Structured material and method of producing the same
View Patent ↗A method for producing a structured material for accommodating passage of fluids, particularly high viscosity fluids, through the structured material. In one embodiment, the structured material is a composite material formed of a first layer, for example a polypropylene polymer, having a first shrinkage extent and a second layer bonded to the first layer, for example an ethylene-propylene copolymer, having a second shrinkage extent different from the first shrinkage extent. In another embodiment, a structured heterogenous material is made of a heterogeneous mixture of at least two homogeneous fiber sets or components having different shrinkage extents.
1. A method for producing a structured composite material for accommodating passage of viscous fluids through the structured composite material, the method comprising the steps of:
forming a first layer having a first shrinkage extent, the first layer comprising a nonwoven web;
forming a second layer having a second shrinkage extent different from the first shrinkage extent, the second layer comprising a film and having openings through the second layer;
bonding the second layer to the first layer to form a composite material; and
shrinking the second layer relative to the first layer, thereby forming a plurality of fiber loop pores in the first layer and shrinking the openings through the second layer to form a plurality of pores smaller than the fiber loop pores.
2. The method of claim 1 , wherein the first layer comprises a propylene polymer and the second layer comprises an ethylene-propylene copolymer.
3. The method of claim 1 , further comprising the step of heating the composite material to effect shrinkage of the second layer.
4. The method of claim 1 , wherein the second layer is bonded to the first layer by one of thermal bonding, pin bonding and differential speed bonding.
5. The method of claim 1 , further comprising the step of stretching the second layer before the second layer is bonded to the first layer.
6. The method of claim 5 , wherein the second layer is stretched in a machine direction to about 1.5 to about 6.0 times an initial length.
7. The method of claim 5 , wherein the second layer is stretched in a machine direction to about 2.0 to about 4.0 times an initial length.
8. A method for producing a structured composite material for accommodating passage of viscous fluids through the structured composite material, the method comprising the steps of:
forming a first layer having a first shrinkage extent;
forming a second layer having a second shrinkage extent different from the first shrinkage extent, the second layer comprising a film and having openings through the second layer;
bonding the second layer to the first layer to form a composite material;
creping the composite material; and
shrinking the second layer relative to the first layer, thereby forming a plurality of fiber loop pores in the first layer and shrinking the openings through the second layer to form a plurality of pores smaller than the fiber loop pores.
9. A method for producing a composite material having a structure for accommodating passage of viscous fluids through the composite material, the method comprising the steps of:
forming a first layer having a first shrinkage extent, the first layer comprising a nonwoven web;
applying a second layer to the first layer to form the composite material, the second layer comprising a film, having a second shrinkage extent different from the first shrinkage extent and having openings through the second layer; and
heating the composite material to produce the structure, wherein the second layer shrinks relative to the first layer, thereby forming a plurality of fiber loop pores in the first layer and shrinking the openings through the second layer to form a plurality of pores smaller than the fiber loop pores.
10. A method for producing a composite material having a structure for accommodating passage of viscous fluids through the composite material, the method comprising the steps of:
forming a first layer having a first shrinkage extent;
creping the first layer;
applying a second layer to the first layer to form the composite material, the second layer having a second shrinkage extent different from the first shrinkage extent and comprising a film and having openings through the second layer; and
heating the composite material to produce the structure, wherein the second layer shrinks relative to the first layer, thereby forming a plurality of fiber loop pores in the first layer and shrinking the openings through the second layer to form a plurality of pores smaller than the fiber loop pores.
11. The method of claim 9 , further comprising the step of stretching the second layer before the second layer is applied to the first layer.
12. The method of claim 9 , further comprising the step of pattern embossing the first layer to form thermal bonds which extend through the first layer.