency, high strength, and high elastic modulus, and the coating. It aims at providing the film which has the outstanding transparency which consists of a composition, high intensity | strength, and a high elasticity modulus.

  As a result of intensive studies to achieve the above object, the inventors of the present invention obtain a coating composition that can more reliably obtain a film having superior transparency, high strength, and high elastic modulus as compared with the prior art. For this purpose, the present inventors have found that it is extremely effective to disperse a small amount of nanodiamond particles in polyvinyl alcohol (PVA), and have reached the present invention.

  That is, the present invention provides a coating composition comprising polyvinyl alcohol (PVA) and nanodiamond (ND) particles.

  Since the coating composition of the present invention has polyvinyl alcohol having an excellent affinity for water, the polyvinyl alcohol interacts with the surface of the nanodiamond particles, and the nanodiamond particles in the dispersion medium are substantially uniformly and for a long period of time. It is considered that the dispersibility is improved by this.

  The coating composition of the present invention can be applied to an object (base material or the like) while maintaining a well-dispersed state of nanodiamond particles, and a film having excellent transparency, high strength and high elastic modulus. It is considered to be obtained. The “dispersibility” in the present invention means whether or not the dispersion state of the nanodiamond particles in the coating composition is excellent immediately after the coating composition of the present invention is prepared (whether it is uniform). It is shown.

  The coating composition of the present invention preferably contains 4.0% by mass or less of nanodiamond particles with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles. That is, the content of nanodiamond particles is preferably polyvinyl alcohol: nanodiamond particles = 96.0: 4.0 or less. In the coating composition of the present invention, when the content of nanodiamond particles is 4.0% by mass or less with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles, a film made of the coating composition The mechanical properties of can be made sufficient, which is preferable. As a lower limit, what is necessary is just about 0.1 mass%.

  Furthermore, the coating composition of the present invention preferably contains 1.0% by mass or less of nanodiamond particles with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles. That is, the content of nanodiamond particles is preferably polyvinyl alcohol: nanodiamond particles = 99.0: 1.0 or less. In the coating composition of the present invention, when the content of nanodiamond particles is 1.0% by mass or less with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles, a film made of the coating composition The optical physical properties can be made satisfactory.

  Here, “dry state” of “total amount of polyvinyl alcohol and nanodiamond particles (dry state)” is a state of a solid content obtained by removing volatile components from a mixture of polyvinyl alcohol and nanodiamond particles. After removing the dispersion medium from the coating composition using silica gel or the like, for example, it means the state of the solid content remaining when dried at room temperature of 30 ° C. or lower (for example, 25 ° C.) for 24 hours. .

  Various methods can be adopted as a method of removing the dispersion medium from the coating composition using silica gel. For example, the coating composition is applied onto a glass substrate and placed in a sealed container containing silica gel. What is necessary is just to remove a dispersion medium by leaving a glass substrate with a coating film for 24 hours or more.

The present invention also provides a film comprising the above-described coating composition of the present invention.
As a result of intensive studies, the present inventors have found that when a film is formed using the coating composition of the present invention, the resulting film has excellent transparency, high strength, and high elastic modulus. .

The film of the present invention may have a transmittance of 50 to 90% / 100 μm with respect to visible light of 380 nm.
Thus, if a film is formed using the coating composition of the present invention, the resulting film has excellent transparency.

  According to the present invention, a coating composition capable of more reliably obtaining a film having excellent transparency, high strength and high elastic modulus, and excellent transparency, high strength and high elastic modulus comprising the coating composition. Can be provided.

It is a figure which shows the measurement result of the breaking strength in an Example. It is a figure which shows the measurement result of the Young's modulus in an Example. It is a figure which shows the measurement result of the light absorbency (transmittance) in an Example.

  Hereinafter, a preferred embodiment of the coating composition of the present invention and a preferred embodiment of a film using the coating composition of the present invention will be described in detail. In the following description, overlapping description may be omitted.

[Coating composition]
First, a preferred embodiment of the coating composition of the present invention will be described. The coating composition of this embodiment has a configuration mainly including polyvinyl alcohol, a solvent for polyvinyl alcohol (optional component), nanodiamond particles, and a dispersion medium for nanodiamond particles.

  By having such a configuration, the coating composition of the present embodiment has polyvinyl alcohol having an excellent affinity for water. Therefore, the polyvinyl alcohol interacts with the surface of the nanodiamond particles, and the coating composition contains It is considered that the nanodiamond particles in can be dispersed almost uniformly over a long period of time, which improves the dispersibility. The coating composition of the present invention can be applied to an object (base material or the like) while maintaining a well-dispersed state of nanodiamond particles, and a film having excellent transparency, high strength and high elastic modulus. It is considered to be obtained.

