U.S. patent application number 10/289558 was filed with the patent office on 2004-05-06 for low slough tissue products and method for making same.
Invention is credited to Branham, Kelly Dean, Bunyard, William Clayton, Flugge, Lisa Ann, Shannon, Thomas Gerard.
Application Number | 20040084162 10/289558 |
Document ID | / |
Family ID | 32176093 |
Filed Date | 2004-05-06 |
United States Patent
Application |
20040084162 |
Kind Code |
A1 |
Shannon, Thomas Gerard ; et
al. |
May 6, 2004 |
Low slough tissue products and method for making same
Abstract
The present invention is a soft tissue sheet having reduced lint
and slough. The tissue sheet comprises papermaking fibers and a
synthetic co-copolymer. The synthetic co-polymer has the general
structure: 1 wherein R.sup.1, R.sup.2, R.sup.3 are independently
selected from a group consisting of: H; C.sub.1-4 alkyl radicals;
and, mixtures thereof; R.sup.4 is selected from a group consisting
of C.sub.1-C.sub.8 alkyl radicals and mixtures thereof; Z.sup.1 is
a bridging radical attaching the R.sup.4 functionality to the
polymer backbone; and, Q.sup.1 is a functional group containing at
least a cationic quaternary ammonium radical. w, x, y.gtoreq.1 and
the mole ratio of x to (x+y) is about 0.5 or greater.
Inventors: |
Shannon, Thomas Gerard;
(Neenah, WI) ; Branham, Kelly Dean; (Winneconnne,
WI) ; Bunyard, William Clayton; (DePere, WI) ;
Flugge, Lisa Ann; (Neenah, WI) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
|
Family ID: |
32176093 |
Appl. No.: |
10/289558 |
Filed: |
November 6, 2002 |
Current U.S.
Class: |
162/109 ;
162/158; 162/168.3 |
Current CPC
Class: |
D21H 17/455 20130101;
D21H 21/24 20130101 |
Class at
Publication: |
162/109 ;
162/168.3; 162/158 |
International
Class: |
D21H 017/33 |
Claims
We claim:
1. A soft tissue sheet having reduced lint and slough comprising
papermaking fibers and a synthetic co-copolymer, the synthetic
co-polymer having the general structure: 5wherein: R.sup.1,
R.sup.2, R.sup.3 are independently selected from a group consisting
of: H; C.sub.1-4 alkyl radicals; and, mixtures thereof; R.sup.4 is
selected from a group consisting of C.sub.1-C.sub.8 alkyl radicals
and mixtures thereof; Z.sup.1 is a bridging radical attaching the
R.sup.4 functionality to the polymer backbone; and, Q.sup.1 is a
functional group containing at least a cationic quaternary ammonium
radical; wherein w, x, y.gtoreq.1 and the mole ratio of x to (x+y)
is about 0.5 or greater.
2. The soft tissue sheet of claim 1, wherein the amount of the
synthetic co-polymer is from about 0.02 to about 5 weight percent
by weight of dried papermaking fibers.
3. The soft tissue sheet of claim 1, wherein the soft tissue sheet
has a Wet Out Time of about 180 seconds or less.
4. The soft tissue sheet of claim 1, wherein Z.sup.1 is selected
from a group consisting of: --O--; --COO--; --OOC--; --CONH--;
--NHCO--; and, mixtures thereof.
5. The soft tissue sheet of claim 1, wherein the soft tissue sheet
has a basis weight of about 5 to about 150 g/m.sup.2 and a bulk of
about 2 cm.sup.3/g or greater.
6. The soft tissue sheet of claim 5, wherein the soft tissue sheet
has a bulk of about 4 cm.sup.3/g or greater.
7. The soft tissue sheet of claim 1 wherein R.sup.1 is H, R.sup.2
is H, R.sup.3 is H or --CH.sub.3, and R.sup.4 is selected from the
group consisting of: methyl radicals; ethyl radicals; propyl
radicals; butyl radicals; and, mixtures thereof.
8. The soft tissue sheet of claim 1, wherein Q.sup.1 of the
synthetic co-polymer is derived from monomers selected from the
group consisting of: [2-(methacryloyloxy)ethyl]trimethylammonium
methosulfate; [2-(methacryloyloxy)ethyl]trimethylammonium
ethosulfate; dimethyldiallyl ammonium chloride;
3-acryloamido-3-methyl butyl trimethyl ammonium chloride; vinyl
benzyl trimethyl ammonium chloride;
2[(acryloyloxy)ethyl]trimethylammonium chloride;
[2-(methacryloyloxy)ethy- l]trimethylammonium chloride; and,
mixtures thereof.
9. The soft tissue sheet of claim 1, wherein the mole ratio of x to
(x+y) of the synthetic co-polymer is about 0.75 or greater.
10. The soft tissue sheet of claim 1, wherein the mole ratio of x
to (x+y) of the synthetic co-polymer is about 0.90 or greater.
11. The soft tissue sheet of claim 1, wherein the synthetic
co-polymer is water soluble or water dispersible.
12. A soft tissue sheet having reduced lint and slough comprising
papermaking fibers and a synthetic co-copolymer, the synthetic
co-polymer having the general structure: 6wherein: w, x,
y.gtoreq.1; the mole ratio of (x+z) to (x+y+z) is about 0.5 or
greater and the mole ratio of z to (x+z) is from about 0 to about
0.8; R.sup.1, R.sup.2, R.sup.3 are independently selected from a
group consisting of H, C.sub.1-4 alkyl radicals, and mixtures
thereof; R.sup.4 is selected from a group consisting of
C.sub.1-C.sub.8 alkyl radicals and mixtures thereof; Z.sup.1 is a
bridging radical attaching the R.sup.4 functionality to the polymer
backbone; Q.sup.1 is a functional group containing at least a
cationic quaternary ammonium radical; and, Q.sup.2 is selected from
a group consisting of: non-ionic hydrophilic monomers; water
soluble monomers; and, mixtures thereof.
13. The soft tissue sheet of claim 12, wherein the amount of the
synthetic co-polymer is from about 0.02 to about 5 weight percent
by weight of dried papermaking fibers.
14. The soft tissue sheet of claim 12, wherein the soft tissue
sheet has a Wet Out Time of about 180 seconds or less.
15. The soft tissue sheet of claim 12, wherein Z.sup.1 is selected
from a group consisting of: --O--; --COO--; --OOC--; --CONH--;
--NHCO--; and, mixtures thereof.
16. The soft tissue sheet of claim 12, wherein Q.sup.2 is derived
from monomers selected from the group of: hydroxyalkyl acrylates;
hydroxyalkyl methacrylates; hydroxyethyl acrylate; polyalkoxyl
acrylates; polyalkoxyl methacrylates; diacetone acrylamide;
N-vinylpyrrolidinone; N-vinylformamide; and, mixtures thereof.
17. The soft tissue sheet of claim 12, wherein the soft tissue
sheet has a basis weight of about 5 to about 150 g/m.sup.2 and a
bulk of about 2 cm.sup.3/g or greater.
18. The soft tissue sheet of claim 12, wherein the soft tissue
sheet has a bulk of about 4 cm.sup.3/g or greater.
19. The soft tissue sheet of claim 12, wherein R.sup.1 is H,
R.sup.2 is H, R.sup.3 is H or --CH.sub.3, and R.sup.4 is selected
from the group consisting of methyl radicals; ethyl radicals;
propyl radicals; butyl radicals; and, mixtures thereof.
20. The soft tissue sheet of claim 12, wherein Q.sup.1 of the
synthetic co-polymer is derived from monomers selected from the
group consisting of: [2-(methacryloyloxy)ethyl]trimethylammonium
methosulfate; [2-(methacryloyloxy)ethyl]trimethylammonium
ethosulfate; dimethyldiallyl ammonium chloride;
3-acryloamido-3-methyl butyl trimethyl ammonium chloride; vinyl
benzyl trimethyl ammonium chloride;
2[(acryloyloxy)ethyl]trimethylammonium chloride;
[2-(methacryloyloxy)ethy- l]trimethylammonium chloride; and,
mixtures thereof.
21. The soft tissue sheet of claim 16, wherein the polyalkoxyl
acrylate is a polyethyleneglycol acrylate.
22. The soft tissue sheet of claim 16, wherein the polyalkoxyl
methacrylate is a polyethyleneglycol methacrylate.
23. The soft tissue sheet of claim 12, wherein the synthetic
co-polymer is water soluble or water dispersible.
24. A tissue chemical additive capable of debonding a tissue sheet
containing papermaking fibers treated with the chemical additive
while reducing the lint and slough of the tissue sheet treated with
the chemical additive.
25. The tissue chemical additive of claim 24 comprising a synthetic
co-polymer having the general structure: 7Wherein: R.sup.1,
R.sup.2, R.sup.3 are independently selected from a group consisting
of: H; C.sub.1-4 alkyl radicals; and, mixtures thereof; R.sup.4 is
selected from a group consisting of C.sub.1-C.sub.8 alkyl radicals
and mixtures thereof; Z.sup.1 is a bridging radical attaching the
R.sup.4 functionality to the polymer backbone; and, Q.sup.1 is a
functional group containing at least a cationic quaternary ammonium
radical; wherein w, x, y>1 and the mole ratio of x to (x+y) is
about 0.5 or greater.
