JP6770322B2 - UV reflective film forming paint and UV reflective film - Google Patents

Description

The present invention relates to a coating material for forming an ultraviolet reflecting film suitable for forming an ultraviolet reflecting film, and an ultraviolet reflecting film using the coating material for forming an ultraviolet reflecting film. The present invention also relates to an ultraviolet irradiation device having an ultraviolet reflective film and an applied product using the ultraviolet irradiation device.

In order to inactivate and kill bacteria and viruses in water and air, a method using ultraviolet rays having a short wavelength of 200 to 350 nm, which is generally called "deep ultraviolet rays", is being put into practical use.

Deep ultraviolet rays are short-wavelength ultraviolet rays that damage the double helix structure of DNA and RNA, so that irradiation with deep ultraviolet rays can inactivate and kill bacteria and viruses.

The ultraviolet irradiation device that generates deep ultraviolet rays uses an LED, a mercury lamp, or the like as an ultraviolet ray generating part. The ultraviolet rays radiated from the ultraviolet emitting part are irradiated to bacteria and viruses directly or via the reflecting part.

Of these, the reflective portion is roughly classified into either the vicinity of the ultraviolet generating portion, which is the vicinity of the ultraviolet generating portion, or the inner wall portion of the container used for actually inactivating or killing bacteria or viruses.

It is necessary to use a material having high durability against ultraviolet rays and sufficiently high reflectance of ultraviolet rays in the vicinity of the ultraviolet ray generating portion and the inner wall portion. If the durability against ultraviolet rays is not high, the vicinity of the ultraviolet rays generating part and the inner wall part will be deteriorated by ultraviolet rays (discoloration, tissue collapse, etc.) during use, and if the reflectance cannot be maintained high during use, This is because the ultraviolet rays are attenuated before reaching the bacteria or virus to be irradiated, and the usage efficiency of the device is reduced.
Materials that are relatively suitable for these members are aluminum oxide, titanium oxide, zirconium oxide and the like. These ceramic materials are clearly higher in durability against ultraviolet rays and in reflectance than organic materials having many carbon-carbon bonds.

However, it is difficult to manufacture the above-mentioned ceramic material in accordance with the shape of the vicinity of the ultraviolet ray generating portion or the inner wall portion of the container, and there is a problem that the manufacturing cost is high for manufacturing. Furthermore, when exposed to a short wavelength of, for example, about 300 nm or less even with ultraviolet rays, many ceramic materials deteriorate in quality and decrease in reflectance after being irradiated with ultraviolet rays for about several tens of hours, deteriorate, and start discoloration, surface peeling, and collapse. .. In this case, it is necessary to replace the vicinity of the ultraviolet ray generating portion and the inner wall portion of the ultraviolet irradiation device, but as described above, the manufacturing cost increases and the operating rate of the device is significantly lowered.

If a resin that is cheaper than the ceramic material, such as epoxy resin, is used, it is possible to manufacture and replace each stage at low cost, but the usable time until deterioration is extremely short, for example, several hours, and the device There is a big hindrance to operation.

As a material that achieves both durability against ultraviolet rays and manufacturing cost as described above, a material in which a ceramic filler having high reflectance and durability against ultraviolet rays is dispersed in a polymer material having Si—O as a main chain. Can be considered. A polymer material having Si—O as a main chain is less likely to deteriorate with ultraviolet rays of 200 nm or more if the number of “carbon-carbon” bonds in the polymer material is small. This polymer material can be obtained in the form of organopolysiloxane by dehydrating, polymerizing, and heat-treating Si arcoxide. Further, as the filler, aluminum oxide, zirconium oxide, titanium oxide and the like have durability to ultraviolet rays having a certain wavelength. This material is disclosed in, for example, Patent Document 1 and Patent Document 2. These documents describe an ultraviolet reflection composition using an Al ₂ O ₃ filler having a high ultraviolet reflectance, but the Al—O bond is easily broken by ultraviolet irradiation of about 250 nm, and the ultraviolet reflection It cannot be said that it is sufficient for use as a filler.