  Here, the present inventors use the UV / V is spectrometer U-2000 manufactured by Hitachi, Ltd. to measure the absorbance by a visible light absorption method, and use Autograph AGS-1kND manufactured by Shimadzu Corporation. The film obtained using the coating composition of the present embodiment (more specifically, the coating composition of the examples described later) by the tensile test, has excellent transparency, high strength and high elastic modulus. Have confirmed.

(1) Polyvinyl alcohol As polyvinyl alcohol, various types can be used as long as the effects of the present invention are not impaired. For example, polyvinyl alcohol represented by (—CH ₂ CH (OH) —) _n (in the formula, For example, n may be 200 to 2,400).

  Since vinyl alcohol, which is a monomer, has an unstable structure and immediately changes to formaldehyde, as a general production method, polyvinyl acetate is hydrolyzed (saponified) to produce polyvinyl alcohol. obtain. There are various levels of treatment of hydrolysis of ester groups, and in general, those having a low saponification degree of about 70 mol% to those having a complete saponification degree of 100 mol% are commercially available. Without being limited to the above, various types can be used as long as the effects of the present invention are not impaired.

  One characteristic of polyvinyl alcohol is its high affinity for water, but it can also be said that its water resistance is low. About this point, the method of providing water resistance by formalizing a hydroxyl group by methods, such as acetalization using formalin, is established. Also in the present invention, acetalized polyvinyl alcohol may be used.

(2) Solvent for polyvinyl alcohol The solvent used for dissolving polyvinyl alcohol to form a solution is not particularly limited as long as polyvinyl alcohol can be dissolved. Water, dimethyl sulfoxide, dimethylformamide, formaldehyde, acetaldehyde, ethylene oxide, Methyl acetate, N-methylacetamide, dimethoxymethane, methyl ethyl ketone, 1,1-dimethoxyethane, phenol, aniline, 1,3-dimethyl-2-imidazolidinone, low molecular weight alcohols (eg methyl alcohol, ethyl alcohol, propyl alcohol) , Ethylene glycol, propylene glycol, triethylene glycol, glycerin) and the like. These can be used alone or in combination. Water is most preferably used from the viewpoint of fire hazard, environmental load and human health.

  In addition, since polyvinyl alcohol has a strong intermolecular hydrogen bond, warming is generally used at the time of dissolution. Also in this embodiment, it can heat at the time of melt | dissolution of polyvinyl alcohol.

(3) Nanodiamond particles The nanodiamond particles that can be used in the present embodiment have an average primary particle size of 1 nm to 11 nm, preferably 3 nm to 7 nm.
Further, the primary particles are usually present as secondary aggregates with a size of several tens of nanometers to several hundreds of nanometers (aggregated particle diameter), and the coating composition of this embodiment and the nanodiamond particles are included as secondary aggregates. May be.

Here, the average primary particle diameter of the nanodiamond particles in the coating composition can be measured by a transmission electron microscope, and the aggregated particle diameter of the nanodiamond particles is determined by a dynamic light scattering method (Doppler scattering light analysis). For example, it can be represented by a volume-based median diameter (D ₅₀ ) measured by a dynamic light scattering particle size distribution measuring device LB-550 manufactured by Horiba, Ltd.

  Specifically, a few samples of nanodiamond particle dispersion are dropped into 10 ml of pure water, and the sample for measurement is prepared by vibrating and dispersing by hand. Next, 3 ml of the measurement sample is put into a cell of a dynamic light scattering particle size distribution analyzer LB-550 manufactured by Horiba, Ltd., and measurement is performed under the following conditions.

・ Measurement conditions Data reading frequency: 100 times Cell holder temperature: 25 ℃
-Display conditions Distribution form: Standard Number of repetitions: 50 times Particle diameter standard: Volume standard Dispersion medium refractive index: 1.33 (when water is the main component)
・ System condition setting Strength standard: Dynamic
Scattering intensity range upper limit: 10000.00
Scattering intensity range lower limit: 1.00

  There are various methods for producing synthetic diamond. For example, in addition to a method of synthesizing a film diamond by a vapor phase (low pressure) synthesis method represented by chemical vapor deposition (CVD) or the like, the production of diamond in the natural world is simulated. As a method, an impact method, an explosion method, an explosion method, a detonation method, a flux method, a high temperature and high pressure method, and the like have been implemented.

