EP0122519B1 - Method and apparatus for dotting moulding devices by means of droplets of a liquid or suspended lubricant during the manufacture of moulded objects in the pharmaceutical, food or catalytic field - Google Patents

Abstract

The invention is directed to a process and apparatus for dotting molding tools with droplets of liquid or suspended lubricant in the production of shaped articles in the pharmaceutical, food, or catalyst fields. Pressurized lubricant solutions or suspensions and pressurized gas are alternately passed through capillaries, in conjunction with alternating single-substance nozzles, in such a way that drops are formed on the nozzle surface, in between the jets of gas, and are then detached from this surface and directed to specific zones of pressing tools. The apparatus comprises fast-acting valves for the brief release of pressurized gases and lubricant liquids or suspensions. The delivery lines of a gas valve and a liquid valve combine upstream of a capillary, and single-substance nozzles are mounted at the end of the capillaries.

Description

The invention relates to an improved method and devices for spotting molds with droplets of liquid or suspended lubricants in the production of moldings in the pharmaceutical, food or catalyst sector.

US-A-4,323,530 describes a method for compressing granules into tablets, dragee cores and the like, in which a certain amount of lubricant in liquid or suspended form by means of an intermittently operating nozzle system before each pressing operation on the stressed zones of the pressing tools is applied. This type of lubrication allows the granules to be compressed to have no lubricant, e.g. B. magnesium stearate, more must be added; this leads, for example, to drugs with a significantly improved bioavailability of the active ingredient contained therein. Otherwise, you can get by with significantly reduced amounts of lubricant. According to the method of this patent, the application is accomplished by directed spraying of certain zones of the pressing tools with the liquid or suspended lubricant with the aid of preferably single-substance or two-substance nozzles. When using these nozzles, but especially when using two-substance nozzles, in which air and lubricant liquid escape at the same time, it has been shown that droplets are formed with a particle spectrum which is dependent on the width of the air supply; these nozzles tend to form an undesirable mist which can lead to contamination of the tablet press, in particular of the press plate.

The use of single-component nozzles, through which the liquid lubricant is sprayed intermittently and briefly before each individual pressing process onto the corresponding points on the pressing tools, also showed a tendency to become dirty due to the formation of a spray cone or the occurrence of stray drops of different diameters within the spray cone jacket Tray plates. However, the single and dual-substance nozzles also generate when used in high-speed tablet presses at actuation intervals of up to 5 msec. no constant detachment of the liquid lubricant, in addition to individual drops there are also drop sequences consisting of drops of different diameters, whereby a constant application of the designated zones of the pressing tools is not always guaranteed.

It has already been proposed (cf. DE-A-29 32 069) to avoid these disadvantages in that the liquid or suspended lubricant before each pressing operation in defined amounts and in the form of discrete droplets of a defined volume onto the stressed zones of the pressing tools by means of piezoelectric Transducer is pointed in connection with corresponding nozzles. It has also been proposed to release a defined, pressurized amount of a lubricant liquid or suspension at single-component nozzles before the individual pressing operation and to accelerate this by means of a directed, metered air flow removed from a separate, contact-controlled nozzle. A certain disadvantage of this method, however, is that the liquids to be sprayed have to meet high requirements with regard to viscosity and surface tension. Only if certain limits for the viscosity and surface tension values are adhered to can the pressing zones provided for this be properly dotted. In addition, this system is sensitive to dust and is not easily used for the lubrication of the pressing tools when pressing dusty or non-granulated materials with a high powder content, such as. B. of sorbitol in the food industry.

