The invention relates to a process for the production of hygienic plastic pallets for use primarily in the food industry, in the pharmaceutical industry, and for transportation by air. During the process low weight pallets with a high load-bearing capacity, having a completely smooth surface are produced, which are easily and perfectly cleanable, washable with 80 °C water, do not absorb other foreign substances, resist fungal growth, and therefore meet the highest hygiene standards. The pallets can be equipped with a microchip, if necessary, thereby the pallet and the load placed on it can be easily tracked.

In addition to wooden pallets, the use of transport pallets made of plastic, offering many more advantageous properties, is also gaining ground in the field of logistics and transportation.

Pallets made of plastic are much more durable, lighter, free from wood-destroying insects, and have a high load-bearing capacity. A wide variety of pallets is known in the prior art, with different sizes, structures, and leg designs.

European Patent Application E06726910 relates to a polymeric load carrying apparatus comprising an outer shell composition and a filled inner core composition within the outer shell composition, wherein the outer shell composition comprises less than 10% filler by weight, and the inner core composition comprises more than 15% filler by weight.

European Patent Application E07008185 relates to a dunnage platform made from an expanded polystyrene core, and a chemical combination process is used to chemically combine a portion of the core proximal to its surface with high impact polymer.

European Patent Application E03254634 relates to a dunnage platform and a method for manufacturing the same, wherein the legs of the pallet are filled with expanded

polystyrene.

Patent Application WO 2007098566 discloses a pallet having a plastic core and at least one plastic coating layer. The coating layer is formed by reactive injection moulding using approximately 60 parts by weight liquid isocyanate component of a polyurethane, and approximately 100 parts per weight liquid polyol component of a polyurethane.

Patent US5,921,189 discloses a tubular pallet apparatus extruded or pultruded in plastic or resin.

One piece, integrated pallets are produced from recycled plastic in various configurations.

Patent Application US20090266276 relates to a method for producing transport pallets from a mixture of recycled plastics with optional addition of fibrous material.

The mixture is portioned in an extruder, liquefied into a paste by heating, and introduced via the conveying screw of the extruder into a closed mould for hardening. The solution according to the invention includes a storage device having an adjustable volume, in which the liquefied mixture can be intermediately stored while the mould is changed.

International Patent Application WO/ 1997/025250 relates to a lightweight plastic pallet made of a thermoplastic material. In the solution according to the invention the pallet is fabricated by thermoforming an extruded plastic parison. The thermoplastic is selected from polyolefins, PVC, ABS, styrene plastics (PA), polyamides (PA) and polycarbonates (PC). The pallet may have a multilayer structure comprising at least one foamed plastic layer.

The commercially available plastic pallets are usually produced by injection moulding, casting or vacuum suction, the structures formed by these processes are typically lattice, beam, or hollow structures. The pallets thus formed are impossible or very difficult to handle hygienically.

The tracking of products is becoming widespread in the field of logistics and

transportation. A known solution is an ultra-high frequency (UHF) or high frequency (HF) RFID tag placed on the packaging, box, or pallet of the products. The tag is typically placed on the surface, preferably the bottom surface of the pallets. A disadvantage of this solution is that the device used for tracking can be easily damaged during loading, transportation, or can be easily removed from a visible surface.

The aim of the invention is to produce plastic pallets that have a high load-bearing capacity, are light, bounded by a completely closed smooth surface, with the outer surface having a non-hollow structure, and therefore are easily and maximally cleanable, and can be quickly and economically produced.

A further aim of the invention is to place safely inside the pallets, in a practically nonremovable manner, a microchip used for identifying and tracking the products stored or transported on the pallet.

The idea of the invention comes from the recognition that the food industry and the pharmaceutical industry need pallets that can be simply sterilized, and that is impossible or very difficult to do in the case of wooden pallets or plastic pallets having a lattice structure. The injection moulded pallets produced by the current conventional technology are hollow, have a lattice structure, are complicated to clean, have a high tare weight, and accordingly, are expensive.