  The impact method is a method in which a dynamic impact is applied to a graphite-structured raw material, for example, by detonating an explosive, and the graphite-structured raw material is directly converted into diamond-structured particles to obtain granular diamonds. The method uses, for example, a metal catalyst such as iron or cobalt, and after dissolving graphite, which is a raw material powder material, in a metal catalyst at a static pressure of 4 to 6 GPa and a temperature of 1500 to 2000 ° C., diamond Is a method of precipitating.

  In addition, the high-temperature and high-pressure method realizes stable conditions for diamond by holding the raw graphite powder in an atmosphere of high static pressure of 13 to 16 GPa and high temperature of 3000 to 4000 ° C. in a sealed high-pressure vessel, for example. In this method, the graphite powder is directly phase-transformed into diamond (see, for example, JP-A-2002-66302).

  In recent years, explosives are explode in an oxygen-deficient inert atmosphere such as water, ice, nitrogen or carbon dioxide, and carbon atoms remaining due to incomplete combustion are actively grown into diamond crystals. Is called the detonation method or explosion method. In this method, since the shock wave is rapidly attenuated, the obtained diamond particles have a nano-order particle size, and a single crystal having a uniform particle size of 4.3 ± 0.4 nm can be obtained.

  Trinitrotoluene (TNT) and hexogen (RDX) are often used as raw material explosives, but the hexogen component may be replaced with other explosives such as octogen (HMX) (for example, A. Kruger, F. Katokaka). , M. Ozawa, T. Fujino, Y. Suzuki, A. E. Alexenskii, A. Ya. Vul ', E. Osawa, “Unusually light aggregation in detonation, 17 Id. 2005) or the diamond industry association, see Diamond Technology Overview).

  The nanodiamond particles thus obtained contain a large amount of impurities such as non-diamond carbon components and catalytic metals, so that strong acids or strong acids such as aqua regia, fuming nitric acid or concentrated nitric acid in the presence of heating or catalytic metals are present. A treatment for removing impurities is performed by washing with an alkali (see, for example, JP-A-63-303806, JP-A-2003-146637, and JP-A-2004-238256).

  The method for producing nanodiamond particles in the present embodiment is not particularly limited, but the nanodiamond particles obtained by the detonation method or the explosion method as described above are preferably used from the viewpoint of supply amount, price and quality. be able to.

(3) Dispersion medium for nanodiamond particles The dispersion medium for nanodiamond particles used for preparing the dispersion liquid for nanodiamond particles is not particularly limited as long as it is compatible with the solvent used for dissolving polyvinyl alcohol. The solvent for polyvinyl alcohol described above can be used.

(4) Composition It is preferable that the coating composition of this embodiment contains 4.0 mass% or less nano diamond particles with respect to the total amount (dry state) of polyvinyl alcohol and nano diamond particles. That is, the content of nanodiamond particles is preferably polyvinyl alcohol: nanodiamond particles = 96.0: 4.0 or less. In the coating composition of the present invention, when the content of nanodiamond particles is 4.0% by mass or less with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles, a film made of the coating composition The mechanical properties of can be made sufficient, which is preferable. As a lower limit, what is necessary is just about 0.1 mass%.

  Moreover, it is preferable that the coating composition of this embodiment contains 1.0 mass% or less nanodiamond particles with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles. That is, the content of nanodiamond particles is preferably polyvinyl alcohol: nanodiamond particles = 99.0: 1.0 or less. In the coating composition of the present invention, when the content of nanodiamond particles is 1.0% by mass or less with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles, a film made of the coating composition The optical physical properties can be made satisfactory. Also from the viewpoint of optical properties, the lower limit may be about 0.1% by mass.

  What is necessary is just to adjust suitably about content of the other component in the coating composition of this embodiment in the range which does not impair the effect of this invention.

[Method for producing coating composition]
The coating composition of the present embodiment is prepared by mixing a polyvinyl alcohol solution in which polyvinyl alcohol is dissolved in advance by mixing polyvinyl alcohol and a solvent for polyvinyl alcohol, and separately mixing nanodiamond particles and a dispersion medium for nanodiamond particles. The nanodiamond particle dispersion can be mixed to satisfy the above composition.

  The polyvinyl alcohol solution can be obtained by mixing and stirring polyvinyl alcohol and a solvent for polyvinyl alcohol by a conventional method. In addition, without preparing such a polyvinyl alcohol solution, a polyvinyl alcohol powder can be put into a nanodiamond particle dispersion prepared as described below, followed by heating and stirring to obtain the coating composition of this embodiment.

