GB1565906A - Encapsulated materials - Google Patents

Description

(54) ENCAPSULATED MATERIALS (71) We, STANDARD TELE PHONES AND CABLES LIMITED, a British Company of 190 Strand, London W.C.2. England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to materials for the controlled release of chemicals, e.g. drugs, fertilisers or pesticides into solution.

Our published specification No. 1,512,637 describes a water soluble glass composition for the controlled release of an active material into any aqueous solution. The release rate of this material slowly decreases with time. In some situations, e.g. in the supply of a drug to the bloodstream of an animal, it is desirable to provide either a steady release rate or a periodic dose. In other applications it may be desirable to provide a release rate that increases over a period of time.

According to one aspect of the invention there is provided liquid soluble body adapted to provide for the controlled release of a material into solution in a surrounding liquid, the body being formed from a glass soluble in said liquid and having an array of cavities therein, each said cavity containing a quantity of said material.

According to another aspect of the invention there is provided a method of making a controlled release glass body, including rolling a heated water soluble glass into strip form, forming indentations in the strip, filling at least some of the indentations in the strip with a water soluble material, and sealing the indentation with a water insoluble glass ribbon fused to the glass strip.

An embodiment of the invention will now be described with reference to the drawing accompanying the Provisional Specification in which: Fig. 1 is a cross-section of a glass body containing cavities each containing an active material; Fig. 2 is a plan cross-section of the glass body of Fig. 1 and Fig. 3 shows a method of preparing a glass strip containing cavities filled with active material.

Referring to Figs. I and 2, a pellet 11 formed from a water soluble glass contains an array of cavities 12 each of which is filled with a material 13 to be released on dissolution of the glass pellet 11. The cavities 12 are arranged in a layer in the central plane of the pellet and may form, as shown in Fig. 2, a series of concentric circles. The upper and lower surface of the pellet may be coated with a protective layer 14 of an insoluble glass.

When the pellet is immersed in water the glass slowly dissolves so as to expose the cavities 12 as indicated by the broken line 15 in Fig. 1. The rate of release of the active material into solution is determined by the solution rate of the glass and by the spatial disposition of the cavities 12 within the pellet.

Fig. 3 shows a method of preparing a cavity containing glass material in strip form. Molten glass 31 is drawn from a furnace (not shown) between a pair of rollers 32 which roll the glass into a strip 33.

The glass strip 31 is then passed across a support 34 under a roller 35 provided with an array of teeth 36 so as to provide a series of indentations 37 in the strip surface. The indentations are each supplied with one or more active materials 38 from an array of nozzles 39 and a layer 40 of an insoluble glass is bonded to the surface of the strip 33 thus sealing in the active material or materials 38.

The sealing layer 40 may be applied by fast hot rolling, by overlapping the strip 33 with a thin ribbon of the insoluble glass and flash radiation sealing, or by plasma spraying of the sealing glass. The water soluble glass may be a P2OICaO glass, i.e. a melt of a glass forming oxide and a glass modifying oxide, together with one or more glass modifying oxide such as sodium oxide (Na > O) and aluminium oxide (Al203) or magnesium oxide (MgO) for adjusting the solubility rate.

For example, increasing the proportion of sodium oxide in the glass leads to an increase in water solubility whereas increasing the proportion of aluminium oxide and/or magnesium oxide leads to a decrease in solubility. Dissolution rate control is discussed more fully in our published specification No. 1,512,637.

The active material may be introduced into the cavities prior to sealing by vacuum filling, by capilliary absorption or by introduction as a powdered solid. The material may be a drug for a continuous treatment of animal or human diseases, an insecticide or fungicide for soil and/or water treatment, a hormone for the treatment of a pathological condition, a contraceptive hormone, or a nitrogen containing fertiliser in which case the other nutrient element may be included in the water soluble glass.

WHAT WE CLAIM IS: 1. A liquid soluble body adapted to provide for the controlled release of a material into solution in a surrounding liquid, the body being formed from a glass.

soluble in the liquid and having an array of cavities therein, each said cavity containing a quantity of said material.

2. A body as claimed in claim 1, and in which the glass is a P2OJCaO2 glass.

3. A body as claimed in claim 2, and in which the glass contains one or more solubility modifying oxides.

4. A body as claimed in claim 3, and in which the solubility modifying oxide is sodium oxide, aluminium oxide, magnesium oxide or mixtures thereof.

5. A body as claimed in any one ot claims 1 to 4 and in which is in strip form.

6. A liquid soluble glass body substantially as described herein with reference to the drawings accompanying the Provisional Specification.

7. A method of making a controlled release glass body, including rolling a heated water soluble glass into strip form, forming indentations in the strip, filling at least some of the identations with a water soluble material, and sealing the indentations with a water insoluble glass ribbon fused to the glass strip.

8. A method of making a controlled release glass body substantially as described herein with reference to the drawing accompanying the Provisional Specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. glass modifying oxide such as sodium oxide (Na > O) and aluminium oxide (Al203) or magnesium oxide (MgO) for adjusting the solubility rate. For example, increasing the proportion of sodium oxide in the glass leads to an increase in water solubility whereas increasing the proportion of aluminium oxide and/or magnesium oxide leads to a decrease in solubility. Dissolution rate control is discussed more fully in our published specification No. 1,512,637. The active material may be introduced into the cavities prior to sealing by vacuum filling, by capilliary absorption or by introduction as a powdered solid. The material may be a drug for a continuous treatment of animal or human diseases, an insecticide or fungicide for soil and/or water treatment, a hormone for the treatment of a pathological condition, a contraceptive hormone, or a nitrogen containing fertiliser in which case the other nutrient element may be included in the water soluble glass. WHAT WE CLAIM IS:

1. A liquid soluble body adapted to provide for the controlled release of a material into solution in a surrounding liquid, the body being formed from a glass.

soluble in the liquid and having an array of cavities therein, each said cavity containing a quantity of said material.

2. A body as claimed in claim 1, and in which the glass is a P2OJCaO2 glass.

3. A body as claimed in claim 2, and in which the glass contains one or more solubility modifying oxides.

4. A body as claimed in claim 3, and in which the solubility modifying oxide is sodium oxide, aluminium oxide, magnesium oxide or mixtures thereof.

5. A body as claimed in any one ot claims 1 to 4 and in which is in strip form.

6. A liquid soluble glass body substantially as described herein with reference to the drawings accompanying the Provisional Specification.

7. A method of making a controlled release glass body, including rolling a heated water soluble glass into strip form, forming indentations in the strip, filling at least some of the identations with a water soluble material, and sealing the indentations with a water insoluble glass ribbon fused to the glass strip.

8. A method of making a controlled release glass body substantially as described herein with reference to the drawing accompanying the Provisional Specification.