Further, Patent Document 1 and Patent Document 2 also describe an example in which a BN filler is added to a paint as an ultraviolet reflective filler having ultraviolet durability. BN (h-BN) alone has extremely high durability against ultraviolet rays, but since its powder has a scaly shape, when it is used as a filler in paints, its leveling property is weak and smooth. It is difficult to obtain a coated surface, and the coating method may be restricted.

In the above, the device that inactivates and kills bacteria and viruses is given as an application example of the main ultraviolet reflective film, but by using ultraviolet rays with shorter wavelengths, the application points are more than those of the prior art. There are increasing technologies.

For example, by making the ultraviolet rays used to cure the ultraviolet curable resin shorter in wavelength, it becomes possible to use different types of resins, and there is a possibility that characteristics different from those of conventional materials can be obtained. There is. Although it has been realized that ultraviolet rays themselves are generated by, for example, an LED element, materials suitable for the vicinity of an ultraviolet ray generating portion and the inner wall of an apparatus have problems of durability and deterioration. If these problems are solved, it will be possible to expand the types of ultraviolet rays and resins that can be used for resin curing.

Japanese Unexamined Patent Publication No. 2012-209425 JP-A-2010-248484

The present invention solves any of the problems described below with respect to the above-mentioned current technology.
(1) A paint for forming an ultraviolet reflective film that can form an ultraviolet reflective film with high durability and reflectance against short wavelength ultraviolet rays by subjecting it to a dehydration polymerization reaction by treatment such as heating (hereinafter, also simply referred to as "paint"). (2) There are few restrictions on the coating method, it is easy to obtain a smooth surface when coated, it is durable against short wavelength ultraviolet rays, and it is a highly reflective ultraviolet reflective film (hereinafter, simply "coating"). (3) A UV-reflecting film that does not easily deteriorate even when used near the UV-generating part or the inner wall of the UV-irradiating device and can maintain high reflectance at a relatively low cost. Get in

The above-mentioned problems have been solved by using a paint for forming an ultraviolet reflective film as a paint having a liquid component of organopolysiloxane and a fluoride filler of an alkaline earth metal dispersed therein as an essential composition. Further, by applying the coating material to the surface of a base material on which an ultraviolet reflective film is to be formed and subjecting it to a polymerization reaction by a treatment such as heating, an organopolysiloxane cured product is subjected to a fluoride of an alkaline earth metal. An ultraviolet reflective film in which the filler is dispersed can be obtained. The obtained ultraviolet reflective film is durable against short wavelength ultraviolet rays and has high reflectance.

According to the present invention, it can be applied to various members by a wide range of methods at a relatively low cost, and after application, it is cured by a dehydration polymerization reaction, and has durability against short wavelength ultraviolet rays and high reflectance. A coating material for forming an ultraviolet reflective film capable of forming the above can be obtained.

The paint and the ultraviolet reflective film can be used as an ultraviolet reflecting film by forming as a film on a member that is deteriorated or deteriorated due to the influence of deep ultraviolet rays. For example, it is suitable for the vicinity of an ultraviolet ray generating portion and the inner wall of an ultraviolet ray using device.

Measurement graph of UV reflectance of various elemental ceramic particles Measurement graph of UV reflectance of the UV reflective film of the present invention and the comparative sample

First, the coating material for forming an ultraviolet reflective film of the present invention will be described. The coating material of the present invention has a liquid component of organopolysiloxane and a fluoride filler of an alkaline earth metal dispersed therein as an essential composition. It is desirable that the liquid component of the organopolysiloxane contains almost no "carbon-carbon" bonds.

The coating material of the present invention is obtained by adding and mixing a fluoride filler to an organopolysiloxane solution obtained by stirring and mixing organoalkoxysilane, water and a catalyst, and hydrolyzing and dehydrating and polymerizing the catalyst.

