Miscible blends of normally immiscible polymers
First and second virgin polymers, not normally miscible when combined in one or more conventional melt-processing means, are combined in a known melt-processing means having mechanical vibration, referred to as a TekFlow® “processor” in which the polymers are extensively shear-thinned, substantially disentangled and stress-fatigued. A process in which melts of each virgin polymer are separately modified, mixed and melt-processed in a conventional extruder, is also effective if the melt of one polymer, modified in a processor, is mixed with virgin melt before being modified in another processor. In each embodiment, the resulting blend is unexpectedly found to be a single phase, that is, a miscible blend.
1 . In a process for blending a virgin first polymer with at least one other virgin polymer normally immiscible with each other as evidenced by the presence of more than one phase in a blend made with conventional melt-processing means, the improvement comprising,
feeding the virgin first polymer melt from a conventional first melt-processing means to a first stress-fatiguing means and removing modified polymer therefrom;
feeding a virgin second polymer from a conventional second melt-processing means to a first mixing means selectively chosen from a mixing station and a second stress-fatiguing means;
providing a blend of first and second virgin polymers having polymer chains at a chosen level of disentanglement at the mixing station;
feeding the blend from the mixing station to a second mixing means selectively chosen from a third conventional melt-processing means and a third stress-fatiguing means; and,
recovering a single phase blend of the first and second polymers.
2 . The process of claim I comprising feeding the virgin second polymer from the conventional second melt-processing means to the second stress-fatiguing means;
forming a blend of modified first polymer and modified second polymer in the mixing station;
flowing blended modified first and second polymers to the third conventional melt-processing means.
3 . The process of claim I comprising feeding the virgin second polymer directly from the conventional second melt-processing means to the mixing station;
forming a blend of modified first polymer and virgin second polymer in the mixing station;
and, flowing the blend to the third stress-fatiguing means.
4 . The process of claim 1 wherein each virgin polymer is fluidized at a fluidization temperature in the range from 10° C. to 100° C. above the conventional melting point or melt-controlling glass transition temperature of the virgin polymer; and, one polymer is present in an amount at least 5% by weight of the single phase blend.
5 . The process of claim 1 wherein the virgin first and second polymer is each independently selected from the group consisting of a substantially crystalline polymer, a substantially amorphous polymer and a partially crystalline polymer.
6 . The process of claim 1 wherein the fluidization temperature of virgin first polymer entering the first stress-fatiguing means is at least 10° C. above the melting point or melt-controlling glass transition temperature of the polymer, and the temperature leaving the first stress-fatiguing means is at least 10° C. below the fluidization temperature at which the melt enters the first stress-fatiguing means.
7 . The process of claim 2 wherein the fluidization temperature of virgin second polymer entering the second stress-fatiguing means is at least 10° C. above the melting point or melt-controlling glass transition temperature of the polymer, and the temperature leaving the second stress-fatiguing means is at least 10° C. below the fluidization temperature at which the melt enters the second stress-fatiguing means.
8 . The process of claim 5 wherein the first polymer has a molecular weight which is less than 50% of the molecular weight of the second polymer, independent of its crystallinity.
9 . The process of claim 5 wherein the first polymer is an amorphous polymer and the second polymer is substantially crystalline.
10 . A single phase blend of a first virgin polymer with at least one other virgin polymer normally immiscible with each other as evidenced by the presence of more than one phase in a blend made with conventional melt-processing means, the single phase being the product of a process comprising,
feeding the virgin first polymer melt from a conventional first melt-processing means to a first stress-fatiguing means and removing modified polymer therefrom;
feeding a virgin second polymer from a conventional second melt-processing means to a first mixing means selectively chosen from a mixing station and a second stress-fatiguing means;
providing a blend of first and second virgin polymers having polymer chains at a chosen level of disentanglement at the mixing station;
feeding the blend from the mixing station to a second mixing means selectively chosen from a third conventional melt-processing means and a third stress-fatiguing means; and,
recovering the first and second polymers as the single phase blend.
11 . The single phase blend of claim 10 produce by feeding the virgin second polymer from the conventional second melt-processing means to the second stress-fatiguing means; forming a blend of modified first polymer and modified second polymer in the mixing station; flowing blended modified first and second polymers to the third conventional melt-processing means.
12 . The single phase blend of claim 10 produced by feeding the virgin second polymer directly from the conventional second melt-processing means to the mixing station; forming a blend of modified first polymer and virgin second polymer in the mixing station; and, flowing the blend to the third stress-fatiguing means.
13 . The single phase blend of claim 10 wherein the virgin first and second polymer is each independently selected from the group consisting of a substantially crystalline polymer, a substantially amorphous polymer and a partially crystalline polymer.