In the practical further development of the method according to the above-mentioned US patent, it has now been shown that all negative side effects can be largely eliminated if valve systems based on the electromagnetic or piezomechanical or piezoelectric effect, which are in the range of 50 usec. up to 5 msec. work, preferably 1 to 2 msec., alternately defined amounts of liquid, dissolved or suspended lubricants and defined volumes of gases, e.g. B. air, are released via one or more capillary systems, which in turn are provided with nozzle openings. In addition to the bulging of the menisci of the lubricant liquid or suspension on the nozzle surfaces, the subsequent gas surge causes the droplets to detach perfectly at the “interchangeable single-substance nozzles” and accelerate the droplets on their trajectory in the direction of the zones of the press tools to be acted upon. The term "interchangeable single-component nozzles" was chosen because, in contrast to known single-component and dual-component nozzles, the two substances, liquid and gas, alternately leave the same nozzle opening in succession. At the same time, the gas surge also causes thorough nozzle cleaning; the nozzle opening is thus pulsed and continuously cleaned. In order to achieve a targeted formation of droplets, the relationship between liquid pressure and liquid quantity per unit of time as well as gas pressure and gas quantity per unit of time, but also the nature of the capillary and nozzle system is of great importance. in the In general, a 10 to 50 times greater amount of gas volume, measured by the volume of the liquid, in the same unit of time is sufficient for the gas pressures which are preferably used. The alternating mode of operation of the valve system leads to a clean detachment of the lubricant droplet from the nozzle opening without an undesirable formation of mist of the lubricant being observed. Individual liquid droplets are formed, detached from the nozzle and directed and accelerated in the direction of the zones to be acted upon, the formation of a mist is avoided and the contamination of the tabletting machine is thus prevented. The acceleration of the droplet flight to the pressing tools also enables this device to be used with very fast tableting machines (stamp circulation speed up to approx. 10 m / s).

If several nozzles are used, they can be arranged in rows or over a large area on the surface and, if appropriate, also on the lower surface of a so-called spotting shoe. The attachment of the nozzles on such a spotting shoe depends on the shape and size of the compacts; the spotting shoe itself is preferably attached directly in front of the filling shoe between the die plate and the upper punch, so that the applied lubricant droplets reach and lubricate the active surfaces of the pressing tools in the shortest possible way and in a directional manner. The term "liquid lubricants" is also understood to mean lubricant melts.

Each capillary in the spotting shoe is connected to a valve system either alone or together with certain associated capillaries; the valve system releases a small but defined amount of lubricant and gas or air alternately with each actuation. The valve system is actuated and the control program is triggered by a light barrier attached to the tableting press, by a bit transmitter or by a capacitive or inductive proximity switch via electrical or magnetic or mechanical (e.g. pneumatic) pulses which act on the valves.

The principle according to the present invention thus consists in the metering of a small but defined amount of a liquid lubricant into the capillary system of the spotting shoe and in the subsequent detachment of the lubricant drops from the nozzle opening and application of the detached lubricant drops to the zones of the pressing tools provided for this purpose by a later inflowing, volume-dosed gas (e.g. air), this dosed gas simultaneously accelerating the drops to a predeterminable extent, predeterminable by setting certain pulse sizes. The amount of gas or amount of air is measured in such a way that there is no uncontrolled bursting and thus nebulization of the drops.

The pulse time for metering in the lubricant liquid or suspension is preferably kept small compared to the pulse time for metering in the air. However, it is advisable to keep the pressure of the lubricant liquid or suspension lower than the pressure of the following air. It has proven to be advantageous to have the pulse for air metering set in at the moment the lubricant metering is ended.

In general, nozzle outlet openings between 0.05 and 0.3 mm are used with a liquid pressure between 0.1 and 2 bar and a gas pressure between 0.5 and 8 bar, the pulse times for metering the liquid are then preferably between 1.0 and 2.5 msec., for the gas between 1.0 and 2.0 msec. In compliance with the above criteria, a quantity of lubricant of approximately 10 to 500 g / hour can then be dispensed through a single-component nozzle. At a tableting speed of 200,000 compacts per hour, a diameter of the compacts of 19 mm and a weight of 2.0 g come for applying the lubricant to the upper and lower punches. B. 10 interchangeable single-substance nozzles are used, each delivering 0.5 to 25 mg of lubricant liquid to the upper and lower punches.

In the case of capillaries with a plurality of nozzle outlet openings along the course of the capillary, a pressure drop can occur in the region of the terminal nozzle outlet openings, which leads to a deterioration in droplet detachment at these nozzle openings. In order to avoid such a disturbance in the droplet dispensing, it is advisable to taper the capillaries in the direction of the terminal nozzle openings. Such tapering can be gradual or conical.