The raw material, organoalkoxysilane, is
Formula 1: R _{1 m} Si (OR ₂ ) _4-m (where R ₁ is a methyl group or trifluoromethyl group having 1 carbon atom, R ₂ is an alkyl group having 1 to 4 carbon atoms, m = 0, 1, 2 Any of 3)
It may be selected from the organoalkoxysilanes represented by, and one type or a combination of two or more types can be selected. The organoalkoxysilanes that can be selected are those in which 95% or more of the carbons thereof do not have a "carbon-carbon" bond. This is because "carbon-carbon bonds" are compared to "carbon-hydrogen" bonds, "carbon-fluorine" bonds, "silicon-carbon" bonds, "silicon-hydrogen" bonds, and "silicon-oxygen bonds". This is because it is easily cut off by ultraviolet rays. Carbon without a "carbon-carbon" bond is bonded only to a hydrogen atom (H), a silicon atom (Si) and a fluorine atom (F).

First, as the primary aging, water is added at a ratio of 0.05 to 10 mol to 1 mol of the organoalkoxysilane represented by the above formula 1 and stirred at 20 to 80 ° C. to obtain an organopolysiloxane solution. If necessary, water may be further added as secondary aging and stirred at 20 to 80 ° C. Water is added in the aging process in order to generate organohydroxysilane by hydrolysis of organoalkoxysilane, and by continuing stirring, the organohydroxysilane undergoes a dehydration polymerization reaction to become an organopolysiloxane polymer.

When water is added, a catalyst may be added as necessary to adjust the reaction rate and degree of polymerization of hydrolysis and dehydration polymerization of organoalkoxysilane. As the catalyst, organic acids such as formic acid, acetic acid and boric acid, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and boric acid, and bases such as ammonia are suitable. Alternatively, a method of producing a catalyst by a chemical change without directly adding these catalysts may be used. This includes, for example, a method of adding diphosphorus pentoxide together with water. An organopolysiloxane solution is obtained by the above procedure.

Next, a fluoride filler is added to the obtained organopolysiloxane solution and sufficiently mixed by ball milling or the like to obtain a filler mixed solution. At this time, in addition to the fluoride powder, various additives and solvents may be added. Examples of additives include, for example, a surface modifier for improving filler dispersibility and a defoaming agent for suppressing foaming. The type and amount of the solvent are appropriately determined according to the purpose such as viscosity adjustment and dilution, and are not particularly limited, but for example, alcohol (polyhydric alcohol) solvent, ketone solvent, ester solvent, fragrance. Examples include group solvents. In addition, one or more kinds of additives and solvents can be used in combination. The purity and viscosity of the organopolysiloxane in the mixed solution may be increased by evaporating the water or solvent of the obtained filler mixed solution. At this time, the number average molecular weight of the organopolysiloxane is preferably 300 to 10,000. This is because when the dehydration polymerization reaction is carried out to obtain an ultraviolet reflective film later, if the number average molecular weight is 300 or less, the polymerization reaction is difficult to proceed and low molecular weight siloxane is likely to be generated, while the number average molecular weight exceeds 10,000. This is because the viscosity becomes too high and the coatability deteriorates.

As the filler, for example, a fluoride of granular alkaline earth metal (Mg, Ca, Sr, Ba) having an average particle diameter of about 0.05 to 50 μm can be used. As the fluoride powder, those having granular crystals are suitable. The paint containing these fluoride particles can be easily and smoothly applied unlike the paint containing scaly particles such as BN. Further, among the fluorides of alkaline earth metals, it is preferable to use MgF ₂ and CaF ₂ in consideration of price, availability, and presence / absence of toxicity. Of these, CaF ₂ has stronger binding energy and is also excellent in UV durability. All of the fluorides of alkaline earth metals have the characteristic that they do not easily absorb ultraviolet rays. Among them, CaF ₂ is stable and has high reflectance to deep ultraviolet light. The reflectance of a single powder of CaF ₂ is shown in FIG. It can be seen that the reflectance of deep ultraviolet rays is higher than that of TiO ₂ and ZrO _2, which are frequently used as fillers for ceramic materials in the light reflecting film. Although Al ₂ O ₃ in the figure has an extremely high reflectance, Al ₂ O ₃ has a refractive index close to that of the polymer of organopolysiloxane, and cannot increase the reflectance when it becomes an ultraviolet reflective film.

