JP2000154374A - Antifogging agent and antifogging-treated base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antifogging agent with high storage stability, exhibiting high antifogging effect from just after being applied, and improved in antifogging sustainability by making the agent include water, a water-soluble cellulose and a specific colloidal silica and by bringing the alkali component concentration of the agent to a specified level. SOLUTION: This antifogging agent is obtained by including (A) 98.0-99.8 wt.% of water, (B) 0.01-0.40 wt.% of a water-soluble cellulose, and (C) 0.16-1.99 wt.% of colloidal silica with an average particle size of 3-50 (pref. 5-30) nm and by bringing the alkali component concentration of the agent to <=50 ppm, pref. <=10 ppm, more pref. <=8 ppm; where the viscosity of the component B (at 25 deg.C, in the form of a 5% aqueous solution) is pref. 1,000-100,000 cPs, and the component B is e.g. methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethylcellulose, hydroxyethylmethyl cellulose.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifogging agent and an antifogging substrate, and more particularly to an antifogging agent capable of imparting excellent antifogging performance by coating and drying, and a coating formed therefrom. The present invention relates to an antifogging treated substrate having excellent antifogging properties, antifogging durability and transparency.

[0002]

2. Description of the Related Art Synthetic resins and glass are currently used in a wide range of fields because of their excellent properties, such as transparency and durability. However, depending on the usage environment, depending on conditions such as temperature and humidity, moisture adsorbed or condensed on the surface of a base material such as synthetic resin or glass covers the surface as fine water droplets, causing fogging or water droplets growing and dropping May cause various inconveniences. For example, when a synthetic resin film is used as a covering material for an agricultural house, water evaporated from the surface or the crop condenses on the inner surface of the film as fine water droplets, impeding the transmission of light rays and slowing the growth of the crop. Drops of water on crops cause disease. Further, in goggles, bathroom windows, etc., the visibility is greatly deteriorated because water droplets cover the surface.

In order to prevent these drawbacks, in the case of a resin material, a surfactant is added to the resin in advance in order to impart anti-fogging properties to the surface, and the bleeding exerts the anti-fogging properties. Generally, a method of causing the above is used.
However, this method is not sufficient to maintain the anti-fogging effect over a long period of time, since the anti-fogging effect is lost if all the surfactant in the resin bleeds.

[0004] Therefore, research has been made on an antifogging agent which forms an excellent antifogging film by applying it to the surface of a substrate and drying it, particularly for the purpose of maintaining the antifogging effect for a long period of time (Japanese Patent Application Laid-Open No. HEI 5 (1993) -5980). -59202, JP-A-7-53747, JP-A-7-82398, JP-A-8-2958
No. 76, JP-A-8-319476, JP-A-9
-302119). As the antifogging agent, those having characteristics such as storage stability and ease of application are required, and the antifogging agent layer formed on the film or glass has an initial antifogging property, antifogging durability, It is required to have properties such as transparency and coating film uniformity. Furthermore, it is important that the cost of the entire process be low. However, JP-A-7-53
747, JP-A-7-82398 and JP-A-8
-295876, JP-A-8-319476 and JP-A-9-302119 require the use of colloidal silica and colloidal alumina in combination, so that the colloidal particles are stable. Absent, storage stability is deteriorated, coating workability is reduced, and the film becomes non-uniform due to gelation, and a sufficient anti-fogging effect cannot be obtained. JP-A-5-59202 discloses an antifogging agent composed of colloidal silica and a surfactant. In this composition, the surfactant is washed away by water, and the antifogging effect is long. Does not last for a period.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an antifogging agent having excellent storage stability, exhibiting excellent antifogging properties immediately after application, and having significantly improved antifogging durability. Another object of the present invention is to provide an anti-fogging treatment film formed by applying the anti-fogging agent and having an excellent anti-fogging effect over a long period from the initial stage of formation.

[0006]

In order to solve the above-mentioned problems, the present invention provides 98.0 to 99.8% by weight of water, 0.01 to 0.40% by weight of water-soluble cellulose, and an average particle size. 3 to 50 nm colloidal silica 0.16 to 1.99
% By weight, wherein the concentration of the alkali component is 50 ppm or less, an antifogging treated substrate having a film formed from the antifogging agent of the present invention on at least a part of the surface of the substrate, and a film of the present invention Provided is an agricultural coating material comprising an antifogging substrate. Water-soluble cellulose has excellent film-forming ability and durability. On the other hand, when colloidal silica having the above average particle diameter is densely present on the surface of the base material as an inorganic substance, an excellent antifogging effect can be exhibited over a long period from the initial stage of film formation.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the antifogging agent and the antifogging substrate of the present invention will be described in detail. The main components of the anti-fogging agent of the present invention are 1) a water-soluble cellulose exhibiting functions of film formation and anti-fogging durability, and 2) colloidal silica for maintaining an excellent anti-fogging effect over a long period from the initial stage of film formation. is there.

