JPH0615166A - Slow releasable sheet - Google Patents

Abstract

PURPOSE:To increase a holding capacity of medicines on an adsorbent and to slowly release the medicines stably over a long period. CONSTITUTION:The medicines are deposited on the sheet-like adsorbent consisting of the sintered body of compression molded active carbon. The sheet- like adsorbent is obtd. by molding a mixture composed of the active carbon, such as active carbon fibers, and a sinterable binder in a fibrous or other form under heating and pressurizing, then sintering the molding and is carbonaceous. The density of the sintered body is 0.4 to 1.0g/cm<3> and the thickness about 0.05 to 5mm. The medicines include perfumes, fertilizers, mildewproof agents, repellents, agricultural chemicals, etc. The amt. of the medicines to be deposited is about 0.1 to 90wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sustained release sheet capable of releasing a drug over a long period of time.

[0002]

2. Description of the Related Art Various sustained-release materials have been proposed in order to stably release chemicals such as fragrances over a long period of time. For example, a sustained-release material in which a fragrance is supported on granular activated carbon; a sustained-release material in which an activated carbon on which a fragrance is adsorbed is covered with a synthetic resin film having communication holes; a sustained-release material in which a fragrance is supported on a honeycomb-shaped activated carbon molded body. Wood is proposed.

However, these sustained-release materials have a small holding capacity for perfume and a small amount of the carried perfume.
Moreover, the sustained release amount sharply decreases with the passage of time, and the aromaticity cannot be maintained for a long period of time. Further, handling of the granular sustained-release material is complicated. Furthermore, in order to obtain a honeycomb-shaped activated carbon molded body, for example, 25% or more of an organic binder is required, so that the binder blocks the pores of the activated carbon and reduces the amount of pores effective for retaining the drug. Also,
The properties of the sustained-release material are largely influenced by the properties of the organic binder, but the organic binder used for bonding the activated carbon is usually inferior in mechanical strength, heat resistance and chemical resistance. Therefore, the application of the sustained release material is limited.

Therefore, an object of the present invention is to provide a sustained-release sheet which has a large drug retention capacity and can slowly and stably release a drug over a long period of time.

Another object of the present invention is to provide a sustained release sheet which is excellent in mechanical strength, heat resistance and chemical resistance.

[0006]

As a result of intensive studies, the inventors of the present invention enhance the retention amount of a drug per unit volume by supporting a drug on an adsorbent obtained by compression-molding and firing at least activated carbon. In addition to the above, it was found that the drug can be stably released over a long period of time, and the present invention has been completed.

That is, the present invention provides a sustained-release sheet in which a drug is supported on a sheet-shaped adsorbent made of a sintered compact of compression-molded activated carbon.

The sheet-shaped adsorbent used in the present invention is
Since it is composed of a compression-molded sintered sheet of activated carbon, it has a characteristic that it substantially constitutes a carbonaceous adsorbent and almost no binder exists. Therefore, the content of activated carbon per unit volume is large, and the retention capacity and mechanical strength of the drug are remarkably large. This brings various advantages. That is, (1) since it is a carbonaceous material having high chemical resistance and corrosion resistance, it can also support corrosive agents, etc. (2) Since it has high heat resistance, it can be used even in a high temperature environment. ) It can be used as an underlaying sheet for various places where drug release is required, such as tatami mat, carpet, furniture, refrigerator, etc. It has excellent properties and is easy to handle.

Further, since the sheet-shaped adsorbent is a carbonaceous material having high electrical conductivity and thermal conductivity, it is possible to heat and dissipate the loaded drug by electric heating.

The activated carbon contained in the adsorbent may be in any form such as fiber or powder. In particular, when activated carbon fibers are used, a high-strength sintered body can be obtained with a small amount of binder based on structural characteristics such as entanglement of fibers and high strength in the fiber orientation direction.