26. The tissue chemical additive of claim 25, wherein R.sup.1 is H,
R.sup.2 is H, R.sup.3 is H or --CH.sub.3, and R.sup.4 is selected
from the group consisting of: methyl radicals; ethyl radicals;
propyl radicals; butyl radicals; and, mixtures thereof.
27. The tissue chemical additive of claim 25, wherein Q.sup.1 is
derived from monomers selected from the group consisting of:
[2-(methacryloyloxy)ethyl]trimethylammonium methosulfate;
[2-(methacryloyloxy)ethyl]trimethylammonium ethosulfate;
dimethyldiallyl ammonium chloride; 3-acryloamido-3-methyl butyl
trimethyl ammonium chloride; vinyl benzyl trimethyl ammonium
chloride; 2-[(acryloyloxy)ethyl]trimethylammonium chloride;
[2-(methacryloyloxy)eth- yl]trimethylammonium chloride; and,
mixtures thereof.
28. The tissue chemical additive of claim 25, wherein Z.sup.1 of
the synthetic co-polymer is selected from a group consisting of:
--O--; --COO--; --OOC--; --CONH--; --NHCO--; and, mixtures
thereof.
29. The tissue chemical additive of claim 25, wherein the mole
ratio of x to (x+y) of the synthetic co-polymer is about 0.75 or
greater.
30. The tissue chemical additive of claim 25, wherein the mole
ratio of x to (x+y) of the synthetic co-polymer is about 0.90 or
greater.
31. The tissue chemical additive of claim 25, wherein the synthetic
co-polymer has an average molecular weight between about 10,000 to
about 5,000,000.
32. The tissue chemical additive of claim 25, wherein the synthetic
co-polymer is water dispersible or water soluble.
33. The tissue chemical additive of claim 24 comprising a synthetic
co-polymer having the general structure: 8Wherein: w, x,
y.gtoreq.1; the mole ratio of (x+z) to (x+y+z) is about 0.5 or
greater and the mole ratio of z to x is from about 0 to about 0.8;
R.sup.1, R.sup.2, R.sup.3 are independently selected from a group
consisting of: H; C.sub.1-4 alkyl radicals; and, mixtures thereof;
R.sup.4 is selected from a group consisting of C.sub.1-C.sub.8
alkyl radicals and mixtures thereof; Z.sup.1 is a bridging radical
attaching the R.sup.4 functionality to the polymer backbone;
Q.sup.1 is a functional group containing at least a cationic
quaternary ammonium radical; and, Q.sup.2 is selected from a group
consisting of: non-ionic hydrophilic monomers; water soluble
monomers; and, mixtures thereof.
34. The tissue chemical additive of claim 33, wherein Z.sup.1 of
the synthetic co-polymer is selected from a group consisting of:
--O--; --COO--; --OOC--; --CONH--; --NHCO--; and, mixtures
thereof.
35. The tissue chemical additive of claim 33, wherein Q.sup.2 of
the synthetic co-polymer is derived from monomers selected from the
group of: hydroxyalkyl acrylates; hydroxyalkyl methacrylates;
hydroxyethyl acrylate; polyalkoxyl acrylates; polyalkoxyl
methacrylates; diacetone acrylamide; N-vinylpyrrolidinone;
N-vinylformamide; and, mixtures thereof.
36. The tissue chemical additive of claim 35, wherein the
hydroxyalkyl methacrylate is a hydroxyethyl methacrylate.
37. The tissue chemical additive of claim 35, wherein the
polyalkoxyl acrylate is a polyethyleneglycol acrylate.
38. The tissue chemical additive of claim 35, wherein the
polyalkoxyl methacrylate is a polyethyleneglycol methacrylate.
39. The tissue chemical additive of claim 33, wherein the mole
ratio of (x+z) to (x+y+z) of the synthetic co-polymer is about 0.75
or greater.
40. The tissue chemical additive of claim 33, wherein the mole
ratio of (x+z) to (x+y+z) of the synthetic co-polymer is about 0.90
or greater.
41. The tissue chemical additive of claim 33, wherein the mole
ratio of z to (x+z) of the synthetic co-polymer is from about 0 to
about 0.4.
42. The tissue chemical additive of claim 33, wherein the mole
ratio of z to (x+z) of the synthetic co-polymer is from about 0 to
about 0.2.
43. The tissue chemical additive of claim 33, wherein the synthetic
co-polymer has an average molecular weight between about 10,000 to
about 5,000,000.
44. The tissue chemical additive of claim 33, wherein the tissue
chemical additive is water soluble or water dispersible.
45. A method of making a soft, low lint tissue sheet, comprising:
(a) forming an aqueous suspension comprising papermaking fibers;
(b) depositing the aqueous suspension of papermaking fibers onto a
forming fabric thereby forming a wet tissue sheet; (c) dewatering
the wet tissue sheet thereby forming a dewatered tissue sheet; and,
(d) applying a synthetic co-copolymer to the papermaking fibers,
the synthetic co-polymer having the general structure: 9Wherein:
R.sup.1, R.sup.2, R.sup.3 are independently selected from a group
consisting of: H; C.sub.1-4 alkyl radicals; and, mixtures thereof;
R.sup.4 is selected from a group consisting of C.sub.1-C.sub.8
alkyl radicals and mixtures thereof; Z.sup.1 is a bridging radical
attaching the R.sup.4 functionality to the polymer backbone; and,
Q.sup.1 is a functional group containing at least a cationic
quaternary ammonium radical, wherein w, x, y>1 and the mole
ratio of x to (x+y) is about 0.5 or greater.
46. The method of claim 45, wherein the amount of the synthetic
co-polymer is from about 0.02 to about 5 weight percent by weight
of dried papermaking fibers.
47. The method of claim 45, wherein the synthetic co-polymer is
applied to the wet tissue sheet having a consistency from about 10
percent to about 80 percent.
48. The method of claim 45, wherein the synthetic co-polymer is
applied to the wet sheet having a consistency from about 10 percent
to about 50 percent.
49. The method of claim 45, wherein the synthetic co-polymer is
applied to the aqueous suspension of pulp fibers having a
consistency from about 0.2% to about 50%.
50. The method of claim 45, further comprising drying the treated
dewatered tissue sheet thereby forming a dried treated tissue
sheet.
51. The method of claim 45, wherein Z.sup.1 of the synthetic
co-polymer is selected from a group consisting of: --O--; --COO--;
--OOC--; --CONH--; --NHCO--; and, mixtures thereof.
52. The method of claim 45, wherein R.sup.1 is H, R.sup.2 is H,
R.sup.3 is H or --CH.sub.3, and R.sup.4 is selected from the group
consisting of: methyl radicals; ethyl radicals; propyl radicals;
butyl radicals; and, mixtures thereof.
53. The method of claim 45, wherein Q.sup.1 of the synthetic
co-polymer is derived from monomers selected from the group
consisting of: [2-(methacryloyloxy)ethyl]trimethylammonium
methosulfate; [2-(methacryloyloxy)ethyl]trimethylammonium
ethosulfate; dimethyldiallyl ammonium chloride;
3-acryloamido-3-methyl butyl trimethyl ammonium chloride; vinyl
benzyl trimethyl ammonium chloride;
2[(acryloyloxy)ethyl]trimethylammonium chloride;
[2-(methacryloyloxy)ethy- l]trimethylammonium chloride; and,
mixtures thereof.
54. The method of claim 45, wherein the mole ratio of x to (x+y) of
the synthetic co-polymer is about 0.75 or greater.
55. The method of claim 45, wherein the mole ratio of x to (x+y) of
the synthetic co-polymer is about 0.90 or greater.
56. The method of claim 45, wherein the synthetic co-polymer has an
average molecular weight between about 10,000 to about
5,000,000.
57. The method of claim 45, wherein the synthetic co-polymer is
water soluble or water dispersible.
58. The method of claim 50, wherein the dried tissue sheet has a
Wet Out Time of about 180 seconds or less.
59. The method of claim 50, wherein the dried tissue sheet has a
basis weight of about 5 to about 150 g/m.sup.2 and a bulk of about
2 cm.sup.3/g or greater.
60. The method of claim 58, wherein the dried tissue sheet has a
bulk of about 4 cm.sup.3/g or greater.
61. A method of making a soft, low lint tissue sheet, comprising:
(a) forming an aqueous suspension comprising papermaking fibers;
(b) depositing the aqueous suspension of papermaking fibers onto a
forming fabric thereby forming a wet tissue sheet; (c) dewatering
the wet tissue sheet thereby forming a dewatered tissue sheet; and,
(d) applying a synthetic co-copolymer to the papermaking fibers,
the synthetic co-polymer having the general structure: 10Wherein:
w, x, y>1; the mole ratio of (x+z) to (x+y+z) is greater than
0.5 and the mole ratio of z to (x+z) is from about 0 to about 0.8;
R.sup.1, R.sup.2, R.sup.3 are independently selected from a group
consisting of: H; C.sub.1-4 alkyl radicals; and, mixtures thereof;
R.sup.4 is selected from a group consisting of C.sub.1-C.sub.8
alkyl radicals and mixtures thereof; Z.sup.1 is a bridging radical
attaching the R.sup.4 functionality to the polymer backbone;
Q.sup.1 is a functional group containing at least a cationic
quaternary ammonium radical; and, Q.sup.2 is selected from a group
consisting of: non-ionic hydrophilic monomers; water soluble
monomers; and, mixtures thereof.
