JP2022155422A - Photocatalyst slurries, photocatalyst masterbatches, and photocatalyst molded articles, and methods of producing them - Google Patents

Abstract

To provide photocatalyst slurries, photocatalyst masterbatches, and photocatalyst molded articles, and methods of producing them which are need when producing photocatalyst products, can save the work for producing particles, and greatly reduce the production cost.SOLUTION: A photocatalyst slurry producing method is used, which includes a mixing step of mixing photocatalyst particles, water, and a plastic while evaporating the water. A photocatalyst masterbatch producing method is used, which includes the mixing step and a first molding step of melting the plastic and molding it into a chip-shaped masterbatch. A photocatalyst molded-article producing method is used, which further includes a second molding step of incorporating the chip into the plastic and molding it. A photocatalyst slurry, which is a mixture of the photocatalyst particles, water, and the plastic, is used. A photocatalytic masterbatch containing the photocatalyst particles and the plastic is used. The photocatalyst molded article containing the photocatalyst particles and the plastic is used.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a photocatalyst slurry, a photocatalyst masterbatch, a photocatalyst molded product, and methods for producing them.

When the photocatalyst is exposed to light, electrons and holes are generated at the same time, and react with oxygen to form active oxygen. This active oxygen has a stronger oxidizing power than ozone, and can convert harmful chemical substances, odors, bacteria and viruses into non-toxic substances such as water and carbon dioxide. This photocatalytic reaction can be applied to various applications such as environmental purification simply by using light.

Conventionally, there have been sheets and films in which a photocatalyst is mixed in resin (Patent Documents 1, 2, and 3).

In general, photocatalysts are carried by means of kneading, embedding, or the like in the manufacturing process of organic fibers or plastic moldings. In particular, a molded product is produced by kneading a melted polymer and a photocatalyst using an extruder and extruding the mixture. At that time, a polymer such as plastic pellets is melted and kneaded with photocatalyst particles to uniformly disperse them to prepare a masterbatch, which is further kneaded with molten plastic and extruded to uniformly disperse the photocatalyst particles. A dispersed high-performance photocatalyst material can be produced. It can be spun to produce threads, woven to produce fibers, non-woven fabrics, synthetic paper, etc. By molding these, it is possible to form boards, sheets, and various other forms of high-performance photocatalyst molding. product is obtained.

In that case, a particulate photocatalyst or a photocatalyst slurry in which a photocatalyst is dispersed in water is used. Photocatalyst slurries are obtained when photocatalysts are produced in a wet process, and therefore photocatalyst slurries are often cheaper than particulate photocatalysts. Photocatalyst slurries containing 70 to 80% water are usually commercially available.

JP 2007-307884 A JP-A-2005-097608 JP 2013-136216 A

However, when photocatalyst slurry is used for kneading, mixing, or embedding in plastics or fibers, the heat of evaporation of water is extremely high, so the temperature of the melted polymer drops and solidifies. It cannot be wrought, mixed, or embedded. Therefore, it was necessary to dry the photocatalyst slurry to once produce photocatalyst particles, but at that time, the particles adhered to each other to form hard particles with a large particle size. In addition, a great amount of expense was required to pulverize hard particles having a large particle size into fine particles.

If the particle size of the photocatalyst is large, there is a problem that when the photocatalyst is kneaded, mixed, embedded in plastics or fibers and supported, it is difficult to mix, unevenly distributed, and the photocatalyst particles are easily removed. If the photocatalyst particles do not protrude from the surface of the plastic or fiber and are not widely distributed, the photocatalytic reaction cannot occur efficiently. It was difficult to disperse it, and it was difficult to produce a high-performance photocatalyst molded article that could be put to practical use.

