MXPA00006585A - Device and procedure for measuring the fluidity of granular means and powder - Google Patents

Abstract

The present invention refers to a device and method for determining the flow speed of granules and powder. It is a procedure that uses in a novel way the flow of multi-particulate systems through an orifice of fixed or variable specific diameter. A specific quantity of powder is placed in the flow control unit, pouring it cascade-like. The poured or pre-densified powder flow is initiated when the orifice is open, by free-fall or by means of a variable amplitude and speed pounding therefore allows fluidizing powders and granules of very different cohesion. The internal pressure of the receptive receptacle is balanced with an outlet orifice. The powder flow is measured in powder mass units per time unit or per pound, constituting a measure of the material fluidity. This device permits also the measurement of the apparent densities of powder, inferring the material fluidity by the calculation of different indexes. The invented technique is of great utility for the pharmaceutical industry and other industries as a method for diagnosing the behavior of materials.

Description

DEVICE AND PROCEDURE FOR MEASURING THE FLUIDITY OF GRANULAR AND POWDER MEDIA BACKGROUND OF THE INVENTION The present invention generally relates to devices for measuring the fluidity of a powder and more particularly refers to a rheometer for powders and granules. The rheometer is an instrument created for the measurement of the Theological or flow characteristics of a powder. powders and granules, as well as other properties of multiparticulate systems such as the apparent density of the powder poured and that of the sedimented powder, and the volumes of the poured powder and the sedimented powder, as well as the indices, coefficients and values of them derive. It is considered useful to study, forecast and control the behavior of powders and granules in the industrial processes where they are handled. Correlating the determinations in this instrument with the behavior during the handling, transport and processing of the powders and granules. The control or verification of the critical variables that determine the static or motion equilibrium of the particles of the solid materials during their processing requires the quantitative measurement of certain parameters related to their properties, among them are the apparent density of the poured powder and of the sedimented powder as well as the flow velocity. The flow velocity of a powder is determined as the amount of material that is capable of flowing from a container, for example a funnel or hopper, at a given time or as the time necessary for a specific amount of powder to flow. Most of the instruments used basically include a hopper or funnel and a balance that allows the registration of the quantity or weight of the material that flows. Some instruments also have a vibrator or fixed speed agitator, as a means to drive dust, while others are more complex and much more expensive. The fluidity is a property of the powders to flow uniformly under the action of gravity and other forces. Its determination is used to set the operating parameters of tableting machines and capsule filling machines as well as for the establishment of quality assurance specifications for the purchase of materials. In order to avoid high coefficients of variation and thus ensure a sufficient uniformity of the product. This determination of the fluidity of the powders allows to measure the effect of the different characteristics of the particles that affect the fluidity. Characteristics such as particle size and shape, the presence of "fines", surface area, density, porosity and electrostatic charges. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of the powder flow control unit of the present invention. Figure 2 is a general diagram of the powder flow control unit and the power unit. Figure 3 is a diagram showing the response surface calculated for the flow rate of microcrystalline cellulose under different conditions of speed and tapping height.

Fig. 4 is a diagram showing the calculated response surface for the flow velocity of lactose dried on rollers under different conditions of speed and knocking height.

DETAILED DESCRIPTION OF THE INVENTION The equipment consists of two fundamental parts, the pulse electromechanical unit and the powder flow control unit. The powder flow control unit is shown in figure 1 and is generally designated by numeral 1. It is a novel device not previously used to measure the powder flow, which consists of two parts, the first is a funnel or hopper with calibrated orifice and connection 2 that serves to contain the dust and the other is a graduated cylinder with ground-in entry 3 adaptable to the funnel, joined by frosted parts, to receive dust that will flow through a frosted hole, of a specific internal diameter of the funnel (eg between 5 and 30 mm), towards the graduated cylinder. The powder flow control unit is separable into two parts, to facilitate the emptying of the powder after the measurement. In a second embodiment of the invention, the same powder flow control unit is in one piece. This second modality is more comfortable and recommendable when working powders or granules of more or less free flow. The first alternative is for powders of certain cohesiveness that are not easy to empty, at the end of the test. Due to the knocking, used as driving force of the powder, it is recommended to use adhesive tape on the frosted parts of the flow unit in two pieces, to avoid adhesion and difficulties to separate it after the measurement.