The activated carbon fiber usually has a fiber diameter of 2
~ 30 μm, fiber length 0.1 ~ 10 mm, pore diameter 8
It is preferable to use activated carbon having fine pores of about 20 angstroms and a specific surface area of about 500 to 2500 m ² / g. As the granular activated carbon, in terms of adsorption and desorption characteristics,
For example, an average particle size of about 10 to 100 μm and a specific surface area of 50
Activated carbon of 0 m ² / g or more is preferable.

The origin of activated carbon is not particularly limited.
It may be any of coal-based, petroleum-based, phenolic resin-based, polyacrylonitrile-based, cellulose-based, coconut husk-based, wood-based, and the like.

The sintered body of activated carbon is 100 parts by weight of activated carbon and, if necessary, 20 parts by weight or less, preferably 2 to 20 parts by weight.
It is manufactured by adding about 1 part by weight of a binder, mixing, shaping, and sintering. It is not necessary to use a binder if a sintered body having sufficient strength can be obtained even if the activated carbon alone is sintered.

When a binder is used, a sinterable binder which is integrated with activated carbon by a sintering operation is particularly suitable. Examples of the sinterable binder include infusible carbon made of unfired carbon obtained by infusibilizing raw material pitch; thermosetting resin such as aramid resin, phenol resin, epoxy resin, urea resin; infusible acrylic resin, An infusible heat-fusible resin such as a melted polyvinyl alcohol resin is exemplified.

Among these sinterable binders, binders that can be carbonized are preferable. Unlike the heat-meltable binder, these sinterable binders are characterized in that the ratio of blocking the pores of the activated carbon is extremely low. Further, when the sinterable binder is used in a fibrous form (for example, when using unfired carbon fiber which is obtained by spinning raw material pitch and infusibilized), the ratio of plugging pores of activated carbon Will be less. As a fibrous sinterable binder,
It is preferable to use a yarn having a diameter of about 5 to 100 μm and a length of about 0.1 to 5 mm.

If necessary, the activated carbon or the blend of the activated carbon and the binder may be added to 100 parts by weight of the activated carbon.
You may further add a reinforcing material up to about 50 parts by weight.
Examples of such a reinforcing material include natural fibers such as hemp and paper pulp, and heat-meltable fibers such as polyethylene yarn and polypropylene yarn.

The binder and the reinforcing material can be carbonized and / or gasified depending on the temperature in the sintering step described later.

The density of the sheet-shaped adsorbent may be within a range that does not impair characteristics such as adsorption capacity and strength, but is 0.4 g / c.
It is preferably m ³ or more, particularly 0.4 to 1.0 g / cm ³ . Such a high-density adsorbent has not only high strength, but also is excellent in adsorbability and drug retention because it is mostly composed of activated carbon. Furthermore, since the density of the adsorbent is high, the activated carbon content per unit volume is large,
The sustained release effect can be maintained for a long time with a small amount of the sustained release material.

The thickness of the sheet-shaped adsorbent is, for example, 0.0
It is about 5 to 5 mm, preferably about 0.2 to 1 mm. If the thickness of the adsorbent exceeds 5 mm, the activated carbon present inside may not be effectively used because the adsorbent has a high density.

As long as the adsorbent contains activated carbon and has a sheet shape, irregularities or grooves may be formed regularly or irregularly on the surface. By forming such irregularities and the like, the surface area of the sheet-shaped adsorbent can be increased, and the drug release property can be enhanced. Further, since the sheet-shaped adsorbent made of a sintered body has high mechanical strength, even when used as an underlayment sheet for furniture, etc., due to the uneven portion,
It is possible to secure a space where the drug is diffused between the lower surface of furniture or the like and the sheet-shaped adsorbent. Therefore, it is possible to ensure the radiation of the drug.

The irregularities and grooves may be formed on the sheet-shaped adsorbent itself, or may be formed by spacers arranged on the sheet-shaped adsorbent.

The adsorbent can be produced by at least a forming step of forming activated carbon and a sintering step of firing the obtained formed product.