62. The method of claim 61, wherein the amount of the synthetic
co-polymer is from about 0.02 to about 5 weight percent by weight
of dried papermaking fibers.
63. The method of claim 61, wherein the synthetic co-polymer is
applied to the wet tissue sheet having a consistency from about 10
percent to about 80 percent.
64. The method of claim 61, wherein the synthetic co-polymer is
applied to the wet sheet having a consistency from about 10 percent
to about 50 percent.
65. The method of claim 61, wherein the synthetic co-polymer is
applied to the aqueous suspension having a consistency from about
0.1% to about 50%.
66. The method of claim 61, further comprising drying the dewatered
tissue sheet thereby forming a dried tissue sheet.
67. The method of claim 61, wherein Z.sup.1 of the synthetic
co-polymer is selected from a group consisting of: --O--; --COO--;
--OOC--; --CONH--; --NHCO--; and, mixtures thereof.
68. The method of claim 61, wherein Q.sup.2 is derived from
monomers selected from the group of: hydroxyalkyl acrylates;
hydroxyalkyl methacrylates; hydroxyethyl acrylate; polyalkoxyl
acrylates; polyalkoxyl methacrylates; diacetone acrylamide;
N-vinylpyrrolidinone; N-vinylformamide; and, mixtures thereof.
69. The method of claim 68 wherein the hydroxyalkyl methacrylate is
a hydroxyethyl methacrylate.
70. The method of claim 68, wherein the polyalkoxyl acrylate is a
polyethyleneglycol acrylate.
71. The method of claim 68, wherein the polyalkoxyl methacrylate is
a polyethyleneglycol methacrylate.
72. The method of claim 61, wherein the mole ratio of (x+z) to
(x+y+z) of the synthetic co-polymer is about 0.75 or greater.
73. The method of claim 61, wherein the mole ratio of (x+z) to
(x+y+z) of the synthetic co-polymer is about 0.90 or greater.
74. The method of claim 61, wherein the mole ratio of z to (x+z) of
the synthetic co-polymer is from about 0 to about 0.4.
75. The method of claim 61, wherein the mole ratio of z to (x+z) of
the synthetic co-polymer is from about 0 to about 0.2.
76. The method of claim 61, wherein the synthetic co-polymer has an
average molecular weight between about 10,000 to about
5,000,000.
77. The method of claim 61, wherein the synthetic co-polymer is
water soluble or water dispersible.
78. The method of claim 68, wherein the dried tissue sheet has a
Wet Out Time of about 180 seconds or less.
79. The method of claim 66, wherein the dried tissue sheet has a
basis weight of about 5 to about 100 g/m.sup.2, and a bulk of about
2 cm.sup.3/g or higher.
80. The method of claim 79, wherein the dried tissue sheet has a
bulk of about 4 cm.sup.3/g or greater.
Description
BACKGROUND OF THE INVENTION
[0001] In the manufacture of paper products, such as facial tissue,
bath tissue, paper towels, dinner napkins and the like, a wide
variety of product properties are imparted to the final product
through the use of chemical additives applied in the wet end of the
tissue making process. Two of the most important attributes
imparted to tissue through the use of wet end chemical additives
are strength and softness. Specifically for softness, a chemical
debonding agent is normally used. Such debonding agents are
typically quaternary ammonium compounds containing long chain alkyl
groups. The cationic quaternary ammonium entity allows for the
material to be retained on the cellulose via ionic bonding to
anionic groups on the cellulose fibers. The long chain alkyl groups
provide softness to the tissue sheet by disrupting fiber-to-fiber
hydrogen bonds in the sheet.
[0002] Such disruption of fiber-to-fiber bonds provides a two-fold
purpose in increasing the softness of the tissue sheet. First, the
reduction in hydrogen bonding produces a reduction in tensile
strength thereby reducing the stiffness of the tissue sheet.
Secondly, the debonded fibers provide a surface nap to the tissue
sheet enhancing the "fuzziness" of the tissue sheet. This tissue
sheet fuzziness may also be created through use of creping as well,
where sufficient interfiber bonds are broken at the outer tissue
surface to provide a plethora of free fiber ends on the tissue
surface.
[0003] Both debonding and creping increase levels of lint and
slough in the product. Indeed, while softness increases, it is at
the expense of an increase in lint and slough in the tissue sheet
relative to an untreated control. It can also be shown that in a
blended (non-layered) tissue sheet that the level of lint and
slough is inversely proportional to the tensile strength of the
tissue sheet. Lint and slough can generally be defined as the
tendency of the fibers in the paper sheet to be rubbed from the
sheet when handled.
[0004] A multi-layered tissue structure to enhance the softness of
the tissue sheet. One such embodiment, a thin layer of strong
softwood fibers is used in the center layer to provide the
necessary tensile strength for the product. The outer layers of
such structures are composed of the shorter hardwood fibers, which
may or may not contain a chemical debonder. A disadvantage to using
layered structures is that while softness is increased the
mechanism for such increase is believed due to an increase in the
surface nap of the debonded, shorter fibers. As a consequence, such
structures, while showing enhanced softness, do so with a trade-off
of an increase in the level of lint and slough.
[0005] A chemical strength agent may be added in the wet-end to
counteract the negative effects of the debonding agents. In a
blended tissue sheet, the addition of such chemical strength agents
reduces lint and slough levels. However, such reduction is done at
the expense of surface feel and overall softness of the tissue
sheet and becomes primarily a function of tissue sheet tensile
strength. In a layered tissue sheet, strength chemicals are added
preferentially to the center layer. While this perhaps helps to
give a tissue sheet with an improved surface feel at a given
tensile strength, such structures actually exhibit higher slough
and lint at a given tensile strength, with the level of debonder in
the outer layer being directly proportional to the increase in lint
and slough. Co-pending U.S. patent application Ser. No. 09/736,924
(Shannon et al.) published on Aug. 22, 2002 discloses low slough
tissue products made with acrylamides containing hydrophobic
moieties. These synthetic polymers, while reducing the amount of
slough compared to traditional debonders, still show an increase in
slough with decreasing tensile strength.
[0006] Therefore there is a need for a means of reducing lint and
slough in soft tissue sheets while maintaining the softness and
strength of the tissue sheets. It is an objective of the present
invention to design paper-making chemicals, more specifically
tissue making chemicals, capable of reducing hydrogen bonding while
also possessing ability to reduce lint and slough. It is a further
objective to develop a process for making soft, low slough, low
lint tissue products via wet end application of chemistry. It is a
further objective of the present invention to make soft, absorbent,
low lint and slough tissue products such as sanitary bath tissue,
facial tissue, paper towels and the like via wet end application of
such chemistry.
SUMMARY
[0007] It has now been discovered that certain cationic water
dispersible synthetic copolymers when applied to the wet end of the
tissue machine may act as debonding chemicals while at the same
time reducing the amount of lint and slough. Hence, soft tissue
sheets having low lint and slough levels are obtained. The
chemicals of the present invention are synthetic co-polymers formed
from two or more different monomers. The synthetic co-polymers of
the present invention are the polymerization product of a cationic
monomer and at least one hydrophobic monomer. Additionally, the
synthetic co-polymers of the present invention may also be the
polymerization product of a cationic monomer, at least one
hydrophobic monomer and optionally at least one non-ionic
hydrophilic monomer. While not wishing to be bound by theory, it is
believed that the synthetic copolymers attach to the fibers via
electrostatic attraction for the anionic fibers. As the synthetic
co-polymers have no hydrogen or covalent bonding entity, they
debond the fibers via the traditional mechanism by which chemical
debonding agents function.
[0008] The synthetic co-polymers of the present invention are,
however, good film forming agents and have good inter-molecular
adhesive properties. Hence, the fibers are held in place by the
co-polymer to co-polymer cohesive properties and good slough
reduction occurs. The aliphatic hydrocarbon portion of the
synthetic co-polymer molecule enables a significant level of
debonding to occur and insures that the tissue sheet product has
good surface nap or "fuzzy" feel. Yet, these fibers retain a
significant inter-fiber bonding potential due to intra- and
inter-molecular associative forces present in the synthetic
copolymers that help the fibers remain anchored to the tissue
sheet. As such, fibers treated with these synthetic co-polymers
produce a tissue sheet having lower lint and slough at a given
tensile strength than a tissue sheet prepared with conventional
softening agents or a combination of conventional softening agents
and conventional strength agents.
[0009] The term "water dispersible" as used herein, means that the
cationic synthetic copolymers are either water soluble or capable
of existing as stable colloidal, self-emulsifiable or other type
dispersions in water without the presence of added emulsifiers.
Added emulsifiers may be employed within the scope of the present
invention to aid in the polymerization of the cationic synthetic
co-polymers or assist in compatiblizing the cationic synthetic
co-polymers with other chemical agents used in the tissue sheet,
however, the emulsifiers are not essential to formation of stable
dispersions or solutions of the cationic synthetic co-polymers in
water.