Thus the invention relates to a process for the production of hygienic plastic pallets for use primarily in the food industry and the pharmaceutical industry, or in fields where having a low tare weight is important, primarily in the field of transportation by air. The shell of the pallet is produced by extrusion blow moulding in such a way that compressed air is blown into a plastic parison formed from plastic granules melted by the feed screw of the extruder, which inflates the ductile plastic into the shape of a mould consisting of two halves, with the two halves of the mould closed. One half of the mould gives the shape of the upper part of the shell, the other half gives the shape of the lower part of the shell. The lower part is formed integrally with the legs. The shell has at least one bore.

After the solidification of the shell enclosed by the two halves of the mould, the one piece, integrated shell having a hollow interior is removed from the mould, then the dispensing head of a dispensing device, e.g. a foam sprayer is connected to the bore of the shell, and through it the whole shell is filled with a filler material.

The pallet produced by the process according to the invention has a shell bounded by a smooth, continuous, coherent, closed surface, with integrated legs, which shell is non- hollow, filled completely with a filler material.

During the process according to the invention first the shell is produced, then the shell is filled with a filler material.

The hollow pallet form, the shell is produced by extrusion blow moulding from plastic granules or recycled plastic. The feed screw of the extruder melts the plastic granules, which become fluid during the operation of the extruder, then the molten granules are extruded into a parison. The still warm, ductile plastic parison, vertically elongated in a curtain-like manner, is inflated with compressed air into the shape of a mould consisting of two halves by blowing compressed air into the plastic parison through blowing pins, with the two halves of the mould closed. Then the ductile plastic takes the shape of the mould. The "burrs" formed at the closing of the mould are removed from the product and recycled.

One half of the mould gives the shape of the upper part of the shell, the other half gives the shape of the lower part of the shell with integrated legs, preferably 9 legs. The half of the shaping mould producing the lower part of the shell is formed in such a way that there are circular bores on the legs.

After the solidification of the shell enclosed by the two halves of the mould, the one piece, integrated shell having a hollow interior is removed from the mould.

The dispensing heads of a dispensing device are automatically connected to each bore on the legs of the continuous hollow shell removed from the mould, then the hollow interior of the shell is filled with a filler material through the dispensing heads. The filler material fills the hollow interior of the shell completely, then solidifies. The filler material overflowing at the bores is removed.

A microchip can be placed inside either by placing it in the hollow shell before it is filled with the filler material, or by filling it into the interior of the pallet together with the filler material.

The solidity, and thereby the load-bearing capacity of the surface of the pallet produced by the process according to the invention can be further increased, if a plastic-based glass fibre, plastic fibre or fabric fibre synthetic resin layer is applied to the surface of the pallet by spraying or dipping. Then a pallet having an extremely high mechanical, static load- bearing capacity is obtained.

The plastic granules used for producing the shell of the pallet are preferably high density polyethylene (HDPE), polybutane, polypropylene, or polystyrene. The filler material is preferably a composite, polyurethane (PUR-foam), or geopolymer.

A common characteristic of the filler materials is that they can be filled into the shell of the pallet in a fluid/ductile form, then they solidify, filling the space available in the hollow interior completely. The filler material is selected according to the intended use of the pallet.

With the process according to the invention the wall thickness of the hollow shell can be adjusted at will to the load-bearing capacity, mechanical load.

The pallets produced by the process according to the invention comprise a shell having a completely smooth surface, which is filled uniformly with a filler material.

The pallets produced by the process according to the invention will now be described by way of the following examples:

Example 1

The shell of the pallet is made of polybutane by extrusion blow moulding, the filler material is polyurethane.

The weight of the produced pallet is max. 4 kg.

Example 2

The shell of the pallet is made of polypropylene by extrusion blow moulding, the filler material is polyurethane. The produced pallet is dipped in glass/fabric fibre synthetic resin, or a synthetic resin layer is applied by a spray gun.

The load-bearing capacity of the produced pallet is higher than that of a pallet without a fabric fibre synthetic resin layer.

Example 3

The shell of the pallet is made of HPDE by extrusion blow moulding, the filler material is geopolymer. The weight of the produced pallet is max. 8 kg.

Example 4

The shell of the pallet is made of polyethylene (PE) by extrusion blow moulding, the filler material is polyurethane.

The weight of the produced pallet is max. 4 kg.

A further advantage of the process according to the invention is that pallets adjusted to the needs can be produced, taking into account the field of use.