For example, when a photocatalyst cutting board is made by kneading and mixing a photocatalyst into the cutting board, if the surface of the cutting board is scratched with a kitchen knife, the photocatalyst particles will come out of the scratched surface and will cause a photocatalytic reaction when exposed to light. If photocatalyst particles with a large particle size are used and the dispersion is poor, the photocatalyst particles will not come out and the photocatalytic reaction will not occur even when exposed to light. Therefore, it is necessary to uniformly disperse the photocatalyst in the state of fine particles in the plastic or fiber, knead, mix, embed, and carry the photocatalyst.

In view of the problems of the prior art as described above, the object of the present invention is to support a photocatalyst by kneading, mixing, embedding, etc. in polymers such as plastics and fibers to remove odors and reduce harmful effects in the air. Reduces the time and effort required to create particles necessary to create photocatalyst products that can effectively, economically and safely purify the environment, such as decomposition and removal of substances or dirt, wastewater treatment and purification, antibacterial and antifungal. To provide a photocatalyst slurry, a photocatalyst masterbatch, a photocatalyst molded article, and a method for producing them, which can save and greatly reduce the production cost.

A method for producing a photocatalyst slurry is used, which includes a mixing step of mixing photocatalyst particles, water, and plastic while evaporating the water. Also, a method for producing a photocatalyst masterbatch is used, which includes the mixing step and a first molding step of melting the plastic and molding it into a chip-shaped masterbatch. Furthermore, a method for manufacturing a photocatalyst molded article is used, which further includes a second molding step of incorporating the chip into plastic and molding.

Photocatalyst slurry, which is a mixture of photocatalyst particles, water, and plastic, is used. Also, a photocatalyst masterbatch containing photocatalyst particles, plastic and water is used. Furthermore, a photocatalyst molded article containing photocatalyst particles and plastic is used.

The photocatalyst slurry containing photocatalyst particles, water and plastic of the present invention can be easily obtained by adding plastic particles, flakes, pellets, and a mixture thereof to water containing photocatalyst particles and mixing while evaporating water. By heating and kneading it, a masterbatch in which fine photocatalyst particles are uniformly dispersed can be easily obtained.

Then, the obtained masterbatch is kneaded with molten plastic and molded to obtain a photocatalyst material, which is spun to produce yarn, which is then woven to produce fibers, nonwoven fabrics, synthetic paper, etc. be able to. By molding them, high-performance photocatalyst moldings of various shapes such as plates and sheets can be obtained. As a result, it can be used in a wide range of fields as an environmental purification material such as decomposing and removing bad odors, harmful substances in the air, dirt, wastewater treatment, water purification treatment, antibacterial, antiviral, antifungal, etc. Photocatalyst molding that can be used effectively and safely. Products can be produced easily and economically.

When a photocatalyst is supported on a base material such as organic fiber or plastic by coating, the photocatalyst can be easily removed by human touch. Since the photocatalyst comes out of the base material, it has excellent durability and can be used repeatedly over a long period of time.

In addition, since bacteria and viruses in water and air are easily decomposed into water and carbon dioxide by the strong oxidizing power generated in the photocatalyst by irradiation with light, they can be killed reliably and efficiently. Normally, drug-resistant bacteria occur when drugs are used, but photocatalysts are also effective against drug-resistant bacteria, photocatalyst-resistant bacteria do not occur, and they are effective against mutated viruses. be. In addition, it can perform multiple functions at the same time, such as antibacterial, antiviral, deodorant, air purification, water purification, soil purification, and freshness preservation, and can be used anywhere in the world as long as there is light.

(Embodiment)
In the embodiment, the following steps are performed.
(1) Water, photocatalyst powder, and plastic particles are mixed to prepare a photocatalyst slurry.
(2) A masterbatch, which is pellets for molding, is produced from the photocatalyst slurry of (1).
(3) A molded product is produced from the masterbatch of (2) and the plastic.
<Photocatalyst>
Various photocatalysts such as titanium oxide, tungsten oxide, zinc oxide, iron oxide, lead oxide, indium oxide, silicon carbide, molybdenum sulfide, and cadmium sulfide are used as the photocatalyst used in this embodiment.