1) Water-soluble cellulose Examples of the water-soluble cellulose include methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and hydroxyethyl methyl cellulose. Among them, methylcellulose and hydroxyethylcellulose are excellent in terms of film-forming ability, and hydroxyethylcellulose is particularly excellent in terms of antifogging property of the coating film itself. The viscosity of water-soluble cellulose is 2
At 5 ° C., a 5% by weight aqueous solution, preferably 1000
~ 100,000 cps. If the viscosity is less than 1000 cps, a sufficiently thick film cannot be formed because the viscosity is too low. 1
If it exceeds 00000 cps, the viscosity is too high, and it becomes difficult to disperse colloidal silica, and an antifogging agent having good dispersibility cannot be obtained.

The amount of the water-soluble cellulose to be added is 0.01 to 0.40% by weight, preferably 0.02 to 0.2% by weight, based on the total solid content of the antifogging agent. If the amount is less than 0.01% by weight, the initial and long-term anti-fogging effects cannot be obtained because the film forming ability of the anti-fogging agent is inferior. If the content exceeds 0.40% by weight, colloidal silica is taken into cellulose at the time of film formation, and the initial antifogging effect cannot be obtained.

2) Colloidal Silica Colloidal silica having an alkali component concentration of 50 ppm or less in the antifogging agent is preferable in that it is stably present in an aqueous cellulose solution. The concentration is particularly stable at a concentration of 10 ppm or less, more preferably 8 ppm or less. Therefore, the silica is densely present in the formed coating film, and the coating film exhibits excellent antifogging properties from the initial stage of formation to a long period of time.

The alkali component in the antifogging agent is mainly
It means sodium oxide (Na ₂ O) which is an impurity generated during the production of silica. When the alkali component concentration in the antifogging agent exceeds 50 ppm, in the aqueous cellulose solution,
Colloidal silica cannot exist stably. Even if such an antifogging agent is applied, silica is not densely present in the coating film,
Since the colloidal silica is easily washed away, the long-term antifogging property is poor.

The colloidal silica usually has a particle size of 3 to 50.
nm, preferably 5 to 30 nm. If it is less than 3 nm, the silica particles are likely to flow away from the film, and the antifogging property is not maintained for a long time. If it exceeds 50 nm, the adhesion of the silica particles is poor, and the antifogging effect is not exhibited in the initial stage of film formation. The amount of colloidal silica to be added is 0.16 to 1.99% by weight, preferably 0.20 to 0.9% by weight of the whole antifogging agent in terms of solid content.
40% by weight. If the amount is less than 0.16% by weight, the amount of silica in the coating film is small, and the initial antifogging effect is lacking. 1.
If it exceeds 99% by weight, the amount of silica becomes too large.
Cellulose film formation is inhibited.

The type of the substrate on which the antifogging agent of the present invention is applied is as follows:
It is not particularly limited, and is selected from glass, resin molded products (for example, films), etc., for which antifogging treatment is conventionally required. Examples of the material resin of the resin molded product include polycarbonate, polyester, vinyl chloride resin, acrylic resin, fluororesin, and polyolefin resin.

Among them, fluorine resins, for example, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinyl ether Copolymers, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, and the like are preferably used. In particular, ETFE is preferred from the viewpoint of transparency and moldability.

As ETFE, for example, JP-A-59-1
Ethylene, as described in US Pat.
A fluorine-containing vinyl monomer other than tetrafluoroethylene, which is a third component copolymerizable therewith, having a molar ratio of ethylene to tetrafluoroethylene of 40:60 to 60:40, and ETFE having a vinyl monomer content of 0.1 to 10 mol% is particularly preferred from the viewpoint of excellent moldability, transparency and mechanical strength.

The fluorine-containing vinyl monomer includes:
formula:

A compound represented by the formula: CH ₂ ＣＦCFRf (wherein Rf represents a fluoroalkyl group having 2 to 10 carbon atoms) is preferred.

In order to further improve the applicability of the anti-fogging agent, the surface of the resin molded product is preferably subjected to a hydrophilic treatment.
Methods for the hydrophilization treatment include chemical surface treatment (chemical treatment) and physical surface treatment (ultraviolet / radiation irradiation, discharge treatment, flame treatment), etc., but discharge treatment in terms of productivity and safety. Is preferred. Examples of molded articles include films, resin goggles, spectacle lenses, underwater glasses, optical lenses, lightweight mirrors used in bathrooms and washrooms, and the like.