[0010] It is known in the art to add latex polymer emulsions of
styrene butadiene rubber binders and ethylene vinyl acetate binders
topically to a formed tissue sheet to decrease strength loss
associated with topical application of debonders and other
softening agents. Large amounts of emulsifiers are used in the
production of such latex polymers and these emulsifiers are
critical to the stability of the latex polymers in water. The latex
polymers are not of themselves water dispersible. The emulsions are
susceptible to breaking, causing a film of the latex polymer to
develop on processing equipment. This film continues to deposit on
equipment to the point where shutdown and clean-up of the equipment
is required. As the latex polymers are not water dispersible
clean-up can be time consuming, costly and environmentally
unfriendly. Furthermore, the lack of water dispersability makes
tissue sheets made with these latex polymers difficult to
impossible to redisperse, causing a significant economic penalty to
be incurred in tissue sheets employing these traditional latex
polymers. As these latex polymers are not cationic, wet end
application of these latex polymers is significantly constrained
and the latex polymers demonstrate ability to only increase
strength. The disadvantages to using these materials have severely
limited commercial use of traditional latex polymers in
tissue-based products.
[0011] It is known wherein a procedure for creping paper comprises
incorporation in paper pulp or a paper sheet of a cationic water
soluble addition polymer containing amine groups and optionally
quaternary ammonium groups. Optionally the addition polymer may
contain units of one other monoethylenically unsaturated monomers
in a level such that the addition polymer remains water soluble. A
critical aspect of such a procedure is the presence of free amine
groups which, when used in conjunction with the optional quaternary
group, must be present in a ratio>1:1 relative to the quaternary
group. The addition polymers are used as creping facilitators to
promote enhanced Yankee dryer adhesion. However, enhanced Yankee
dryer adhesion is typically not a desirable characteristic when
making low slough and lint tissue-based products, such adhesion
being known to those skilled in the art to increase levels of lint
and slough. Furthermore, the presence of the free amine groups
makes the addition polymers sensitive to pH when applied in the wet
end of tissue making processes, turning the tissue sheet
hydrophobic under acidic conditions and imparting undesired wet
strength when used under basic conditions. An additional
consideration when using the addition polymers is the presence of
the free amine groups, capable of reacting with other papermaking
additives, such as those containing aldehyde and azetidinium
groups, thereby risking the reduction of the efficacy of those
additives.
[0012] Hence, in one aspect, the present invention resides in a
tissue chemical additive capable of simultaneously debonding and
reducing lint and slough, the tissue chemical additive comprising a
cationic synthetic water dispersible co-polymer containing a
hydrophobic portion such that the hydrophobic portion is capable of
demonstrating intra-molecular adhesive properties in the dry state
while exhibiting ability to debond a tissue sheet when applied to
the tissue sheet at a low consistency. The synthetic co-polymers
have the following general structure: 2
[0013] Wherein:
[0014] R.sup.1, R.sup.2, R.sup.3 are independently H, C.sub.1-4
alkyl radical, or mixtures thereof.
[0015] R.sup.4 is a C.sub.1-C.sub.8 alkyl radical or mixtures
thereof.
[0016] Z.sup.1 is a bridging radical attaching the R.sup.4
functionality to the polymer backbone. Examples include, but are
not limited to, --O--, --COO--, --OOC--, --CONH--, --NHCO--, and
mixtures thereof.
[0017] Q.sup.1 is a functional group containing a cationic
quaternary ammonium radical.
[0018] Q.sup.2 is an optional group comprised of a non-ionic
hydrophilic or water soluble monomer or monomers (and mixtures
thereof) incorporated into the synthetic co-polymer so as to make
the synthetic co-polymer more hydrophilic. Q.sup.2 possesses
limited ability to hydrogen or covalently bond to cellulose fibers,
such bonding resulting in an increase in stiffness of the tissue
sheet. Suitable hydrophilic monomers or water-soluble nonionic
monomers for use in the cationic synthetic co-polymers of the
present invention include, but are not limited to, monomers, such
as, hydroxyalkyl acrylates and hydroxyalkyl methacrylates, such as
hydroxyethyl methacrylate (HEMA); hydroxyethyl acrylate;
polyalkoxyl acrylates, such as polyethyleneglycol acrylates; and,
polyalkoxyl methacrylates, such as polyethyleneglycol methacrylates
("PEG-MA"). Other suitable hydrophilic monomers or water-soluble
nonionic monomers for use in the ion-sensitive cationic synthetic
copolymers of the present invention include, but are not limited
to, diacetone acrylamide, N-vinylpyrrolidinone, and
N-vinylformamide.
[0019] The mole ratio of z:x will specifically range from about 0:1
to about 4: 1, more specifically from about 0:1 to about 1:1, and
most specifically from about 0:1 to about 1:3. The mole ratio of
(x+z):y may be from about 0.98:0.02 to about 1:1, and most
specifically from about 0.95:0.05 to about 0.70:0.30.
[0020] Hence, in another aspect, the present invention resides in a
soft, low lint and slough absorbent paper sheet, such as a tissue
sheet, comprising a cationic synthetic water dispersible co-polymer
containing a hydrophobic portion such that the hydrophobic portion
is capable of demonstrating intermolecular associative properties
in the dry state while exhibiting ability to debond a tissue sheet
when applied to the tissue sheet at a low consistency. The cationic
water dispersible synthetic co-polymers have the following general
structure: 3
[0021] Wherein:
[0022] R.sup.1, R.sup.2, R.sup.3 are independently H, C.sub.1-4
alkyl radical, or mixtures thereof.
[0023] R.sup.4 is a C.sub.1-C.sub.8 alkyl radical or mixtures
thereof.
[0024] Z.sup.1 is a bridging radical attaching the R.sup.4
functionality to the polymer backbone. Examples include, but are
not limited to, --O--, --COO--, --OOC--, --CONH--, --NHCO--, and
mixtures thereof.
[0025] Q.sup.1 is a functional group containing a cationic
quaternary ammonium radical.
[0026] Q.sup.2 is an optional group comprised of a non-ionic
hydrophilic or water soluble monomer or monomers (and mixtures
thereof) incorporated into the synthetic co-polymer so as to make
the synthetic co-polymer more hydrophilic. Q.sup.2 possesses
limited ability to hydrogen or covalently bond to cellulose fibers,
such bonding resulting in an increase in stiffness of the tissue
sheet. Suitable hydrophilic monomers or water-soluble nonionic
monomers for use in the cationic synthetic co-polymers of the
present invention include, but are not limited to, monomers, such
as, hydroxyalkyl acrylates and hydroxyalkyl methacrylates, such as
hydroxyethyl methacrylate (HEMA); hydroxyethyl acrylate;
polyalkoxyl acrylates, such as polyethyleneglycol acrylates; and,
polyalkoxyl methacrylates, such as polyethyleneglycol methacrylates
("PEG-MA"). Other suitable hydrophilic monomers or water-soluble
nonionic monomers for use in the ion-sensitive cationic synthetic
copolymers of the present invention include, but are not limited
to, diacetone acrylamide, N-vinylpyrrolidinone, and
N-vinylformamide.
[0027] The mole ratio of z:x will specifically range from about 0:1
to about 4:1, more specifically from about 0:1 to about 1:1, and
most specifically from about 0:1 to about 1:3. The mole ratio of
(x+z):y may be from about 0.98:0.02 to about 1:1, and most
specifically from about 0.95:0.05 to about 0.70:0.30.
[0028] In another aspect, the present invention resides in a method
of making a soft, low lint tissue sheet, comprising the steps of:
(a) forming an aqueous suspension comprising papermaking fibers;
(b) depositing the aqueous suspension of papermaking fibers onto a
forming fabric to form a wet tissue sheet; and, (c) dewatering and
drying the wet tissue sheet to form a paper sheet, wherein a
cationic water dispersible synthetic co-polymer containing a
hydrophobic portion such that the hydrophobic portion is capable of
demonstrating intra-molecular adhesive properties in the dry state
while exhibiting an ability to debond the tissue sheet is added to
the aqueous suspension of the paper-making fibers or topically to
the wet tissue sheet at a consistency of about 80% or less, the
cationic water dispersible synthetic co-polymer has the following
general structure: 4
[0029] Wherein:
[0030] R.sup.1, R.sup.2, R.sup.3 are independently H, C.sub.1-4
alkyl radical, or mixtures thereof.
[0031] R.sup.4 is a C.sub.1-C.sub.8 alkyl radical or mixtures
thereof.
[0032] Z.sup.1 is a bridging radical attaching the R.sup.4
functionality to the polymer backbone. Examples include, but are
not limited to, --O--, --COO--, --OOC--, --CONH--, --NHCO--, and
mixtures thereof.
[0033] Q.sup.1 is a functional group containing a cationic
quaternary ammonium radical.
