PROCESS FOR THERMOFORMING INFUSION PACKETS
Provided is a process for thermoforming a gas and liquid permeable layer ( 10 ) of thermoplastic material having an average thickness of less than 1.0 mm, the process comprising the steps of bringing the layer of thermoplastic material, at a temperature below that required for thermoforming, into contact with a mould ( 16 ) at a temperature above that of a thermoforming temperature of the thermoplastic material; pressing the mould into contact with the layer of thermoplastic material, the contact between mould and thermoplastic material causing heat to transfer from the mould to the thermoplastic material and raising the temperature of the thermoplastic material to a thermoformable temperature; such pressing thereby causing thermoforming of the thermoplastic material to conform to the shape of the mould.
1 . A process for thermoforming a gas and liquid permeable layer of thermoplastic material having an average thickness of less than 1.0 mm, the process comprising the steps of bringing the layer of thermoplastic material, at a temperature below that required for thermoforming, into contact with a mould at a temperature above that of a thermoforming temperature of the thermoplastic material; pressing the mould into contact with the layer of thermoplastic material, the contact between mould and thermoplastic material causing heat to transfer from the mould to the thermoplastic material and raising the temperature of the thermoplastic material to a thermoformable temperature; such pressing thereby causing thermoforming of the thermoplastic material to conform to the shape of the mould, followed by the step of depositing a particulate product into the thermoformed thermoplastic material.
2 . A process according to claim 1 , wherein the thermoplastic material exhibits plastic deformation behaviour over a temperature range of at least 20° C., preferably over a temperature range of at least 40° C.
3 . A process according to claim 1 , wherein the thermoplastic material comprises polyethylene terephthalate or poly lactic acid.
4 . A process according to claim 1 , wherein the temperature difference between the mould and the thermoplastic material before coming into contact with the mould is greater than 40° C., preferably greater than 60° C., more preferably greater than 80° C.
5 . A process according to claim 1 , wherein the thermoplastic material, before coming into contact with the mould, is at a temperature of from 15° C. to 35° C.
6 . A process according to claim 1 , wherein the thermoplastic material has an average thickness of less than 0.5 mm, preferably less than 0,20 mm, more preferably less than 0.10 mm.
7 . A process according to claim 1 , wherein the thermoplastic material is made from fibres of thermoplastic material.
8 . A process according to claim 7 , wherein the fibres are woven thermoplastic fibres.
9 . A process according to claim 8 , wherein the fibres have a diameter of less than 0.5 mm, preferably less than 0.25 mm, more preferably less than 0.10 mm, most preferably less than 0.05 mm.
10 . A process according to claim 1 , wherein the temperature of the mould is at least 100° C., more preferably at least 120° C.
11 . A process according to claim 1 , wherein the thermoplastic material is formed into a tetrahedral or hemispherical shape.
12 . A process according to claim 1 , wherein the particulate product comprises infusible entities such as tea leaves.
13 . A process according to claim 12 , which is followed by sealing the thermoformed material to produce a sealed porous infusion packet.