Heat-weldable cellular material

Beginning of the patent period: 15.Feber 1966.

The invention relates to a process for the production of moldings from particles of a foamed plastic, which are brought to their softening temperature and connected in a mold under pressure, wherein from granules, flakes od. Ähnl. Cellular structure particles, shaped articles such as blocks, plates, films, tapes or the like. getting produced.

There is already known a method in which wastes of foamed polystyrene crushed, compressed and treated while maintaining the pressure with steam. In this case, the polystyrene particles continue to expand due to the foaming agent still present in them from their preparation in an unknown excess under mutual welding. The end products of this process have sites of different density and are therefore not usable in all cases, especially for insulation purposes.

The invention is based on the finding that the immediate cause for the different density of the end products is located in different levels of foaming agent in the individual particles.

A complete remedy of this deficiency according to the invention is achieved by carrying out the process according to the invention particles of a completely foamed plastic of

Exposure to pressure and heat.

The inventive method differs from the previously known method for joining particles of foamed plastics by expansion, for example in a closed form, characterized in that in the previously known method, the pressure required for the compound from the Verflüchti20 movement of the propellant contained in the particles, while he acts on the particles in the present case from the outside.

In compliance with the measure according to the invention, it is possible to produce products of consistently the same density, which have a perfect quality especially as an insulating agent. They are also characterized by an improved dimensional stability, since they are not subject to any subsequent drift and can be deformed in this way.

The starting material particles may be any cell-structured thermoplastic material which may be made by any method known per se, but which has been fully expanded and which does not contain any unreacted blowing agent. The particles may be present as waste materials from other manufacturing processes. It is also possible to use particles 30 of different shapes in a mixture. It is also possible fillers such as cork waste, mineral particles or the like. add.

The combination of particles with cellular structure, such as granules, which is only partially expanded, is known to occur only when the granules have been ripened for a while. This maturing time must not be undercut if a still usable homogeneity of the final product is to be achieved. But it must not be exceeded, so that the propellant capacity of the granules not ver2

No. 249989 is reduced, which generates the required pressure during the welding process to the finished end product. The

The need to determine and maintain this maturity time is a complication of the older one

Manufacturing process and increases the investment costs, because thereby the arrangement of their own ripening container is necessary. The particles used in the process according to the invention, however, are already fully expanded in the initial state and can therefore be used both immediately after their expansion and after transport or after storage of any duration.

The pressing pressure may be generated in any known manner mechanically, pneumatically, hydraulically or otherwise. In particular, it is done using a mold whose Deckelkolben10 is arranged slidably like. The required pressure can also be generated in a closed form by pneumatic compression of the contents.

The heating required to bring the material up to its softening temperature can be achieved in any manner known per se, for example by means of steam, infrared radiation, high frequency or the like. be achieved.

The following are some examples of the implementation of the method according to the invention using the various aforementioned pressure medium listed.

Example 1: A mold with perforated walls and a lid sliding between them as a piston is filled with polystyrene beads which have been completely foamed in free air. The lid is then depressed until the volume of trapped beads is substantially reduced, for example by 20-30%. This is then heated by blowing steam under pressure through the openings of the mold. The strongly compressed particles soften and fuse together to form a homogeneous mass which is shaped.

Example 2: In a mold with perforated walls and a hinged lid, polystyrene was poured in, which was completely foamed in an earlier operation.

In the form is also an inflatable cushion. Once the mold is filled, the lid is locked and the pad inflated with compressed air. It thereby reduces the volume originally occupied by the foamed plastic wastes in the mold. The mold is then heated with an infrared radiator. The heating causes a welding of the particles with each other. During molding, a molded article having a homogeneous structure is obtained.

Example 3: A preferably closed mold is used which has an opening which is connected to a reservoir filled with spherical granules of fully foamed polystyrene. The granules are pressed by compressed air under such pressure in the mold that its density is significantly increased in the compressed state. The injection opening is then closed and the mold is heated by immersion in boiling water. In this case, the granules welded together and there is a homogeneous molded body, which has a cell structure. Example 4: Fully expanded beads of polystyrene are fed to a calender with a nip of 20 mm. The beads are compressed and heated by the rollers in a single operation. Through the simultaneous application of heat and pressure, the beads weld together to form a homogeneous flexible mat.

Example 5: Cladding parts with cellular structure for heat insulating purposes are manufactured as follows: A tubular shape is used in which a piston is movably arranged. To the one heart of the

Form is a hopper connected. The other end of the same can be closed by a suitable lid. After this lid is placed, the mold is filled through the hopper with granules, which consists of fully foamed plastic, such as polystyrene. The

Form is then heated with steam while its contents are compressed by the piston to about 50% of its original volume. The lid is then opened and the resulting tube, which has cell structure, is expelled from the mold. The tube is then divided into two half-shells which are suitable for installation for insulation purposes.

Example 6: The procedure is as in Example 5, worked, but with the difference that the

Compression of the filled plastic in the mold only partly by the movement of the piston and the other part, preferably during a subsequent piston stroke, by the braking action of the frictional forces between the plastic and the wall of a mouthpiece takes place. In this way, an endless shaped body is produced by means of discontinuously acting pressure forces.

Example 7: Beads of fully foamed polystyrene are conveyed through an extruder ge 55 are set at the portions of the pumping chamber to such temperatures that the material is brought to its softening temperature.

Nr.249989

When pressed, the beads are welded under the action of the pressing pressure and the heating to a continuous strand of fully foamed polystyrene.

The examples focus on the processing of foamed polystyrene. It is understood, however, that the process according to the invention can generally be applied to all thermoplastic foamed plastics, the process conditions and in particular the heating temperature in each case depending on the type of plastic to be processed and of course chosen by the skilled person so that a compound obtained by thermal welding. The pressing pressure is chosen as a function of the density which is to be produced

Wishes to give moldings.