Soft tissue having temporary wet strength

1. A soft low density paper product with temporary wet strength, said paper product having a density, a basis weight, a wet burst strength, an initial wet strength, a thirty minute wet strength, and a dry strength, said paper product comprising:

papermaking fibers wherein said papermaking fibers comprise between about 13% and about 25% softwood fibers; and

a chemical strength additive consisting essentially of a temporary wet strength resin;

wherein said density is less than about 0.6 grams per cubic centimeter, said basis weight is between about 10 and about 65 grams per square meter, said dry strength is less than about 500 grams per inch (197 grams per centimeter), said wet burst strength is at least about 35 grams, the ratio of said initial wet strength to said dry strength is greater than about 0.15:1, and the ratio of said thirty minute wet strength to said initial wet strength is less than about 0.4.

2. A soft low density paper product according to claim 1 wherein said dry strength is less than about 450 grams per inch (177 grams per centimeter).

3. A soft low density paper product according to claim 2 wherein said dry strength is less than about 425 grams per inch (167 grams per centimeter).

4. A soft low density paper product according to claim 3 wherein said dry strength is less than about 375 grams per inch (148 grams per centimeter).

5. A soft low density paper product according to claim 1 wherein said ratio of said initial wet strength to said dry strength is greater than about 0.2:1 .

6. A soft low density paper product according to claim 5 wherein said ratio of said initial wet strength to said dry strength is greater than about 0.25:1.

7. A soft low density paper product according to claim I wherein said ratio of said thirty minute wet strength to said initial wet strength is less than about 0.4:1.

8. A soft low density paper product according to claim 7 wherein said ratio of said thirty minute wet strength to said initial wet strength is less than about 0.3:1.

9. A soft low density paper product according to claim 1 wherein said temporary wet strength resin is used at a level of between about 0.2% and about 0.8%.

10. A soft low density paper product according to claim 1 wherein said paper product is layered, having two outer layers and a center layer therebetween.

11. A soft low density paper product according to claim 10 wherein said papermaking fibers comprise both softwood fibers and short fibers, wherein said papermaking fibers in said center layer consist essentially of softwood papermaking fibers and said papermaking fibers in said outer layers consist essentially of short papermaking fibers.

12. A soft low density paper product according to claim 11 wherein said paper product comprises between about 13% and about 25% softwood fibers.

13. A soft low density paper product according to claim 1 wherein said softwood fibers are refined so as to provide a change in PFR of between 0 and about 1.5 seconds.

14. A soft low density paper product according to claim 1 wherein said paper product has a total tensile modulus and said total tensile modulus is less than about 12 grams/cm%.

15. A soft low density paper product according to claim 1 wherein said wet burst strength is between about 35 grams and about 70 grams.

16. A soft low density paper product according to claim 1 wherein said paper product is pattern densified having a relatively high bulk field of relatively low fiber density and an array of densified zones of relatively high fiber density.

17. A soft low density paper product according to claim 16 wherein said densified zones are interconnected.

18. A soft low density paper product according to claim 1 wherein said temporary wet strength resin comprises a cationic polyaldebyde polymer.

19. A soft low density paper product according to claim 11 wherein both said center layer and said outer layers are provided with a temporary wet strength resin.

20. A soft low density paper product according to claim 19 wherein said center layer is provided with said temporary wet strength resin at a first level and said outer layers are provided with said temporary wet strength resin at a second, lower level.

21. A soft low density paper product according to claim 20 wherein said temporary wet strength resin comprises a cationic polyaldehyde polymer.

22. A soft low density paper product according to claim 20 wherein said paper product has a lint value and said lint value is less than about 8.

23. A soft low density paper product with temporary wet strength, said paper product having a density less than about 0.6 grams per cubic centimeter, a basis weight between about 10 and about 65 grams per square meter, an initial wet strength, a thirty minute wet strength, a dry strength less than about 500 grams per inch (197 grams per centimeter), a wet burst strength between about 35 grams and about 70 grams, wherein the ratio of said initial wet strength to said dry strength is greater than about 0.15:1, and the ratio of said thirty minute wet strength to said initial wet strength is less than about 0.4, said paper product comprising:

two outer layers comprising short papermaking fibers and a temporary wet strength resin; and

an inner layer positioned between said outer layers, said inner layer comprising softwood long papermaking fibers and a temporary wet strength resin;

wherein said softwood papermaking fibers comprise between about 13% and about 25% of the total combined weight of said short papermaking fibers and said softwood papermaking fibers and the level of said temporary wet strength resin in said outer layers is between about 0.1% and about 0.2% of the combined weight of said short papermaking fibers and said softwood papermaking fibers and the level of said temporary wet strength resin in said inner layer is between about 0.2% and about 0.4% of the combined weight of said short papermaking fibers and said softwood papermaking fibers.

