Melt spun elastic tape and process
View Patent ↗Articles such as melt spun elastic tape and heaving denier monofilament fibers are made from thermoplastic polyurethane (TPU) polymers. The process to make the articles involves using a substantially horizontal cooling to cool the melt spun articles. Preferably, the cooling is accomplished by a water bath. A crosslinking agent is added to the TPU polymer melt to enhance the elastic properties of the articles.
1. A melt spinning process to produce an elastic tape having a thickness of from about 0.001 inch to about 0.10 inch and a width of from about 0.1 inch to about 2.0 inches comprising:
(a) feeding a preformed TPU polymer consisting of a thermoplastic polyurethane polymer in pellet form having a Shore A hardness of from about 65A to about 95A to a melt mixing machine;
(b) melting said TPU polymer pellets to form a TPU polymer melt;
(c) adding a cross-linking agent to said TPU polymer melt wherein the amount of said crosslinking agent added is from about 2.0% to about 20.0% by weight of the final weight of said tape and wherein said crosslinking a rent has a number average molecular weight (M n ) of from about 1,000 to about 10,000 Daltons;
(d) mixing said crosslinking agent with said TPU polymer melt;
(e) feeding said TPU polymer melt to a manifold;
(f) dividing said TPU polymer melt into multiple melt streams by using said manifold;
(g) feeding each of said multiple melt streams to multiple spinnerets by using a melt pump for each melt stream, wherein each spinneret has a single opening where the melt exits to form the desired shape of said tape;
(h) cooling the tape by passing said tape through a substantially horizontal water cooling bath, wherein said water cooling bath is located from 1.0 inch to 2.0 feet from the exit of said each spinneret; and
(i) winding said tape into a roll.
2. The process of claim 1 , wherein the amount of said crosslinking agent added is from about 8.0% to about 15.0% by weight of the final weight of said tape.
3. The process of claim 2 , wherein the amount of said crosslinking agent added is from about 10.% to about 13.0% by weight of the final weight of said tape.
4. The process of claim 1 , wherein said crosslinking agent has a M n of from about 1,500 to about 2,800 Daltons.
5. The process of claim 1 , wherein said crosslinking agent is mixed with said TPU polymer melt with a dynamic or static mixer.
6. The process of claim 1 , wherein said TPU polymer has a M w of from about 150,000 to about 350,000 Daltons.
7. The process of claim 1 , wherein said TPU polymer has a Shore A hardness of from about 75A to about 85A.
8. The process of claim 1 , wherein said melt mixing machine is an extruder.