Most preferred is titanium oxide. The reason is described below.
(1) Regarding tungsten oxide, molybdenum sulfide, and indium oxide, tungsten, molybdenum, and indium are rare metals and are scarce and expensive in terms of resources. Being the ninth most abundant element in the earth's crust, titanium oxide is abundant in resources, inexpensive and readily available.

(2) While cadmium sulfide and lead oxide are toxic, titanium oxide is recognized as a food additive, is used in toothpaste and white chocolate, and is a safe and non-toxic substance.

(3) When zinc oxide, lead oxide, cadmium sulfide, etc. are placed in water and exposed to light, a phenomenon called photodissolution occurs and they are decomposed into cations and anions and disappear, but titanium oxide is photodissolved. It is most preferable as a photocatalyst because it is stable and has excellent durability.

<Titanium oxide>
Titanium oxide used in the present embodiment includes not only crystals such as anatase, rutile, and brookite, but also those having oxygen defects, metal-doped, nitrogen, sulfur, etc.-doped titanium oxides. .
In addition, the particles may be those in which silica, alumina, or ceramics such as apatite, which are inactive as photocatalysts, are supported on the surface of the particles in the form of islands. That is, in this embodiment, the type of titanium oxide is not particularly limited.

<Particle size of photocatalyst particles>
The particle size of the photocatalyst particles used in the present embodiment is desirably 1 nm or more and 10 μm or less, and more preferably greater than 10 nm and less than 1 μm. If it is less than this, the wavelength of light that can be absorbed by the photocatalyst is blue-shifted due to the quantum effect, and light with a long wavelength makes it difficult for the photocatalytic reaction to occur. The photocatalyst is unevenly distributed, resulting in a molded article with deteriorated performance.

<Plastic>
Plastics used in this embodiment include polyethylene, nylon, polyvinyl chloride, polyvinylidene chloride, polyester, polypropylene, polyethylene oxide, polyethylene glycol, polyethylene terephthalate, silicon resin, polyvinyl alcohol, vinyl acetal resin, polyacetate, and ABS resin. , epoxy resins, vinyl acetate resins, cellulose, cellulose derivatives, polyamides, polyurethanes, polycarbonates, polystyrenes, urea resins, fluororesins, polyvinylidene fluoride, phenolic resins, celluloid, chitin, and starch sheets.

<Plastic shape>
The shapes of plastics are particles, flakes, flakes, and pellets, and the particles are spherical, cylindrical, columnar, prismatic, disk-shaped, square-plate-shaped, rugby-ball-shaped, and amorphous. All kinds of shapes of The size of the plastic used in this embodiment is preferably 1 to 10 mm in diameter in the case of a spherical shape, and 0.5 to 2 cm in length, 1 to 5 mm in thickness, and 1 to 3 cm in width in the case of a rectangular parallelepiped (flake). . When it is cylindrical, it preferably has a diameter of 1 to 10 mm and a length of 0.5 to 2 cm. If it is larger than this, it becomes difficult to uniformly disperse the photocatalyst particles in the plastic when the photocatalyst masterbatch is produced, and if it is smaller than this, the production cost increases too much.

(Production method)
<Conventional kneading>
The conventional method of fixing a photocatalyst by kneading, mixing, or embedding it in plastic or fiber will be explained.
Step 1: First, a polymer in the form of plastic pellets is poured into an extruder. The polymer is then melted.
Second step: A slurry containing a photocatalyst is poured and kneaded to uniformly disperse to prepare a masterbatch.
Here, if a photocatalyst slurry, which is a mixture of a photocatalyst and water, is used as the photocatalyst, the water comes into contact with the molten plastic. In this case, the water evaporates, and the heat of evaporation lowers the temperature of the plastic melt, causing the melt to solidify. Therefore, the plastic melt and the photocatalyst cannot be sufficiently kneaded.

