Peelable composite thermoplastic sealants in packaging films
View Patent ↗A peelable sealing structure includes a sealing layer and one or more optional additional layers. The peelable sealing structure includes a sealing surface that is formable into a peelable seal upon contact with a sealing substrate at all temperatures in a peelable seal temperature range. Moreover, the peelable sealing structure comprises a thermoplastic polymer and an additive dispersed within at least a portion of the thermoplastic polymer with the peelable sealing structure defining the sealing surface.
1. A method of forming a packaging system that includes a sealing layer, the method comprising:
combining a thermoplastic polymer with an organoclay to form an organoclay-polymer blend, the organoclay comprising platelets having an average separation of at least 20 angstroms;
forming the sealing layer from the organoclay-polymer blend, the sealing layer having a seal initiation temperature from about 170° F. to about 350° F. and a tensile modulus from about 500 to about 2000 MPa; and
forming an open packaging system from the sealing layer.
2. The method of claim 1 wherein the step of forming the sealing layer is accomplished by extrusion, co-extrusion, blow molding, casting, extrusion blow molding, and film blowing.
3. The method of claim 1 wherein the sealing layer is formed by extrusion from a die.
4. The method of claim 1 wherein the thermoplastic polymer and the organoclay organoclay are premixed and then introduced into an extruder.
5. The method of claim 1 further comprising forming additional layers by providing material from additional extruders.
6. The method of claim 1 further comprising sealing the open packaging system.
7. The method of claim 6 wherein an object is placed in the open packaging system prior to sealing.
8. The method of claim 6 wherein the sealing layer is formed by contacting the layer with a sealing substrate.
9. The method of claim 8 wherein the sealing layer is formed by conduction heat sealing, ultrasonic sealing, or induction sealing.
10. The method of claim 1 wherein the thermoplastic polymer is combined with the organoclay by mixing a master batch with a neat polymer.
11. The method of claim 10 wherein the master batch includes from 10 to 80 wt % organoclay.
12. The method of claim 1 wherein the sealing layer is formable into a peelable seal at all temperatures within a peelable seal temperature range, the peelable seal temperature range being from the seal initiation temperature to a temperature that is at least 100° F. above the seal initiation temperature.
13. The method of claim 1 wherein the organoclay comprises a plurality of particles having a spatial dimension less than 200 nm.
14. The method of claim 1 wherein the average separation is between 20 to 45 angstroms.
15. The method of claim 1 wherein the platelets have an average separation of at least 30 angstroms.
16. The method of claim 1 wherein the organoclay comprises a clay selected from the group consisting of kaolinite, montmorillonite-smectite clays, bentonite clays, illite clays, and combinations thereof.
17. The method of claim 1 wherein the organoclay is present in an amount from 1 wt % to 20 wt % of the combined weight of the thermoplastic polymer and the organoclay.
18. The method of claim 1 wherein the organoclay is present in an amount from 2 wt % to 10 wt % of the combined weight of the thermoplastic polymer and the organoclay.
19. The method of claim 1 wherein the thermoplastic polymer further comprises a component selected from the group consisting of nylons, polyolefins, polystyrenes, polyesters, polycarbonates, copolymers of ethylene, copolymers of propylene, ethylene vinyl acetate, and mixtures thereof.
20. The method of claim 1 wherein the thermoplastic polymer comprises a component selected from the group consisting of ethylene acrylic acid, ethylene ethyl acrylate, ethylene ionomers, and combinations thereof.