JP2564520B2 - Contact lens manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a contact lens made of chitin and a method for producing the same, more specifically, it is made of chitin having excellent biocompatibility and has high strength even when wet. The present invention relates to a method of manufacturing a contact lens that maintains the above properties and has excellent optical characteristics.

(Prior Art) Known methods of manufacturing soft type contact lenses include cutting and polishing, pressing, and centrifugal casting.

However, contact lenses made of chitin have not been put into practical use because high-quality molded xin as a lens matrix has not been obtained so far. The chitin molded body as a lens base material may have a film shape, a cylindrical shape, or the like, but there is no information on the cylindrical chitin molded body so far.

As a method for producing a chitin film, for example, Japanese Patent Publication No. 55-35
Japanese Patent No. 412 describes that a water-soluble organic solvent is used for forming and coagulating chitin dissolved in a mixed solvent of trichloroacetic acid and a halogenated hydrocarbon. In the publication, as a reference example, it is described that the film of the chitin solution was blanched by directly immersing it in water without treating it with an organic solvent, and that the film was blanched when the solvent composition of the chitin solution was changed. .

On the other hand, in Examples 6, 8, 9 and 10 of the publication, there is a qualitative description such as "pale white transparent film" or "colorless transparent film". Similarly, in Example 4, the film thickness is 10 It is stated that it changes up to -30 μm.

Further, Japanese Patent Publication No. 57-14204 discloses that the film obtained by the above method is further subjected to alkali treatment. Although there is no description regarding the transparency of the obtained chitin film, the film thickness was 14 μm and 16 μm in Examples 2 and 4, respectively, and the wet thickness was 38 μm in Example 3. Is listed.

In all of the above-mentioned methods for producing a chitin film, a chitin solution is cast on a glass plate and then immersed in a coagulation bath. In the process of coagulation, the film is separated from the glass plate and coagulated. How to finish.

A contact lens made of chitin is disclosed in JP-A-56-9432.
It has been proposed in Japanese Patent Publication No. 2) that chitin, chitosan and derivatives thereof are made into a solution and placed in a mold such as glass or metal to remove the solvent to form a contact lens. In Example 1 of the same publication, it is described that a lens is prepared by cross-linking an acetic acid aqueous solution of chitosan with glutaraldehyde and coagulating in a lens mold. However, the obtained lens is only described as being “optically transparent”, and the manufacturing method is essentially different from the method of performing wet molding using a coagulating liquid. .

(Problems to be Solved by the Invention) Among the various properties of the chitin film, the items examined so far are mechanical strength and elongation, water permeability, pore size, etc., which are important as materials for contact lenses. The optical properties have not been examined in detail. Most of the film thickness is 10 to 40 μm, and at least as a material for cutting and polishing to obtain a contact lens.
Despite the need for a thickness of around 100 μm, no such film has been developed. That is, it can be said that there was no technical idea of manufacturing a contact lens by cutting and polishing the chitin film.

Further, the contact lens obtained by the method described in JP-A-56-94322 has extremely low mechanical strength,
Further, it has a big drawback that it has low transmittance of visible light.

It is an object of the present invention to provide a contact lens made of chitin, which has excellent mechanical strength and also has excellent visible light transmittance, and a method for producing the same.

(Means for Solving Problems) The inventors of the present invention have conducted extensive studies to achieve the above-mentioned objects, and as a result, obtained by performing a wet process of chitin dope by a specific method from solidification to drying. The inventors have found that the above object can be achieved by cutting and polishing the formed body, and have reached the present invention.

That is, according to the present invention, when a chitin dope obtained by dissolving water-insoluble chitin in a solvent is wet-molded to manufacture a contact lens, the chitin dope is applied to the outer peripheral portion of the solid matter and immersed in a coagulation bath to coagulate. After that, the obtained solidified product is dried while being held on the outer peripheral portion of the solid product to obtain a molded product, and then the resulting molded product is cut and polished. It is what

The water-insoluble chitin in the present invention means poly (N-acetyl-D-glycosamine) obtained by treating the exoskeleton of cereals, insects, etc. with hydrochloric acid and caustic soda to remove proteins and calcium. , Or those derivatives that do not dissolve in water. Examples of such chitin derivatives include those obtained by deacetylating a part of acetylamine groups of chitin, etherified products,
Examples thereof include esterified products, hydroxyethylated products, O-ethylated products, and specific examples include poly [N-acetyl-6-O].
-(2-hydroxyethyl) -D-glycosamine], poly [N-acetyl-6-O- (ethyl) -D-glucosamine] and the like.

