Method for enveloping pellets of foamed poly-styrene suitable for producing lightened manufactured articles of cement

Start of patent period: 1980 06 15 Longest possible duration:

© Issued on: 1981 01 26 © Inventor: CATTANEO MARIO

ALMENNO S · SALVATORE ITALY © Dependency: '

AT 360 762 © Pamphlets considered as delimiting from the state of the art:

AT-PS 226947 DE-AS1704531 US-PS 3239878 US-PS3261056

US-PS 3645505 US-PS 3679788

- 2 No. 360762

The invention relates to a method for wrapping foamed polystyrene pellets

Preparation of molded pieces, wherein the pellets are mixed with water, synthetic resin and filler and then the mixture is dried.

For the production of lightweight and good heat and sound insulating fittings, it is known to use a filling material, which is gebüdet by foamed pellets, which are coated with synthetic resin. A known method for coating such pellets is to introduce them together with epoxy resins and cement or lime in a vessel provided with a stirrer and to mix. However, by doing so, a wet product is obtained insofar as the resin surrounding the pellets is not polymerized, whereby they tend to form lumps. By lumping the pellets, however, the quality of the fittings is deteriorated.

It is also known to use adhesives instead of the epoxy resins. However, since many common adhesives are water-soluble, the polystyrene-coated pellets come in contact with water during the manufacture of the fittings. As a result, the sheath is peeled off, whereby a quality deterioration occurs. It has also been found that cement or lime contained in a cladding reacts chemically with water and other chemical products used, which is why pellets coated in this way do not correspond as fillers for shaped articles, since the chemical reactions increase the resistance of the finished shaped articles is severely impaired.

According to all hitherto known wrapping method, a predetermined amount of polystyrene pellets, resin and cement or lime are introduced into the processing vessel, whereupon the entire change is processed and then the container is emptied again. However, this method is disadvantageous in that it is not continuous. This manifests itself particularly when it is performed directly at the processing site, since the subsequent plants operate at a much faster rate as well as continuously, which may cause undesirable business interruptions. Another disadvantage of known methods is that no drying of the envelope takes place by polymerization, which is why a use of the pellets is not ensured even after a longer intermediate storage.

The invention is therefore an object of the invention to provide a method which is fast, continuous and economical feasible and by which the deficiencies inherent in the prior art are avoided.

This is inventively achieved in that in a conventional manner, a continuous stream is formed on foamed pellets, the water and resin is metered, whereupon the so-called pellet stream an inert filler is added and finally the pellet stream delayed and the pellets in the deceleration zone be dried under polymerization.

Foamed vinyl resins and dispersants or thickening agents are preferably added to the continuous stream of foamed pellets in a manner known per se in the water.

According to a preferred embodiment, per m³ Pellets of foamed polystyrene a mixture of the following composition used: 10 1 of water, 2 kg of polyvinyl acetate with a high degree of polymerization, 20 to 40 g of thickening agent (methyl cellulose) and 20 to 40 g of inert fillers, such as diatomaceous earth, steatite, dolomite, especially brownspar.

A preferred apparatus for carrying out the method according to the invention consists of containers for the individual components as well as a mixer producing a continuous stream, in which after the filling points of the components a drying zone and a storage zone, which causes a delay of the material flow in the heating and polymerization area, are provided ,

The invention is explained in more detail below with reference to embodiments of devices according to the invention shown in the drawings. 2 shows a part of the device according to FIG. 1, FIG. 3 shows a partial view of an input device, and FIG. 4 shows a modified form of embodiment compared to FIG.

The device according to Fig.l contains a first container -1- for foamed polystyrene pellets, which are to be wrapped, and two further containers -2 and 2'- for a mixture of water and synthetic resins. Due to the double arrangement of these second containers -2, 2'- a continuous operation is ensured even if one of the two containers -2, 2 '- is empty. If eg

- 3 - No. 360762 the container - 2-- is empty, a control tap -5-- in the discharge line from the containers -2, 2'- switched and is during the refilling of the container --2-- from the container - 2 '- from loaded. By means of a pump --5 '-, which is likewise arranged in the line leading from the containers -2, 2' -, the resinous liquid is sprayed. Finally, there is a third container

--3-- in which there is an inert filler, which is also used for the enclosure.