After the antifogging agent is applied to the substrate and dried under appropriate conditions, an antifogging treated substrate is obtained. When the substrate is a resin film, the antifogging treatment substrate (film) of the present invention
Is an agricultural coating material, for example, an agricultural house coating material,
It can be used as a coating material for agricultural tunnels. Further, a substrate made of a resin film can be used by being bonded to the above-mentioned molded product.

[0019]

The present invention will be described below in more detail with reference to examples and comparative examples. In Examples and Comparative Examples,
The storage stability test and the accelerated anti-fogging test were performed as follows.

Storage stability test Each anti-fogging agent is placed in a 50 cc sample bottle and stirred well. After standing for 2 hours, the state of separation of the solid content is evaluated. Evaluation criteria A: No separation at all. Δ: Slightly separated. X: completely separated.

Accelerated antifogging test A required number of test pieces are cut out from a film spray-coated with each antifogging agent. The test piece is immersed in a warm bath at 50 ° C., and after a predetermined time, the test piece is taken out and dried at room temperature. After drying, the contact angle of water on the anti-fog treated surface of each test piece is measured. Evaluation criteria ◎; 0 ° ≦ contact angle <25 °; 25 ° ≦ contact angle <35 ° ×; 35 ° ≦ contact angle

Example 1 Hydroxyethyl cellulose (SP500, manufactured by Daicel Chemical Industries, Ltd.) was added to pure water at a solid concentration of 0.02% by weight.
And colloidal silica (STOS, manufactured by Nissan Chemical Industries, Ltd.) having an average particle size of about 10 nm and an alkali component content of 190 ppm (corresponding to an alkali component concentration of 3.1 ppm in the antifogging agent) was dissolved in this aqueous solution. Solid concentration 0.3
Add to 2% by weight and stir well.

A storage stability test is performed on the antifogging agent. The results are shown in Table 1 below. This anti-fogging agent was treated with an ethylene-tetrafluoroethylene copolymer film (one-sided corona treated product; through light TE0 manufactured by Daikin Industries, Ltd.).
063) on the treated surface by spray coating (the applied amount is 0.5
g / m ² (after drying)) and dried at room temperature. A test piece is taken from the antifogging agent-coated film and subjected to an accelerated antifogging test.
The results are shown in FIG. In addition, "initial" in Table 1
Is the contact angle one hour after the start of the test, and "long term" is the contact angle after 1500 hours.

Example 2 An average particle size of about 15 nm and an alkali content of 290 ppm
An antifogging agent was prepared in the same manner as in Example 1 except that a colloidal silica (STN manufactured by Nissan Chemical Industries, Ltd.) dispersion liquid (equivalent to an alkali component concentration of 4.7 ppm in the antifogging agent) was used. An agent-coated film was prepared. The test results are shown in FIG.

Comparative Example 1 An average particle diameter of about 10 nm and an alkali component content of 4200 pp
m (equivalent to an alkali component concentration of 67.5 ppm in the anti-fog agent) of colloidal silica (ST manufactured by Nissan Chemical Industries, Ltd.)
S) An antifogging agent was prepared in the same manner as in Example 1 except that a dispersion was used, and a film coated with the antifogging agent was prepared. The test results are shown in FIG.

Comparative Example 2 Average particle size: about 77 nm, alkali content: 510 ppm
An antifogging agent was prepared in the same manner as in Example 1 except that a colloidal silica (STZL manufactured by Nissan Chemical Industries, Ltd.) dispersion liquid (equivalent to 8.2 ppm of the alkali component in the antifogging agent) was used. A coating film was prepared. The test results are shown in FIG.

Comparative Example 3 A higher fatty acid amide (Chemistat 2500 manufactured by Sanyo Chemical Industries, Ltd.) was dissolved in pure water at a solid concentration of 0.02% by weight, and the resulting aqueous solution had an average particle size of about 10 nm and an alkali component content. A dispersion of colloidal silica (STOS manufactured by Nissan Chemical Industries, Ltd.) of 190 ppm (corresponding to an alkali component concentration of 3.1 ppm in the antifogging agent) at a solid content of 0.32% by weight is added and stirred well.