[0034] Q.sup.2 is an optional group comprising a non-ionic
hydrophilic or water soluble monomer or monomers (and mixtures
thereof) incorporated into the synthetic co-polymer so as to make
the synthetic co-polymer more hydrophilic. Q.sup.2 possesses
limited ability to hydrogen or covalently bond to cellulose fibers,
such bonding resulting in an increase in stiffness of the tissue
sheet. Suitable hydrophilic monomers or water-soluble nonionic
monomers for use in the cationic synthetic co-polymers of the
present invention include, but are not limited to, monomers, such
as, hydroxyalkyl acrylates and hydroxyalkyl methacrylates, such as
hydroxyethyl methacrylate (HEMA); hydroxyethyl acrylate;
polyalkoxyl acrylates, such as polyethyleneglycol acrylates; and,
polyalkoxyl methacrylates, such as polyethyleneglycol methacrylates
("PEG-MA"). Other suitable hydrophilic monomers or water-soluble
nonionic monomers for use in the ion-sensitive cationic synthetic
copolymers of the present invention include, but are not limited
to, diacetone acrylamide, N-vinylpyrrolidinone, and
N-vinylformamide.
[0035] The mole ratio of z:x will specifically range from about 0:1
to about 4:1, more specifically from about 0:1 to about 1:1, and
most specifically from about 0:1 to about 1:3. The mole ratio of
(x+z):y may be from about 0.98:0.02 to about 1:1, and most
specifically from about 0.95:0.05 to about 0.70:0.30.
[0036] The amount of the cationic synthetic co-polymer additive
added to the papermaking fibers or the paper or tissue sheet may be
from about 0.02 to about 5 weight percent, on a dry fiber basis,
more specifically from about 0.05 to about 3 weight percent, and
still more specifically from about 0.1 to about 2 weight percent.
The synthetic co-polymer may be added to the fibers or paper or
tissue sheet at any point in the process, but it can be
particularly advantageous to add the synthetic co-polymer to the
fibers while the fibers are suspended in water, before or after
formation but prior to final drying of the sheet. This may include,
for example, addition in the pulp mill or to the pulper, a machine
chest, the headbox, or to the paper or tissue sheet prior to being
dried where the consistency of the tissue sheet is about 80% or
less.
[0037] In order to be an effective cationic synthetic co-polymer or
cationic synthetic polymer additive suitable for use in tissue
applications, the cationic synthetic co-polymer or cationic
synthetic co-polymer additive should desirably be (1) water soluble
or water dispersible; (2) safe (not toxic); and, (3) relatively
economical. In addition to the foregoing factors, the cationic
synthetic co-polymers and cationic synthetic co-polymer additives
of the present invention, when used as a binder composition for a
tissue sheet substrate, such as a facial, bath or towel product
should be (4) processable on a commercial basis; i.e., may be
applied relatively quickly on a large scale basis, such as by
spraying (which thereby requires that the binder composition have a
relatively low viscosity at high shear); and, (5) provide
acceptable levels of sheet or substrate wettability. The cationic
synthetic co-polymers and cationic synthetic co-polymer additives
of the present invention and articles made therewith, especially
facial tissue, bath-tissue and towels comprising the particular
compositions set forth below, can meet any or all of the above
criteria. Of course, it is not necessary for all of the advantages
of the preferred embodiments of the present invention to be met to
fall within the scope of the present invention.
DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a graph comparing GMT and slough values for a
topical application to a wet sheet of a particular synthetic
co-polymer of the present invention and controls.
[0039] FIG. 2 is a graph comparing GMT and softness values for a
topical application to a wet sheet of a particular synthetic
co-polymer of the present invention and controls.
[0040] FIG. 3 is a graph comparing slough and softness values for a
topical application to a wet sheet of a particular synthetic
co-polymer of the present invention and controls.
[0041] FIG. 4 is a graph comparing GMT and slough values for a
topical application to a wet sheet of various synthetic co-polymers
of the present invention and controls.
[0042] FIG. 5 is a graph comparing slough and softness values for a
topical application to a wet sheet of various synthetic co-polymers
of the present invention and controls.
[0043] FIG. 6 is a graph comparing GMT and slough values for bulk
wet end application of various synthetic co-polymers of the present
invention and controls.
[0044] FIG. 7 is a graph comparing slough and softness values for
bulk wet end application of various synthetic co-polymers of the
present invention and controls.
[0045] FIG. 8 is a schematic diagram of testing equipment used to
measure lint and slough.
DETAILED DESCRIPTION OF THE INVENTION
[0046] Cationic Synthetic Co-polymer Formulations
[0047] Suitable hydrophobic monomers for incorporating a
hydrophobic functionality into the cationic synthetic co-polymers
of the present invention include, but are not limited to, alkyl
acrylates, methacrylates, acrylamides, methacrylamides, tiglates
and crotonates, including butyl acrylate, butyl methacrylate,
methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacrylate, 1-Ethylhexyl tiglate, t-butyl acrylate, butyl
crotonate, butyl tiglate, sec-Butyl tiglate, Hexyl tiglate,
Isobutyl tiglate, hexyl crotonate, butyl crotonate, n-butyl
acrylamide, t-butyl acrylamide, N-(Butoxymethyl)acrylamide,
N-(Isobutoxymethyl) acrylamide, and the like including mixtures of
the monomers all of which are known commercially available
materials. Also known are various vinyl ethers including, but not
limited to, n-butyl vinyl ether, 2-ethylhexyl vinyl ether, and the
corresponding esters including vinyl pivalate, vinyl butyrate,
2-ethylhexanoate, and the like including mixtures of the monomers,
all of which are suitable for incorporation of the hydrophobic
aliphatic hydrocarbon moiety.
[0048] Suitable monomers for incorporating a cationic charge
functionality into the synthetic co-polymer include, but are not
limited to, [2-(methacryloyloxy)ethyl]trimethylammonium
methosulfate (METAMS); dimethyldiallyl ammonium chloride (DMDAAC);
3-acryloamido-3-methyl butyl trimethyl ammonium chloride (AMBTAC);
trimethylamino methacrylate; vinyl benzyl trimethyl ammonium
chloride (VBTAC); 2-[(acryloyloxy)ethyl]trimeth- ylammonium
chloride; [2-(methacryloyloxy)ethyl]trimethylammonium chloride.
[0049] Examples of preferred cationic monomers for the cationic
synthetic co-polymers of the present invention are
[2-(methacryloyloxy)ethyl]trimet- hyl ammonium chloride,
[2(methacryloyloxy)ethyl]trimethyl ammonium methosulfate,
[2-(methacryloyloxy)ethyl]trimethyl ammonium ethosulfate.
[0050] Suitable hydrophilic monomers or water-soluble nonionic
monomers for use in the cationic synthetic co-polymers of the
present invention include, but are not limited to N- and
N,N-substituted acrylamide and methacrylamide based monomers, such
as N,N-dimethyl acrylamide, N-ethyl acrylamide, N-isopropyl
acrylamide, and hydroxymethyl acrylamide; acrylate or methacrylate
based monomers, such as, hydroxyalkyl acrylates; hydroxyalkyl
methacrylates, such as hydroxyethyl methacrylate (HEMA);
hydroxyethyl acrylate; polyalkoxyl acrylates, such as
polyethyleneglycol acrylates; and, polyalkoxyl methacrylates, such
as polyethyleneglycol methacrylates ("PEG-MA"). Other suitable
hydrophilic monomers or water-soluble nonionic monomers for use in
the ion-sensitive cationic synthetic co-polymers of the present
invention include, but are not limited to, N-vinylpyrrolidinone and
N-vinylformamide.
[0051] For the cationic synthetic co-polymers of the present
invention the mole % of hydrophobic monomers will range from about
40 mole % to about 98 mole % of the total monomer composition, the
amount of cationic monomers will range from about 2 mole % to about
50 mole % of the total monomer composition. The amount of optional
hydrophilic monomers will range from about 0 mole % to about 58
mole % of the total monomer composition. Most preferably, the mole
percent of hydrophobic monomers is from about 50 mole % to about 95
mole % of the total monomer composition, the mole % of cationic
monomers is most preferably from about 5 mole % to about 30 mole %
of the total monomer composition, and the amount of optional
hydrophilic monomers is most preferably from about 0 mole % to
about 20 mole % of the total monomer composition.
[0052] The synthetic co-polymers of the present invention may have
an average molecular weight average molecular weight ranging from
about 10,000 to about 5,000,000. More specifically, the cationic
water dispersible synthetic co-polymers of the present invention
have a weight average molecular weight ranging from about 25,000 to
about 2,000,000, or, more specifically still, from about 50,000 to
about 1,000,000.
[0053] Another advantage to the disclosed cationic synthetic
co-polymers is ability to produce sheets having low stiffness due
to relatively low glass transition temperatures. While the cationic
synthetic co-polymers of the present invention may have a wide
range of glass transition temperature the glass transition
temperature may be about 100.degree. C. or less, more specifically
about 70.degree. C. or less, and most specifically about 40.degree.
C. or less. Some of the cationic synthetic co-polymers of the
present invention may show more than one glass transition
temperature. In such cases, the glass transition temperature of the
lowest glass transition temperature may be about 100.degree. C. or
less, more specifically about 70.degree. C. or less, and most
specifically about 40.degree. C. or less.
[0054] The cationic synthetic co-polymers of the present invention
may be prepared according to a variety of polymerization methods,
desirably a solution polymerization method. Suitable solvents for
the polymerization method include, but are not limited to, lower
alcohols such as methanol, ethanol and propanol; a mixed solvent
comprising water and one or more lower alcohols mentioned above;
and, a mixed solvent comprising water and one or more lower ketones
such as acetone or methyl ethyl ketone.