The foamed polystyrene pellets, the water / resin mixture and the inert filler are fed to a mixer - 7-- at locations Α, B and C. The mixer --7-- consists of a tubular container in which two winged waves --8--, which serve to 10 promote the filled material, are moved in opposite directions. In the area which is downstream of the filling points Α, B, C, there is a drying zone -10-. At the outlet of the mixer -7- a storage space --11-- is provided. Since the pellets are accumulated in this, they remain a little longer in the drying zone, from which the vapors are removed by means of a suction line.

The introduction of the pellets at the point A can take place in free fall or by means of a conveyor 15, for example a screw 4, which is drivable for variable-speed metering.

Due to the counter-rotation of the shafts -8-, which are also driven at variable speed by means of transmission disks, the pellets are shifted to the right and thereby reach the area below the point B, where by means of the pump. 20 the addition of water and resin takes place. This addition takes place via a nozzle tube running transversely to the feed direction of the pellets, whereby a uniform moistening is achieved. This distributor device, which is provided with a metering cock, can have any design and can cause a sprinkling or pollination.

The thus moistened pellets are guided at their further feed in the area below the 25 point C, where by means of a metering device -6- the addition of the inert filler takes place. This metering device --6--, which is shown enlarged in Figure 3, consists of a tubular container --14-, in which a screw is located and whose bottom is formed with a transverse, chute-shaped slot -12-. The worm is driven by a controllable reducer --13--. The pellets, which are to be wrapped in the container, then enter the heating zone, in which they are completely dried, so that the starting product is completely dry. The drying in the heating zone -10- takes place by means of a hot air stream -15--, with which the double jacket of the mixer is heated, as well as by infrared radiator. The use of infrared rays is required for rapid polymerization of the resins. The product moved to the outlet --16-- then reaches a storage zone -11-- where it remains longer and from which vapors are sucked upwards.

FIG. 4 shows a device modified with respect to the embodiment according to FIG. The same or similar parts are provided with the same reference numerals. The difference with respect to the device according to Fig.l is that the first portion of the mixer consists of a vertical part formed by a tubular tower, in the interior of which at 40 points A and B the polystyrene Pellets and the mixture of water and resin can be entered. These materials are by means of a winged and via a gear --19-- operated shaft --18- in the tower -17- up u.zw. to a horizontal area -7'-, transported. The inert filler is added at point C in the same way as described with reference to FIG._4S Hot air flow -15'- is heated.

The invention also relates to a formulation for the method according to the invention. It has already been mentioned that the components used for coating consist of a mixture of resin and water and an inert filler. Instead of the expensive epoxy resins used according to the known methods, cheaper vinyl resins are used, to which dispersants are added to favor the dispersion of the resin 50 in the water and thickening agents. A good result is achieved if per m³ Volume of foamed polystyrene pellets a mixture of water and resin in the following

Composition is used:

- 4 No. 360762

1 water, 2 kg polyvinyl acetate with a high degree of polymerization; 20 to 40 g thickener, for example methyl cellulose (ie between 0.1 and 0.2% based on the amount of resin); 20 to 40 g (ie 0.1 to 0.2% based on the amount of resin) components as an active ingredient for inhibiting fluidity (roughening of the polystyrene pellets) and for weight gain without affecting the products used (inert fillers), such as diatomaceous earth (dust fine), steatite (dust fine), dolomite, especially brown feldspar (dust fine).

An experiment has shown that a molded piece with pellets coated according to the above composition has a considerably increased pressure and bending resistance.

Although the process according to the above formulation gives excellent results, it is also suitable for other resins, for example for epoxy resins, since the material obtained after completion of the process according to the invention is formed by coated, already dry pellets which are not prone to disadvantageous formation of lumps ,