Method for forming protrusions in a substrate used to manufacture absorbent articles
A method is presented for altering a portion of a substrate. The method includes providing a first device including an outer surface and a second device including a source of vibration energy. The method also includes forming a nip between the source of vibration energy and the outer surface. The method also includes conveying the substrate through the nip and intermittently altering the portion of the substrate in the nip to create a pattern of altered areas forming a shape. The altered areas have a pattern balance that includes one or more of: an average area of the substrate altered in the nip is within a threshold range across the portion of the substrate; and a simple area of integral areas within the altered areas is within a threshold range across the portion of the substrate.
1 . A method of altering a portion of a substrate comprising:
providing a first device comprising an outer surface;
providing a second device comprising a source of vibration energy;
forming a nip between the source of vibration energy and the outer surface;
conveying the substrate through the nip; and
intermittently altering a portion of the substrate in the nip to create a pattern of altered areas forming a shape, wherein the altered areas have a pattern balance, and wherein the pattern balance comprises at least one of:
an average area of the substrate, altered in the nip being within a threshold range across the portion of the substrate, wherein the threshold range of the average area of the substrate, altered in the nip comprises:
a threshold range maximum; and
a threshold range minimum, wherein a ratio between the threshold range maximum and the threshold range minimum is between about 2:1 and about 4:1; and
a simple area of integral areas within the altered areas being within a threshold range across the portion of the substrate, wherein the threshold range of the simple area of integral areas within the altered areas is between about 10 mm 2 and about 40 mm 2 .
2 . The method of claim 1 , wherein the shape comprises a non-symmetrical shape with respect to one of a cross-machine direction or a machine direction.
3 . The method of claim 1 , wherein the pattern balance further comprises at least one of:
a rate of change of the average area of the substrate, altered in the nip being less than a threshold value across the portion of the substrate; and
a rate of change of the simple area of integral areas within the altered area being less than a threshold value across the portion of the substrate.
4 . The method of claim 1 , wherein the altered areas are registered on the substrate, in a machine direction and a cross-machine direction.
5 . The method of claim 1 , comprising cooling the source of vibrational energy or the first device.
6 . The method of claim 1 , wherein the second device is a rotary sonotrode, and wherein the vibration energy is ultrasonic energy.
7 . The method of claim 1 , wherein the second device is a blade sonotrode, and wherein the vibration energy is ultrasonic energy.
8 . The method of claim 1 , comprising providing a plurality of recesses in the outer surface of the first device, wherein the recesses have a shape configured to produce projections in the altered areas suitable for use in a touch fastener.
9 . The method of claim 1 , wherein the substrate, comprises more than one layer or more than one material.
10 . The method of claim 1 , comprising imparting thermal energy to the portion of the substrate, upstream of the nip to heat the portion of the substrate, to a temperature below a melting temperature of the portion of the substrate.
11 . The method of claim 1 , wherein the altered areas have a cross-machine directional width in the range of about 20 mm to about 45 mm.
12 . The method of claim 1 , wherein the altered areas comprise unaltered portions to contribute to the pattern balance.
13 . The method of claim 1 , wherein the altered areas comprise hooks for a touch fastener.
14 . A method of altering a portion of a substrate, comprising:
providing a first device comprising an outer surface;
providing a second device comprising a source of vibration energy;
forming a nip between the source of vibration energy and the outer surface;
conveying the substrate, through the nip; and
intermittently altering a portion of the substrate, in the nip to create a pattern of altered areas forming a shape, wherein the altered areas have a pattern balance, and wherein the pattern balance comprises at least one of:
a rate of change of an average area of the substrate, altered in the nip being less than a threshold value across the portion of the substrate, wherein the threshold value of the rate of change of an average area of the substrate:
is the difference between an average area between a first nip area and a second nip area, divided by the average area at the first nip area and multiplied by 100; and
is between about −50% and about 50%; and
a rate of change of a simple area of integral areas within the altered area being less than a threshold value across the portion of the substrate, wherein the threshold value of the rate of change of a simple area of integral areas is between about −20 mm 2 and about 20 mm 2 .
15 . The method of claim 14 , wherein the shape comprises a non-symmetrical shape with respect to one of a cross-machine direction or a machine direction.
16 . The method of claim 14 , wherein the pattern balance further comprises at least one of:
the average area of the substrate, altered in the nip being within a threshold range across the portion of the substrate; and
the simple area of integral areas within the altered area being within a threshold range across the portion of the substrate.
17 . The method of claim 16 , wherein the altered areas comprise unaltered portions to contribute to the pattern balance.
18 . The method of claim 14 , comprising imparting thermal energy to the portion of the substrate, upstream of the nip to heat the portion of the substrate, to a temperature below a melting temperature of the portion of the substrate.
19 . A method of creating protrusions in a portion of a substrate, comprising:
providing a first device comprising an outer surface;
providing a second device comprising a source of vibration energy;
forming a nip between the source of vibration energy and the outer surface;
conveying the substrate, through the nip;
continuously creating the protrusions in a portion of the substrate in the nip to create a continuous area of the protrusions; and
flattening a portion of the continuous area of the protrusions to create intermittent areas of the protrusions in the substrate intermediate flattened portions.
20 . The method of claim 19 , comprising imparting thermal energy to the portion of the substrate upstream of the nip to heat the portion of the substrate to a temperature below a melting temperature of the portion of the substrate.