JPS6254733A - Production of antifogging transparent article - Google Patents

Abstract

PURPOSE:To obtain a transparent article having good transparency and other properties and an excellent antifogging effect, by saponifying the surface of a transparent article with a strongly alkaline solution of sodium silicate and coating this surface with a surfactant. CONSTITUTION:A molding, sheet, film or the like of a transparent plastic such as cellulose acetate, propionate or butyrate is saponified by immersion in a strongly alkaline solution of sodium silicate. By this treatment, the interfacial tension to water is decreased through the formation of hydrophilic functional groups on the surface, so that coagulation of water drops on it can be prevented and at the same time the retention of a surfactant applied later can be improved. An immersion temperature in a range of 30-75 deg.C is the most suitable to perform effective treatment within a short time and not to damage the base material. An immersion time of 30-120min is desirable. The surface of the transparent plastic article saponified in this way is coated with a surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an anti-fog transparent plastic body (molded product, sheet or film).

Recently, transparent plastics have been used for goggles, eyeglass lenses, mirror surfaces, windshields, underwater glasses, etc. However, in high temperature, high humidity environments or at boundaries with large temperature differences, plastics can fog up on their surfaces and significantly reduce their transparency. It had a fatal flaw:

In order to improve this point, conventional methods have been to apply surfactants or hydrophilic polymers to the plastic surface, but the anti-fog effect is insufficient or its durability is poor. There were drawbacks.

In order to develop a transparent body with good transparency and other physical properties and an excellent antifogging effect, the inventors of the present invention have conducted intensive research, and as a result, they have developed a transparent material that has good transparency and other physical properties, and as a result, has been treated with a strong alkali using silicon visoda, and the interface It has been unexpectedly discovered that when an activator is applied, excellent antifogging properties are imparted to the material without damaging its properties. The present invention has been made based on this knowledge.

In the first step of the present invention, molded products, sheets, and films of cellulose acetate, propionate, and butyrate are saponified by immersing them in a strong alkaline solution of sodium silicate. This treatment produces hydrophilic functional groups on the surface, lowering the interfacial tension with respect to water, preventing agglomeration of water droplets, and improving the retention of the surfactant applied later.

The immersion temperature can range from 15 to 80°C, but in order to perform effective treatment in a short time and not damage the base material, the temperature should be 30 to 80°C.
A range of 75°C is optimal.

Anti-fogging effects can be obtained over a wide range of immersion times, from 2 to 3 minutes to 5 hours or more, but if the immersion time is too short, the anti-fog effect will be insufficient, and even if immersed for more than 2 hours, the effect will be no more. 30 to 120 minutes is desirable since no improvement is observed.

In the second step of the present invention, a surfactant is applied to the surface of the saponified cellulose acetate, propionate, or butyrate. The saponification treatment produces some antifogging effect, but by applying a surfactant, a better and more stable antifogging effect can be obtained.

To apply the surfactant, saponified cellulose acetate, propionate, or butyrate is immersed in a 1-10% aqueous solution of the surfactant at a temperature of 30-50° C. for 5-60 minutes, and then dried.

As the surfactant, any of cationic type, anionic type, and inine type can be used.

A similar effect can be observed even when treated with a solution of a hydrophilic low-molecular-weight pickling substance such as ethylene glycol, diethylene glycol, ethanolamine, jetanolamine, or triethanolamine.

Note that even if a surfactant or the like is applied in a similar manner to cellulose acetate, propionate, or butyrate that has not been saponified, it will peel off immediately and no long-term antifogging effect will be obtained.

Next, the present invention will be explained in more detail with reference to Examples.

(Example) Cellulose acetate, propionate, and butyrate with a thickness of 1.0 mm were added to a 25% aqueous solution of silica soda at 50°C.
11! After washing with water and drying, it was immersed in a 2% aqueous solution of a nonionic surfactant (ZONYL FSNJ DuPont Co., Ltd.) at 50°C for 1 hour, and then air-dried.

(Comparative example) When an anti-fog test was conducted using the data obtained in the above examples using the test equipment shown in the drawing, all control numbers fogged within one second, and the sign board became invisible. On the other hand,
In the example materials, there was no clouding at all, and the markings could be clearly seen.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of the anti-fog test device. 1... Sign board, 2... Glass container, 3... Heat insulating material, 4... 10°C hot water, 5... Sample.

Claims (2)

[Claims] (1) A method for producing an anti-fogging transparent body, which comprises saponifying the surface of a plastic transparent body with a strong alkaline solution of sodium silicate, and further applying a surfactant. (2) The method for producing an antifogging transparent body according to claim 1, wherein the plastic is cellulose acetate or propionate and butyrate.