In addition, commercially available CaF ₂ raw materials are mainly classified into two types. The first is natural CaF ₂ mainly produced from mines and the like, and the second is chemically synthesized CaF ₂ obtained by treating a raw material containing CaCO ₃ with HF or the like. Both can be used as fillers, but since natural CaF _{2 having} a low purity easily absorbs ultraviolet rays, it is more preferable to use chemically synthesized CaF ₂ having a purity of 99% or more. The amount of the CaF ₂ filler added is preferably in the range of 5 to 98% by volume of the ultraviolet reflective film as the volume ratio when the ultraviolet reflective film is finally formed. This is because the reflectance of ultraviolet rays is not sufficient at 5% by volume or less, and the density of the coating film is lowered at 98% by volume or more. In particular, in the range of 40 to 70% by volume of the ultraviolet reflecting film, a dense ultraviolet reflecting film having sufficient ultraviolet reflectance and having no cracks can be easily obtained.
By the above method, the coating material of the present invention can be obtained.

Next, the ultraviolet reflective film of the present invention using the paint will be described.

The ultraviolet reflective film of the present invention has, in the matrix of the cured organopolysiloxane, granular alkaline earth fluoride dispersed therein as an essential constitution. It is desirable that the organopolysiloxane contains few "carbon-carbon" bonds.

A method for forming the coating material for forming an ultraviolet reflective film of the present invention as an ultraviolet reflecting film will be described. Examples of the material of the base material that can be coated include metal, ceramic, cement, glass, plastic, paper, fiber, and wood, and the coating method includes a dipping method, a salivation method, a spinner method, a spray method, a bar coating method, and a dispenser. A known method such as a method can be used. After the above-mentioned paint is applied and formed on the surface of the base material, the solvent in the paint is evaporated by heating at 120 to 350 ° C. for about 10 minutes to 5 hours, moisture absorption, etc. It is possible to form an ultraviolet reflective film on the surface of the base material.
In the film cured after dehydration polymerization, 95% or more of the carbon atoms in the cured organopolysiloxane are bonded only to hydrogen and silicon atoms, and are bonded to carbon atoms (“carbon-carbon” bond). It is preferable that there is no such thing. If the "carbon-carbon" bond is 5% or more, when irradiated with ultraviolet rays, the ultraviolet rays are absorbed, the "carbon-carbon" bond is broken, and deterioration is likely to occur.
Further, the ultraviolet reflective film of the present invention has a high reflectance of 80% or more for any ultraviolet rays of 250 to 350 nm and 65% or more for any ultraviolet rays of 250 to 350 nm. Therefore, in a device having an ultraviolet light source, for example, an ultraviolet illumination unit or an ultraviolet irradiation device, it can be used as a reflecting member for efficiently extracting ultraviolet light and preventing attenuation of ultraviolet light.

By the above method, the coating film of the present invention can be obtained on a substrate.

(Example 1)
First, 20 mol of water and 3 mol of acetic acid were added to 20 mol of methyltriethoxysilane as the primary aging, and the mixture was stirred at 70 ° C. for 12 hours for hydrolysis. Next, 70 mol of water and 10 mol of acetic acid were additionally added as secondary aging, and dehydration polymerization was carried out by stirring at 70 ° C. for 24 hours to obtain an organopolysiloxane solution.

A chemically synthesized CaF ₂ (purity 99% or more) powder was added to the obtained organopolysiloxane solution, and the mixture was sufficiently stirred to obtain a coating material.

The obtained paint is applied on an aluminum substrate using a squeegee so that the thickness of the film cured after dehydration polymerization is approximately 70 to 80 μm, and is heated at 300 ° C. for 1 hour to cause a dehydration polymerization reaction and cure. An ultraviolet reflective film was obtained in (Example). Of this UV reflective film, CaF ₂ accounted for 60% by volume, and the rest was an organopolysiloxane cured product.

In addition, as a comparative paint, the requirements other than the filler are exactly the same, and only the filler is used instead of CaF ₂ powder, ZrO ₂ powder (HSY-3.0: manufactured by Daiichi Rare Element Chemical Industry Co., Ltd.), TiO ₂ powder. (CR-50: manufactured by Ishihara Sangyo Co., Ltd.) and Al ₂ O ₃ powder (AA-03: manufactured by Sumitomo Chemical Co., Ltd.) were also prepared in the same manner (Comparative Samples 1 to 3). The amount of these fillers added was adjusted so that the volume ratio was the same as that of the examples (60% by volume) when the ultraviolet reflective film was formed.

