JPH0762120A - Surface treatment of transparent plastic article - Google Patents

Abstract

PURPOSE:To obtain a transparent plastic article improved in antifogging properties or adhesiveness without detriment to gloss, transparency, smoothness, optical properties and toughness by relatively short-time hydrolysis. CONSTITUTION:The treatment process comprises applying an aqueous alkaline alcohol solution to the surface of a transparent plastic article made of cellulose acetate or cellulose propionate to hydrolyze the surface part of the article, and applying an aqueous acidic solution at once to the surface to neutralize the above aqueous alkaline alcohol solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for transparent plastic products made of cellulose acetate or cellulose propionate. More specifically, it relates to a surface treatment method suitable for imparting antifogging property or adhesiveness to transparent plastic products.

[0002]

2. Description of the Related Art This type of plastic product is glossy and has excellent transparency and processability. Transparent plastic products made of cellulose acetate are used as protective films and sheets for polarizing films, or underwater glasses and goggles.
These products are usually subjected to saponification treatment, the protective film or sheet is provided with adhesiveness and adhesion, and the underwater glasses and goggles are provided with antifogging property. However, since cellulose acetate is not sufficient in terms of toughness and heat resistance, transparent plastic products made of cellulose propionate have come to be used for molded articles such as underwater glasses and goggles.

Conventionally, as a method for imparting antifogging property to this type of plastic product, the surface of the transparent plastic product is saponified with a strong alkaline solution of sodium silicate, and then a surfactant is applied to the antifogging transparent body. Has been proposed (Japanese Patent Laid-Open No. 62-54733). In order to obtain a long-lasting antifogging property by this saponification treatment method, for example, a transparent plastic product is immersed in a strong alkaline solution of a 25% aqueous solution of sodium silicate at 50 ° C. for 2 hours, then washed with water and dried to obtain a surface active agent. Soak in 2% aqueous solution of agent for 60 minutes at 50 ℃,
It's air-dried.

[0004]

However, although the transparent plastic product obtained by the above method is provided with antifogging property, it has a characteristic glossiness, transparency or smoothness due to its long-term treatment. There has been a problem that the optical characteristics are impaired by generation of stripes or star dust. Further, the toughness as the physical strength is liable to decrease, and the reliability of the user is lacking for products such as underwater glasses and goggles. Further, since the product is dipped in the treatment, the treatment is performed on the portion which does not require the treatment, resulting in a further decrease in strength.

The object of the present invention is to perform saponification treatment in a relatively short time without impairing glossiness, transparency, smoothness, optical characteristics or toughness, and to provide a transparent material having good antifogging property or adhesiveness. It is to provide a surface treatment method for plastic products.

[0006]

In order to achieve the above-mentioned object, the surface treatment method for a transparent plastic product of the present invention comprises applying an aqueous alkaline alcohol solution to the surface of a transparent plastic product comprising cellulose acetate or cellulose propionate. In this method, the surface portion of the product is saponified, and then an acidic aqueous solution is immediately applied to the surface portion of the product to neutralize the alkaline alcohol solution.

The present invention will be described in detail below. The transparent plastic product of the present invention comprises cellulose acetate or cellulose propionate. The form of the product is not limited to a film or a sheet, and includes plastic molded products such as hydroscopic glasses and goggles. The alkaline alcohol aqueous solution is preferably prepared by mixing a 1-10 normal alkaline aqueous solution with a water-soluble alcohol, preferably 10-40% by volume. Examples of the alkaline aqueous solution include an aqueous solution of sodium hydroxide or potassium hydroxide. This aqueous solution may be either an aqueous solution of sodium hydroxide or potassium hydroxide, or an aqueous solution in which these are mixed. When the concentration of the alkaline aqueous solution is less than 1 N, the saponification reaction rate becomes slow and the processing time becomes long, which is not preferable. Also, if the number exceeds 10 regulations,
The saponification reaction proceeds too rapidly, the surface of the plastic product is whitened, or alkali cracks occur, which is not preferable.

Examples of the water-soluble alcohol include methyl alcohol, ethyl alcohol, isopropyl alcohol, diacetone alcohol and acetylene alcohol. These alcohols may be used alone or in combination of two or more. If this alcohol is less than 10% by volume, the surface of the plastic product is not sufficiently swollen or wet, and the saponification rate becomes slow, which is not preferable. On the other hand, if it exceeds 40% by volume, cracks and whitening phenomena due to the solvent tend to occur, which is not preferable.

To the saponification treatment liquid of the present invention, in order to make the saponification treatment proceed smoothly, 1 to 10% by volume of a surfactant may be added and mixed in addition to the alkaline alcohol aqueous solution.
The surfactant preferably has a structure having nonionic and aionic groups. Surfactants of this type act effectively because they are not hydrolyzed by acids or alkalis.

