JPS5943598B2 - Dyeing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dyeing resin bodies such as molded articles, sheets, and coating layers made of water-swellable hydrophilic polymers, ie, hydrogel resins.

Hydrogel resin has a hydroxyl group and a partially cross-linked molecular structure, and is characterized as a resin that is insoluble in water but has excellent hygroscopicity and water-swellability.

There are many types of resins known as hydrogels, and some are newly discovered. Typical examples include hydroxyalkyl methacrylate resins and their derivatives,
or copolymers with other hydrophilic polymers, polyacrylamide resins and their derivatives, graft polymers of polysiloxane with hydrophilic polymers, N-vinylpyrrolidone-methacrylate copolymers, polyion complexes, hydroxyethyl cellulose, Examples include resins made of crosslinked polymers such as substituted products thereof or copolymers with other polymers.

Several applications have been developed that take advantage of these properties by processing these idrogel resin bodies into films, membranes, molded products, etc.

It is natural that these materials need to be dyed or printed with images such as letters and designs depending on their purpose.

However, due to the characteristics of this resin, it is often used in an atmosphere of water or steam, so it is impossible to print with normal oil-based ink, and it cannot be printed or dyed with water-based ink or dyeing liquid. However, because the resin swells with water, the image is not dyed and is eluted.

To give an example of what has been attempted in the past, for example, when a hydrogel resin body is brought into contact with a water-soluble dye solution, it is easily stained and a clear image is obtained, but if it is kept in water for a long time, the dye gradually dissolves. The image disappears.

In addition, if you print on the surface of this resin body with a general ink made by dissolving and dispersing dyes, pigments, binder resin, etc. in an oil-based solvent, you may be able to print clearly temporarily, but if you keep it in water for a long time, the ink will deteriorate. The adhesive strength weakens and the printed image gradually becomes fainter.

As shown in the above examples, it has become clear that when printing and dyeing hydrogel resin bodies, the commonly thought of methods that utilize the adhesive strength of ink or methods that simply dye the resin are inappropriate. Ta.

Considering this point, the present inventors first infiltrated into the resin a water-soluble dye having a strong affinity for the hydroxyalkyl methacrylate resin, which has a particularly high water swelling property, or its leuco form, or its colorless form. , patent application filed in 1973, describes an extremely effective method that theoretically eliminates the drawbacks of conventional dyeing or printing methods, which are characterized by water-insolubilization and coloring treatment to form a dyed image within the resin. The application was filed as No.-74653.

However, although this method is extremely effective when dyeing or printing with a resin that has a relatively high water swelling rate, such as the resin mentioned above, depending on the application, the water swelling rate is not very high. When applied to the dye, the penetration of the dye or its leuco substance or its colorless substance may be insufficient, resulting in thin or uneven dye density or image density.
In addition, if left in contact with water for a long time, the color gradually became thinner, and good dyeing or printing could not be achieved.

The present invention is an improvement on this, in which the hydrogel resin is immersed in advance in a solvent that is more swellable than water and has good compatibility with water, and the surface or the whole of the resin body is sufficiently swollen. After that, if the desired part of the resin body is dipped or printed with a water-soluble dye that has a strong affinity for the resin, or a dye solution or ink containing the leuco body or its colorless body, the desired part of the resin body will be immersed or printed. The dye or its leuco form or its colorless form will penetrate easily.

This takes advantage of the effective effect of highly swelling solvents, which further expand the structure of the resin and make it easier for dye molecules to enter.

Here, the solvent having a higher swelling property than water is selected from solvents having extremely high compatibility with water, and lower alcohols, lower ketones, lower glycols, lower glycol esters, etc. are generally effective.

When comparing the swelling ratio with poly-2-hydroxyethyl methacrylate homopolymer (crosslinked) as -flJ,
16% water, 38% methanol, 31% ethanol
, 46% ethyl cellosolve, and 23% acetone, all of which are found to be effective solvents for this purpose.

There is a close relationship between the swelling rate of a hydrogel resin and the radius of molecules that can pass through the crosslinked structure of the resin.

Por molecules can pass through the resin swollen by water.
e radius is, for example, 2-hydroxyethyl methacrylate-1
・4.0 people for resin, 6.0 people for polyacrylamide resin. oA
However, considering that the molecular radius of the dye used in the present invention, its leuco form, or its colorless form varies depending on the molecule, it is at least 7 to 8 Å, so it is difficult to imagine whether these molecules can easily pass through. This means that we are at the limit of what we can do.

Therefore, it is necessary to further increase the pore radius of the resin.

Therefore, as shown in the above data, if the dye is further swollen with a solvent that has a higher swelling rate than water, the passage of dye molecules becomes easier.

After sufficiently permeating the dye, its leuco form, or its colorless form into the resin in this way, water insolubilization and coloring treatment are performed to allow the dye to penetrate into the resin and to form a polymer network of the resin. It is tightly entangled within the structure and can form extremely fast dyed images within the resin.