[0055] In the polymerization methods which may be utilized in the
present invention, any free radical polymerization initiator may be
used. Selection of a particular polymerization initiator may depend
on a number of factors including, but not limited to, the
polymerization temperature, the solvent, and the monomers used.
Suitable polymerization initiators for use in the present invention
include, but are not limited to, 2,2'-azobisisobutyronitrile,
2,2'-azobis(2-methylbutyronitrile),
2,2'-azobis(2,4-dimethylvaleronitrile),
2,2'-azobis(2-amidinopropane)dihy- drochloride,
2,2'-azobis(N,N'-dimethyleneisobutylamidine), potassium persulfate,
ammonium persulfate, and aqueous hydrogen peroxide. The amount of
polymerization initiator may desirably range from about 0.01 to
about 5 weight percent based on the total weight of monomer
present.
[0056] The polymerization temperature may vary depending on the
polymerization solvent, monomers, and polymerization initiator
used, but in general, ranges from about 20.degree. C. to about
90.degree. C. The polymerization time generally ranges from about 2
to about 8 hours.
[0057] The cationic synthetic co-polymer formulations of the
present invention may also be delivered in emulsion form, whereby
an aqueous polymerization process is used in conjunction with a
surfactant or set of surfactants, such polymerization methods being
known to those skilled in the art. The surfactants may be cationic
or non-ionic, but more specifically non-ionic.
[0058] The amount of the cationic synthetic co-polymer additive
added to the papermaking fibers or the paper or tissue sheet may be
from about 0.01 to about 5 weight percent, on a dry fiber basis,
more specifically from about 0.05 to about 3 weight percent, and
still more specifically from about 0.1 to about 2 weight percent.
The cationic synthetic co-polymer may be added to the papermaking
fibers or the paper or tissue sheet at any point in the process. In
one embodiment, the cationic synthetic co-polymers of the present
invention may be added after the tissue sheet is formed, more
specifically, to an existing wet tissue sheet. The solids level of
the wet tissue sheet is preferably about 80% or lower (i.e., the
tissue sheet comprises about 20 grams of dry solids and about 80
grams of water). More specifically, the solids level of the tissue
sheet during the application of the cationic synthetic co-polymers
may be most specifically about 60% or less, and most specifically
about 50% or less. The application of the cationic synthetic
co-polymer to the tissue sheet via this process may be accomplished
by any method known in the art including but not limited to:
[0059] A spray applied to the fibrous tissue sheet. For example,
spray nozzles may be mounted over a moving wet tissue sheet to
apply a desired dose of a synthetic co-polymer chemical additive
solution to the wet tissue sheet. Nebulizers can also be used to
apply a light mist to a surface of a wet tissue sheet.
[0060] Non-contact printing methods such as ink jet printing,
digital printing of any kind, and the like.
[0061] Coating onto one or both surfaces of the wet tissue sheet,
such as blade coating, air knife coating, short dwell coating, cast
coating, and the like.
[0062] Extrusion from a die head such as UFD spray tips, such as
available from ITWDynatec of Henderson, Tenn., of the cationic
synthetic co-polymer or cationic synthetic co-polymer additive in
the form of a solution, a dispersion or emulsion, or a viscous
mixture.
[0063] Impregnation of the wet tissue sheet with a solution or
slurry, wherein the compound penetrates a significant distance into
the thickness of the wet tissue sheet, such as about 20% or greater
of the thickness of the wet tissue sheet, more specifically about
30% or greater, and most specifically about 70% or greater of the
thickness of the wet tissue sheet, including completely penetrating
the wet tissue sheet throughout the full extent of its thickness.
One useful method for impregnation of a wet tissue sheet is the
Hydra-Sizers system, produced by Black Clawson Corp., Watertown,
N.Y., as described in "New Technology to Apply Starch and Other
Additives," Pulp and Paper Canada, 100(2): T42-T44 (February 1999).
This system consists of a die, an adjustable support structure, a
catch pan, and an additive supply system. A thin curtain of
descending liquid or slurry is created which contacts the moving
tissue sheet beneath it. Wide ranges of applied doses of the
coating material, such as the cationic synthetic co-polymer, or
cationic synthetic co-polymer additive, may be achieved with good
runnability. The system may also be applied to curtain coat a
relatively dry tissue sheet, such as a tissue sheet just before or
after creping.
[0064] Foam application of the cationic synthetic co-polymer or
cationic synthetic co-polymer additive to the wet tissue sheet
(e.g., foam finishing), either for topical application or for
impregnation of the cationic synthetic co-polymer or cationic
synthetic co-polymer additive into the wet tissue sheet under the
influence of a pressure differential (e.g., vacuum-assisted
impregnation of the foam). Principles of foam application of
additives such as binder agents are described in U.S. Pat. No.
4,297,860, issued on Nov. 3, 1981 to Pacifici et al. and U.S. Pat.
No. 4,773,110, issued on Sep. 27, 1988 to G. J. Hopkins, the
disclosures of both which are herein incorporated by reference to
the extent that they are non-contradictory herewith.
[0065] Application of the cationic synthetic co-polymer or cationic
synthetic co-polymer additive by spray or other means to a moving
belt or fabric which in turn contacts the tissue sheet to apply the
cationic synthetic co-polymer or cationic synthetic co-polymer
additive to the tissue sheet, such as is disclosed in WO 01/49937
under the name of S. Eichhorn, published on Jun. 12, 2001.
[0066] The cationic synthetic co-polymer or cationic synthetic
co-polymer additive may also be added prior to formation of the
tissue sheet such as when the fibers are suspended in water. This
may include, for example, addition in the pulp mill or to the
pulper, a machine chest, the headbox or to the tissue sheet prior
to being dried where the consistency is about 80% or less.
[0067] The most preferred means for addition prior to the tissue
sheet formation is direct addition to a fibrous slurry, such as by
injection of the cationic synthetic co-polymer or cationic
synthetic co-polymer additive into a fibrous slurry prior to entry
in the headbox. Slurry consistency can be from about 0.2% to about
50%, specifically from about 0.2% to about 10%, more specifically
from about 0.3% to about 5%, and most specifically from about 1% to
about 4%.
[0068] Application of the cationic synthetic co-polymer or cationic
synthetic co-polymer additive to individualized fibers. For
example, comminuted or flash dried fibers may be entrained in an
air stream combined with an aerosol or spray of the cationic
synthetic co-polymer or cationic synthetic co-polymer additive to
treat individual fibers prior to incorporation of the treated
fibers into a tissue sheet or other fibrous product.
[0069] The tissue sheet comprising the cationic synthetic
co-polymers of the present invention may be blended or layered
sheets, wherein either a heterogeneous or homogeneous distribution
of fibers is present in the z-direction of the sheet. In some
embodiments, the cationic synthetic co-polymers may be added to all
the fibers in the tissue sheet. In other embodiments, the cationic
synthetic co-polymers may be added to only selective fibers in the
tissue sheet, such methods being well known to those skilled in the
art. In a specific embodiment of the present invention, the tissue
sheet is a layered tissue sheet comprising two or more layers
comprising distinct hardwood and softwood layers, wherein the
cationic synthetic co-polymers of the present invention are added
to only the hardwood fibers. In another embodiment, the cationic
synthetic co-polymers of the present invention may be added to all
the fibers.
[0070] The tissue sheet to be treated may be made by any method
known in the art. The tissue sheet may be wetlaid, such as tissue
sheet formed with known paper-making techniques wherein a dilute
aqueous fiber slurry is disposed on a moving wire to filter out the
fibers and form an embryonic tissue sheet which is subsequently
dewatered by combinations of units including suction boxes, wet
presses, dryer units, and the like. Examples of known dewatering
and other operations are disclosed in U.S. Pat. No. 5,656,132,
issued on Aug. 12, 1997 to Farrington, Jr. et al. Capillary
dewatering may also be applied to remove water from the tissue
sheet, as disclosed in U.S. Pat. No. 5,598,643, issued on Feb. 4,
1997 and U.S. Pat. No. 4,556,450, issued on Dec. 3, 1985, both to
S. C. Chuang et al., the disclosures of both which are herein
incorporated by reference to the extent that they are
non-contradictory herewith.
[0071] Drying operations can include drum drying, through drying,
steam drying such as superheated steam drying, displacement
dewatering, Yankee drying, infrared drying, microwave drying,
radiofrequency drying in general, and impulse drying, as disclosed
in U.S. Pat. No. 5,353,521, issued on Oct. 11, 1994 to Orloff and
U.S. Pat. No. 5,598,642, issued on Feb. 4, 1997 to Orloff et al.,
the disclosures of both which are herein incorporated by reference
to the extent that they are non-contradictory herewith. Other
drying technologies may be used, such as methods employing
differential gas pressure include the use of air presses as
disclosed U.S. Pat. No. 6,096,169, issued on Aug. 1, 2000 to
Hermans et al. and U.S. Pat. No. 6,143,135, issued Nov. 7, 2000 to
Hada et al., the disclosure of both which are herein incorporated
by reference to the extent they are non-contradictory herewith.
