Method of manufacturing food packaging plastic films and food packaging plastic films thus produced

1. A detectable thermoplastic food packaging film comprising detectable particles incorporated therein in homogeneous distribution,

wherein the detectable particles are permanently magnetic and comprise a hydrophobic surface-modification being at least one of protective against oxygen and protective against oxidation,

wherein the surface-modification of the detectable particles is bonded to the surfaces of the detectable particles,

wherein the detectable particles comprise a weight-related specific saturation magnetization of at least 50 Am 2 /kg iron (Fe),

wherein the detectable particles comprise absolute particle sizes in the range of from 0.01 to 1,000 micrometers, and

wherein the surface-modification of the detectable particles comprises inorganic, organic or inorganic-organic polymers selected from the group consisting of polysiloxanes, polyacrylates, polymethacrylates, polyacrylamides, starch-based polymers, cellulose-based polymers, polysaccharides, polyaminosaccharides and biopolymers as well as mixtures and combinations thereof;

wherein the detectable thermoplastic food packaging film is a multilayer film comprising:

as a core layer, a plastic film comprising all the detectable particles; and

to opposing sides of the core layer, at least one other plastic film co-extruded with the core layer, each of the at least one other plastic film providing one of outer layers of the multilayer film, each of the at least one other plastic film comprising a plastic material different than that of the core layer;

wherein the plastic film of the core layer comprises a polyethylene resin; and

wherein the plastic material of the at least one other plastic film providing the outer layers comprises a polyamide resin.

2. A detectable thermoplastic food packaging film comprising detectable particles incorporated therein in homogeneous distribution,

wherein the detectable particles are permanently magnetic and comprise a hydrophobic surface-modification being at least one of protective against oxygen and protective against oxidation,

wherein the surface-modification of the detectable particles is bonded to the surfaces of the detectable particles,

wherein the detectable particles comprise a weight-related specific saturation magnetization of at least 50 Am 2 /kg iron (Fe), and

wherein the surface-modification of the detectable particles comprises inorganic, organic or inorganic-organic polymers selected from the group consisting of polysiloxanes, polyacrylates, polymethacrylates, polyacrylamides, starch-based polymers, cellulose-based polymers, polysaccharides, polyaminosaccharides and biopolymers as well as mixtures and combinations thereof; and

wherein the detectable thermoplastic food packaging film is a multilayer film comprising:

as a core layer, a plastic film comprising all the detectable particles; and

to opposing sides of the core layer, at least one other plastic film co-extruded with the core layer, each of the at least one other plastic film providing one of outer layers of the multilayer film, each of the at least one other plastic film comprising a plastic material different than that of the core layer;

wherein the plastic film of the core layer comprises a polyethylene resin; and

wherein the at least one other plastic film providing the outer layers each comprises a polyamide resin.

3. The thermoplastic film as defined in claim 2 :

wherein the detectable particles are ferromagnetic, ferrimagnetic, paramagnetic or superparamagnetic.

4. The thermoplastic film as defined in claim 2 :

wherein the detectable particles comprise at least one metal or metal oxide selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni) and their oxides.

5. The thermoplastic film as defined in claim 2 :

wherein the detectable particles comprise at least one magnetic iron oxide selected from the group consisting of magnetite (Fe 3 O 4 ), maghemite (Fe 2 O 3 ), hematite (Fe 2 O 3 ), ferrite, goethite (FeO(OH)), lepidocrocite (FeO(OH)) and ferroxyhyte (FeO(OH)).

6. The thermoplastic film as defined in claim 2 :

wherein the detectable particles comprise iron (Fe) in weight-related amounts in the range of from 20 to 80 wt. %, based on the overall particle weight.

7. The thermoplastic film as defined in claim 2 :

wherein the detectable particles comprise absolute particle sizes in the range of from 0.01 to 1,000 micrometers.

8. The thermoplastic film as defined in claim 2 :

wherein the detectable particles and the thermoplastic film comprising the detectable particles incorporated therein are detectable by at least one of a metal detection device, an induction-based detection device, a magnetism-based device, a conductivity-based detection device, an optically based detection device and a photodetection device.

9. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film comprises 0.1 to 75 wt. % of the detectable particles, based on the overall thermoplastic film weight.

10. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film comprises 0.2 to 60 wt. % of the detectable particles, based on the overall thermoplastic film weight.

11. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film further comprises at least one food-compatible plasticizer.

12. The thermoplastic film as defined in claim 11 :

wherein the thermoplastic film comprises the at least one food-compatible plasticizer in amounts of from 0.5 to 40 wt. %, based on the overall weight of the thermoplastic film.

13. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film forms a tubular film or a seamless tubular film.

14. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film forms a casing, a tubular casing or a seamless tubular casing.

15. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film forms a shirred seamless tubular casing.

16. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film has an overall thickness in the range of from 1 to 2,000 micrometers.

17. The thermoplastic film as defined in claim 2 :

wherein the thermoplastic film has been obtained by a method comprising the following steps:

a first step of introducing the detectable particles into a molten plastic resin to produce a mixture comprising the molten plastic resin and the detectable particles, and

wherein the detectable particles are introduced into the molten plastic resin in the form of a particulate compounded mixture comprising the detectable particles together with and distributed in a carrier plastic resin, wherein the particulate compounded mixture comprises the detectable particles in amounts in the range of from 10 to 80 wt. %, based on the particulate compounded mixture; and

(ii) followed by a second step of extruding the mixture comprising the molten plastic resin and the detectable particles, wherein the step of extruding the mixture comprising the molten plastic resin and the detectable particles is performed as a co-extrusion process wherein the plastic film comprising the detectable particles incorporated therein is co-extruded with the at least one other plastic film of different plastic material on both sides of the plastic film so as to obtain:

as the core layer, the plastic film comprising the detectable particles incorporated therein in homogeneous distribution; and

as the outer layers on the both sides of the plastic film of the core layer, the at least one other plastic film.

18. A foodstuff article packaged in a thermoplastic film as defined in claim 2 .

19. The thermoplastic film as defined in claim 2 ,

further comprising an adhesive layer between the plastic film of the core layer and each of the at least one other plastic film providing the outer layers.

20. A method of manufacturing the detectable thermoplastic food packaging film of claim 2 ,

wherein the method comprises the following steps:

(i) a first step of introducing detectable particles into a molten plastic resin to produce a mixture comprising the molten plastic resin and the detectable particles,

wherein the detectable particles are permanently magnetic and comprise a hydrophobic surface-modification being at least one of protective against oxygen and protective against oxidation,

wherein the surface-modification of the detectable particles is bonded to the surfaces of the detectable particles,

wherein the detectable particles comprise a weight-related specific saturation magnetization of at least 50 Am 2 /kg iron (Fe),

wherein the surface-modification of the detectable particles comprises inorganic, organic or inorganic-organic polymers selected from the group consisting of polysiloxanes, polyacrylates, polymethacrylates, polyacrylamides, starch-based polymers, cellulose-based polymers, polysaccharides, polyaminosaccharides and biopolymers as well as mixtures and combinations thereof, and

wherein the detectable particles are introduced into the molten plastic resin in the form of a particulate compounded mixture comprising the detectable particles together with and distributed in a carrier plastic resin, wherein the particulate compounded mixture comprises the detectable particles in amounts in the range of from 10 to 80 wt. %, based on the particulate compounded mixture;

(ii) followed by a second step of extruding the mixture comprising the molten plastic resin and the detectable particles, so as to obtain a thermoplastic food packaging film comprising the detectable particles incorporated therein in homogeneous distribution.

21. The method as defined in claim 20 :

wherein the detectable particles comprise at least one metal or metal oxide selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni) and their oxides.

22. The method as defined in claim 20 :

wherein the detectable particles comprise at least one magnetic iron oxide selected from the group consisting of magnetite (Fe 3 O 4 ), maghemite (Fe 2 O 3 ), hematite (Fe 2 O 3 ), ferrite, goethite (FeO(OH)), lepidocrocite (FeO(OH)) and ferroxyhyte (FeO(OH)); and

wherein the detectable particles comprise iron (Fe) in weight-related amounts in the range of from 20 to 80 wt. %, based on the overall particle weight.

23. The method as defined in claim 20 :

wherein the method further comprises adding at least one plasticizer to the thermoplastic film, wherein the plasticizer is used in such amounts that the resulting thermoplastic film comprises 0.5 to 40 wt. %, based on the overall weight of the thermoplastic film comprising the detectable particles incorporated therein, and wherein the plasticizer is a food-compatible plasticizer.