JPH0840718A - Porous silica containing antifogging agent and antifogging polymer film - Google Patents

Abstract

PURPOSE:To obtain a polymer film having high transparency and excellent in durability of antifogging effect. CONSTITUTION:Spherical porous silica containing an antifogging agent is obtained by compounding a porous silica with the antifogging agant having refractive index of >=1.48 at 30 deg.C in a weight ratio of >=0,1 to the spherical porous silica. The obtained spherical porous silica has an average particle diameter of 1-20mum. The objective antifogging polymer film is produced from a polymer composition containing 1-50wt.% of the spherical porous silica containing the antifogging agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifogging agent-containing spherical porous silica and an antifogging polymer film.

[0002]

2. Description of the Related Art Polymer films made of various materials have been conventionally used for packaging foods. At that time, the appearance of the foods containing the contents is improved and water droplets, which tend to become a culture medium for bacteria, are prevented. Therefore, the polymer film used is required to have antifogging property.

Further, in the field of agriculture, when water drops adhere to the film of an agricultural house, the light transmittance is reduced and the growth of plants is adversely affected, and the adhered water drops fall on agricultural crops, causing disease. Also, a film having anti-fogging property is required because it causes deterioration of quality.

As a method for imparting antifogging property to an organic polymer material, (1) a method of coating the surface with a hydrophilic metal oxide such as silica or alumina (Japanese Patent Laid-Open No. 123237/1989)
(See Japanese Patent Laid-Open No. 5-59202),
(2) A method of applying a surfactant or a modified silicone oil to the surface, and (3) a method of kneading a surfactant or a modified silicone oil are known.

However, the method (1) has a problem that the transparency is lowered even when ultrafine particles of metal oxide or a thin film is used. The method (2) has problems such as poor sustainability and stickiness because the antifogging agent is exposed on the surface. In the method (3), a porous material such as silica, alumina, or zeolite is used in combination for the purpose of improving durability (JP-A-60-4).
No. 9047), a method of supporting on porous silica (see Japanese Patent Laid-Open No. 5-125220), and the like have been proposed. However, even in these methods, there is a problem that the transparency when formed into a film or sheet is low.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a polymer film having high transparency and excellent durability of antifogging effect.

[0007]

Means for Solving the Problems The present invention contains an antifogging agent having a refractive index of 1.48 or more at 30 ° C. in a weight ratio of 0.1 or more with respect to spherical porous silica. Diameter is 1
A spherical porous silica containing an antifogging agent having a size of 20 μm is provided.

In the present invention, the antifogging agent contained in the spherical porous silica has a refractive index at 30 ° C. of 1.48 or more. When the refractive index at 30 ° C. is less than 1.48, the transparency of the film becomes low when blended with a polymer, which is unsuitable.

When the antifogging agent is solid at 30 ° C., it is preferable that the refractive index is 1.48 or more as compared with the case where it is liquid. Further, an antifogging agent that is solid at 30 ° C. is more preferable because it has a slower diffusion rate from the pores of the spherical porous silica to the film than that of a liquid and is excellent in the durability of the antifogging effect. .

The antifogging agent is not particularly limited, but is a sorbitan ester surfactant, a sorbitan ester ether surfactant, a glycerin ester surfactant, a polyoxyethylene ether surfactant, a polyoxyethylene ester surfactant. One or more selected from the group consisting of surfactants is desirable because the one having the above-mentioned refractive index can be easily obtained.

In the present invention, the shape of the porous silica is
It must be spherical. If the shape of the porous silica is irregular, the outer surface area of the particles becomes large and light is easily scattered, which impairs the transparency of the film, which is not desirable. In addition, in the present invention, the spherical shape includes not only a true spherical shape but also a slightly irregular shape. Also,
The spherical porous silica may contain amorphous silica and the like as long as the effects of the present invention are not impaired.

The average particle size of the spherical porous silica is 1-2.
0 μm is preferable. If the average particle size is less than 1 μm,
This is not desirable because it may reduce the transparency of the film. When the average particle size exceeds 20 μm, silica may look like foreign matter in the film, which is not desirable.

The ratio of the antifogging agent to the weight of the spherical porous silica must be 0.1 or more. If the ratio of the antifogging agent to the weight of the porous silica powder is less than 0.1, it is necessary to add a large amount of the porous silica containing the antifogging agent in order to exhibit a predetermined antifogging effect. However, there are problems such as a decrease in transparency and a decrease in film strength, which is not preferable. It is more preferable that the ratio of the antifogging agent to the weight of the spherical porous silica is 0.3 or more.

When a large amount of antifogging agent is contained, the antifogging agent is released outside the pores and the porous silica becomes a paste. When the antifogging agent is free in this way, the antifogging agent tends to bleed out and the surface becomes sticky even when blended into a film and molded, so that the antifogging agent is contained in the pores. It is desirable that the powder is in powder form. Therefore, it is desirable that the porous silica containing the antifogging agent be in the form of powder.

The oil absorption of the spherical porous silica is 100 to 4
00 ml / 100 g is preferable. Oil absorption is 100
When the amount is less than 100 ml / ml, the antifogging agent contained in the spherical porous silica is rapidly diffused into the film and sustainability may be deteriorated, which is not desirable. Also, oil absorption is 400 ml
When it exceeds / 100 g, the strength of the spherical porous silica becomes low, and it may be disintegrated when kneaded into the film to elute the antifogging agent and the durability may not be exhibited, which is not desirable.

The average pore diameter of the spherical porous silica is 40 n.
It is preferably m or less. Average pore diameter is 40 nm
If it exceeds, the rate of diffusion from the inside of the pores of the contained antifogging agent to the organic polymer material is increased, the durability is deteriorated, and the surface becomes sticky, which is not preferable.