  The nanodiamond particle dispersion can be prepared by mixing and stirring the nanodiamond particles and the nanodiamond particle dispersion medium in a conventional manner. As an apparatus used for preparing the nanodiamond particle dispersion, a generally known disperser can be used. For example, an ultrasonic irradiator, an ultrasonic homogenizer, an ultrahigh pressure homogenizer, a ball mill, a paint shaker, an attritor, a sand mill, Examples include, but are not limited to, a bead mill, a roll mill, an agitator, a Henschel mixer, a colloid mill, and a pearl mill.

[Film (Substrate with Film) and Method for Producing the Same]
The film of the present embodiment is formed using the coating composition of the present embodiment, and contains polyvinyl alcohol and nanodiamond particles as main components, and remains after drying and heating as necessary. Solvent and dispersion medium, and other optional ingredients.

Next, the manufacturing method of the film (substrate with a film) of this embodiment mainly comprises (a) a coating composition preparation step, (b) a coating composition application step, and (c) a film formation step. Contains. And the manufacturing method of the film (base material with a film) of this embodiment uses the coating composition of this embodiment described previously in the coating composition application | coating process, and is a coating composition after application | coating in a film formation process. The product is dried to a predetermined temperature and heated as necessary to form a film. Thereby, the film (base material with a film) of this embodiment described previously can be obtained more reliably.
Hereinafter, each process of the manufacturing method of the film (base material with a film) of this embodiment is demonstrated.

(A) Coating composition preparation process A coating composition preparation process is a process of preparing the coating composition of this embodiment described above. As described above, the coating composition is polyvinyl alcohol, a polyvinyl alcohol solution in which polyvinyl alcohol and a polyvinyl alcohol solvent are mixed in advance and dissolved, and separately, for nanodiamond particles and nanodiamond particles. It can be obtained by mixing a nanodiamond particle dispersion prepared by mixing with a dispersion medium. As described above, the polyvinyl alcohol solution is not prepared, but the polyvinyl alcohol powder is put into the nanodiamond particle dispersion prepared as described below, and the coating composition of this embodiment can be obtained by heating and stirring.

(B) Coating composition application | coating process A coating composition application | coating process is a process of apply | coating the coating composition of this embodiment described above to a base material.

  As a base material which can be used in this embodiment, as long as it has an at least 1 main surface which can apply | coat a coating composition, and can dry (and heat as needed) and can mount a film Although there is no particular limitation, a base material excellent in heat resistance is preferable.

  A base material comprises the target object which should be protected by the film obtained by apply | coating, drying, and the heating as needed from the coating composition of this embodiment. Examples of such objects include building walls, floors, handrails, signboards, sign boards, advertising boards, windows, glass, lighting covers, panels such as various display displays and solar cells, housings for electrical and electronic products, mice Pads, vehicle bodies, and various furniture such as desks and tables.

  Accordingly, examples of the material constituting the base material include polyesters such as polyimide (PI), polyamideimide (PAI), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polyethersulfone. (PES), fluororesin, liquid crystal polymer, ceramics, glass or metal can be used.

  Further, the substrate may have various shapes such as a plate shape or a strip shape, and may be rigid or flexible. The thickness of the substrate can also be selected as appropriate. In order to improve adhesiveness or adhesion, or for other purposes, a substrate on which a surface layer is formed or a substrate that has been subjected to a surface treatment such as a hydrophilic treatment may be used.

  In the step of applying the coating composition to the substrate, various methods can be used. For example, a casting method, a dispenser method, an ink jet method, a flexo method, a gravure method, a screen method, and a coater method. A spin coating method, a brush coating method, a syringe method, or the like can be used.

  In addition, the shape of the coating film made of the coating composition in a state before being applied, dried and heated, if necessary, is made into a desired shape according to the shape of the film finally obtained. Therefore, “application” in the present embodiment is a concept that includes a case where the coating composition is applied in a planar form or a linear application (drawing). The film is a concept including both planar and linear coating films and films. Moreover, these planar and linear coating films and films may be continuous or discontinuous, and may include a continuous portion and a discontinuous portion.

