JPS6345432B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface-applied antifogging agent applied to synthetic resin molded articles, glass, and the like. More specifically, when applied to the surface of low-energy objects such as synthetic resin films, sheets, plates, and glass products, it can be applied thinly and evenly without causing repellency, and it does not become sticky after drying. This relates to a surface-applied antifogging agent, which is difficult to peel off due to mechanical friction, etc., and cannot maintain the antifogging property imparted to the surface of the object over a long period of time. The surfaces of synthetic resin molded products such as polyethylene, polypropylene, polyvinyl chloride, polyester, and polymethyl methacrylate, especially their films, sheets, plates, and glasses, are hydrophobic and have little affinity for water. For example, when films, sheets, etc. of these synthetic resins are used for agricultural greenhouses, etc., water vapor evaporating from soil or crops condenses on the surface of the film, sheet, etc., forming water droplets. This obstructs the light transmittance of the film, etc., and not only makes it impossible to see the crops inside the greenhouse from the outside, but also significantly adversely affects the growth of the crops due to the reduced light transmittance. Furthermore, depending on the crop, various problems such as leaf rot caused by falling water droplets occur. Measures to prevent water droplets from adhering to water droplets include kneading surfactants and hydrophilic polymer compounds into the synthetic resin before molding, or applying these to the surface of synthetic resin moldings, glass, etc. Therefore, attempts have been made to impart hydrophilicity to the surfaces of synthetic resin molded articles and the like. Partial esterification products of polyhydric alcohols (eg, sorbitol, glycerin, pentaerythritol) are known as typical internally kneaded surfactants used for this purpose. In addition, surface-applied surfactants include ether-type or ester-type non-containers such as polyoxyethylene alkylamine, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene polyhydric alcohol alkyl ester. Ionic surfactants; anionic surfactants such as polyoxyethylene alkyl phosphate salts, alkyl sulfonate salts, and alkyl sulfate salts; and cationic surfactants such as alkyl amine salts and quaternary ammonium salts. It is being Furthermore, hydrophilic polymer compounds are used exclusively as surface-coated compounds, such as polyvinyl alcohol, carboxymethyl cellulose,
Polyvinylpyrrolidone, polystyrene sulfonate, polyalkyl polyamine, etc. are known. However, these conventionally known surfactants and hydrophilic polymer compounds all have the following drawbacks, making it difficult to put them into practical use, and improvements have been desired. (i) Both surfactants and hydrophilic polymer compounds in surface-applied products have poor wettability on low-energy surfaces such as synthetic resin moldings, causing repellency and making it difficult to apply uniformly. . (ii) Even if the coating can be applied by increasing the concentration of the coating solution, the surface of the coating after drying will become sticky due to the surfactant, etc., and blocking will occur when they are overlapped. Therefore, it is not practical for producing antifogging films and sheets by in-line coating. (iii) Surfactants and hydrophilic polymers applied to the surface are washed away by moisture that condenses on the surface during use of the film, etc., and even if they have good antifogging properties at the beginning of use, they are extremely poor. It loses its effectiveness in a short period of time. (iv) An antifogging agent in which a small amount of silica sol is added to a mixture of a cationic surfactant and a nonionic surfactant has already been proposed for the purpose of suppressing the outflow of surfactant, but its antifogging effect is is not sufficient, and the stickiness of the surface is not improved. (v) With internally kneaded type, even if the surfactant leaks out, it bleeds out from inside and compensates for it.
Although the effect lasts longer than that of the surface-applying type, the entire amount still flows out in a relatively short period of time, and the effect is still not long-lasting. If the amount of surfactant mixed in is increased in an attempt to increase the sustainability of the effect, excessive bleed-out may cause surface whitening, resulting in greater adverse effects such as decreased transparency and blocking. The durability of the antifogging effect is not improved. The present inventors conducted various studies to improve the drawbacks of conventional antifogging agents of this type, and as a result, they were able to provide an excellent surface-coated antifogging agent. That is, the present invention comprises colloidal silica stabilized with monovalent cations (excluding colloidal silica that is positively charged by bonding aluminum cations to the surface), a nonionic surfactant, and/or a nonionic surfactant.
or an anionic surfactant, in which colloidal silica is 40% by weight based on the total amount of colloidal silica and surfactant.
