Process for producing stent
A stent comprising a tubular stent matrix of which diameter is extendable and a flexible polymer layer covering the stent matrix. The polymer layer is closely attached to and covers the entire surface of the stent matrix. Since the flexible polymer layer closely covers the entire surface of the stent matrix not only the outer periphery of the stent matrix, the stent has no problem of causing allergic to metal, stimulus of tissues due to metal, and rust development. Since the inner periphery of the stent is a flat and smooth surface covered by the polymer layer without convexes and concaves, the formation of thrombus can be inhibited well. There is no problem of drift between the polymer layer and the stent matrix, thereby maintaining the positional relationship between the stent matrix and the polymer layer before and after the expansion of the stent.
1. A process of producing a stent, comprising:
preparing a tubular stent matrix extendable in a diametric direction,
forming flexible solid polymer layers on said stent matrix to cover entire inner and outer surfaces of the stent matrix, and
perforating a plurality of fine through pores in the solid polymer layers at portions only where the stent matrix does not exist,
wherein said forming the solid polymer layers comprises
a step of installing the stent matrix on an inner polymer layer disposed on an outer surface of a mandrel;
a step of forming an outer polymer layer by impregnating the mandrel into a liquid resin material for forming the outer polymer layer and pulling up the mandrel; and
a step of equalizing the thickness of the outer polymer layer by pulling up the mandrel in a vertical direction and controlling a pulling-up speed, and
wherein said fine pores are formed after the polymer layers are formed.
2. A process of producing a stent as claimed in claim 1 , wherein the pulling-up speed is gradually lowered.
3. A process of producing a stent as claimed in claim 1 , wherein the outer polymer layer is made of a base resin material only.
4. A process of producing a stent as claimed in claim 1 , wherein the outer polymer layer comprises a base layer made of a base resin material and a layer of a biodegradable polymer covering the surface of the base layer.
5. A process of producing a stent as claimed in claim 3 , wherein the liquid base resin material is a solution of segmented polyurethane polymer.
6. A process of producing a stent as claimed in claim 1 , wherein said fine pores are formed by laser machining.
7. A process of producing a stent as claimed in claim 1 , wherein said forming the solid polymer layers further comprises a step of impregnating the mandrel into a polymer liquid for the inner layer and pulling up the mandrel to form the inner polymer layer, on which the stent matrix is installed.