In order to obtain the contact lens of the present invention, chitin is first dissolved into chitin dope, and the solidification and drying of the chitin dope are performed under a fixed length to obtain a molded body.

As mentioned above, the chitin dope is a chitin solution in which chitin is dissolved in a solvent, and preferred solvents for obtaining the chitin dope include, for example, a mixture of trichloroacetic acid and a halogenated hydrocarbon, lithium chloride and dimethylacetamide. Mixture, or lithium chloride and N
-Methylpyrrolidone and the like.

The preferred concentration of chitin in the chitin dope varies depending on the degree of polymerization of chitin used, but is generally in the range of 0.05 to 50, more preferably 0.1 to 25, optimally 0.3 to 10 W / W%.

In order to carry out the process from coagulation of chitin dope to drying under a fixed length, for example, the following method can be adopted. First, chitin dope may be continuously and continuously applied to the outer peripheral portion of the solid matter, immersed in a coagulation bath, and after solidification, dried in that state. In this case, the coagulated material shrinks as the coagulation proceeds, and as a result, the coagulated material is not separated from the outer periphery of the solid, but remains on the surface, that is, from solidification to drying under a fixed length. Is performed. In this way, performing coagulation and drying under a fixed length means that when the coagulated product is obtained from the chitin dope, the coagulated product retains the shape of the chitin dope when applied, and is further obtained by coagulating the chitin dope. When the solidified product is dried to obtain a molded product, it is to obtain a molded product that maintains the shape of the solidified product.

To obtain a solidified product that retains the shape of chitin dope,
For example, the chitin dope may be applied to the outer peripheral portion of the solid material and immersed in the coagulation bath.

In order to obtain a molded product that maintains the shape of the solidified product, for example, the solidified product may be dried while being held on the outer peripheral portion of the solid product.

In this way, when solidification and drying are carried out while being supported by the solid matter, there is no dimensional change and solidification and drying can be carried out under a fixed length.

When the solidified product is peeled off from the outer periphery of the solid product and dried, the obtained molded product shrinks considerably, and therefore the process is not performed under a fixed length. The contact lens obtained by this method is inferior in contact with visible light when wet, and thus is not preferable as a contact lens. Even when the chitin dope was solidified by a solvent evaporation method such as vacuum drying, the molded body obtained after drying contracted considerably from the shape of the chitin dope, so that it was not a treatment under a fixed length and was obtained. The visible light transmittance when the contact lens is wet is also inferior,
It is not preferable as a contact lens.

As the solid material, any shape such as spherical, rod-shaped, columnar, or polygonal column can be used, and the material is metal,
Any solid material made of inorganic or organic material such as glass, plastic, and wood may be used. Further, the surface of the solid material may be smooth, but it is advantageous to have unevenness in consideration of the cutting and polishing process.

To apply the chitin dope to the outer peripheral portion of such a solid material, the viscosity of the chitin dope itself may be utilized. For example, when the solid material is a cylindrical shape, the cylindrical shape is used in a larger-mouthed tubular material. Then, chitin dope may be put in the gap between the outside of the cylinder and the inner wall of the tube. The thickness of the chitin dope applied to the outer peripheral portion varies depending on the concentration of the chitin dope and the thickness of the contact lens material to be obtained.
1 ~ 50mm, more preferably 1 ~ 30mm, optimally 2 ~ 20mm
Range.

The chitin dope applied as described above is brought into contact with a coagulating liquid to coagulate, and examples of the coagulating liquid to be used include alcohols such as methanol and ethanol, ketones such as acetone, dimethyl sulfoxide or water, and the like. These may be used alone or as a mixed solution of two or more kinds. The temperature of the coagulation bath is preferably in the range of 0 to 60 ° C. The bath ratio is preferably 5 times or more the capacity of the chitin dope. By contacting the chitin dope with the coagulating liquid in this manner, a coagulated product attached to the outer peripheral portion of the solid product can be obtained.