This is a surface-applied antifogging agent that does not substantially contain a cationic surfactant. The colloidal silica used in the present invention is
It is “stabilized with monovalent cations”,
and "colloidal silica that has been positively charged by binding aluminum cations is excluded", but in the description of this specification, these will be additionally noted regarding the colloidal silica used in the present invention. may be omitted. Colloidal silica, a nonionic surfactant and/or anionic surfactant can be used separately as an antifogging agent, or colloidal silica can be used in combination with a nonionic surfactant and a cationic surfactant. Although it is not possible to obtain an excellent surface-applied antifogging agent even as an antifogging agent, the present invention provides a solution by using colloidal silica in combination with a nonionic surfactant and/or an anionic surfactant. As a result, it was possible to create an excellent surface-coated antifogging agent. In other words, the antifogging agent of the present invention not only can be applied thinly and uniformly to the surface of synthetic resin molded articles without causing repellency, but also does not become sticky after application and dries, and is resistant to mechanical friction. It will not peel off even if it gets twisted. Therefore, this antifogging agent is particularly suitable for producing antifogging films and sheets by in-line coating. In addition, the duration of its antifogging effect is extremely long, and the transparency of films, plates, etc. coated with this antifogging agent is hardly impaired, or in some cases, the transparency may even be improved. . The colloidal silica used in the present invention is an aqueous silica sol, and has particular characteristics such as compatibility with nonionic surfactants and/or anionic surfactants, stability of the compatibility, and after application of an antifogging agent. From the viewpoint of transparency and the like, an aqueous silica sol with a small dispersed particle size is preferred. Usually, the particle size is preferably 100 mμ or less, more preferably around 10 mμ.
Further, the silica sol is stabilized with monovalent cations such as sodium and ammonium ions. This type of aqueous silica sol is commercially available as, for example, Snowtex (trade name of Nissan Chemical Industries, Ltd.), Ludotux (trade name of Dupont Co., Ltd.), Cataroid (trade name of Catalysts Kasei Co., Ltd.), and the like.
In the present invention, these commercially available products can be used as appropriate. Note that, as is clear from the claims of the present specification, the colloidal silica used in the present invention does not include those to which aluminum cations are bonded to the surface to give a positive charge. Furthermore, examples of the nonionic surfactants used in the present invention include the following. (i) Ether type: These include polyoxyalkylene alkylphenyl ether and polyoxyalkylene alkyl ether. The alkylphenyl group or alkyl group preferably has 8 to 22 carbon atoms. Further, the alkylene oxide to be added preferably has 2 to 4 carbon atoms, and the number of moles added is preferably 2 to 30.
The addition of alkylene oxide may be a single addition of one type or a mixed addition of two or more types, and in the case of a mixed addition, the addition form may be block addition or random addition. (ii) Ester types: These include polyoxyalkylene alkyl esters, polyalkylene glycol alkyl esters, and polyoxyalkylene polyhydric alcohol esters. In this case, the alkylene oxide to be added and the number of moles thereof added are the same as in (i). In addition, the alkylene glycol has 2 to 4 carbon atoms, and even if one type of each is used alone, 2 to 4 carbon atoms are used.
A mixture of more than one species may be used, and the mixture may be block or random. Furthermore, the polyhydric alcohols include glycerin, sorbitol, pentaerythritol and trimethylolpropane. (iii) Polyalkylene glycol: Polyalkylene glycol is an addition polymer of the alkylene oxide mentioned in (i), and the number of moles added is 2 to 500. (iv) Futsuso-based nonionic surfactants: These include fluoroalkyl group-containing alkylene oxide adducts, such as perfluoroalkyl ethylene oxide adducts. Fluorine-based nonionic surfactant has a purity of 0.01
% aqueous solution is preferably 60 dynes/cm or less, particularly 30 dynes/cm or less.
If the surface tension is too high, it is not preferable because it reduces the wettability of the antifogging agent to the surface of the synthetic resin molded article. (v) Silicone-based nonionic surfactant: Surfactant containing organopolysiloxane,
For example, an alkylene oxide adduct of organopolysiloxane can be used. Furthermore, examples of the anionic surfactant used in the present invention include the following. (i) Sulfate ester salts: Examples include various higher alcohol sulfate ester salts and various liquid fatty oil sulfate ester salts. (ii) Sulfonate type: For example, there are various alkylaryl sulfonates, various alkyl sulfonates, etc. (iii) Sulfate type: Examples include sulfates of various aliphatic amines and sulfates of various aliphatic amides. (iv) Phosphate ester salts: For example, there are phosphate ester salts of various aliphatic alcohols. (v) Futsuso-based anionic surfactants: Examples include fluoroalkyl group-containing carboxylic acids, carboxylic acid salts thereof, and fluoroalkyl group-containing phosphate esters. Specific examples thereof include perfluoroalkyl carboxylic acids, perfluoroalkyl carboxylates, and perfluoroalkyl phosphates. Similar to the case of futsuso-based nonionic surfactants, the pure content of futsuso-based anionic surfactants is
Preferably, the surface tension in a 0.01% aqueous solution is 60 dynes/cm or less, particularly 30 dynes/cm or less. (vi) Silicone-based anionic surfactant: For example, an organopolysiloxane-containing carboxylic acid or a salt thereof. In the antifogging agent of the present invention, it is desirable that the amount of colloidal silica blended is as large as possible relative to the total amount of colloidal silica and surfactant. To this end, it is necessary to use only a fluorine-based surfactant alone as a nonionic surfactant and/or anionic surfactant (in this case, a combination of two or more types of fluorine-containing surfactants may be used alone). ), or it is desirable to use a combination of a fluorine-based surfactant and a surfactant other than the fluorine-containing surfactant. Among surfactants other than the fluorine-containing surfactants, ether-type nonionic surfactants with an HLB value of 5 to 15 are desirable.