A fundamental part of the powder flow unit is the air pressure control orifice 4 placed in the upper part of the graduated cylinder 1, which has the function of dislodging the air contained in the specimen, to avoid the rebound effect of dust, by increasing the pressure of the air contained in the graduated cylinder, by filling different levels, over time. The unit also has a closing rod 5. The determination of the density is done by emptying an exactly heavy amount of the powder, through the walls of the hopper or funnel 2, to deposit the disaggregated powder, gently, on the inside of the graduated cylinder 3, in a specific amount of powder, to measure its volume, or in an amount sufficient to occupy a specific volume, for example of 100 ml. An advantage of the presence of the hopper 2 on the graduated cylinder 1 is that it allows a smooth sliding of the powder, which allows a more uniform and constant filling, compared to the direct filling of the test piece used by the equipment currently on the market. A filling alternative is through an extra device that consists of a circular frame with a mesh number 10 stainless steel that serves to deagglomerate the powder when pouring it into the funnel. The density of the sedimented powder would follow the previous process, filling the graduated cylinder to its limit, for example 100 ml / to start after the tapping of the test piece, until the minimum volume of the content is reached, then measuring its volume, to calculate its density. The equipment currently on the market are devices of arrangement and different composition and fixed speed and height or amplitude, the presence of variable heights and speeds, in the powder rheometer, allows greater versatility for the treatment of samples. Referring now to figure two, a drive unit 6 is observed which consists of a mechanical receptacle 7 for the graduated cylinder 3, provided with a receptacle that guarantees its position during the test and a variable speed drive unit (not shown) which transmits the movement through an eccentric (not shown), towards the graduated cylinder 3, generating a lifting and dropping movement from a variable height, regulated by the fall height control system 8 through discs 9 which shorten or increase the fall height of the specimen. To control the time in which a certain amount of dust flows, this device counts, alternatively, with an electronic counter of the falls of the test piece or a digital timer (figure 2). This device also has an ignition control and a momentary stop, in order to start, stop or read at different time intervals, the course of sedimentation or volume reduction that occurs in a powder deposited in the graduated cylinder , during the determination of the density of the sedimented powder. To measure the flow velocity of the powders, it is recommended to place a quantity of powder equivalent to a volume of 100 ml, on the hopper that will have the exit hole closed with a closing rod 5, distributing the powder uniformly, just like It could be done with the equipment currently on the market. However, the powder rheometer has the option of giving some previous blows, with the exit hole closed, in order to settle the powder and make its distribution more uniform, before starting the flow test, which would be an advantage . Once the powder is added, the apparatus starts its operation, while withdrawing the closing rod 5, allowing the flow of the powder, by free fall or by knocking on the graduated cylinder 3, which can be done at different heights between 0 and 25 mm and at different speeds between zero and 80 falls / minute. Other equipment in the market only have a vibrator, at fixed speed and amplitude, which causes difficulties to force the flow of powders, basically serving only for more or less free flow granules. This circumstance makes the rheometer much more widely used for both powders and granules. Another advantage of the rheometer, on the equipment currently on the market would be its simpler construction and therefore a much lower cost, both for acquisition and maintenance. Another advantage of this device is a less violent powder fluidization system than the vibrators of current flow rate measuring equipment, which allows less emission of solid particles into the air, which benefits the operator and the environment surrounding. Examples of the versatility and handling possibilities of this device are Figures 3 and 4 where calculated response surfaces are presented for the flow of two -i excipients for pharmaceutical use, microcrystalline cellulose and lactose dried by rollers.

Claims (11)

1. A device for measuring the fluidity of granular media and powders, characterized in that it comprises a unit and an opening for controlling the internal pressure of the cylinder, the hopper has a means for controlling the flow of the powder. The device according to claim 1, further characterized in that the unit comprises a graduated cylinder and a hopper. 3. The device according to claim 2, further characterized in that the cylinder and the hopper form two separate pieces. 4. The device according to claim 2, further characterized in that the cylinder and the hopper form a single piece. The device according to claim 3 or 4, further characterized in that the flow control device is an orifice of specific diameter that can be variable and because this orifice is located in the hopper. The device according to claim 5, further characterized in that the material flow is effected from a powder bed with varying degrees of compaction, through the powder flow control device 7. The device according to claim 6, further characterized in that it further comprises a drive unit comprising a variable speed motor, a lifting eccentric of the powder flow control unit and a mechanical device for adjusting the fall height of the powder flow control unit . The device according to claim 6, further characterized in that this drive unit is controlled by means of a momentary stop system, a fall counter and a motor speed controller. The device according to claim 8, further characterized in that the graduated cylinder comprises an orifice for balancing the internal pressure of this cylinder. A method for measuring the flow velocity of multiparticulate materials using the device according to claim 1, characterized in that it comprises the steps of: a) placing a quantity of powder in the hopper, 100 ml is recommended, with the orifice outlet blocked by the closing rod. b) using the control unit to give previous blows to accommodate the dust. c) adjust the exit opening of the material exit orifice if it is of variable diameter and open the hole to balance the pressures of the graduated cylinder. d) start the operation of the motor unit by previously adjusting the parameters of height and number of blows or falls per minute, depending on the characteristics of cohesiveness of the multiparticulate material. The use of the device according to claim 1, for measuring the fluidity of a multiparticulate material through a specific fixed or variable diameter orifice and for determining the apparent densities of such materials.