Also relevant are the paper machines disclosed in U.S. Pat. No.
5,230,776, issued on Jul. 27, 1993 to 1. A. Andersson et al.
[0072] For tissue sheets, both creped and uncreped methods of
manufacture may be used. Uncreped tissue production is disclosed in
U.S. Pat. No. 5,772,845 issued on Jun. 30, 1998 to Farrington, Jr.
et al., the disclosure of which is herein incorporated by reference
to the extent that they are non-contradictory herewith. Creped
tissue production is disclosed in U.S. Pat. No. 5,637,194, issued
on Jun. 10, 1997 to Ampulski et al.; U.S. Pat. No. 4,529,480,
issued on Jul. 16, 1985 to Trokhan; U.S. Pat. No. 6,103,063, issued
on Aug. 15, 2000 to Oriaran et al.; and, U.S. Pat. No. 4,440,597,
issued on Apr. 3, 1984 to Wells et al., the disclosures of all
which are herein incorporated by reference to the extent that they
are non-contradictory herewith. Also suitable for application of
the synthetic co-polymers and synthetic co-polymer chemical
additives of the present invention are tissue sheets that are
pattern densified or imprinted, such as the tissue sheets disclosed
in any of the following U.S. Pat. No. 4,514,345, issued on Apr. 30,
1985 to Johnson et al.; U.S. Pat. No. 4,528,239, issued on Jul. 9,
1985 to Trokhan; U.S. Pat. No. 5,098,522, issued on Mar. 24, 1992;
U.S. Pat. No. 5,260,171, issued on Nov. 9, 1993 to Smurkoski et
al.; U.S. Pat. No. 5,275,700, issued on Jan. 4, 1994 to Trokhan;
U.S. Pat. No. 5,328,565, issued on Jul. 12, 1994 to Rasch et al.;
U.S. Pat. No. 5,334,289, issued on Aug. 2, 1994 to Trokhan et al.;
U.S. Pat. No. 5,431,786, issued on Jul. 11, 1995 to Rasch et al.;
U.S. Pat. No. 5,496,624, issued on Mar. 5, 1996 to Steltjes, Jr. et
al.; U.S. Pat. No. 5,500,277, issued on Mar. 19, 1996 to Trokhan et
al.; U.S. Pat. No. 5,514,523, issued on May 7, 1996 to Trokhan et
al.; U.S. Pat. No. 5,554,467, issued on Sep. 10, 1996, to Trokhan
et al.; U.S. Pat. No. 5,566,724, issued on Oct. 22, 1996 to Trokhan
et al.; U.S. Pat. No. 5,624,790, issued on Apr. 29, 1997 to Trokhan
et al.; and, U.S. Pat. No. 5,628,876, issued on May 13, 1997 to
Ayers et al., the disclosures of which are incorporated herein by
reference to the extent that they are non-contradictory herewith.
Such imprinted tissue sheets may have a network of densified
regions that have been imprinted against a drum dryer by an
imprinting fabric, and regions that are relatively less densified
(e.g., "domes" in the tissue sheet) corresponding to deflection
conduits in the imprinting fabric, wherein the tissue sheet
superposed over the deflection conduits was deflected by an air
pressure differential across the deflection conduit to form a
lower-density pillow-like region or dome in the tissue sheet.
[0073] The term "tissue" as used herein is differentiated from
other paper or tissue products in terms of its bulk. The bulk of
the tissue products of the present invention is calculated as the
quotient of the Caliper (hereinafter defined), expressed in
microns, divided by the basis weight, expressed in grams per square
meter. The resulting bulk is expressed as cubic centimeters per
gram. Writing papers, newsprint and other such papers have higher
strength and density (low bulk) in comparison to tissue products
which tend to have much higher calipers for a given basis weight.
For writing and printing papers, both bulk and surface strength are
extremely important as well as high stiffness. The use of bulk or
surface debonders to create bulk in papers other than tissue
products goes against maximizing bulk and surface strength in
printing papers. The tissue products of the present invention have
a bulk about 2 cm.sup.3/g or greater, more specifically about 2.5
cm.sup.3/g or greater, and still more specifically about 3
cm.sup.3/g or greater.
[0074] Optional Chemical Additives
[0075] Optional chemical additives may also be added to the aqueous
paper-making furnish or to the embryonic tissue sheet to impart
additional benefits to the tissue product and process and are not
antagonistic to the intended benefits of the present invention. The
following materials are included as examples of additional
chemicals that may be applied to the tissue sheet with the cationic
synthetic co-polymers and cationic synthetic co-polymer additives
of the present invention. The chemicals are included as examples
and are not intended to limit the scope of the present invention.
Such chemicals may be added at any point in the papermaking
process, such as before or after addition of the cationic synthetic
co-polymers and/or cationic synthetic co-polymer additives of the
present invention. They may also be added simultaneously with the
cationic copolymers and/or cationic synthetic co-polymer additives,
either blended with the cationic synthetic co-polymers and/or
cationic synthetic co-polymer additives of the present invention or
as separate additives.
[0076] Charge Control Agents
[0077] Charge promoters and control agents are commonly used in the
paper-making process to control the zeta potential of the
papermaking furnish in the wet end of the process. These species
may be anionic or cationic, most usually cationic, and may be
either naturally occurring materials such as alum or low molecular
weight high charge density synthetic polymers typically of
molecular weight of about 500,000 or less. Drainage and retention
aids may also be added to the furnish to improve formation,
drainage and fines retention. Included within the retention and
drainage aids are microparticle systems containing high surface
area, high anionic charge density materials.
[0078] Strength Agents
[0079] Wet and dry strength agents may also be applied to the
tissue sheet. As used herein, "wet strength agents" refer to
materials used to immobilize the bonds between fibers in the wet
state. Typically, the means by which fibers are held together in
paper and tissue products involve hydrogen bonds and sometimes
combinations of hydrogen bonds and covalent and/or ionic bonds. In
the present invention, it may be useful to provide a material that
will allow bonding of fibers in such a way as to immobilize the
fiber-to-fiber bond points and make them resistant to disruption in
the wet state. In this instance, the wet state usually will mean
when the product is largely saturated with water or other aqueous
solutions, but could also mean significant saturation with body
fluids such as urine, blood, mucus, menses, runny bowel movement,
lymph, and other body exudates.
[0080] Any material that when added to a tissue sheet or sheet
results in providing the tissue sheet with a mean wet geometric
tensile strength:dry geometric tensile strength ratio in excess of
about 0.1 will, for purposes of the present invention, be termed a
wet strength agent. Typically these materials are termed either as
permanent wet strength agents or as "temporary" wet strength
agents. For the purposes of differentiating permanent wet strength
agents from temporary wet strength agents, the permanent wet
strength agents will be defined as those resins which, when
incorporated into paper or tissue products, will provide a paper or
tissue product that retains more than 50% of its original wet
strength after exposure to water for a period of at least five
minutes. Temporary wet strength agents are those which show about
50% or less than, of their original wet strength after being
saturated with water for five minutes. Both classes of wet strength
agents find application in the present invention. The amount of wet
strength agent added to the pulp fibers may be about 0.1 dry weight
percent or greater, more specifically about 0.2 dry weight percent
or greater, and still more specifically from about 0.1 to about 3
dry weight percent, based on the dry weight of the fibers.
[0081] Permanent wet strength agents will typically provide a more
or less long-term wet resilience to the structure of a tissue
sheet. In contrast, the temporary wet strength agents will
typically provide tissue sheet structures that had low density and
high resilience, but would not provide a structure that had
long-term resistance to exposure to water or body fluids.
[0082] Wet and Temporary Wet Strength Agents
[0083] The temporary wet strength agents may be cationic, nonionic
or anionic. Such compounds include PAREZ.TM. 631 NC and PAREZ.RTM.)
725 temporary wet strength resins that are cationic glyoxylated
polyacrylamide available from Cytec Industries (West Paterson,
N.J.). This and similar resins are described in U.S. Pat. No.
3,556,932, issued on Jan. 19, 1971 to Coscia et al. and U.S. Pat.
No. 3,556,933, issued on Jan. 19, 1971 to Williams et al. Hercobond
1366, manufactured by Hercules, Inc., located at Wilmington, Del.,
is another commercially available cationic glyoxylated
polyacrylamide that may be used in accordance with the present
invention. Additional examples of temporary wet strength agents
include dialdehyde starches such as Cobond.RTM. 1000 from National
Starch and Chemcial Company and other aldehyde containing polymers
such as those described in U.S. Pat. No. 6,224,714 issued on May 1,
2001 to Schroeder et al.; U.S. Pat. No. 6,274,667 issued on Aug.
14, 2001 to Shannon et al.; U.S. Pat. No. 6,287,418 issued on Sep.
11, 2001 to Schroeder et al.; and, U.S. Pat. No. 6,365,667 issued
on Apr. 2, 2002 to Shannon et al., the disclosures of which are
herein incorporated by reference to the extend they are
non-contradictory herewith.
[0084] Permanent wet strength agents comprising cationic oligomeric
or polymeric resins may be used in the present invention.
