JPS6291272A - Film coating method - Google Patents

Abstract

PURPOSE:To enhance coating workability by enhancing the concn. of the solid in a gel dispersion, by using a low viscosity gel dispersion prepared by gelling a hydrosol of a water-soluble polymer. CONSTITUTION:For example, in preparing a hydrosol by dissolving a hydroxyalkyl derivative of cellulose or hydroxypropyl cellulose in water as a water-soluble polymer, the concn. thereof is adjusted so that the viscosity of a gel dispersion formed by gelling said hydrosol is set to about 1,000cp or less. If the obtained gel dispersion is applied to a solid by a known method, the concn. of the solid in the gel dispersion can be increased and, therefore, a coating time for obtaining a predetermined film thickness is shortened. That is, because the gel of the water-soluble polymer has already destroyed its hydration, the drying speed after the solid has been coated becomes extremely fast and the mutual stickiness of the film is also prevented.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method of film coating a solid material with a water-soluble polymer, and more specifically, a low-viscosity gel obtained by gelling a hydrosol of a water-soluble polymer. This invention relates to an aqueous film coating method for solid materials using a dispersion.

In the method of the present invention, it is possible to increase the concentration of solids in the gel dispersion, thereby improving the workability (time reduction, etc.) of film coating.

The film coating method of the present invention can be used for coating solid materials in the fields of medicine, cosmetics, food, feed, agricultural chemicals, etc., because a gel dispersion of a highly concentrated water-soluble polymer can be used for coating in a short time. .

[Conventional technology]

Until now, various film coatings using water-soluble polymers have been used in the fields of medicine, cosmetics, food, feed, agricultural chemicals, etc. for the purposes of moisture proofing, deodorizing, preventing changes over time, controlling elution, etc.

In general film coating methods using water-soluble polymers, coating liquids prepared using organic solvents have been used to improve workability by increasing drying properties and shortening coating time.

However, in recent years, coating methods using water as a solvent have been actively researched due to problems such as pollution, toxicity of residual solvents, and handling of hazardous materials.

When water is used as a solvent, drying properties are poor compared to organic solvents, and the formed coating film is sticky, so various additives are used to improve these problems.

For example, in the pharmaceutical field, a method using a Coinda liquid (dispersion liquid) prepared by emulsifying and dispersing higher fatty acids or their metal salts and waxes in an aqueous solution (hydrosol) of a water-soluble film coating base is known. 261
It is described in Publication No. 25.

In addition, a method using a coating liquid (dispersion liquid) prepared by adding oil to an aqueous solution (hydrosol) of a water-soluble polymer and mechanically dispersing the liquid is described in JP-A-58-118511. , water containing vegetable oil, etc.? 8? A method of adjusting and using &(dispersion?&) is described in Japanese Patent Application Laid-Open No. 171451/1983.

[Problem that the invention seeks to solve]

Film coating methods that use water as the coating solution solvent are safe when considering pollution, toxicity, flammability, etc.; however, organic solvents, such as alcohols such as ethanol, chlorinated hydrocarbons such as methylene chloride, etc. Compared to other solvents, it has a higher boiling point and poor drying properties of the coating film, so the coated substances tend to stick together.

Therefore, it is necessary to perform coating by slowing down the supply speed of the coating liquid or increasing the drying temperature, which poses problems such as the coating process takes a long time and requires a large amount of drying energy. There is.

An object of the present invention is to provide an aqueous film coating method that can shorten the coating operation time and lower the drying temperature.

[Means for solving problems]

The present invention is a solid film characterized in that a hydrosol of a water-soluble polymer whose viscosity is reduced by gelation is gelled, and the surface of the solid is coated with the obtained low-viscosity gel dispersion and dried. This is a coating method.

In the present invention, the water-soluble polymer includes a heating agent for its hydrosol (hereinafter simply referred to as "hydrosol") and/or a gelling agent for the hydrosol, such as a water-soluble electrolyte,
By adding water-soluble polysaccharides, etc., a low-viscosity gel dispersion (
Hereinafter, it will be simply referred to as "gel dispersion". ), there is no particular restriction as long as it generates.