The lubricant liquid generally contains 5-50% lubricant, the rest is a solvent or suspending agent. In the case of lubricating oils or fat melts, the concentration is 100% lubricant. Depending on the concentration of the lubricant liquid, 0.025 to 25 mg, based on the tablet weight, of 0.001-1% lubricant liquid are thus dispensed per compact (19 mm diameter, 2.0 g weight). The preferred range is 0.1 to 2 mg (0.005% to 0.1%) of lubricant fluid. In addition to stearic acid, palmitic acid, the alkali metal or alkaline earth metal salts of these acids, such as magnesium stearate, potassium stearate, aluminum stearate, mono-, di- and triglycerides and their mixtures of medium-chain to long-chain fatty acids, such as glycerol monostearate or glycerol monolaurate, are used as lubricants. for use. Water or alcohols, such as ethanol, isopropyl alcohol or mixtures thereof, are very particularly suitable as solvents or suspending agents. The viscosity of the lubricant solutions is preferably between 2 and 100 mPa xs (millipascal seconds), the surface tension between 20 and 40 mN / m (millinewtons per meter). With viscous lubricants, the viscosity can be drastically reduced by heating to 100 ° C. Of course, all of the values given above can be significantly below or exceeded, depending on the properties of the lubricants to be used.

While the active surfaces of the pressing tools are passed above and below the spotting shoe, the lubrication process, consisting of lubricant and air metering, is triggered one or more times, with a spotting of the pressing tools with the lubricant being achieved. Depending on the shape of the compact, all the nozzles or only a certain part of the nozzles can be excited to dispense drops; in principle, each nozzle can also be controlled separately, if desired. Particularly stressed zones of the pressing tools, e.g. B. zones for the formation of engravings in the compact, can preferably be dotted with drops of lubricant; this happens through a higher alternating pulse sequence in the capillaries provided for this. The dotting shoe can also be divided into two separate units, which are attached offset to one another in the press and dotted the upper punch and press chamber or lower punch separately. The arrangement of the nozzles on the surfaces of the spotting shoe generally depends on the geometry of the zones of the pressing tools that are particularly stressed during the pressing process, the heavily stressed zones being spotted more with the lubricant than less stressed zones.

In order to achieve a clean detachment of the lubricant drops from the nozzle opening (s), the control program, the nozzles, the capillary system as well as the physical nature of the lubricant liquid and the air supply must be coordinated with the speed of the tableting press. The viscosity and surface tension of the lubricant liquid contribute to the stabilization of the droplet formation and to the easing or aggravation of the droplet detachment from the nozzle opening, but, what is a particular advantage of this method according to the invention, adjustments can be made over a very wide spectrum with regard to viscosity and surface tension, for example by varying the dosage and the cycle sequences of the liquid or air or by changes in the capillary system or in the nozzle openings. Another possibility is the introduction of warm air into the spotting shoe. The temperature can be up to 100 ° C. The warm air ensures that e.g. B. when using lubricant solutions, the solvent of the droplets has already largely evaporated when it hits the tools. This prevents solvents from penetrating into the granules or into the tablet. The air therefore not only has the task of supporting the metering and acceleration of the droplets, but can also have a drying function.

It was not readily foreseeable that it would be possible to avoid the formation of mist by observing certain ratios of the liquid pressure, the liquid quantity, the air pressure and the air quantity and the chronological sequence of the metering of these media into the capillaries of the spotting shoe, all lubricant droplets always being present can only be dotted onto the dies in a discrete form.

It has proven to be advantageous if the lifting force of the compacts, which is measured by means of strain gauges, is used as a regulator for the number of lubricant droplets in the unit of time (for example, per second). If the strain gauges under the compacts show an increase in the lifting force, the number of droplets per unit of time increases automatically. This happens because the determined and z. B. digitized measured values on the electronic control affect the opening times of the lubricant valves within certain limits.

In contrast to the known two-fluid nozzles, in which air and liquid emerge simultaneously, which often leads to the formation of mists, the method according to the invention succeeds in a certain number of droplets of the same diameter on a certain surface of the pressing tool even at very high temperatures to apply the tablet press at high speeds (rotary speeds of up to 10 m / s).

Due to the exact application of the lubricant to the active pressing surface of the lower punch and the creeping ability of the lubricant used, sufficient lubricant obviously reaches the die wall when the lower punch is removed. The lower stamp can thus be dotted immediately after the tablet has been ejected before being immersed under the filling shoe. It is a particular advantage of this system that the lower punch generally does not have to be lowered so that the spotting shoe can lubricate the free die wall. It has also been shown that the immediate lubrication of the tabletting tools is extremely effective. For the usual 2-station high-performance presses, ie one punch presses 2 tablets per revolution, one lubrication of the tool per revolution is usually sufficient.