Examples of such ether-type nonionic surfactants having an HLB value of 5 to 15 include polyoxyethylene (5 mol) nonylphenyl ether, polyoxyethylene (10 mol) nonylphenyl ether, and polyoxyethylene (4 mol). lauryl ether,
Examples include polyoxyethylene (10 moles) lauryl ether, polyoxyethylene (4 moles) lauryl amine, and the like. In addition, in the preparation of this type of antifogging agent, if a cationic surfactant or amphoteric surfactant is used as a surfactant, the stability of colloidal silica is destroyed and silica particles agglomerate. It is not at all an excellent antifogging agent like the antifogging agent of the present invention. In the present invention, as described above, an aqueous silica sol as colloidal silica and a nonionic surfactant and/or anionic surfactant are mixed, and the total amount of colloidal silica and surfactant is Colloidal silica is 40% by weight or more, preferably 50% by weight or more, more preferably 75% by weight
A surface coating type antifogging agent is obtained in the above manner.
When using this antifogging agent, it is diluted with water or the like to a desired concentration and used for coating. In the antifogging agent of the present invention, the content of colloidal silica is preferably 50% relative to the total amount of colloidal silica and surfactant.
If the content is at least 75% by weight, preferably at least 75% by weight, it is possible to avoid the stickiness of the applied surface, which was considered the biggest drawback of conventional surface-applied antifogging agents, and significantly extend the duration of the antifogging effect. You can force it. Moreover, even though this antifogging agent contains a high concentration of colloidal silica, when it is applied to a substrate such as a film or board, it hardly reduces the transparency of the substrate, or in some cases. In some cases, it may even improve its transparency. The antifogging agent of the present invention is of an aqueous dispersion type, and an alcohol having 1 to 3 carbon atoms, a polyhydric alcohol, acetone, or the like may be added thereto depending on the case. The amount of these alcohols and the like to be added is appropriately selected within a range that does not impair the adhesion of the antifogging agent to the base material. The concentration of this antifogging agent during coating varies depending on the type of substrate to be coated, but is usually 0.01 to 50% by weight as the total concentration of colloidal silica and surfactant, preferably 0.01 to 50% by weight. is 0.1-15% by weight. According to experiments conducted by the present inventors, the antifogging agent of the present invention has been found that if the concentration during coating is too high, the amount of coating will be too large, and if the amount of coating is too large, the antifogging effect will not last long. It turned out that the period was shortened. Therefore, within the range that ensures a uniform antifogging agent coating,
Rather, it has been found that it is desirable to apply the antifogging agent thinly, and for this purpose, it is desirable to use the antifogging agent at a relatively low concentration in the coating process. There are no particular restrictions on the substrate to which the antifogging agent of the present invention is applied, and the antifogging agent of the present invention can be applied to various substrates including various synthetic resin moldings, glass, and the like. However, the antifogging agent of the present invention can be particularly effective when applied to synthetic resin moldings, in particular those for which it has been difficult to maintain the antifogging effect for a long period of time with conventional antifogging agents. Film or sheet. In addition, the antifogging agent of the present invention has excellent applicability to substrates and adhesion to substrates, so
Even if the base material before application is not subjected to surface treatment such as corona discharge treatment, fully satisfactory uniform application and adhesion properties can be obtained. However, in some cases, it is also possible to previously perform a surface treatment such as a corona discharge treatment on the base material before applying the antifogging agent of the present invention. The method for applying the antifogging agent of the present invention to a base material is as follows:
Any method may be used as long as it can be applied uniformly. Examples of the coating method include a roller touch method, a bar coater method, a spray method, a dipping method, and a brush coating method. In particular, there is a method for manufacturing films and sheets with excellent anti-fog effects by continuously coating synthetic resin films and sheets using an in-line coating method using the roller touch method.