The solidified matter may be washed by an organic solvent treatment or hot water treatment, if necessary.

Drying may be performed while the solidified matter is attached to the outer periphery of the solid matter. Thus, a chitin molded body suitable as a contact lens material is obtained. As a drying method,
Natural drying, hot air drying, vacuum drying, etc. can be adopted. The drying temperature is preferably in the range of 0 to 120 ° C.

In the present invention, the obtained chitin molded body has a thickness of
It is preferably 0.1 to 5 mm, particularly 0.2 to 4 mm, more preferably 0.3 to 3 mm. The thickness can be adjusted by appropriately selecting the dope concentration, the dope coating amount, the coagulation condition or the drying condition.

In the present invention, next, the chitin molded body obtained as described above is cut and polished to prepare a contact lens. To carry out cutting and polishing, conventionally known methods and devices may be appropriately selected and employed.

By the above method of the present invention, 50 g / mm ² or more, preferably
A contact lens having a wet strength of 200 g / mm ² or more, more preferably 500 g / mm ² or more, and a visible light transmittance when wet of 50% or more, preferably 60% or more, more preferably 70% or more is obtained. .

The wet strength referred to in the present invention means that a sample is immersed in ion-exchanged water at 25 ° C. for 1 hour and then taken out from the ion-exchanged water.
The breaking strength was measured using a tensile tester, and the strength obtained was measured with a cross-sectional area calculated from the thickness and width of the strength-preliminary sample that had been conditioned at 25 ° C and 60% RH for 5 hours or more. It is the value obtained by dividing.

In addition, the visible light transmittance when wet means that the sample is immersed in ion-exchanged water at 25 ° C for 1 hour, then taken out from the ion-exchanged water, and the sample is placed on the sample side of the cube holder using a double-beam spectrophotometer. It means the transmittance of visible light (400 to 800 nm) measured by fixing it with an adhesive tape.

EXAMPLES Next, the present invention will be described more specifically with reference to examples.

Example 1 6 g of chitin powder (manufactured by Shin Nippon Chemical Co., Ltd.) was dissolved in 94 g of dimethylacetamide containing 8 W / W% lithium chloride at room temperature,
A chitin dope was obtained. This chitin dope was applied to the outer surface of a glass tube having a diameter of 10 cm to a thickness of about 10 mm, and then immersed in dimethyl sulfoxide to solidify. It was washed for about 48 hours while exchanging the solvent, further washed for about 24 hours with methanol, left at room temperature for 24 hours, and then vacuum dried for about 10 hours.
The contact lens material obtained by peeling from the glass tube is
The average film thickness is 3.2 mm, and the wet strength and the visible light transmittance when wet are 3060 g / mm ² and 65.4 (400 nm) to 96.8, respectively.
(800 nm)%.

This lens material was cut and polished in consideration of the swelling ratio (75%) when it contains water to obtain a lens.

The lenses obtained had wet strength and visible light transmittance of 2700 g / mm ² and 85.5 (400 nm) to 99.6 (80 nm), respectively.
0 nm)%, which was suitable for use as a contact lens.

Example 2 8 g of chitin powder (manufactured by Shin Nippon Chemical Co., Ltd.) was dissolved in 92 g of N-methylpyrrolidone containing 8 W / W% lithium chloride at room temperature,
A chitin dope was obtained. This chitin dope was applied to the outer surface of a glass tube with a diameter of about 10 cm to a thickness of about 10 mm, and immersed in methanol to solidify. After washing for about 48 hours while exchanging the solvent, it was immersed in ion-exchanged water and treated at 120 ° C for 1 hour. After being left overnight at room temperature, it was vacuum dried for about 6 hours. The contact lens material obtained by peeling from the glass tube had an average film thickness of 3.8 mm, and the wet strength and the visible light transmittance when wet were 2660 g / mm ² and 62.1 (400 n
m) -89.7 (800 nm)%.

The lens material was cut and polished in consideration of the swelling ratio (72%) when containing water to obtain a lens.