As mentioned at the beginning, the invention also relates to devices for spotting molds with droplets of liquid or suspended lubricants. The devices consist of a spotting shoe with single substance nozzles abutting capillaries and with separate feed lines for the lubricant liquid or suspension and the gas abutting the other ends of the capillaries. High-speed valves to release defined amounts of liquid or gas are installed in the liquid and gas line. The pressure in the supply system is regulated absolutely and relative to one another by pressure control valves. All valves are controlled, for example, by an electronic control device.

Figures I to IV are intended to explain the devices according to the invention in more detail; they describe preferred embodiments of the present invention.

Figure la shows a cross section through a dotting shoe (5), consisting of a capillary (1) with a fork, which is formed by a compressed air supply line (2) and a lubricant supply line (3). The capillary (1) has several nozzles (4) in a row, this row also being continued on the opposite side.

FIG. 1b shows a top view of the dotting shoe with a row of nozzle openings (4a).

FIG. 1a shows a plan view of a round spotting shoe (5) with a number of nozzle openings (4a) arranged in a geometrical distribution and the inlets (2) and (3) for the lubricant solution or suspension and the air.

FIG. 11b shows a cross section through the same spotting shoe, the nozzles being indicated by (4). The supply of the lubricant liquid or suspension and the air via the channels (2) or (3) continues either via a capillary system (not shown) to the individual nozzles or in each case to a row of nozzles, so that it becomes possible individual nozzles or from geometrically assigned nozzles to point out lubricant and air independently of one another in an individual pulse sequence or the feeds (2) and (3) end in the capillary-like chamber (6), from which individual nozzles (4) after one or both Guide the sides away at a right angle or at a certain angle to the plane of symmetry of the spotting shoe.

FIG. 111 describes a cross section through a dotting shoe (5) that is specially adapted to the die and upper punch. Here are (1) the capillaries that are in a fork

converging supply lines of air and lubricant are not shown. With (4) the nozzles are shown, (7) the upper punch, (8) the lower punch and (9) the die. The nozzles are arranged at different angles to each other and to the axis of the spotting shoe and thus enable particularly intensive lubrication of the active pressing surfaces of the upper punch and the die wall.

FIG. IV shows a cross section through a lubricant puncturing system according to the invention on a tableting machine. Here is (1) a capillary in the dotting shoe (5) with the fork of the compressed air supply (2) and lubricant supply (3) and a row of nozzles (4). The spotting shoe (5) is attached off-center to the axis of the lower punch (8) and upper punch (7); the die is marked with (9). (10a) and (10b) are valves for releasing the compressed air from the compressed air tank (11) and for controlling the lubricant from the lubricant tank (12).

With (13) pressure valves for regulating the pressure of the two media air and lubricant liquid are called; these pressure valves allow an individual adjustment of the pressure of both the liquid and the air, but also the adjustment of these pressures to one another; (14) is a proximity switch and (15) is an electronic control device for controlling the valves (10a) and (10b).

Examples for the production of compacts example 1

With a coating shoe as shown in FIG. 1 a and the arrangement according to the invention described further, sorbitol compresses (diameter 15 mm) were produced by the method according to the invention with direct lubrication. The output was 180,000 tablets / hour, about 900 g of a lubricant consisting of 4% stearic acid and 20% caprylic-capric acid triglyceride in ethanol were consumed per hour.

It was with 1.5 bar liquid pressure and 1.5 msec. dosed into the scoring shoe and then with air of 3.5 bar and a pulse width of 2.5 msec. dosed out.

This process, which was triggered by an induction switch, was repeated twice per press tool and press process.

The tablets thus obtained showed no negative changes in their surface quality compared to conventionally produced compressed products. In contrast, the taste was significantly better than that after

conventional processes with the addition of magnesium stearate sorbitol compressed. In contrast to these, a scanning electron micrograph of a tablet fracture surface showed that the absence of a lubricant means that the sorbitol crystals are completely sintered together. There is no longer any roughness on the tongue.

