Method and plant for the manufacture of container preforms

The present application claims the benefit of priority of German Application No. 102010002054.0, filed Feb. 17, 2010. The entire text or the priority application is incorporated herein by reference in its entirety.

The disclosure relates to a method as well as to a plant for manufacturing container performs, such as in beverage bottling operations.

The manufacture of container preforms from recycled plastic material, in particular PET flakes, requires a very heat-intensive process. Moreover, the provision of recycled plastic material, in particular PET flakes, requires enormous heat supply to decontaminate the plastic material and optionally carry out an SSP treatment for processing. The SSP treatment is a standard process known in the field of PET plastic technology and means that an influence on the molecular chain (extension, shortening or maintenance) is performed (solid state polycondensation), i.e. a heat treatment over a certain period. Decontamination and SSP treatment can be carried out in a recycling machine in one reactor or in separate reactors, as is disclosed in DE 10 2005 013 701 A1. Decontamination is performed e.g. with hot gas, for example air or nitrogen, where heat is supplied via different heat transfer media until temperatures of, for example, between 100° C. and 180° C. are reached. The SSP treatment is carried out e.g. under subatmospheric pressure conditions, where temperatures up to at most the melting temperature of the plastic material of 150° C. to 250° C., preferably between 170° C. and 210° C. are set. The SSP treatment can run in an inert gas atmosphere, e.g. using nitrogen or carbon dioxide. In the recycling machine known from DE 10 2005 013 701 A1, after the SSP treatment, the recycled plastic material is cooled in a cooling reactor to a temperature between 50° C. and 100° C., preferably even to below 70° C., i.e. to a temperature below the second order transition temperature of the plastic material. For cooling, a cooling coil, a vibratory hopper conveyor, or a fluidized reactor, or another cooling device can be used, for example by supplying ambient air. Although at least the SSP treatment can be carried out in batches, by a multi-part SSP reactor arrangement, a quasi continuous discharge of recycled plastic material can be achieved. The recycled plastic material cooled to below 65° C. is then fed to a preform machine, or it is optionally previously completely cooled to room temperature. In the preform machine, the recycled plastic material then must be reheated to be able to produce the preforms.

One aspect of the disclosure is to provide a method and a plant for the manufacture of container preforms from recycled plastic material which permit at least an improved thermal balance in view of a considerable saving of primary thermal energy.

As at least a major portion of the introduced and stored heat required by the process for the provision of the recycled plastic material is transferred into the preform machine, the heat demand in the preform machine is significantly reduced, so that the thermal energy balance can be considerably improved in the manufacture of container preforms from recycled plastic material, supported, as an accompanying effect, by the elimination of the expenditure of time and the energy demand for cooling the recycled plastic material before it is transferred to the preform machine.

The connection of the recycling machine with the preform machine ensures in the plant that the recycled plastic material does no longer have to be force-cooled but is transferred into the preform machine such that at least a major portion of the heat introduced into the recycling machine during the heat treatment of the plastic material is transferred to the preform machine. Thus, the heat requirement of the preform machine is reduced and an advantage is achieved for the device in that a cooling unit for forced cooling of the recycled plastic material can be omitted.

In a functional method variant, the recycled plastic material, which is preferably provided predominantly in the form of flakes e.g. of PET, is transferred into the preform machine either directly or via an intermediate storage and in absence of atmospheric oxygen at a temperature that is in any case above the glass transition temperature of about 65° C. to 70° C. In this manner, heat is saved in the preform machine which would be required initially to bring recycled cold plastic material to this temperature again. Moreover, the duration of the process is shortened as forced cooling is eliminated. The at least substantial absence of oxygen in the transfer of the recycled plastic material into the preform machine excludes influences on the recycled plastic material that affect processing quality.

In a particularly functional way, the recycled plastic material is transferred into the preform machine at a temperature of at least about 180° C., so that for reaching the processing temperature of the recycled plastic material in the preform machine, now only low heat supply is required.

In a functional plant variant, the preform machine comprises at least one extruder supplied with the recycled plastic material and injection molds in which the preforms are manufactured. The recycling machine, which is combined in a block with the preform machine directly or via the intermediate storage, comprises at least one reactor, preferably at least one decontamination reactor, and a downstream SSP reactor, or at least one reactor in which decontamination and a further treatment, e.g. an SSP treatment, are carried out together. To achieve a quasi continuous discharge of recycled plastic material, it can be even functional to provide multi-part decontamination and SSP reactors, or several reactors operated in an alternating and/or overlapping manner, or operated in combination. Furthermore, several preform machines can be fed with still hot recycled plastic material from the recycling machine simultaneously or in an alternating manner.

In a functional plant variant, a reactor, e.g. the decontamination reactor or the SSP reactor, and the extruder are combined in a block directly or via the at least one intermediate storage, preferably a silo. The combination in a block can preferably be heat-insulated and/or embodied such that the transfer of the recycled plastic material is effected at least substantially without the presence of oxygen. The absence of oxygen permits to carry out the transfer with a maximum portion of the heat introduced into the recycling machine without compromising the processing quality of the hot plastic material by the transfer.

In a functional plant variant, the combined block can even be connected to a heat supply which contributes to the increase or maintenance of the temperature of the plastic material during transfer and is possibly also fed by heat supply means of the recycling machine and/or the preform machine.

It is furthermore advantageous to provide a return means for discharged defective preforms between the preform machine and the recycling machine. In this manner, the defective preform discharge can be directly returned into the recycling machine without having to be intermediately stored, cooled and later reheated.