A storage stability test is performed on the antifogging agent. The results are shown in Table 1 below. This antifogging agent was prepared in Example 1
The treated surface of the same ethylene-tetrafluoroethylene copolymer film as used in (1) is spray-coated (the coating amount is 0.5 g / m ² (after drying)) and dried at room temperature. A test piece is taken from the antifogging agent-coated film and subjected to an accelerated antifogging test. The results are shown in FIG.

Comparative Example 4 Hydroxyethylcellulose (Daicel Chemical Industries, Ltd. SP500) was dissolved in pure water at a solid content of 0.02% by weight. A dispersion of colloidal silica (equivalent to 2.3 ppm of alkali component concentration in the fogging agent) (STOS manufactured by Nissan Chemical Industry Co., Ltd.) and alumina sol (520 manufactured by Nissan Chemical Industry Co., Ltd.) were respectively 0.24% by weight and 0.2% solids. Add 0.08% by weight and stir well.

A storage stability test is performed on the antifogging agent. The results are shown in Table 1 below. This antifogging agent was prepared in Example 1
The treated surface of the same ethylene-tetrafluoroethylene copolymer film as used in (1) is spray-coated (the coating amount is 0.5 g / m ² (after drying)) and dried at room temperature. A test piece is taken from the antifogging agent-coated film and subjected to an accelerated antifogging test. The results are shown in FIG.

[0031]

[Table 1]

In Comparative Example 1, the alkali component content in the colloidal silica dispersion was as high as 4200 ppm, which corresponds to the alkali component concentration in the antifogging agent of 67.5 ppm. Does not exist. Therefore, even when this antifogging agent is applied, the silica does not exist densely in the coating film, and the colloidal silica is easily washed away, and thus lacks long-term antifogging properties. In Comparative Example 2, since the particle size of the colloidal silica was as large as 77 nm, the adhesion of the silica particles was poor, and the initial and long-term antifogging properties were poor. In Comparative Example 3, a higher fatty acid (surfactant) was used as the film-forming substance.
Since the film is used, the film itself is washed away early, and the long-term antifogging property is inferior. In Comparative Example 4, since the colloidal silica and the colloidal alumina were used in combination, the storage stability of the antifogging agent was poor.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of an accelerated anti-fog test in Examples.

FIG. 2 is a graph showing the results of an accelerated antifogging test in a comparative example.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 1/06 C08L 1/06 1/28 1/28 C09D 101/08 C09D 101/08 (72) Inventor Market Shigeru 1-1, Nishi-Ichitsuya, Settsu-shi, Osaka Daikin Industries, Ltd. F-term in Yodogawa Works (reference) 4F100 AA20B AJ04B AJ06B AK01A AK17A AK18A AT00A BA02 CA10 CA23B CC00 EH462 EJ551 EJ862 EJ862 GB01 JA02B JA05B02A01B02A01 AB031 DE026 DJ017 HA06 4J038 BA021 HA156 HA446 MA14 PC08

Claims (12)

[Claims] 1. 98.0 to 99.8% by weight of water, 0.01 to 0.40% by weight of water-soluble cellulose and an average particle size of 3 to 9%.
0.16 to 1.99% by weight of 50 nm colloidal silica
An anti-fogging agent comprising an alkali component having a concentration of 50 ppm or less. 2. The water-soluble cellulose is 5% at 25 ° C.
The antifogging agent according to claim 1, wherein the weight% aqueous solution is cellulose having a viscosity of 1,000 to 100,000 cps. 3. The water-soluble cellulose is methyl cellulose, ethyl cellulose, hydroxyethyl cellulose,
The antifogging agent according to claim 1 or 2, wherein the antifogging agent is at least one kind of cellulose selected from the group consisting of carboxymethylcellulose and hydroxyethylcellulose. 4. The antifogging agent according to claim 3, wherein the water-soluble cellulose is hydroxyethyl cellulose. 5. The colloidal silica has an average particle size of 5 to 30.
The antifogging agent according to any one of claims 1 to 4, which has a nm. 6. The antifogging agent according to claim 1, wherein the concentration of the alkali component is 10 ppm or less. 7. The antifogging agent according to claim 1, wherein the concentration of the alkali component is 8 ppm or less. 8. The method according to claim 1, wherein at least a part of the surface of the substrate is provided.
7. An antifogging treatment base material having a film formed from the antifogging agent according to any one of 7. 9. The antifogging substrate according to claim 8, wherein the substrate is a resin film. 10. The antifogging substrate according to claim 8, wherein the substrate is a fluororesin film. 11. The fluororesin film is an ethylene-tetrafluoroethylene copolymer film.
0 The antifogging treatment base material described in 0. 12. An agricultural coating material comprising the antifogging substrate according to any one of claims 9 to 11.