In the molding step, not only activated carbon alone but also a mixture of activated carbon and a sinterable binder or a mixture further containing a reinforcing material can be used. Preferably, a mixture containing activated carbon and a sinterable binder can be used.

In the molding step, the activated carbon and the mixture are placed in a mold and at least pressure-molded. At the time of molding, it is preferable to perform heating and pressure molding.

The molding is performed according to the density of the adsorbent, for example,
Pressure of about 5 to 1000 kgf / cm ² , preferably 1
It can be performed at about 00 to 300 kgf / cm ² . When the pressurizing pressure is less than 5 kgf / cm ² , the strength is low, and an adsorbent with a low density is easily formed,
If it exceeds f / cm ² , the pores of the activated carbon may be destroyed and the amount of the adsorbent retained by the drug may decrease.

When fibrous activated carbon is used, a low-density preform may be prepared in advance by a dry method or a wet method and then sintered.

In the case of the wet method, activated carbon alone, a mixture of activated carbon and a sinterable binder, or a mixture further containing a reinforcing material is dispersed in water and mechanically stirred to prepare a uniform aqueous slurry. Then, the aqueous slurry is put into a molding die having a suction port and suctioned to obtain a preform. After drying the obtained preform, it is put into a mold, shaped, and subjected to a sintering step. In the case of the dry method, a preformed body in the form of a non-woven fabric or the like may be put in a mold in advance by the dry method and sintered under the same conditions as above.

When using these preforms,
It is easy to handle and uneven density can be prevented. In particular, when a preformed body produced by a wet method is used, the uneven density of the basis weight is small, and the uneven density of the sintered body is also small.

A preferable method for forming a preformed body is a method in which a slurry containing activated carbon fibers and a binder is suction molded using a suction molding die.

The sheet-shaped molded product obtained in the molding step has a temperature of, for example, about 500 to 1500 ° C., preferably 80.
It is subjected to a sintering process in which it is sintered under the condition of 0 to 1300 ° C. If the sintering temperature is less than 500 ° C., the sintering will be insufficient, and the strength will be low, and the adsorbent will have a low density. If the sintering temperature exceeds 1500 ° C., the pores of the activated carbon will change, and the sinterable binder will tend to close the pores, resulting in a decrease in the ability of the adsorbent to retain the drug.

The sheet-like adsorbent obtained by the above-mentioned sintering has a high density, a high mechanical strength, and a carbonaceous material having a high activated carbon content. When the sheet-shaped molded product contains a sinterable binder, the mechanical strength of the adsorbent can be further increased. Since the adsorbent is carbonaceous, it has high heat resistance and chemical resistance. Furthermore, since the compression molded product is sintered,
The dimensional accuracy of the obtained adsorbent is also high. Note that the binder and the reinforcing material can be carbonized and / or gasified with the sintering.

Sintering can be carried out in an inert atmosphere such as nitrogen gas, helium gas or argon gas or under vacuum. The sintering time can be appropriately selected according to the type of activated carbon used, the shape of the molded body, the type and amount of the sinterable binder, etc., but is usually about 5 seconds to 30 minutes.

A drug is carried on such a sheet-shaped adsorbent. As the drug, various drugs that require sustained release can be used. Examples of the drug include fragrances such as natural fragrances, synthetic fragrances, and mixed fragrances; fertilizers such as nitrogenous fertilizers, phosphate fertilizers, potash fertilizers, organic fertilizers, compound fertilizers; organic tin compounds, organic sulfur compounds, chlorine-based compounds Antifungal agents such as compounds and phenolic compounds; mice, birds,
Repellents against snakes, cats, dogs, cockroaches, mosquitoes; organophosphorus, organochlorine, dithiocarbamate compounds, fungicides, insecticides, rodenticides, acaricides, termite control agents, etc. . These agents may be liquid or solid.