The reflectance of each ultraviolet reflective film was measured using an ultraviolet visible spectrophotometer UV-3150 manufactured by Shimadzu Corporation. The measurement results are shown in FIG. From FIG. 2, in the comparative sample using the ZrO ₂ , TiO ₂ and Al ₂ O ₃ fillers, the reflectance is greatly reduced from 200 nm to 350 nm in the ultraviolet region, but the ultraviolet reflection of the present invention using the CaF ₂ filler It was found that the film maintained high reflectance with almost no decrease in reflectance and exhibited excellent ultraviolet reflection.

(Example 2)
By providing the ultraviolet reflective film of the present invention on the surface of a member exposed to deep ultraviolet rays, deterioration of the member due to new ultraviolet rays can be significantly prevented. On the other hand, since it hardly absorbs ultraviolet rays and almost reflects them, it is possible to improve the efficiency of extracting ultraviolet rays. As an example, it can be applied to an apparatus for sterilizing a liquid such as water at a wavelength of about 200 to 350 nm. It can be applied to the device part near the ultraviolet ray generating part, the inner wall part of the container and the flow pipe, and the like.

(Example 3)
Further, by applying it to the vicinity of the ultraviolet ray generating portion of the ultraviolet curing device or the wall surface of the device, the irradiation efficiency can be improved and the durability of the members used in the device can be improved. Therefore, a resin that can be cured at a shorter wavelength (for example, about 200 to 300 nm), which has not been put into practical use until now, can be used as an ultraviolet curable resin.

Claims (13)

A liquid component consisting of organopolysiloxane and
It has a fluoride of an alkaline earth metal dispersed in the liquid component and having an average particle diameter of 0.05 to 50 μm .
A paint for forming an ultraviolet reflective film having a reflectance of 80% or more for arbitrary ultraviolet rays having a wavelength of 250 nm to 350 nm . Further having one or more liquid components of an antifoaming agent and a surface modifier.
The coating material for forming an ultraviolet reflective film according to claim 1. The number average molecular weight of the organopolysiloxane is in the range of 300 to 10,000.
The coating material for forming an ultraviolet reflective film according to any one of claims 1 and 2. The ultraviolet reflective film-forming coating material according to any one of claims 1 to 3, wherein 95% or more of the carbon atoms in the organopolysiloxane do not have a "carbon-carbon" bond. The ultraviolet reflective film forming according to any one of claims 1 to 4, wherein 95% or more of the carbon atoms in the organopolysiloxane are bonded only to hydrogen atoms, silicon atoms and fluorine atoms. paint. The coating material for forming an ultraviolet reflective film according to any one of claims 1 to 5, wherein the alkaline earth metal is Ca. Ultraviolet rays having a reflectance of 80% or more with respect to arbitrary ultraviolet rays having a wavelength of 250 nm to 350 nm, in which fluoride of an alkaline earth metal having an average particle diameter of 0.05 to 50 μm is dispersed in a matrix of an organopolysiloxane cured product. Reflective film. The ultraviolet reflective film according to claim 7, wherein the volume ratio of the fluoride of the granular alkaline earth metal is 5 to 98% with respect to the volume of the ultraviolet reflective film of 100%. The ultraviolet reflective film according to any one of claims 7 or 8, wherein the volume ratio of the fluoride of the granular alkaline earth metal is 40 to 70% with respect to the volume of the ultraviolet reflective film of 100%. The ultraviolet reflective film according to any one of claims 7 to 9, wherein 95% or more of the carbon atoms of the organopolysiloxane do not have a "carbon-carbon" bond. The ultraviolet reflective film according to any one of claims 7 to 10, wherein 95% or more of the carbon atoms of the organopolysiloxane are bonded only to hydrogen atoms, silicon atoms and fluorine atoms. The ultraviolet reflective film according to any one of claims 7 to 11 , wherein the reflectance to any ultraviolet ray having a wavelength of 200 nm to 350 nm is 65% or more. The ultraviolet reflective film according to any one of claims 7 to 12 , wherein the alkaline earth metal is Ca.

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