A polymer film having an antifogging property can be obtained by containing 1 to 50% by weight of the above-described antifog-containing spherical porous silica in the polymer composition. As a polymer,
Although not particularly limited, a film-forming thermoplastic synthetic resin can be preferably used. Specifically, polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, polystyrene, polycarbonate, polyethylene terephthalate and the like can be preferably used. Particularly when the refractive index of the polymer is in the range of 1.49 to 1.60, the transparency of the film is high, which is preferable. A fluororesin film may have a slightly low transparency because of its low refractive index, but it is possible to add spherical antifogging agent-containing spherical porous silica.

[0018]

[Function] Since ordinary polymers have a refractive index of about 1.49 to 1.60 and spherical porous silica has a refractive index of 1.45 to 1.47 in the visible light region, film molding It is considered that the scattering of light is suppressed and the transparency of the film is improved by using an antifogging agent whose refractive index at the time of later use (30 ° C.) shows a value between these values.
In addition, by using spherical silica having an average particle diameter of 1 to 20 μm as the porous silica, light scattering on the outer surface of silica is reduced as compared with amorphous silica, and the transparency of the film is excellent. It is considered to be a thing.

[0019]

【Example】

Example 1 Spherical porous silica having an average particle diameter of 3 μm (manufactured by Asahi Glass Co., Ltd., trade name “Sildex”, oil absorption 280 ml / 10)
Sorbitan monopalmitate (melting point 45.0-51.0 ° C,
50 g of a refractive index of 1.486 at 30 ° C. was uniformly impregnated. As a result, powdery antifogging agent-containing spherical porous silica was obtained.

1. The spherical porous silica containing the antifogging agent as described above, 2.
After mixing with polyvinyl chloride at a ratio of 5 PHR and kneading well, a film having a thickness of 100 μm was formed. The results of measuring the haze of this film are shown in Table 1.

Further, in order to evaluate the antifogging effect of the antifogging agent-containing porous silica, water was put in a container and the temperature was kept at 40 ° C., the above film was covered on the container, and the container was sealed and left in an environment of 20 ° C. Then, the degree of haze of the film after 1 hour was observed. One day after the film was formed and one half a year after the film formation were observed, and the durability was also evaluated. The results are shown in Table 1.

Example 2 Instead of the sorbitan monopalmitate of Example 1, sorbitan monostearate (melting point 49.0-55.0) was used.
Using a refractive index of 1.486) at 30 ° C. and 30 ° C., powdery antifog-containing spherical porous silica was obtained. In the same manner as in Example 1, polyvinyl chloride was mixed to form a film, and the haze and antifogging effect were measured. The results are shown in Table 1.

Comparative Example 1 Sorbitan monooleate (melting point: 0 ° C. or less, refractive index at 30 ° C .: 1.470) was used in place of the sorbitan monopalmitate of Example 1, and powdery antifogging agent-containing spherical particles were used. A porous silica was obtained. In the same manner as in Example 1, polyvinyl chloride was mixed to form a film, and the haze and antifogging effect were measured. The results are shown in Table 1.

Comparative Example 2 Instead of the spherical porous silica of Example 1, an average particle size of 2.
Amorphous porous silica of 5 μm was used to obtain powdery porous silica impregnated with sorbitan monopalmitate.
In the same manner as in Example 1, polyvinyl chloride was mixed to form a film, and the haze and antifogging effect were measured. The results are shown in Table 1.

Comparative Example 3 Sorbitan monopalmitate was kneaded into polyvinyl chloride at a ratio of 0.9 PHR and similarly formed into a film.
Table 1 shows the results of measuring the antifogging effect in the same manner as in Example 1.

Comparative Example 4 With respect to a polyvinyl chloride film in which an antifogging agent was not kneaded, the antifogging effect was measured in the same manner as in Example 1 and the results are shown in Table 1.

[0027]

[Table 1]

From this example, the film in which the anti-fog agent-containing spherical porous silica of the present invention is kneaded has high transparency, a high anti-fog effect, and excellent durability. I understand.

[0029]

The polymer film in which the spherical porous silica containing the antifogging agent of the present invention is kneaded has high transparency and excellent antifogging effect durability. Further, when an antifogging agent having an antistatic effect is selected, a film having high transparency and excellent durability of both the antifogging effect and the antistatic effect can be obtained.

Further, the film in which the spherical porous silica is kneaded has anti-blocking property and the handling property is significantly improved. Furthermore, the use of spherical porous silica also has the effect of reducing the kneading load during film formation.

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Claims (5)

[Claims] 1. An antifogging agent having a refractive index at 30 ° C. of 1.48 or more in a weight ratio of 0.1 or more with respect to spherical porous silica and having an average particle diameter of 1 to 20 μm. Spherical porous silica containing a clouding agent. 2. An antifogging agent is selected from a sorbitan ester-based surfactant, a sorbitan ester ether-based surfactant, a glycerin ester-based surfactant, a polyoxyethylene ether-based surfactant, and a polyoxyethylene ester-based surfactant. The spherical porous silica containing an antifogging agent according to claim 1, which is one or more selected from the group consisting of: 3. The spherical porous silica containing an antifogging agent according to claim 1 or 2, wherein the antifogging agent is solid at 30 ° C. 4. An antifog polymer film comprising a polymer composition containing 1 to 50% by weight of the antifog agent-containing spherical porous silica according to any one of claims 1 to 3. 5. The anti-fogging polymer film according to claim 4, wherein the polymer is one or more selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, polystyrene, polycarbonate and polyester.