Conductive webs and process for making same
View Patent ↗Conductive nonwoven webs are disclosed. The nonwoven webs contain pulp fibers combined with conductive fibers. In one embodiment, the webs are made in a wetlaid tissue or paper making process. The pulp fibers contained in the webs may comprise softwood fibers, while the conductive fibers may comprise carbon fibers. Base webs can be produced having a resistance of less than about 100 Ohms/square in one embodiment. Once produced, the conductive material can be cut into slits that are then wound on spools. From the spools, the conductive slits can be fed into a process for making any suitable product.
1. A process for producing a conductive paper web comprising:
depositing an aqueous suspension of fibers onto a porous forming surface to form a wet web, the aqueous suspension of fibers comprising softwood fibers mixed with carbon fibers, the carbon fibers having a length of from about 1 mm to about 6 mm and having a purity of at least about 85%, the carbon fibers being present in an amount of from about 5% to about 15% based on the total weight of the fibers present; flattening the web; drying the web; slitting the web into a plurality of slits having a width of from about 3 mm to about 10 mm, each slit being wound on a separate spool, the slits being wound traversely on the spools.
2. A process as defined in claim 1 , wherein the softwood fibers have a Canadian Standard Freeness of greater than about 350 mL.
3. A process as defined in claim 1 , wherein the carbon fibers are coated with a water soluble size that is removed from the carbon fibers as the web is formed.
4. A process as defined in claim 1 , wherein the carbon fibers have a purity of at least about 88%.
5. A process as defined in claim 1 , wherein the slits have a final bulk of less than 1 g/cc.
6. A process as defined in claim 1 , wherein the web is flattened by calendaring at a pressure of at least about 950 PLI.
7. A process as defined in claim 1 , wherein an aqueous suspension of pulp fibers is formed first and then carbon fibers are injected into the aqueous suspension prior to depositing the fibers onto the forming surface.
8. A process as defined in claim 1 , further comprising the step of incorporating a wet strength agent into the web.
9. A process as defined in claim 1 , wherein the dried web is wound into a roll, the roll then being center driven unwound as the web is slit.
10. A process as defined in claim 9 , wherein the plurality of slits are divided in an alternative fashion to from a first group of slits and a second group of slits, the first group of slits being fed to a first set of corresponding spools, the group of slits being fed to a second group of corresponding spools.
11. A process as defined in claim 1 , wherein each spool is in association with a corresponding web tension device for controlling the tension of the slits as they are wound on the corresponding spools.
12. A process as defined in claim 11 , wherein the tension device contains a dancer roll that is in communication with the slits as they are being wound on the spools, the process further including a traversing arm that directs the slits onto the spools for traversely winding the slits on the spools.