The type of the repellent can be appropriately selected according to the object to be repelled, and for example, cinnamic aldehyde, γ-nonyl lactone, para-cresol acetate, phenylethyl alcohol, geraniol, citronellool, syn Namic alcohol, methyl eugenol, geraniol, citral, lemon oil, rose geranium oil, sandalwood oil, menthol, and the like, and mixtures thereof are mentioned (see Japanese Patent Application No. 2-128623). In addition, the repellent is a phthalate ester (for example,
It may be supported together with a small volatile liquid such as diethyl phthalate, dibutyl phthalate, dihexyl phthalate, 2-ethylhexyl phthalate and dioctyl phthalate.

Since the sheet-shaped adsorbent has a large holding capacity,
The amount of the drug carried can be selected within a wide range. The amount of the drug carried is, for example, 0.1 to 90% by weight, preferably 0.5 to
The amount is 80% by weight, more preferably 1 to 75% by weight.

The loading of the drug can be carried out by a conventional method such as a dipping method or a spraying method. The drug may be carried on the sheet-shaped adsorbent as it is, or may be dissolved or dispersed in a solvent and carried on the sheet-shaped adsorbent as necessary. Also, the chemicals that do not volatilize at the sintering temperature,
In the manufacturing process of the sheet-shaped adsorbent, the adsorbent may be supported by being mixed with the raw materials.

[0037]

The sustained release sheet of the present invention has the following effects.

(1) Since the adsorbent is composed of a sintered sheet of activated carbon, it has a large amount of activated carbon and can significantly prevent the pores of activated carbon from being clogged. Further, since the adsorbent is compression molded, the activated carbon content can be further increased. Therefore, the amount of the drug held per unit volume can be significantly increased, and the drug can be stably released over a long period of time.

(2) Since the sheet-shaped adsorbent has a large mechanical strength, rigidity and shape-retaining property, it can be used as an underlay sheet and is easy to handle.

(3) Since it has high chemical resistance, it can support corrosive agents and has high heat resistance.
It can also be used in high temperature environments.

[0041]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example Paper was made using a slurry containing activated carbon fibers having a specific surface area of 1000 m ² / g, and the obtained sheet having a paper making structure was formed into a graphite mold having recesses and a flat graphite mold. Sintered sheet with protrusions sandwiched in between, temperature of 920 ° C., sintering for 20 seconds while applying pressure of 1000 kg / cm ² , and protrusions (diameter 1.8 mmφ × height 0.5 mm) scattered every 10 mm vertically and horizontally. Got

Three obtained sintered sheets (0.5 g in total)
In each of them, a repellent for cats was carried by spraying. As a repellent, a mixture of cinnamic aldehyde, γ-nonyl lactone, sandalwood oil, menthol, linalool, geraniol, and diethyl phthalate was used. The amount of the repellent carried on the three sintered sheets is about 1 g.

Then, the above three sintered sheets were loaded into a cylindrical container (inner diameter 20 mmφ × height 20 mm) and left in a windless atmosphere (temperature 8 to 25 ° C.) for 5 days.
It continued to smell.

Comparative Example Cotton-like activated carbon fibers used in Examples (bulk density 0.03 g
/ Cm ³ ) 0.045 g, and the repellent used in the examples of 0.
4 g was carried by spraying and filled in the cylindrical container used in Example 1. When it was left to stand in the same manner as in the example, the odor was emitted only for one day, although the amount of the repellent carried was remarkably large as compared with the example.

Claims (4)

[Claims] 1. A sustained-release sheet in which a drug is supported on a sheet-shaped adsorbent made of a sintered body of compression-molded activated carbon. 2. The density of the sheet-shaped adsorbent is 0.4 to 1.
The sustained release sheet according to claim 1, which has an amount of 0 g / cm ³ . 3. The thickness of the sheet-shaped adsorbent is 0.05 to 5
The sustained release sheet according to claim 1, which has a size of mm. 4. The sustained release sheet according to claim 1, wherein the activated carbon is activated carbon fiber.