Depending on the concentration of the alkaline aqueous solution, the amount of alcohol mixed, etc., the saponification treatment time is about 5 seconds to 10 minutes.
The saponification temperature is preferably 20 to 60 ° C.
If the saponification time is less than 5 seconds, the surface of the plastic product will not swell or wet sufficiently, and the saponification reaction will not proceed rapidly. If it exceeds 10 minutes, the glossiness, transparency or smoothness of the plastic product will be impaired, or stripes or star dust will be generated, and the optical properties will be impaired. When the saponification treatment temperature is lower than 20 ° C, the saponification reaction is slow, which is not preferable. 60 ° C
When it exceeds the above range, the evaporation of alcohol is so intense that it is difficult to obtain a plastic product having a smooth and uniform surface, and the plastic product is likely to deteriorate. As the acidic aqueous solution used in the neutralization reaction of the present invention, an aqueous solution of an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid is preferable because it is inexpensive and easily available. This concentration is determined according to the concentration of the alkaline aqueous solution described above.

The method of applying the saponification treatment solution or the acidic aqueous solution of the present invention to the surface of a plastic product is determined according to the form of the plastic product. When the plastic product is a film or sheet, a roller coating method, a flow coating method, a spray coating method, a dip coating method or the like is adopted, and when the plastic product is a concave shaped article such as underwater glasses or goggles, A method of injecting the liquid into the recess and storing it for a predetermined time is adopted. In this case, a dispenser, a metering pump or the like is used as the injection means.

[0012]

When an aqueous alkaline alcohol solution is applied to the surface of a transparent plastic product made of cellulose acetate or cellulose propionate, the alcohol promotes swelling and wetting of the product surface, so that the saponification reaction with the alkaline aqueous solution is carried out in a short time. Since this saponification reaction is rapid, a neutralization reaction is continuously performed using an acidic aqueous solution to stop the saponification reaction. Here, the heat of neutralization is utilized to make the swollen surface a dense, firm and smooth surface.

[0013]

EXAMPLES Next, examples of the present invention will be described together with comparative examples. The example shown below is an example and does not limit the technical scope of the present invention.

<Examples 1 to 18> Eighteen underwater glasses which were injection-molded products of cellulose propionate were prepared. All of these water glasses have a vertical shape of 35 mm,
The lens unit had a width of 45 mm and a thickness of 1.5 mm. 1
The saponification treatment liquid shown in Table 1 was injected into the inner surface of the lens, which is the concave portion of the eight underwater glasses, using a dispenser with a precision of 3.0 ± 0.01 cc, and the temperature and time shown in Table 1 were used. Was processed in. Then, immediately using the same dispenser, a neutralization reaction was performed with an acidic aqueous solution of dilute hydrochloric acid. After the neutralization reaction, the neutralized aqueous solution on the inner surface of the lens was discarded and the underwater glasses were thoroughly washed with water. Then, 18 types of underwater spectacles were obtained, which were dried by a hot air dryer in a temperature range of 40 to 50 ° C. and saponified.

[0015]

[Table 1]

In Table 1, in the column of alcohol, A is methyl alcohol, B is ethyl alcohol, C is isopropyl alcohol, D is diacetone alcohol, and E is acetylene alcohol. Further, the surfactant is a nonionic trade name PRYSURF A-217E (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

<Comparative Examples 1 to 18> Eighteen types of saponified hydrogel were obtained in the same manner as in Examples 1 to 18 except that the neutralization reaction was not performed with an acidic aqueous solution.

<Comparative test> (a) Breath test The hydrous glasses of Examples 1 to 18 and Comparative Examples 1 to 18 were subjected to a temperature of 2
After standing for 1 hour in an atmosphere of 5 ° C and 65% relative humidity,
The inner surface of the lens of each of these underwater glasses was exhaled, and the one that did not cause fogging was designated as "pass".

(B) Water vapor test The water glasses of Examples 1 to 18 and Comparative Examples 1 to 18 were heated to a temperature of 4
The inner surface of the lens was placed at a position 5 cm above a 0 ° C. water bath with the inner surface of the lens facing, and the presence or absence of fogging on the inner surface of the lens was visually observed. Those that did not fog at all for more than 3 minutes were regarded as "pass", and those that partially fogged "quasi pass"
And the thing which produced cloudiness on the whole was made into "fail".

(C) Wettability test The water glasses of Examples 1-18 and Comparative Examples 1-18 were immersed in a container containing tap water at room temperature for 30 minutes, and then taken out.
The repellency of water droplets on the inner surface of the lenses of these underwater glasses was visually observed. Those that did not repel water droplets were considered "pass", those that partially repelled were "semi-pass", and those that totally repelled were "failed".