24. A soft low density paper product according to claim 23 wherein said paper product has a lint value and said lint value is less than about 8.

25. A method of preparing a papermaking furnish for producing a soft, low density paper product with temporary wet strength of claim 1, said method comprising:

a) providing a first aqueous slurry comprising softwood papermaking fibers, said first slurry having a first pH;

b) providing means to adjust said first pH and adjusting said first pH to a first controlled pH range that is between about 5.0 and about 6.5;

c) providing first acid means to adjust said first controlled pH range to a second, more narrowly controlled pH range that is between about 4.8 and about 5.4;

d) providing a temporary wet strength resin solution;

e) mixing said slurry, said first acid means, and said temporary wet strength resin solution so as to provide a first initially conditioned, resin treated softwood papermaking fiber slurry;

f) providing second acid means to adjust said second controlled pH range so as to control the pH of said papermaking furnish to a range that is between about 4.8 and about 5.4;

g) providing dilution water; and

h) mixing said initially conditioned, resin treated softwood papermaking fiber slurry, said second acid means, and said dilution water to complete preparation of said papermaking furnish.

26. A method for producing a soft low density paper product, said method comprising:

a) directing a first papermaking furnish prepared according to claim 25 to a headbox and depositing said first furnish onto a foraminous substrate therewith, forming an embryonic web; and

b) drying said embryonic web to form a web of said soft low density paper product, wherein said product has a density of less than about 0.6 grams per cubic centimeter, a basis weight between about 10 and about 65 grams per square meter, a dry strength less than about 500 grams per inch (197 grams per centimeter), a ratio of an initial wet strength to said dry strength greater than about 0.15:1, and a ratio of a thirty minute wet strength to said initial wet strength less than about 0.4.

27. The method of claim 26 wherein said paper product is layered with two outer layers and a center layer therebetween and said headbox has three chambers, a pair of outer chambers and a center chamber therebetween, said method further comprises:

a) directing said first paper making furnish is directed to said center chamber;

b) preparing a second papermaking furnish by:

i) providing a second aqueous slurry comprising short papermaking fibers, said slurry having a fourth pH;

ii) providing means to adjust said fourth pH and adjusting said fourth pH to a third controlled pH range that is between about 5.0 and about 6.5;

iii) providing third acid means to adjust said third controlled pH range to a fourth, more narrowly controlled pH range that is between about 4.8 and about 5.4;

iv) providing a temporary wet strength resin solution;

v) mixing said slurry, said third acid means and said temporary wet strength resin solution so as to provide a second initially conditioned, resin treated, short papermaking fiber slurry;

vi) providing fourth acid means to adjust said fourth controlled pH range so as to control the pH of said second papermaking furnish to a range that is between about 4.8 and about 5.4;

vii) providing dilution water;

viii) mixing said second initially conditioned, resin treated, short papermaking fiber slurry, said fourth acid means, and said dilution water to complete preparation of said second papermaking furnish;

c) dividing said second furnish into first and second portions; and

d) directing said first portion to one of said outer chambers and said second portion to the other of said outer chambers.

28. The method of claim 27, said method further comprising:

a) depositing said furnishes onto a foraminous substrate forming an embryonic web; and

b) drying said embryonic web to form a web of said soft low density paper product, wherein said product has a density of less than about 0.6 grams per cubic centimeter, a basis weight between about 10 and about 65 grams per square meter, a dry strength less than about 500 grams per inch (197 grams per centimeter), a ratio of an initial wet strength to said dry strength greater than about 0.15:1, and a ratio of a thirty minute wet strength to said initial wet strength less than about 0.4.

29. The method of claim 28 wherein the embryonic web is dried using a method comprising:

a) transferring said embryonic web from said foraminous substrate to a carrier fabric;

b) blowing heated air through said embryonic web and said carrier fabric to form a semidry embryonic tissue paper web;

c) transferring said semidry embryonic tissue paper web to a Yankee drier;

d) drying said semi-dry embryonic tissue paper web on said Yankee drier and creping said dried web therefrom to form a dried web; and

e) winding said dried web upon a reel.

30. The method of claim 29 wherein said carrier fabric is an imprinting carrier fabric having an interconnected pattern of knuckles.

31. The method of claim 28 wherein the embryonic web is dried using a method comprising:

a) transferring said embryonic web from said foraminous substrate to a carrier fabric to form a shortened embryonic web;

b) transferring said shortened embryonic web to a dryer fabric;

c) blowing heated air through said shortened embryonic web and said dryer fabric to form a dried web; and

d) winding said dried web upon a reel.

32. A soft, low density paper product made according to the method of claim 26.

33. A soft, low density paper product made according to the method of claim 28.