Method of producing coated paper with reduced gloss mottle
View Patent ↗A method of producing a coated paper having reduced gloss mottle and excellent smoothness includes the steps of calendering a base stock at a relatively high pressure in a first calendering step, coating at least one side of the calendered base stock and calendering the coated base stock at a relatively low pressure in a second calendering step.
1. A method of producing a coated paper having reduced gloss mottle comprising:
calendering a base stock at an average nip pressure of at least about 18,000 psi in a first calendering step;
coating at least one side of said base stock with a coating composition to form a coated base stock; and
calendering said coated base stock at a nip pressure not exceeding about 3000 psi in a second calendering step.
2. The method of claim 1 further comprising the step of pre-coating or sizing the base stock prior to the first calendering step.
3. The method of claim 1 wherein said base stock is calendered to a density of at least about 15 lbs/ream per caliper point.
4. The method of claim 3 wherein said base stock is calendered to a density of from about 15.5 to about 18.5 lbs/ream per caliper point.
5. The method of claim 1 wherein said base stock has a moisture content of from about 2 to 10 percent during the first calendering step.
6. The method of claim 1 wherein the first calendering step comprises passing the base stock through a calendering device comprising at least one nip formed between a pair of hard rolls.
7. The method of claim 6 wherein said hard rolls are steel rolls.
8. The method of claim 1 wherein the coated paper has a Tobias mottle index of no more than about 550.
9. The method of claim 1 wherein both sides of the base stock are coated.
10. The method of claim 1 wherein the coating composition is applied at a coat weight of from about 6 to about 12 lbs/ream (ream=3300 ft 2 ) based on the total dry weight of the coating composition.
11. The method of claim 1 wherein the second calendering step comprises passing the coated base stock through at least one nip formed between a hard roll and a soft roll.
12. The method of claim 11 wherein the soft roll has a hardness of less than about 86 Shore D.
13. The method of claim 1 wherein the second calendering step comprises calendering the coated base stock in a shoe calender.
14. The method of claim 1 wherein the coated paper has a basis weight in a range of from about 100 lbs/ream to about 220 lbs/ream.
15. The method of claim 1 further comprising forming a base stock from a plurality of cellulose fibers.
16. The method of claim 1 wherein the coated paper has a Parker Print Surf of less than about 1.2 microns.
17. The method of claim 16 wherein the coated paper has a Tobias mottle index of no more than about 550.
18. The method of claim 17 wherein the coated paper has a basis weight in a range of from about 100 lbs/ream to about 220 lbs/ream.
19. A method of treating a web of cellulose fibers to reduce gloss mottle comprising:
calendering a web of cellulose fibers in a first calendering step at a first average nip pressure to a density of at least about 15 lbs/ream per caliper point;
coating at least one side of the web with a coating composition to form a coated paper web; and
calendering said coated paper web in a second calendering step at a second average nip pressure wherein said first average nip pressure is greater than said second average nip pressure to form a product having a gloss value of at least about 45, a Tobias gloss mottle rating of no more than about 550 and a Parker Print Surf of less than about 1.2 microns.
20. The method of claim 19 wherein said first average nip pressure is at least about 10 times said second average nip pressure.
21. The method of claim 20 wherein said second average nip pressure is less than about 3000 psi.
22. The method of claim 19 wherein said first average nip pressure is at least about 18,000 psi.