Taking into account that a uniform gel dispersion can be prepared relatively easily as a water-soluble polymer, hydroxyalkyl derivatives of cellulose can be preferably used, and more preferably hydroxypropyl cellulose (hereinafter referred to as , r
), hydroxypropyl hydroxybutyl cellulose (hereinafter referred to as [HPHBCJ), etc. are used.

Additionally, common film coating bases such as
Metal cellulose (hereinafter referred to as rMcJ).

), hydroxypropyl methylcellulose (rH
It is written as PMcJ. ), alkyl derivatives that may contain hydroxyalkyl groups of cellulose that do not gel and reduce viscosity, such as hydroxypropyl methyl cellulose phthalate (IIPMcP), shellac, cellulose acetate phthalate (CAP), and ethyl cellulose ([IC)
, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyvinyl acecure diethylaminoacetate (AEA), carboxymethylethyl cellulose (CMEC), etc. They improve the drying properties and strength of the coating film, so they can significantly reduce the viscosity of the gel dispersion. Can be mixed and used as long as it does not increase the amount.

When preparing a hydrosol by dissolving the water-soluble polymer in water, the concentration is preferably such that the viscosity of the gel dispersion produced by gelation is about 1,000 cρ or less, and 2.
More preferably, it is 50 cρ or less.

If the viscosity of the gel dispersion is too high, not only will the drying properties of the coating film decrease and the surface tackiness increase;
In coating by a spray method, the delivery of the gel dispersion liquid becomes irregular, the spray droplets become non-uniform, and the workability of the coating becomes extremely poor.

The low viscosity gel dispersion is prepared by: 111 A method of heating a hydrosol to a temperature higher than its gelling temperature.

(2) A method of adding a water-soluble electrolyte to a hydrosol.

(3) Water-soluble multi-I in hydrosol! How to add

However, if there is a limit on the gelation temperature or the amount of electrolyte or polysaccharide added, it is possible to produce a gel dispersion below the limit by using these methods in combination as appropriate. can do.

H is a typical example of a water-soluble polymer that gels and lowers its viscosity.
In the case of PC, the temperature range in which the hydrosol is heated to gel is 35°C or higher, but it is subject to various practical conditions, such as the degree of water development, the stability of the chemicals to be coated, and the quality of the coating film. Considering smoothness and the like, the temperature is preferably in the range of 50 to 90°C.

Depending on the type of water-soluble polymer, the resulting gel dispersion may not be uniformly dispersed and may separate, or the gel particle size may become non-uniform, resulting in an unstable gel dispersion state. By adding operations such as low-speed stirring or high-speed stirring, it is possible to prevent gel separation and uniformly disperse the gel.

Depending on the practical purpose, additives such as a plasticizer to impart flexibility to the coating film, a pigment for coloring, and other inorganic fillers may be added to the gel dispersion obtained by the above method. Can be added.

Furthermore, in order to increase the evaporation rate of the gel dispersion (drying rate of the coating film), an organic solvent can be added to the hydrosol within a range that does not inhibit gel formation of the water-soluble polymer.

The most suitable coating method for coating a solid substance with the gel dispersion obtained by the above method is a spray method, but there is no particular restriction, and a dropping method, dipping method, etc. may also be employed.

Moreover, various nozzles such as a -fluid nozzle and a two-fluid nozzle can be used in the spray method.

The coating film coated on the solid substance can be dried by ventilation drying, natural drying, etc., and there are no particular restrictions on the drying method.

of the coating if the drying temperature is above room temperature.

It is possible to set the temperature up to the limit depending on the target solids, additives, etc., but it is preferably in the range of room temperature to 70°C.
When C is used, a temperature range of 40 to 60°C is preferably adopted.

Solid substances to be coated are not particularly limited, but tablets, pills, and granules are commonly used in the fields of medicine, food, agricultural chemicals, feed, etc. due to the price, properties, and purpose of coating of water-soluble polymers. , granules, flakes, etc., and there are no particular restrictions on shape or size.

