Plastic and nonmetallic article shaping or treating: processes – Formation of solid particulate material directly from molten... – By vibration or agitation
Patent
1994-06-13
1995-12-05
Theisen, Mary Lynn
Plastic and nonmetallic article shaping or treating: processes
Formation of solid particulate material directly from molten...
By vibration or agitation
264 14, 425 6, 425 10, B29B 910
Patent
active
054726484
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention refers to a method for producing spherical alginate pellets from droplets of an alginate solution delivered from a nozzle, by consolidating the droplets by dropping them into an ion solution, preferably a calcium ion solution, and subsequently washing the alginate pellets removed from the ion solution. The invention further refers to an apparatus for producing spherical alginate pellets from droplets of an alginate solution, comprising a reservoir vessel for the alginate solution; at least one nozzle to which alginate solution can be fed as applicable via a feed line; a collection device, containing an ion solution, for the droplets falling from the nozzle; and at least one device for removing the alginate pellets from the collection device.
Alginate pellets are required, for example, as thickening agents in emulsions, in the cosmetics and food industries, for adhesives and finishes, or as base substances for elastic molding compounds in dentistry, for example. In use, however, the alginate pellets are either completely hardened or only surface-hardened.
Surface-hardened alginate pellets are required, for example, in the cosmetics industry, while completely hardened alginate pellets are required, for example, as supports for enzymes. In order for alginate pellets to be usable to the desired extent, they must be sufficiently pourable and have a narrow particle size spectrum. In particular, a uniform geometry (i.e. a spherical shape) should also be present.
2. Description of the Prior Art FR-A 2 645 439 has disclosed a method for producing spherical alginate pellets intended for the cosmetics industry, according to which an alginate solution is fed to a nozzle from which the alginate solution is delivered in droplet form, subsequently falling into a calcium ion solution. Located in the calcium ion solution is an endless-loop conveyor belt by which the droplets are collected and then transported out of the calcium ion solution.
Since there is no assurance that the droplets are surface-hardened to a sufficient extent as they fall through the calcium ion solution, the alginate pellets removed from the calcium ion solution by the conveyor belt are often flattened. Since the droplets form simply by dripping alginate solution out of the nozzle, a desirable narrow particle size spectrum also cannot be achieved.
SUMMARY OF THE INVENTION
The underlying problem of the present invention is to develop a method and an apparatus of the aforesaid type for producing spherical alginate pellets in such a way that, among other effects, alginate pellets with a spherical geometry and a narrow particle size spectrum are obtained, and that hardening of the alginate pellets themselves can be adjusted in a controlled manner.
According to the invention, the problem is solved in terms of the method by the fact that the alginate solution is formed into drops by vibratory excitation, and that until they achieve the desired consolidation, the droplets are initially, until surface hardening occurs, substantially free to move in the ion solution. In this connection an "ion solution" is understood to mean an ionic solution whose metal ions combine with alginate to form a poorly soluble compound. Preferably the ion solution can be a calcium ion solution.
In contrast to the prior art, the alginate solution is not dripped, but rather formed into drops by the nozzle, which itself can be excited to vibrate. This is not, however, a mandatory feature. Instead vibratory excitation can also occur by exciting the alginate solution in a reservoir container or by acoustic irradiation of the alginate solution itself.
Regardless of the kind of vibratory excitation, however, it is essential that a constant frequency act on the alginate solution, with rotationally symmetrical constrictions being generated and reinforced in a stream of liquid leaving the nozzle, so that uniform disintegration into droplets, called "dropletization," occurs. This ensures that the droplets have identical o
REFERENCES:
patent: 4795328 (1989-03-01), Takano
patent: 5021201 (1991-06-01), Eguchi et al.
Alisch Gerhard
Brandau Egbert
Brauneis Edwin
Iffland Norbert
Pirstadt Bernd
Nukem GmbH
Theisen Mary Lynn
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