This is a method that most effectively utilizes the features of the antifogging agent of the present invention. A more specific explanation will be given below with reference to Examples and Comparative Examples, but the scope of the present invention is not limited in any way by these Examples. Examples 1 to 16 Comparative Examples 1 to 6 The components shown in Table 1 were appropriately mixed in various proportions, diluted with water, and the total concentration of colloidal silica and surfactant (hereinafter referred to as "coating solution concentration") was obtained. Various antifogging agent aqueous solutions containing 30% by weight of antifogging agents were prepared. Regarding each of the antifogging agent aqueous liquids shown in Table 1 obtained in this way, or the antifogging agent aqueous liquids further diluted with water to give various coating solution concentrations, their compatibility and low density polyethylene Film (thickness)
The coating properties, stickiness, transparency, and duration of anti-fogging properties were tested when applied to 20μ). The results were as shown in Table 2. Furthermore, regarding some of the antifogging agents shown in Table 1,
The coating properties, stickiness, transparency and duration of anti-fogging properties were tested when they were applied to unsaturated polyester plates (thickness 2 mm) at various concentrations. The results were as shown in Table 3.

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[Table] Notes to Table 3
The test method and evaluation are in accordance with the notes in Table 2.
As is clear from the results shown in Tables 2 and 3, the antifogging agent of the present invention exhibits excellent performance. Comparative Examples 7 and 8 Instead of the silica sol used in Examples 11 and 12, commercially available alumina sol (dispersed particles had a diameter of 10 mμ,
Feather-like, 100 mμ long, stabilized with organic acids, concentration approx. 10
The antifogging agents of Comparative Example 7 and Comparative Example 8 were prepared in the same manner as in Example 11 or 12 except that the antifogging agents were prepared in the same manner as in Example 11 or Example 12. The antifogging agents obtained in Examples 11 and 12 and the antifogging agents obtained in Comparative Examples 7 and 8 were tested for water droplet prevention performance at low temperatures. That is, a polyethylene film was coated with the antifogging agent to be tested, air-dried for one day, and placed over a 500 ml beaker containing 300 ml of water, with the coated side facing down and tightly covered with a lid. The beaker was placed in a constant temperature bath kept at 5° C., and the cloudy state of the film was observed after one week. The results showed that the films coated with the antifogging agents obtained in Examples 11 and 12 had no fogging at all, but the films coated with the antifogging agents obtained in Comparative Examples 7 and 8 did not. A thick cloud appeared over the entire surface of the film. Furthermore, the antifogging agent of Comparative Example 8 in which an anionic surfactant was blended with alumina sol had extremely poor compatibility, gelled within 2 to 3 days after preparation of the antifogging agent, and had no shelf life. Example 17 Instead of the silica sol (S-2) used in Example 11, a commercially available silica sol Ludox AS (dispersed particle size 13 to 14 mμ, stabilizing ion NH ₄ ⁺ ) was used, and the other conditions were the same as in Example 11. An antifogging agent aqueous solution was prepared under similar conditions and tested in the same manner. The results were similar to those in Example 11.

Claims (1)

[Claims] 1. Colloidal silica stabilized with monovalent cations (excluding colloidal silica that is positively charged by bonding aluminum cations to the surface), a nonionic surfactant, and/or The surface is composed of a stable aqueous dispersion containing anionic surfactant, and has colloidal silica in an amount of 40% by weight or more based on the total amount of colloidal silica and surfactant, and substantially does not contain cationic surfactant. Paintable anti-fog agent. 2. The antifogging agent according to claim 1, wherein the amount of colloidal silica is 50% by weight or more based on the total amount of colloidal silica and surfactant. 3. The antifogging agent according to claim 1, wherein the amount of colloidal silica is 75% by weight or more based on the total amount of colloidal silica and surfactant. 4. The antifogging agent according to claim 1, 2, or 3, wherein all or a part of the surfactant is a fluorine-based surfactant. 5. The antifogging agent according to claim 1, 2, 3, or 4, wherein the surfactant is an ether type nonionic surfactant and has an HLB of 5 to 15. agent. 6 75 to 90 parts by weight of colloidal silica and 25 to 90 parts by weight of nonionic surfactant and/or anionic surfactant
10 parts by weight, and these are contained in the aqueous liquid in a total concentration of 0.1 to 50% by weight according to claim 1, 4, or 5. agent.