(D) Haze test at 5 ° C. (JIS S-730
1 method) The water glasses of Examples 1-18 and Comparative Examples 1-18 were heated at a temperature of 5
After leaving it in the refrigerator at ℃ ± 2 ℃ for 30 minutes,
Those that were taken out in an atmosphere of 65 ° C and 65% relative humidity and that did not cause any fog on the inner surface of the lenses of these underwater glasses were designated as "pass", and those that partially fogged were regarded as "quasi pass", and Those with cloudiness were designated as "fail".

(E) Rubbing test The water glasses of Examples 1 to 18 and Comparative Examples 1 to 18 were immersed in a container containing tap water at room temperature for 30 minutes, and then taken out.
The inner surface of the lenses of these underwater glasses was covered with gauze 100
Place a friction piece of g and reciprocate at a speed of 10 times / minute.
Rubbed 00 times. Scratches on the inner surface of the lens, streaks, turbidity,
Microscopic changes in appearance such as whitening and cracks were observed with the naked eye. The one in which no minute change was generated was designated as "pass", the one partially generated was designated as "quasi-pass", and the one entirely generated was designated as "fail". The test results of the above (a) to (e) are shown in Tables 2 and 3.

[0023]

[Table 2]

[0024]

[Table 3]

As is clear from Tables 2 and 3, the hydrogels of Examples 1 to 18 passed all the tests, while Comparative Examples 1 to 18 all passed the breath test. There was no acceptable product in the wettability test, the cloudiness test and the friction test. Only half passed the steam test.

[0026]

As described above, according to the treatment method of the present invention, the alcohol component of the aqueous alkaline alcohol solution applied to the surface of the transparent plastic product promotes swelling and wetting of the surface of the product. The reaction is carried out for a short time. The saponification reaction is stopped by the subsequent neutralization reaction with an acidic aqueous solution, and the swelling surface can be made into a dense, firm and smooth surface by the heat of neutralization.
As a result, the glossiness, transparency, smoothness, optical characteristics, or toughness is not impaired by a relatively short treatment,
A transparent plastic product having good anti-fogging property or adhesiveness can be obtained.

Especially, since the alkaline aqueous solution and the acidic aqueous solution used in the present invention do not become a harmful waste liquid by the neutralization reaction, they do not pollute the environment, cause no pollution problem, and require a minimum amount of washing water, which is economical. is there. Further, since the heat of neutralization can be used, there is an effect that the energy for heating the saponification treatment liquid can be reduced.

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[Procedure amendment]

[Submission date] September 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

To the saponification treatment liquid of the present invention, in order to make the saponification treatment proceed smoothly, 1 to 10% by volume of a surfactant may be added and mixed in addition to the alkaline alcohol aqueous solution.
The surfactant preferably has a structure having nonionic and anionic groups. Surfactants of this type act effectively because they are not hydrolyzed by acids or alkalis.

Claims (8)

[Claims] 1. A transparent plastic product made of cellulose acetate or cellulose propionate is coated with an aqueous solution of an alkaline alcohol to saponify the surface portion of the product, and then an acidic aqueous solution is immediately coated on the surface of the product. A surface treatment method for a transparent plastic product for neutralizing the aqueous alkaline alcohol solution. 2. The alkaline alcohol aqueous solution is 1-10.
Add 10-4 water-soluble alcohol to the specified alkaline aqueous solution.
The surface treatment method for a transparent plastic product according to claim 1, which is prepared by mixing 0% by volume. 3. The surface treatment method for a transparent plastic product according to claim 2, wherein the alkaline aqueous solution is an aqueous solution of either sodium hydroxide or potassium hydroxide or an aqueous solution in which these are mixed. 4. The water-soluble alcohol is methyl alcohol,
The method for surface treatment of a transparent plastic product according to claim 2, wherein any one kind or two or more kinds of ethyl alcohol, isopropyl alcohol, diacetone alcohol and acetylene alcohol is used. 5. The surface treatment method for a transparent plastic product according to claim 1, wherein the saponification treatment time is 5 seconds to 10 minutes. 6. The surface treatment method for a transparent plastic product according to claim 1, wherein the saponification treatment temperature is 20 to 60 ° C. 7. The surface treatment method for a transparent plastic product according to claim 1, wherein the saponification treatment liquid is prepared by adding and mixing 1 to 10% by volume of a surfactant to an aqueous alkaline alcohol solution. 8. The surface treatment method for a transparent plastic product according to claim 1, wherein the acidic aqueous solution is an aqueous solution of an inorganic acid.