Comparing the dyeing properties when swelling with water alone and when swelling with the same solvent or a mixed solvent with water, in the former case,
Even with hydrogel resin bodies that can only be dyed, the staining density or image density may be thin or uneven, or if left in contact with water for a long time, it will gradually become thinner.
In the latter case, it was found that a highly concentrated and clear dyed image could be easily obtained, and that this image had a strong fastness, that is, it was extremely resistant to long-term contact with water, especially boiling in hot water. did.

Next, water insolubilization and color development treatments will be explained.

A specific example thereof is a method using a soluble vat dye.

As is well known, soluble vat dye reduces vat dye,
It is a water-soluble compound in the form of a sulfonate, and as it is, it is a colorless leuco compound.

A dye solution or ink containing the dye in this state is brought into contact with the resin body which has been sufficiently swollen by the above method.

Thereafter, when the resin is immersed in an aqueous solution of an oxidizing agent, the dye becomes insoluble in water through an oxidation reaction, develops color, and becomes fixed within the resin, forming an extremely stable image.

All commercially available soluble vat dyes can be used as the soluble vat dye.

In addition to this dye, stabilizers and additives for improving printability are added as necessary to form a dyeing liquid or ink.

As a stabilizer, a small amount of peroxidant is added when using a dye sensitive to air oxidation, or a small amount of soda ash is added to make the solution alkaline.

Additives that improve printability include defoaming agents that prevent foaming during stirring, and glycerin and/or glycols that suppress dryness and viscosity.

As the oxidizing agent, an aqueous solution of sulfuric acid or nitrous acid is usually used.

In addition, some soluble vat dyes include dyes that cause photooxidation reactions.

When using this type of dye, instead of treating it with an oxidizing agent aqueous solution, the resin body impregnated with the dye is exposed to light absorbed by the dye, so that the water insolubilization and coloring reactions of the dye occur within the resin in the same way as above. This occurs and a stable dyed image can be obtained.

Examples of such photosensitive soluble vat dyes include 5olubilised vat yellow.
3.4.7.8, Red 1.2.10, Blue
2.5.8, Black 1.4.6, etc.

As another example, tetrazolium salts can be used.

These salts are water soluble and have a strong affinity for hydrogel resins.

When a dye solution or ink containing these salts is brought into contact with the resin body swollen by the above method, it penetrates into the resin.

In this state, there is no point, but after that, when the resin body is immersed in an aqueous solution containing a reducing agent, the tetrazolium salt undergoes a reduction reaction and a water-insoluble formazan dye is generated in the resin, making it possible to form a stable dyed image.

A variety of tetrazolium salts are commercially available as derivatives, and a representative example is 2.3.5-Tri P.
henyltetrazolium Chlorid
e, Tetrazol RedlTetrazoli
um Violet 1Tetrazolium Pu
rple.

Examples include N1tro Blue Tetrazolium.

In addition, as a water insolubilization treatment for tetrazolium salt → formazan dye, instead of immersing it in an aqueous reducing agent solution, the resin body impregnated with tetrazolium salt is exposed to ultraviolet light to generate formazan dye in the resin, resulting in stable dyeing. A method of forming an image may also be used.

Soft contact lenses have recently attracted attention as an example of the application of hydroxyalkyl methacrylate resin-based hydrogels.

This is because when this resin is swollen in water, it is soft and hydrophilic, so it is ideal as a contact lens material because it does not cause any discomfort when worn in the eye.

Since the curvature and lens power of this contact lens differ depending on the user, a code and a number must be displayed near the periphery of the lens to distinguish them.

This displayed print must never disappear, not only while wearing this lens, but also during several times of boiling sterilization in boiling water. also need to endure.

Furthermore, the printed area must not have any protrusions caused by ink binder, etc., so that there will be no discomfort due to eye disease while wearing.

To print under such special conditions, measure the curvature, lens power, etc. after molding the lens, print the results, and store it in water, or leave it in a state where it is sufficiently swollen in water after molding. Whether the curvature, lens power, etc. is measured, printed, and stored underwater varies by manufacturer depending on the measurement method and management method, but in any case, it is printed or dyed to withstand extremely harsh boiling sterilization conditions. As in the present invention, the resin body is pre-immersed in a highly swelling solvent and then dyed with the dye solution or printed with the ink to allow the dye to sufficiently penetrate into the resin, followed by water-insolubilization dyeing. This method became practical for the first time.

This will be explained in more detail in Examples below.

Example 1 A transparent film made of a crosslinked resin made of polymethyl methacrylate-N vinyl pyrrolidone was immersed in methanol for about 20 minutes, taken out, and then impregnated with a 20% aqueous solution of 2,3,5-triphenyltetrazolium chloride. Printed on a porous rubber plate with 2 W mercury lamps 15crr1
．． Exposure for about 30 seconds from a distance of 30 seconds yielded a clear, red, water-insoluble penetrant image.