[For production]

As a result of intensive research into improving the workability of water-based film coating, the present inventors found that water-soluble polymers, such as hydroxyalkyl derivatives of cellulose, have hydroxyalkyl groups that facilitate hydration and dissolve them in water. It forms a hydrosol, but the hydration collapses due to the gelation of the hydrosol, and the hydroxyalkyl derivative of cellulose precipitates to form a gel, which lowers the viscosity and forms a gel dispersion, so it is used as a coating liquid.
The present invention was completed by focusing on the fact that the solid content concentration in the gel dispersion can be increased and the coating time for forming a coating film of a predetermined thickness can be shortened.

In the present invention, since the hydration of the water-soluble polymer gel has already collapsed, the drying speed after being coated on a solid material is lower than that of a hydrosol in which the water-soluble polymer is simply dissolved in water. It is significantly faster than other coating films, and the tackiness of the coating film is also low.

Therefore, immediately using low temperature drying air,
It can be dried, and as a result, adhesion of the films to each other can be prevented.

〔Example〕

The present invention will be explained in more detail by way of examples.

However, the scope of the present invention is not limited in any way by the following examples.

(1) Coach green bean preparation samples 1 to 9 Various water-soluble polymers were dissolved in water, and hydrosols having the composition and viscosity shown in Table 1 were prepared with or without addition of additives.

Next, this hydrosol was gelatinized to obtain a low viscosity gel dispersion having a viscosity shown in Table 1, which was designated as coating liquids 1 to 9.

Comparative Sample Ratio 1 to Ratio 4 Hydrosols prepared by dissolving various water-soluble polymers in water and having the composition and viscosity shown in Table 1 were used as coating liquids Ratio 1 to Ratio 4 for comparison.

The following water-soluble polymers shown in Table 1 were used.

HPC-3L: Nippon Soda ■ RPC-3L: Nippon Soda ■ HPMC: TC-5E Shin-Etsu Chemical ■ MC: Metrose (S-15E) Shin-Etsu Chemical ■ HPHB
C: Hydroxypropoxyl group molar substitution degree 3.3 Hydroxybutoxyl group molar substitution degree 0.36 PVA manufactured by Nippon Soda ■
: Gose) -le ([!G-30) manufactured by Nippon Gosei Chemical Industry ■ (2) Film coating of tablets Using a vented coating pan for tablets (manufactured by Freund Sangyo ■), lens-shaped tablets with a diameter of 8IIIm were coated. The prepared coating solution was spray coated.

The scraping conditions of the device other than those shown in Table 1 were as follows.

lal Tablet preparation 1 300g (bl Pan rotation speed 36 rpsTCI Pan internal temperature 45-55℃ (adjust supply drying air temperature) (dl Air supply rate 800 j!/sin+e
l Spray nozzle 0.7 m-φ two-fluid nozzle (
3) Evaluation The coating time under the above coating conditions was measured.

In addition, the coating film formed on the tablet was evaluated visually and tactilely.

The evaluation results are shown in Table 1.

〔Effect of the invention〕

In the present invention, by gelling a water-soluble polymer hydrosol and using a low-viscosity gel dispersion as the coating liquid, as shown in Table 1, the water-soluble polymer hydrosol of the conventional method can be used as a coating liquid. Compared to the coating liquid of
The concentration of solids in the coating liquid at a given viscosity is
was able to increase it significantly.

As a result, the drying properties of the coating film were improved, the drying air temperature was lowered, the coating time was shortened, and the coating films were prevented from sticking together.

The present invention provides a film coating method for solid materials with improved thermal energy consumption and workability, and its industrial significance is extremely large.

Claims (4)

[Claims] (1) Film coating of a solid material, which is characterized by gelling a hydrosol of a water-soluble polymer whose viscosity decreases through gelation, coating the surface of the solid material with the resulting low-viscosity gel dispersion, and drying it. Method (2) The water-soluble polymer whose viscosity is reduced by gelation is hydroxypropyl cellulose or hydroxypropyl hydroxybutyl cellulose (claim 1).
) Method described in section (3) The method according to claim (1), in which gelation of a hydrosol of a water-soluble polymer is carried out by heating the hydrosol. (4) The method according to claim (1), wherein the coating method of coating the surface of the solid object with a dispersion of a low viscosity gel is a spray method.