Furthermore, the desired hardness could be achieved with a pressure reduced by at least 30%.

Example 2

With a spotting shoe as shown in FIG. 1 a and the arrangement according to the invention described further, acetylsalicylic acid milk sugar / starch compressions (diameter 12 mm) were produced by the method according to the invention with direct lubrication. The output was 180,000 tablets / hour, about 100 g of a lubricant consisting of 4% stearic acid and 6% polyoxyethylene sorbitan monooleate in ethanol being consumed. Here, with 0.8 bar liquid pressure and 1.0 msec. dosed into the spotting shoe and then with 1.5 bar and a pulse width of 2 msec. dosed out.

This process, which was triggered by an induction switch, was repeated 3 times per press tool and press process.

The tablet has a 35% higher breaking strength with the same pressing force. Since the granules have not been mixed with a hydrophobic lubricant, the disintegrant can become fully active. The tablet disintegrates from 65 to 10 seconds.

Example 3

With a spotting shoe, as shown in Fig. Ila, and the arrangement according to the invention described further, sorbitol compresses (diameter 15 mm) were produced by the method according to the invention with direct lubrication. The output was 180,000 tablets / hour, about 700 ml of a lubricant consisting of 4% stearic acid and 20% caprylic-capric acid triglyceride in ethanol were consumed. Here, with 1.0 bar liquid pressure and 2.0 msec. dosed into the spotting shoe and then with 5 bar and a pulse width of 1.0 msec. Air dosed.

This process, which was triggered by an induction switch, was repeated twice per press tool and press process.

The statements made under Example 1 apply to the properties of the tablets.

Similar results have also been obtained when using a lubricant consisting of 5% glycerol monostearate, very finely suspended in water.

Example 4 Ascorbic acid effervescent tablets

Ascorbic acid, sodium bicarbonate, citric acid, dry flavor and sugar were individually sieved and then mixed together.

On a tablet press equipped with a spotting shoe, tablets weighing 3.5 g were produced from the mixture using the process according to the invention with direct lubrication of the tools. The lubricant liquid contained 2% polyethylene glycol 6000 and 3% of a glycerin-polyethylene glycol oxystearate (Cremophor RH40 ( ^R )) in ethanol, the liquid pressure was 1.5 bar, the pulse width 2.5 ms. Dosing was carried out with air at 3.5 bar and a pulse width of 3 ms. The amount of lubricant per tablet was 0.4 mg.

• 1. Man kann jede gewöhnliche Tablettenpresse verwenden.
• 2. Man benötigt keine Unterstempel mit einer Filzpackung, speziell aufgebohrten Matrizen und speziell belegten Ober- und Unterstempeln.
• 3. Die Standzeit ist wesentlich höher und der Reinigungsaufwand an der Maschine stark verringert.
• 4. Die Tablettiergeschwindigkeit kann wesentlich erhöht werden.
• 5. Ein Ankleben der Brausetabletten an den Stempeln wird sicher vermieden.

Compared to the conventional process, there are many advantages for the manufacture of effervescent tablets:

• 1. You can use any ordinary tablet press.
• 2. You do not need a lower stamp with a felt pack, specially drilled matrices and specially coated upper and lower stamps.
• 3. The service life is much longer and the cleaning effort on the machine is greatly reduced.
• 4. The tableting speed can be increased significantly.
• 5. Adhesion of the effervescent tablets to the stamps is safely avoided.

Example 5 Catalyst tablet

A mixture of silicon dioxide, aluminum oxide hydrate and chromium oxide (Cr ₂ 0 ₃ ) with a particle size between 0.1 and 1 mm is mixed and compressed on a tablet press to form cylinders 8 mm in diameter and 5 mm in height. The machine is equipped with a scoring shoe. The lubricant liquid consists of thin liquid paraffin oil. The pulse width of the metering valve is coupled with the measured values for the ejection force. For this purpose, the ejection rail was provided with strain gauges so that the force for ejecting each tablet from the die can be measured. As the ejection force increases also the amount of lubricant dispensed. Normally you need 0.5 mg paraffin oil per tablet.

