DE944458C - Method and device for producing molded articles from organic, thermoplastic or thermosetting plastics, in particular medical and dental medical molded articles - Google Patents

Description

Method and device for the production of moldings from organic, thermoplastic or thermosetting plastics, especially medical and dental moldings The invention relates to manufacturing of molded bodies made of organic, thermoplastic or thermosetting plastics, in particular of medical and dental medical molded bodies. In particular the latter moldings made of synthetic resins are subject to particularly high demands on mechanical strength, dimensional stability, physiological compatibility and exact fit. So far, production has mainly been carried out by polymerisation of pasted powder-liquid mixtures in plaster molds, d. H. by polymerizing a plastically kneadable mixture of polymer particles with monomeric polymerizable Liquids.

Furthermore, a method is known, according to which such shaped bodies by thermoplastic deformation of plastic sheets between the male and female molds will. Although this method provides fittings with an exact fit, it requires however, the production of a correspondingly well-fitting patrix, whereby the strength the plate to be deformed must be given special consideration.

A procedure that uses instead of the patrix seems simpler Liquid or air pressure is being used. However, there is a liability to this method A number of disadvantages which have hindered its use in practice so far stood. Because of the need to keep the molding device pressure-tight, the liquid must or air column upwards tightly against the punch guided by means of a spindle and sealed down against the die by means of a membrane. In the Practice one works z. B. with a pillow of water. If you use the one to be deformed Plastic plate itself as a membrane, this must be in order to achieve the sealing effect firmly clamped. During the molding process, the plastic sheet cannot give in as a whole, so that a considerable deformation at the points of greatest Ver Reduction in cross section can occur. If, on the other hand, the liquid or air column through a separate membrane, e.g. B. by a rubber cushion, so the membrane or the cushion cover prevents an exact reproduction of the smallest bumps. The membrane or the cushion cover can withstand the pressure of several atmospheres sure to be able to withstand, not to be made wafer-thin, which makes the fine The contours of the die model are reproduced only in a blurred manner.

The procedure described below shows one way around the complicated To bypass the embossing process using the die and the patrix and, on the other hand, the one with the Forming method using a die and liquid or air pressure associated inadequacies turn off. It allows the use of plastic sheets as a starting material for the production of such moldings using a very simple device; at the same time, the molded bodies produced in this way show a very precise reproduction even the finest die profiles.

The process for producing moldings from organic, thermoplastic or thermosetting plastics, in particular of medical or dental medicine Moldings, by hot pressing in a mold, according to the invention, that the pressure on the sheet to be deformed and against the molding die Plastic to be pressed by powdery substances, which may be metal powder is added, is transferred. Compared to the known method in which means Liquid or air pressure is deformed, there are considerable advantages, since there is no need to pay attention to print density with the same perfection. Between the plastic plate to be deformed and the pressure-transmitting medium no separating membrane, which - depending on its thickness and elasticity. the replication of the finest depressions is made difficult or impossible. That under the pressure Powder standing on a stamp acts like an extraordinarily well-fitting patrix and ensures the embossing of the thermoplastically deformable plastic sheet also in the finest bumps, e.g. B. in mucosal structures or in fissures of the teeth. If you open the mold after it has been embossed and after it has cooled down, you can see at Choice of a suitable powder material the counterpart to the underlying impression form, z. B. in the manufacture of a dental prosthesis, the hard plaster model, in extraordinary faithful reproduction. The method according to the invention makes a tight clamping the plastic plate to be deformed superfluous. It is sufficient if z. B. by hanging up or sticking a paper, fabric or film ring on the edge of the plastic blank it is ensured that no powder penetrates under the plastic plate. The free Placed plastic plate can give way as a whole when pressure begins, see above that excessive elongation and an associated reduction in cross-section in the last printing phase is avoided.

According to the method according to the invention, for. B. plastics Acrylic and methacrylic compounds, polyvinyl chloride with and without added plasticizers and other thermally deformable plastics.

Figs. I and 2 serve to explain the embodiment in more detail.

On the bottom of the guide cylinder 1 is the base 2, which is used to hold the plaster model 3. over the plaster model is the deformation temperature heated plastic plate 4 placed, which for better sealing against the overlying Powder column 5 can be covered with a fabric ring6. As a stamp slides in the guide cylinder I the press cylinder 7. With the help of a press, e.g. B. a screw press 8 is the Cylinder 7 pressed onto the powder layer, which in turn is the plastic plate 4 embossed on or in the plaster model. For better handling, the bottom part of the Guide cylinder I be designed to be removable.

The base 2, which receives the shaping, is expediently beveled in such a way that that the protruding over the mold edges of the plastic molding on the base slide along and thus create a seal against the powder that pushes in. in the The fabric ring placed on the plastic plate before the embossing has the same effect 6th

Diagram 2 shows the equipment after the end of the embossing process.

For example, the procedure can be carried out in the following ways: The preform is cast from hard plaster of paris and dried well on the bottom of a Brought metal cylinder. The model is heated to the deformation temperature Plastic plate, which is adapted to the diameter of the cylinder, placed. on powder is placed on the plastic plate up to a layer height of 5 to 10 cm. This can either be done outside the apparatus, e.g. B. in the embossing cylinder, up to I60 I800 heated or cold introduced and in the cylinder up to the required deformation temperature the plastic plate are heated. After plasticization is achieved, with a metal stamp, which the cylinder serves as a guide, e.g. B. by means of a screw press, made the embossing. The plastic plate covers the plaster mold like a skin. In some cases it is necessary to penetrate from powder under the plastic plate to prevent a cloth or similar ring (such as described above) over the plate, which is flanged up at the edges.

According to a further embodiment of the method according to the invention such plastics can be used, which only under the influence of for the deformation required heat or at a temperature above that experience their final hardening. For example, a molded body made from prepolymerized Allyl resins deformed in the sense of the process described and then through Heating to about 120 ° can be hardened.

The pressure-transmitting powder has also proven to be advantageous to add such a proportion of metal powder that the thermal conductivity of the mixture increased or its inductive or dielectric heating is made possible.

While the cylinder created during the deformation process expands Can easily lift powder from the plastic molding, it adheres relatively firmly in the guide cylinder. To make it easier to remove the powder body, it has proven to be useful between the powder layer and the guide cylinder to arrange a sleeve that slides easily in the latter, so that the sleeve is in the pressed powder mass can be easily pulled out of the guide cylinder.

The method according to the invention can also be applied to manufacturing Use other than dental moldings, insofar as it is also finest on reproduction Profiling matters. Examples include: letters, dough, Soap and chocolate molds, pictures, characters and advertising symbols, reliefs and relief maps.

In addition to plaster, metals, z. B. highly polished steel, gunmetal, soft metals such. B. lead, glass, filled and unfilled plastics can be used.

Claims (2)

PATENT CLAIMS: I. Method for 7 manufacturing molded bodies from organic, thermoplastic or thermosetting plastics, in particular from medical or dental molded bodies, by hot pressing in one Shape, characterized in that the pressure on the sheet-like to be deformed and plastics to be pressed against the molding die by powdery substances, to which a metal powder is optionally added, is transferred. 2. Apparatus for performing the method according to claim I, characterized characterized in that one of the powdery substances absorbing and at the same time the guide of the plunger serving sleeve in a surrounding guide cylinder Is slidably arranged. Cited publications: German Patent No. 32 666; french Patent No. 584858; U.S. Patent No. 2,333,143.