(C) Film formation process The film (base material with a film) of this embodiment is obtained by drying the coating film after apply | coating as mentioned above. The drying in this embodiment is preferably performed at 10 to 50 ° C. for 12 to 48 hours under a reduced pressure of 1.0 × 10 ^{−3 to} 0.1 atm, for example. What is necessary is just to select suitably in the range which does not receive damage, such as a deformation | transformation and discoloration, by a heat | fever when a coating composition and a base material are heated.

  Thus, the film (base material with a film) of this embodiment can be obtained. Thus, the film of this embodiment obtained is about 0.1-300 micrometers, for example, More preferably, it is 1-100 micrometers. If the coating composition of this embodiment is used, a film having excellent transparency, high strength, and high elastic modulus can be obtained even with the above thickness.

  Moreover, the film of this embodiment obtained in this way can have a transmittance of 50 to 90% / 100 μm with respect to visible light of 380 nm.

  EXAMPLES Hereinafter, although the manufacturing method of the coating composition of this invention and the film (base material with a film) of this invention is further demonstrated with an Example and a comparative example, this invention is not limited to these Examples at all. Absent.

≪Experimental example 1≫
Nanodiamond particles having an average primary particle size of 3 to 10 nm synthesized by the explosion method were mixed with a 4N aqueous sodium hydroxide solution, and the nanodiamond particle content of the obtained mixture was adjusted to 15% by mass. After the mixture was stirred at room temperature for 12 hours, the supernatant was removed by decantation, and the precipitate (nanodiamond particles) was recovered by washing with ion-exchanged water.

  Next, the recovered nanodiamond particles were mixed with concentrated sulfuric acid, and the nanodiamond particle content of the obtained mixture was adjusted to 15% by mass. After stirring this mixture at 70 ° C. for 2.5 hours, the supernatant was removed by decantation, and the precipitate (nanodiamond particles) was recovered by washing with ion-exchanged water.

  Further, the nanodiamond particles recovered in this manner were mixed with 35% by mass hydrochloric acid, and the nanodiamond particle content of the obtained mixture was adjusted to 15% by mass. After stirring this mixture at room temperature for 1.5 hours, the supernatant was removed by decantation, and the precipitate (nanodiamond particles) was washed with ion-exchanged water and collected.

  The nanodiamond particles recovered in this way are mixed with ion-exchanged water, the nanodiamond particle content of the obtained mixture is adjusted to 0.8 mass%, and the electric conductivity of the filtrate is 10 μS / cm. After ultrafiltration, the filtrate is further concentrated until the content of nanodiamond particles in the filtrate reaches 2.75% by mass, and then dispersed by a bead mill, and coarse particles (aggregated particles) are precipitated by centrifugation to form nanodiamond particles. A dispersion was obtained.

  A powder of GOHSENOL NH-18 (polyvinyl alcohol having a saponification degree of 99% or more and a polymerization degree of 1,800) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. is added to the nanodiamond particle dispersion prepared as described above and stirred. While heating to 90 ° C., a coating composition 1 was obtained. The ratio of polyvinyl alcohol and nanodiamond particles in the resulting coating composition was adjusted to 99.5: 0.5.

  The coating composition thus obtained was cast on a glass plate at room temperature, and then dried at 40 ° C. for 48 hours under reduced pressure to obtain a film 1 having a thickness of 100 μm.

«Experimental example 2»
A coating composition 2 was prepared in the same manner as in Experimental Example 1, except that the ratio of polyvinyl alcohol and nanodiamond particles in the obtained coating composition was adjusted to 99.9: 0.1. Film 2 was formed using Product 2.

«Experimental example 3»
A coating composition 3 was prepared in the same manner as in Experimental Example 1 except that the ratio of polyvinyl alcohol and nanodiamond particles in the obtained coating composition was adjusted to 99.0: 1.0. Film 3 was formed using object 3.

≪Experimental example 4 (comparative example) ≫
It is obtained by dissolving powder of Gohsenol NH-18 (polyvinyl alcohol having a saponification degree of 99% or more and a polymerization degree of 1,800) manufactured by Nippon Synthetic Chemical Industry without using nanodiamond particles in ion-exchanged water. A film 4 was formed in the same manner as in Experimental Example 1 using the solution (coating composition 4).

<< Experimental Example 5 >>
A coating composition 5 was prepared in the same manner as in Experimental Example 1 except that the ratio of polyvinyl alcohol and nanodiamond particles in the obtained coating composition was adjusted to 95.0: 5.0. Film 5 was formed using object 5.

«Experimental example 6»
A coating composition 6 was prepared in the same manner as in Experimental Example 1 except that the ratio of polyvinyl alcohol and nanodiamond particles in the obtained coating composition was adjusted to 90.0: 10.0. Film 6 was formed using object 6.