Furthermore, in view of an advantageous thermal energy balance, it can be advantageous to combine the preform machine directly in a block, preferably via a preform heat treatment section for adjusting a certain temperature profile in each preform, with a blow-molding machine. In this manner, heat from the preform machine can also be transferred into the heat treatment section or directly into the blow-molding machine.

Here, a return means for waste material and/or discharged defective containers can be suitably provided between the blow-molding machine and the recycling machine, so that the waste material or the discharged defective containers do not have to be separately stored, cooled and either rejected or recycled in another way. The return means altogether prevent a waste of plastic material.

Embodiments of the subject matter of the disclosure are illustrated with reference to the drawing.

The FIGURE is a schematic representation of a plant for the manufacture of container preforms in accordance with the disclosure.

The plant A in the FIGURE is for the manufacture of container performs P, as an option with a direct block combination with a blow-molding machine B for the manufacture of blow-molded or stretch-blow molded hollow plastic containers, in particular PET bottles F, in particular PET flakes, and this in e.g. a continuous procedure.

More specifically, plant A for the manufacture of container preforms P in the FIGURE essentially consists of a recycling machine R for recycled plastic material K which is directly connected to a preform machine M, e.g. for injection-molding the preforms P, via a block 12 . The block 12 can preferably be at least one intermediate storage 20 for hot recycled plastic material K, such as a silo or the like.

The essential components of the recycling machine R are at least one reactor, e.g. a decontamination reactor 1 and an SSP reactor 2 downstream thereof, or are combinable with it. The reactor, e.g. the decontamination reactor 1 , is fed with plastic material via a metering device 3 (or as an alternative from a device for producing flakes), the plastic material predominantly consisting of flakes, preferably PET flakes from PET bottles.

The plastic material is subjected to a heat treatment in the reactor, e.g. in the decontamination reactor 1 , e.g. within a temperature range T 1 between 20° C. to 200° C., preferably within a temperature range around about 150° C., and over a treatment period that depends, among other things, on the particle size of the flakes. In the process, heat of at least one heat source 4 can be supplied to the reactor.

In the SSP reactor 2 , a molecular chain length influence of the plastic in its solid state (solid state polycondensation) is effected, if provided, where further decontamination can also take place (combination reactor). This is done e.g. over a predetermined process duration within a temperature range T 2 of about 150° C. to 250° C., preferably between about 170° C. and 210° C. Here, heat can be supplied to the SSP reactor 2 from a heat source 5 . The SSP process preferably runs in an inert gas atmosphere (nitrogen or carbon dioxide) in absence of atmospheric oxygen, optionally at subatmospheric pressure.

The recycled plastic material K is, indicated by an arrow 6 , transferred into the preform machine M at a temperature T 3 which is above a temperature of about 65° C. (glass transition temperature of the plastic material), and is preferably about 180° C., this temperature coming from a major portion of the heat supplied in the heat treatment in the recycling machine R. If an SSP reactor 2 is provided, the recycled plastic material K is directly transferred from the SSP reactor 2 into the preform machine M by a block 12 which is embodied such that the transfer and the heat transfer at least essentially take place in absence of atmospheric oxygen. The block 12 can be embodied as intermediate storage 20 , e.g. as silo, and can comprise a heat insulation 13 and optionally even a heat source 14 for supplying heat, at least to maintain the temperature T 3 , or even to increase it. At their hearts, the recycling machine R and the preform machine are connected to each other or combined in a block at least functionally, preferably even structurally.

The preform machine M comprises e.g. at least one extruder 7 which plasticizes the plastic material K and introduces it into injection molds 8 where the container preforms P continuously discharged at a discharge 9 are manufactured. Optionally, at least one further heat source 19 is functionally assigned to the preform machine M.

The manufactured container preforms P can be subsequently stored and cooled and forwarded to a blow-molding machine. In the embodiment in FIG. 1 , however, the plant A for manufacturing the container preforms P from recycled plastic material K is directly combined in a block at least with a blow-molding machine B to be able to utilize the heat of the manufactured container preforms P to a maximum possible extent during blow molding stretch-blow molding). The blow-molding machine B has, for example, a blow rotor with non-depicted blow molds in which the containers, for example the PET bottles F, are continuously produced. As for blow-molding a certain temperature profile is required in each container preform P, a heat treatment section 11 can be provided between the preform machine M and the blow-molding machine B.

As two further options, which are provided either separately or in combination, at least one return means 16 is provided between the discharge 9 of the preform machine M and/or the blow-molding machine B to return discharged defective preforms (sorting out device 15 ) from the preform machine M and/or waste material and discharged defective containers (sorting out means 17 ) from the blow-molding machine B each to the recycling machine R, and this either to the metering or flake production means 3 , or via a separate crushing means 18 directly into the decontamination reactor 1 (or the SSP reactor 2 ).

The recycling machine R can supply several preform machines M simultaneously. To permit a quasi continuous procedure, at least two recycling machines R, R′ (or reactors 1 , 2 ) can be assigned to one preform machine M or several preform machines M, M′. The blow-molding machine does not necessarily have to be combined in a block with the preform machine M. The recycling machine R could also comprise only one reactor which is used for decontamination and for the SSP process.

In the recycling machine R, preferably adiabatic process conditions prevail. The heat sources 4 , 5 , 14 , 19 can be operated with any arbitrary heat transfer media (water, vapor, electrically, thermal oil, or the like). As a further option, instead of the fixed block 12 between the recycling machine R and the preform machine M, an interchangeable container system could also be used, for example such that one interchangeable container each is being filled with a hatch at the recycling machine R, then closed and transferred to the preform machine M and connected there, so that with at least two interchangeable containers, a quasi continuous operation is permitted. These interchangeable containers can be heat-insulated or even heated.