Die and process for extrusion
The present disclosure is related to a die suitable for extrusion of thermoplastic vulcanizate, in particular for co-extrusion of multiple materials comprising a thermoplastic vulcanizate. The die comprises a pool die plate, an orifice die plate, and a profile die plate. By utilizing the die according to the present disclosure in extrusion, the flow of extrudate can be well controlled and balanced due to the design of flow pool and through orifice, thereby an extruded article achieves good shape performance, for example, good surface smoothness, and an undesired effect like edge tear, warpage, die moustache, silver line in the extrusion can be avoided.
1. A process of extrusion molding comprising in sequence the steps of:
a) forming an extrudate in an extruder having a die,
wherein the die comprises:
a pool die plate ( 10 ) comprising a pool die plate flow pool ( 15 ), a flow groove ( 12 ) in communication with said pool die plate flow pool ( 15 ), and a through orifice ( 11 ) extending through said pool die plate ( 10 ) for receiving at one side an extrudate from an extruder head and distributing the extrudate to said flow groove ( 12 ) at another side, said pool die plate flow pool ( 15 ) and said flow groove ( 12 ) disposed in the same surface of said pool die plate ( 10 );
an orifice die plate ( 20 ) arranged in use of the die adjacent said pool die plate ( 10 ) and comprising at least one orifice die plate flow pool ( 22 ) and a plurality of orifice die plate through orifices ( 21 ) extending through said orifice die plate ( 20 ) from one side to another and in communication with said pool die plate flow pool ( 15 ) and said orifice die plate flow pool ( 22 ), said orifice die plate flow pool ( 22 ) grooved into a surface of said orifice die plate; and
a profile die plate ( 40 ) arranged in use of the die adjacent said orifice die plate ( 20 ) and comprising a profile die plate flow channel ( 41 ) for forming a target profile, said profile die plate flow channel ( 41 ) extending through said profile die plate ( 40 ) from one side to another and in communication with said orifice die plate flow pool ( 22 );
b) passing the extrudate from one side of the pool die plate ( 10 ) of the die into the pool die plate flow pool ( 15 );
c) passing the extrudate through said plurality of orifice die plate through orifices ( 21 ) disposed in the orifice die plate ( 20 ) of the die from one side into the orifice die plate flow pool ( 22 ); and
d) passing the extrudate through the profile die plate flow channel ( 41 ) disposed in the profile die plate ( 40 ) of the die to form an article having a target profile.
2. The process of claim 1 further comprising between steps c) and d) a step c′) comprising passing the extrudate through a flow channel which is disposed in a separator die plate of the die, which is arranged in use of the die between said orifice die plate and said profile die plate of the die, and is divided by at least one separating wall along a flow direction of extrudate.
3. The process of claim 1 , wherein said extrudate contains a thermoplastic vulcanizate material.
4. The process of claim 3 , wherein said thermoplastic vulcanizate is prepared by dynamically curing a rubber with a curing agent while mixing said rubber with a thermoplastic polymer.
5. The process of claim 4 , wherein said rubber is olefinic elastomeric copolymer, butyl rubber, natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, acrylonitrile rubber, butadiene-styrene-vinyl pyridine rubber, urethane rubber, polyisoprene rubber, epichlorohydrin terpolymer rubber, polychloroprene, or mixtures of any two or more thereof.
6. The process of claim 5 , wherein said olefinic elastomeric copolymer is ethylene-propylene rubber, propylene-based rubbery copolymer, ethylene-based plastomer or elastomer, or mixtures of any two or more thereof.