[Evaluation test]
(1) Tensile test of film Using autograph AGS-1kND manufactured by Shimadzu Corporation, initial film length: 20 mm, tensile speed: 2 mm / min, and measurement temperature: conditions of films 1 to 6 The breaking strength and Young's modulus were measured. The measurement results of the breaking strength are shown in FIG. 1, and the measurement results of the Young's modulus are shown in FIG.

(2) Measurement of absorbance (transmittance) Using UV / V is spectrometer U-2000 manufactured by Hitachi, Ltd., under conditions of visible light of 380 nm, wavelength scanning rate: 400 nm / min, films 1 to 6 Absorbance (transmittance) was measured. The results are shown in FIG.

The Young's modulus Y (GPa), breaking strength σ _max (MPa), and breaking elongation ε _max (%) of films 3 to 6 obtained in Experimental Examples 3 to 6 are shown in Table 1 below. Summarized. However, in Table 1, PVA represents polyvinyl alcohol, ND represents nanodiamond particles (hereinafter the same), and the numerical value to the right of “PVA / ND” represents nanodiamond particles relative to the total amount of polyvinyl alcohol and nanodiamond particles. The content of is shown.

From the results shown in FIGS. 1 to 3 and Table 1, the following was found.
(A) Viewpoint of mechanical properties (See Fig. 1 and Fig. 2, Table 1)
(A-1) Young's modulus As shown in FIG. 2, even if a small amount of nanodiamond particles are added, the Young's modulus is rapidly improved. Moreover, for the Young's modulus of about 3.7 GPa of the film 4 with no nanodiamond particles added,
About 6 GPa with film 2 of PVA: ND = 99.9: 0.1
About 7.5 GPa with film 1 of PVA: ND = 99.5: 0.5
About 9.7 GPa with film 3 of PVA: ND = 99.0: 1.0
The Young's modulus becomes maximum near PVA: ND = 96.0: 4.0, and the Young's modulus does not change or decreases even if the amount of nanodiamond particles added is increased further.

(A-2) Breaking strength As shown in FIG. 1, the breaking strength of the film 4 with no nanodiamond particles added is about 95.3 MPa,
About 115.8 MPa with film 3 of PVA: ND = 99.0: 1.0,
About 124.3 MPa with film 5 of PVA: ND = 95.0: 5.0,
About 126.8 GPa with film 6 of PVA: ND = 90.0: 10.0
It is.

(B) Viewpoint of optical characteristics (see FIG. 3)
The transmittance of a film with a thickness of 100 μm is for visible light with a wavelength of 380 nm.
About 90% in film 4 with PVA: ND = 100: 0,
About 82% in film 2 of PVA: ND = 99.9: 0.1
About 65% in film 1 with PVA: ND = 99.5: 0.5
About 50% in film 3 with PVA: ND = 99.0: 1.0
It is.

  From the above, from the viewpoint of mechanical properties, the addition amount of the nanodiamond particles is preferably PVA: ND = 96.0: 4.0 or less, and PVA: ND = 99.9: 0.1 or more PVA: ND = 99 It can be seen that 0.0: 1.0 or less is a more preferable range. From the viewpoint of optical properties, the amount of nanodiamond particles added is preferably PVA: ND = 99.0: 1.0 or less, more preferably PVA: ND = 99.5: 0.5, and PVA: ND. = 99.9: 0.1 is more preferable.

  The coating composition obtained by the present invention eliminates the drawbacks of conventional polymer composite materials using nanocarbon materials, and can form a film having excellent transparency, high strength and high elastic modulus. Applications of the film of the present invention obtained include, for example, building walls, floors, handrails, signboards, sign boards, billboards, windows, glass, lighting covers, panels such as various display displays and solar cells, electrical and electronic products A wide range of applications are possible, such as housings, mouse pads, vehicle bodies, and various furniture such as desks and tables.

Claims (5)

  A coating composition comprising polyvinyl alcohol and nanodiamond particles.   The coating composition according to claim 1, comprising 4.0% by mass or less of nanodiamond particles with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles.   The coating composition according to claim 1, comprising 1.0% by mass or less of nanodiamond particles with respect to the total amount (dry state) of polyvinyl alcohol and nanodiamond particles.   The film which consists of a coating composition in any one of Claims 1-3.   The film of Claim 4 whose transmittance | permeability with respect to visible light of 380 nm is 50-90% / 100 micrometers.

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