<Kneading of Embodiment>
In this embodiment, plastic particles, flakes, and pellets are added in advance to a mixture containing photocatalyst particles and water. A photocatalyst slurry containing photocatalyst particles, water, and plastic with a low water content is prepared and used by kneading while evaporating water by heating, pressure reduction, blowing of dry air, or the like.

When the slurry containing the photocatalyst particles and water is dried, the particles stick to each other to form hard particles having a large particle size. However, when plastic is added to a slurry containing photocatalyst particles and water, and kneaded while evaporating water by heating, decompressing, blowing dry air, etc., even if the photocatalyst particles adhere to each other, the plastic will collide. Because it breaks apart, hard grains with a large particle size cannot be formed.

For that purpose, it is necessary to stop kneading before complete drying. Thereby, a photocatalyst slurry with a low water content in which the photocatalyst particles, water and plastic are well dispersed is obtained.
The photocatalyst particles are hydrophilic and the plastic is hydrophobic. The photocatalyst particles are repelled and difficult to mix with the plastic, but by kneading the photocatalyst particles, water, and plastic while evaporating the water, the viscosity of the slurry increases and mixes well, melting it into the plastic. A masterbatch in which the photocatalyst particles are well dispersed can be produced. Here, adsorbed water remains in the photocatalyst in the masterbatch. The amount of adsorbed water is 0.01 to 0.5% by weight of the entire photocatalyst. Plastic is water-repellent and does not contain water.
The shape and size of the masterbatch is, for example, cylindrical. It may be spherical. The size of the masterbatch is preferably 1 to 10 mm in diameter when spherical, and 0.5 to 2 cm long, 1 to 5 mm thick and 1 to 3 cm wide when rectangular parallelepiped (flake). When it is cylindrical, it preferably has a diameter of 1 to 10 mm and a length of 0.5 to 2 cm.

<Composition>
The water content in the photocatalyst slurry of the present embodiment is preferably 5 to 50% by weight, preferably 10 to 40% by weight.
If the temperature is higher than this, the temperature of the plastic melt will drop due to the evaporation of water, and the melt will solidify, making it impossible to knead the plastic melt and the photocatalyst. Below this, hard photocatalyst particles are formed and kneading becomes difficult.
The content of the photocatalyst particles in the photocatalyst slurry of the present embodiment is desirably 10 to 50% by weight, particularly desirably 20 to 30% by weight, relative to the plastic. If it is less than this, the concentration of the photocatalyst is too low to make it difficult to use when producing a photocatalyst masterbatch.

Here, Table 1 shows the composition range of the composition of the photocatalyst slurry.

<Masterbatch>
When the photocatalyst slurry of the present embodiment thus obtained is poured into an extruder and kneaded while being heated or heated and reduced in pressure, water evaporates and polymers such as plastic pellets are melted and mixed with the photocatalyst particles. A masterbatch in which fine photocatalyst particles are uniformly dispersed is obtained.

<Photocatalyst molded product>
When this masterbatch is added to plastic and extruded, a high-performance photocatalyst material in which photocatalyst particles are uniformly dispersed can be produced. Then, it can be spun to produce threads, which can be woven to produce fibers, non-woven fabrics, synthetic paper, and the like. Furthermore, by molding them, high-performance photocatalyst molded articles of various shapes such as plates and sheets can be obtained.

以下の評価の合格基準は、９９％以上である。実施の形態２が最もよい。The conditions of Examples 1 to 3 below are summarized in Table 2.

The acceptance criteria for the following evaluation is 99% or more. Embodiment 2 is the best.

Polyethylene particles with a diameter of 4 mm were added to a photocatalyst slurry prepared by dispersing 30% by weight of 75% anatase-type and 25% rutile-type titanium oxide particles with a particle size of 50 nm in water. The mixture was kneaded while being heated at 50° C. to prepare a photocatalyst slurry.

This was poured into an extruder, heated to 240° C. and kneaded under reduced pressure. As the water evaporated, the polyethylene particles were melted and mixed with the photocatalyst particles to obtain a masterbatch in which fine photocatalyst particles were uniformly dispersed.
This was kneaded into molten polyethylene to contain 4% by weight of photocatalyst. A 20 cm wide, 30 cm long and 1 cm thick board that can be used as a chopping board was produced.