This catalyst tablet has a number of advantages over conventionally manufactured catalyst tablets. As there is no hydrophobic lubricant inside, the tablets become approx. 50% harder. This is of great importance because the filling of meter-high reactors and the temperature conditions during the process require the highest compressive strength, abrasion resistance and internal cohesion of the tablets. The hardness of the new tablets is so good that the usual addition of a binder such as calcium aluminate cement can be dispensed with. This in turn increases the purity of the catalyst, which has a positive influence on the degree of utilization and the service life of the catalyst.

Claims (10)

1. Process for dotting moulding tools with droplets of liquid or suspended lubricant in the production of shaped articles in the pharmaceutical, food or catalyst field, wherein, before the pressing operation, a defined quantity of a pressurised lubricant liquid or suspension is released from single-substance nozzles in order to be detached and speeded towards specific zones of the pressing tools, with the aid of a directed and metered current of gas, characterised in that after the lubricant liquid or suspension the gas is subsequently released through the same capillary or capillaries in conjunction with alternating single-substance nozzles (4), whilst droplets of the lubricant liquid or suspension form at the nozzle openings and, after being detached by the jet of gas, are dotted in directed manner on to specific zones of pressing tools.

2. Process as claimed in claim 1, characterised in that air is used as the gas, the volume of gas used in the same unit of time is about 10 to 50 times as great as the corresponding volume of liquid or suspension and the temperature of the gas is up to 100° C.

3. Process as claimed in claims 1 and 2, characterised in that a liquid pressure of 0.1 to 2 bar and a gas pressure of 0.5 to 8 bar are used.

4. Process as claimed in claims 1, 2 and 3, characterised in that the pulse time for metering the lubricant liquid suspension is less than the pulse time for metering the gas or air.

5. Process as claimed in claims 1, 2, 3 and 4, characterised in that the pressure of the lubricant liquid or suspension is less than the pressure of the gas or air and the times of opening of the lubricant valves are co-determined by the measured values of strain gauges which measure the ejection force of the compressed shapes.

6. Apparatus for dotting moulding tools with droplets of liquid or suspended lubricant in the pharmaceutical, food or catalyst field, for performing the process as claimed in claim 1, consisting of a dotting shoe (5) with one or more capillaries (1) and a nozzle or nozzles (4), a gas feed line (2) and lubricant feed line (3), a source (11) of pressurized gas connected to the gas feed line (2) and a pressurized storage container (12) for the lubricant liquid or suspension, connected to the lubricant feed line (3), characterised in that the separate gas feed line (2) and lubricant feed line (3) join up in front of the capillary or capillaries (1) or in front of a capillary-like chamber (6) and both feed lines are provided with fast-acting valves (10a) and (10b) which open and close in an interval of about 50 jl_Sec. to 5 msec. and with pressure regulating valves (13) in and/or between the feed lines (2) and (3) and the valves (10a) and (10b) are connected to an apparatus (15) for periodically controlling them.

7. Apparatus as claimed in claim 6, consisting of a dotting shoe (5) with one or more capillaries (1) in conjunction with nozzles (4), the nozzle openings (4a) of which are arranged on one side or both sides and in a row or in a geometric distribution, adapted to the configuration of the shapes which are to be compressed, over the surface of the dotting shoe, whilst the capillaries (1) are each connected to their own fork or are together connected to a common fork, consisting of a pressurized gas feed line (2) and a lubricant feed line (3) and, if desired, the capillaries are tapered stepwise or conically towards the nozzle outlet openings at the ends.

8. Apparatus as claimed in claim 6, characterised in that the dotting shoe (5) is round in shape and the nozzles (4) are arranged in a geometric distribution over one or several surfaces or edges of the dotting shoe and the nozzles are connected to the feed lines (2) and (3) via capillaries (1) or via a capillary-like chamber (6).

9. Apparatus as claimed in claims 6, 7 and 8, characterised in that the nozzles (4) are arranged on the dotting shoe in such a way that they point to specific zones of the upper die (7), lower die (8) and matrix (9).

10. Apparatus as claimed in claims 6, 7, 8 and 9, characterised in that pneumatically, electromagnetically, piezomechanically or piezoelectrically operated valves (10a) and (10b) are connected to an electronic control system (15) with a proximity switch (14) and, if desired, specific valves (10a) and (10b) are arranged so as to be actuatable in conjunction with specific nozzles (4) independently of other valves in conjunction with other nozzles.

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