The lenses obtained had wet strength and visible light transmittance of 2140 g / mm ² and 78.5 (400 nm) to 99.7 (80 nm), respectively.
0 nm)%, which was suitable for use as a contact lens.

Comparative Example 1 Of the solidifying and drying steps in manufacturing the lens material, only the solidifying step was performed under a fixed length, and the material of the obtained lens material was evaluated.

The same chitin dope as used in Example 2 was used,
Example 2 was applied to the outer surface of a 10 cm glass tube to a thickness of about 8 mm.
It was immersed in methanol and solidified in the same manner as in. It was washed for about 24 hours while exchanging the solvent, then peeled from the glass tube, then immersed in ion-exchanged water and treated at 120 ° C for 1 hour. Then, it was left at room temperature for one day and then evacuated for about 6 hours. The contact lens material thus obtained is
When dried, it shrinks to about 60% (area ratio) and the average thickness is 4.
It was 5 mm. The wet strength of this lens material was 2170 g / mm ² , but the visible light transmittance when wet was 45.3 (400 nm) to 62.6.
(800 nm)% was inferior.

A lens made of this lens material is not preferable as a contact lens because it has a poor light transmittance when wet on the short wavelength side.

From the above experimental results, it is understood that in order to obtain the contact lens of the present invention, it is necessary to consistently perform the steps of coagulation of chitin dope and drying under a fixed length.

Comparative Example 2 As a solidification method for chitin dope, a solvent evaporation method was adopted.
The properties of the obtained lens material were evaluated.

The same chitin dope as used in Example 2 was used,
Apply to the outer circumference of a 10 cm glass tube to a thickness of about 2 mm, about 80 ° C
After vacuum drying for 24 hours, the solvent was evaporated. The film peeled from the glass tube had an average film thickness of 0.4 mm and a wet strength of 5
Visible light transmittance at wet of 70g / mm ² is 36.8 (400nm) ~ 8
It was 7.7 (800 nm)%.

The lens made from this film is not preferable as a contact lens because it has a poor light transmittance when wet on the short wavelength side.

Comparative Example 3 Chitosan (manufactured by Shin Nippon Kagaku Co., Ltd.) was washed with water, ethanol, and then ether, and then dried. 0.2g of this chitosan
It was added to 20 ml of a 1.5% acetic acid aqueous solution and stirred at room temperature for about 5 hours to obtain a transparent chitosan solution.

Daltaraldehyde was added to the obtained chitosan solution so that the final concentration was 0.1% by weight, mixed well, put in a lower glass mold made of glass, and degassed under reduced pressure for about 24 hours. Then, the convex portion of the upper lens mold was pressed against the lower lens mold, and the temperature was kept at 70 ° C. for 10 hours. The yellow, transparent, jelly-like chitosan lens thus obtained was immersed in a dilute aqueous sodium hydroxide solution (pH 8) for about 8 hours, then transferred to physiological saline and washed for 24 hours while exchanging the physiological saline. did.

The chitosan lens thus obtained was a jelly-like soft one, and the wet strength could not be measured.

(Effect of the Invention) The contact lens obtained by the method of the present invention has excellent wet strength and visible light transmittance when wet, and has a wet strength of at least 50 g / mm ^{2 and} a wet light of at least 50%. It has a visible light transmittance of. Moreover, the contact lens of the present invention is a contact lens made of a natural material, particularly chitin having excellent biocompatibility,
Since it has a high water content of 50% or more, it is an epoch-making contact lens that has good oxygen and ion permeability and water leakage, and has the advantage of being resistant to boiling sterilization.

 ─────────────────────────────────────────────────── ─── Continued Front Page (56) References JP-A-56-94322 (JP, A) US Patent 4532267 (US, A) US Patent 4365050 (US, A)

Claims (1)

(57) [Claims] 1. When manufacturing a contact lens by wet-molding a chitin dope obtained by dissolving water-insoluble chitin in a solvent, the chitin dope is applied to the outer peripheral portion of the solid material,
After being immersed in a coagulation bath for solidification, the solidified product obtained is dried while being held on the outer periphery of the solid product to obtain a shaped product, and then the obtained shaped product is cut and polished. Contact lens manufacturing method.