Using this, an antibacterial performance test was conducted using Escherichia coli according to the photocatalyst performance evaluation test method (JIS R 1702).
As a result, after 24 hours, the number of bacteria decreased to 10 or less compared to 2 million reference bacteria, and a reduction rate of 99.999% or more was obtained. This test was performed at 5 points on the plate, and all of them gave a reduction rate of 99.999% or more.

Add PET particles with a diameter of 3 mm and a length of 8 mm to a photocatalyst slurry in which 20% by weight of anatase titanium particles with a particle size of 40 nm are dispersed in water, and knead while heating at 55 ° C. to prepare a photocatalyst slurry with a water content of 25% by weight. did. When this was poured into an extruder and heated to 295° C. and kneaded, the PET particles were melted while the water was evaporated and mixed with the photocatalyst particles to obtain a masterbatch in which fine photocatalyst particles were uniformly dispersed.

This was kneaded with molten PET to prepare a 5 cm square film containing 5% by weight of photocatalyst. Using this, the test of ISO 18071:2016 was performed.
Fine ceramics (advanced ceramics, advanced technical ceramics) Antiviral performance test was conducted using influenza virus according to the specific test method for antiviral properties of photocatalyst materials under indoor lighting.
As a result, 100% inactivation was obtained after 1 hour for a virus infectious titer of 100,000.

Polypropylene flakes with a thickness of 1.5 mm are added to a photocatalyst slurry in which 80% anatase type and 20% rutile type titanium oxide particles with a particle size of 30 nm are dispersed in water at 25% by weight, and kneaded while heating at 45 ° C. to remove moisture. A photocatalyst slurry with an amount of 30% by weight was prepared.

This was poured into an extruder and heated and kneaded at 280° C. under reduced pressure to obtain a masterbatch in which fine photocatalyst particles were uniformly dispersed.
This was kneaded with polypropylene, spun, and further woven to produce a cloth containing 4% by weight of photocatalyst. Using this, an antibacterial performance test was conducted using Staphylococcus aureus according to JIS R1702 Fine Ceramics-Antibacterial Test Method for Photocatalyst Antibacterial Finished Materials and Antibacterial Effect Method. As a result, after 24 hours, the number of bacteria decreased to 10 or less compared to the reference of 1.5 million, and a reduction rate of 99.999% or more was obtained.
It is preferable to use titanium oxide particles containing an anatase type and a rutile type. Highly active as a photocatalyst. 60-90% anatase is good, preferably 75-80%.

The photocatalyst slurry and photocatalyst masterbatch of the present application and their production methods are widely used in the production of products utilizing photocatalysts. The photocatalyst molded article of the present application is widely used in homes, companies, facilities, and the like.

Claims (7)

A method for producing a photocatalyst slurry, comprising a mixing step of mixing photocatalyst particles, water, and plastic while evaporating the water. The photocatalyst slurry is produced in the mixing step of claim 1,
A method for producing a photocatalyst masterbatch, comprising: a first molding step of melting the plastic using the photocatalyst slurry and molding it into a chip-shaped masterbatch. A method for producing a photocatalyst molded article, further comprising a second molding step of incorporating the masterbatch of claim 2 into plastic and molding. Photocatalyst slurry is a mixture of photocatalyst particles, water and plastic.
A photocatalyst slurry containing 5 to 50% by weight of water. 6. The photocatalyst slurry according to claim 5, wherein the water is 5-50% by weight, and the plastic is 40-90% by weight. A photocatalyst masterbatch comprising photocatalyst particles, plastic and water, wherein the water remains on the surface of the photocatalyst particles. A photocatalyst molded article containing photocatalyst particles and plastic,
A photocatalyst molded product with an evaluation value of 99% or higher in the JIS R 1702 test.