This had excellent abrasion resistance and water resistance.

By the way, when it was swollen with water only, only a very thin dyeing was possible.

Example 2 A crosslinked polymer resin molded product made of 2-hydroxyethyl methacrylate-methyl methacrylate was immersed in an ethyl cellosolve bath for about 2 minutes to swell the surface of the molded product.

This was then added to the soluble vat dye Anthrazole 04G (
65°Be' sulfuric acid and sodium nitrite (65°Be'
When the molded product was immersed in an aqueous solution (coloring solution) with a concentration of about 0, sf/l for 5 minutes, the surface of the molded product could be uniformly dyed blue.

Thereafter, it was washed with water to remove unreacted dye.

In order to investigate this dyeing property, the material was continuously boiled in boiling water for several tens of hours (fastness test), but there was almost no fading.

In addition, when dyeing was carried out in the same manner using other soluble vat dyes, similar results were obtained.

Example 3 5 for the resin molded product pre-pickled in Example 2! When an image was projected from a mercury lamp through a transparent original, a clear blue image was formed.

Thereafter, this was sufficiently boiled in hot water to dissolve the dye in the non-image area.

The dyed image thus formed satisfactorily withstood the same fastness test as in Example 2.

Example 4 A soft contact lens processed from a crosslinked resin consisting only of 2-hydroxyethyl methacrylate is immersed in an ethanol bath for about 15 minutes to swell.

This lens was taken out, and letters were stamped on the predetermined positions around its periphery with a rubber stamp made of porous rubber impregnated with an ink consisting of 15 parts of soluble vat dye Anthrazol Pink 13B (manufactured by Hoechst), 10 parts of glycerin, and 75 parts of water. was printed.

Use this lens under a black light (light intensity 2 mW/crrt
) When exposed to ultraviolet light for about 1 minute, clear red characters developed.

This lens sufficiently withstood a continuous boiling test in boiling water for more than 100 hours.

Although similar dye printing is possible without ethanol dipping, the boiling resistance is considerably inferior.

In addition, in soft contact lenses made of 2-hydroxyethyl methacrylate N-vinylpyrrolidone copolymer, the resin itself has an extremely high water swelling rate, so immersion in ethanol does not have much of an effect. On the contrary, a large difference was observed in soft contact lenses made of acrylate-methyl methacrylate copolymer.

In other words, even if printed without ethanol dipping, there is little penetration of the dye into the resin, so when washed with water after color development, the print becomes faint, but with ethanol dipping, the print becomes clear and has strong boiling resistance. I was able to print something like this.

Example 5 Instead of exposing to ultraviolet light in Example 4, it was immersed in the coloring bath described in Example 2 for about 15 minutes to develop color.
The same good results were obtained.

Example 6 Instead of printing in Example 4, the letters were immersed in the ink bath for about 2 minutes, and then in Step 5, letters were projected and exposed onto the lens surface through a negative transparent original using a W mercury lamp, and the letters began to develop color.

The penetrating liquid in the unexposed area was eluted by boiling the lens.

The boiling resistance of the dyed letters thus formed was as good as in Example 4.

Claims (1)

[Claims] 1. A hydrogel resin body is immersed in advance in a solvent that has a higher swelling rate than water and is compatible with water, or a mixed solvent with water, and the resin surface or, if necessary, the entire body is sufficiently swollen. After that, a desired part of the surface of the resin body is dipped or printed with a staining liquid or ink containing a water-soluble dye, its leuco form, or its colorless form, and the dye, its leuco form, or its colorless form is immersed or printed. A dyeing method in which a dyed image is formed in the resin by infiltrating the body and then performing water insolubilization and coloring treatment. 2. Claim 1, characterized in that after a soluble vat dye leuco substance is infiltrated into a desired part of the resin body as a dyeing liquid or ink, the resin body is immersed in an oxidizing agent aqueous solution. Dyeing method. 3. Claim 1 is characterized in that the resin body is exposed to light after a photosensitive soluble vat dye leuco substance is infiltrated into a desired part of the resin body as a dyeing liquid or ink. Dyeing method. 4. The dyeing method according to claim 1, which comprises impregnating a desired portion of the resin body with a tetrazolium salt as a dye solution or ink, and then immersing the resin body in an aqueous reducing agent solution. . 5. The dyeing method according to claim 1, which comprises infiltrating a desired portion of the resin body with a photosensitive tetrazolium salt as a dye solution or ink, and then exposing the resin body to light. 6 Claims 1, 2, 3, 4,
5. The dyeing method according to item 5, which comprises infiltrating a soft contact lens made of hydroxyethyl methacrylate or a resin containing hydroxyethyl methacrylate as a main monomer component into a desired position.