Polyamide-polyamine-epichlorohydrin type resins such as KYMENE 557H
sold by Hercules, Inc., located at Wilmington, Del., are the most
widely used permanent wet-strength agents and are suitable for use
in the present invention. Such materials have been described in the
following U.S. Pat. No. 3,700,623 issued on Oct. 24, 1972 to Keim;
U.S. Pat. No. 3,772,076 issued on Nov. 13, 1973 to Keim; U.S. Pat.
No. 3,855,158 issued on Dec. 17, 1974 to Petrovich et al.; U.S.
Pat. No. 3,899,388 issued on Aug. 12, 1975 to Petrovich et al.;
U.S. Pat. No. 4,129,528 issued on Dec. 12, 1978 to Petrovich et
al.; U.S. Pat. No. 4,147,586 issued on Apr. 3, 1979 to Petrovich et
al.; and, U.S. Pat. No. 4,222,921 issued on Sep. 16, 1980 to van
Eenam. Other cationic resins include polyethylenimine resins and
aminoplast resins obtained by reaction of formaldehyde with
melamine or urea. It is often advantageous to use both permanent
and temporary wet strength resins in the manufacture of tissue
products with such use being recognized as falling within the scope
of the present invention.
[0085] Dry Strength Agents
[0086] Dry strength agents may also be applied to the tissue sheet
without affecting the performance of the disclosed cationic
synthetic co-polymers of the present invention. Such materials used
as dry strength agents are well known in the art and include but
are not limited to modified starches and other polysaccharides such
as cationic, amphoteric, and anionic starches and guar and locust
bean gums, modified polyacrylamides, carboxymethylcellulose,
sugars, polyvinyl alcohol, chitosans, and the like. Such dry
strength agents are typically added to a fiber slurry prior to
tissue sheet formation or as part of the creping package. It may at
times, however, be beneficial to blend the dry strength agent with
the cationic synthetic co-polymers of the present invention and
apply the two chemicals simultaneously to the tissue sheet.
[0087] Additional Softening Agents
[0088] At times it may be advantageous to add additional debonders
or softening chemistries to a tissue sheet. Examples of such
debonders and softening chemistries are broadly taught in the art.
Exemplary compounds include the simple quaternary ammonium salts
having the general formula
(R.sup.1').sub.4-b--N.sup.+--(R.sup.1").sub.b X.sup.- wherein R1'
is a C1-6 alkyl group, R1" is a C14-C22 alkyl group, b is an
integer from 1 to 3 and X- is any suitable counterion. Other
similar compounds include the monoester, diester, monoamide and
diamide derivatives of the simple quaternary ammonium salts. A
number of variations on these quaternary ammonium compounds are
known and should be considered to fall within the scope of the
present invention. Additional softening compositions include
cationic oleyl imidazoline materials such as methyl-1-oleyl
amidoethyl-2-oleyl imidazolinium methylsulfate commercially
available as Mackernium DC-183 from McIntyre Ltd., located in
University Park, III and Prosoft TQ-1003 available from Hercules,
Inc. Such softeners may also incorporate a humectant or a
plasticizer such as a low molecular weight polyethylene glycol
(molecular weight of about 4,000 daltons or less) or a polyhydroxy
compound such as glycerin or propylene glycol. While these
softeners may be applied to the fibers while in slurry prior to
sheet formation, the cationic synthetic copolymers of the present
invention typically provide sufficient debonding and softness
improvement so as not to require use of additional bulk softening
agents.
[0089] However, it may be particularly advantageous to add such
softening agents simultaneously with the cationic synthetic
co-polymers of the present invention to a formed tissue sheet at a
consistency of about 80% or less. In such situations, dilute
solutions of the softening composition and cationic synthetic
co-polymer are blended directly and then topically applied to the
wet tissue sheet. It is believed in this manner that tactile
softness of the tissue sheet and resulting tissue products may be
improved due to presence of the additional softening compound. An
especially preferred topical softener for this application is
polysiloxane. The use of polysiloxanes to soften tissue sheets is
broadly taught in the art. A large variety of polysiloxanes are
available that are capable of enhancing the tactile properties of
the finished tissue sheet. Any polysiloxane capable of enhancing
the tactile softness of the tissue sheet is suitable for
incorporation in this manner so long as so long as solutions or
emulsions of the softener and polysiloxane are compatible, that is
when mixed they do not form gels, precipitates or other physical
defects that would preclude application to the tissue sheet.
[0090] Examples of suitable polysiloxanes include but are not
limited to linear polydialkyl polysiloxanes such as the DC-200
fluid series available from Dow Corning, Inc., Midland, Mich. as
well as the organo-reactive polydimethyl siloxanes such as the
preferred amino functional polydimethyl siloxanes. Examples of
suitable polysiloxanes include those described in U.S. Pat. No.
6,054,020 issued on Apr. 25, 2000 to Goulet et al. and U.S. Pat.
No. 6,432,270 issued on Aug. 13, 2002 to Liu et al., the
disclosures of which are herein incorporated by reference to the
extent that they are non-contradictory herewith. Additional
exemplary aminofunctional polysiloxanes are the Wetsoft CTW family
manufactured and sold by Wacker Chemie, Munich, Germany.
[0091] Miscellaneous Agents
[0092] It may be desirable to treat a tissue sheet with additional
types of chemicals. Such chemicals include, but are not limited to,
absorbency aids usually in the form of cationic, anionic, or
non-ionic surfactants, humectants and plasticizers such as low
molecular weight polyethylene glycols and polyhydroxy compounds
such as glycerin and propylene glycol.
[0093] In general, the cationic synthetic co-polymers of the
present invention may be used in conjunction with any known
materials and chemicals that are not antagonistic to its intended
use. Examples of such materials and chemicals include, but are not
limited to, odor control agents, such as odor absorbents, activated
carbon fibers and particles, baby powder, baking soda, chelating
agents, zeolites, perfumes or other odor-masking agents,
cyclodextrin compounds, oxidizers, and the like. Superabsorbent
particles, synthetic fibers, or films may also be employed.
Additional options include cationic dyes, optical brighteners,
polysiloxanes and the like. A wide variety of other materials and
chemicals known in the art of papermaking and tissue production may
be included in the tissue sheets of the present invention including
lotions and other materials providing skin health benefits.
[0094] The application point for such materials and chemicals is
not particularly relevant to the present invention and such
materials and chemicals may be applied at any point in the tissue
manufacturing process. This includes pre-treatment of pulp,
co-application in the wet end of the process, post treatment after
drying but on the tissue machine and topical post treatment.
[0095] A surprising aspect of the present invention is that despite
use of the hydrophobically modified cationic synthetic co-polymers,
the tissue sheets still remain absorbent. The Wet Out Time
(hereinafter defined) for treated tissue sheets of the present
invention may be about 180 seconds or less, more specifically about
150 seconds or less, still more specifically about 120 seconds or
less, and still more specifically about 90 seconds or less. As used
herein, the term "Wet Out Time" is related to absorbency and is the
time it takes for a given sample of a tissue sheet to completely
wet out when placed in water.
[0096] Experimental
[0097] Basis Weight Determination (Tissue)
[0098] The basis weight and bone dry basis weight of the tissue
sheet specimens was determined using a modified TAPPI T410
procedure. As is basis weight samples were conditioned at
23.degree. C..+-.1.degree. C. and 50.+-.2% relative humidity for a
minimum of 4 hours. After conditioning a stack of 16--3".times.3"
samples was cut using a die press and associated die. This
represents a tissue sheet sample area of 144 in.sup.2. Examples of
suitable die presses are TMI DGD die press manufactured by Testing
Machines, Inc., Islandia, N.Y., or a Swing Beam testing machine
manufactured by USM Corporation, Wilmington, Mass. Die size
tolerances are .+-.0.008 inches in both directions. The specimen
stack is then weighed to the nearest 0.001 gram on a tared
analytical balance. The basis weight in pounds per 2880 ft.sup.2 is
then calculated using the following equation:
Basis weight=stack wt. in grams/454*2880
[0099] The bone dry basis weight is obtained by weighing a sample
can and sample can lid the nearest 0.001 grams (this weight is A).
The sample stack is placed into the sample can and left uncovered.
The uncovered sample can and stack along with the sample can lid is
placed in a 105.degree. C..+-.2.degree. C. oven for a period of 1
hour.+-.5 minutes for sample stacks weighing less than 10 grams and
at least 8 hours for sample stacks weighing 10 grams or greater.
After the specified oven time has lapsed, the sample can lid is
placed on the sample can and the sample can is removed from the
oven. The sample can is allowed to cool to approximately ambient
temperature but no more than 10 minutes. The sample can, sample can
lid and sample stack are then weighed to the nearest 0.001 gram
(this weight is C). The bone dry basis weight in pounds/2880
ft.sup.2 is calculated using the following equation:
Bone Dry BW=(C-A)/454*2880
[0100] Dry Tensile (tissue):
[0101] The Geometric Mean Tensile (GMT) strength test results are
expressed as grams-force per 3 inches of sample width. GMT is
computed from the peak load values of the MD (machine direction)
and CD (cross-machine direction) tensile curves, which are obtained
under laboratory conditions of 23.0.degree. C..+-.1.0.degree. C.,
50.0.+-.2.0% relative humidity, and after the tissue sheet has
equilibrated to the testing conditions for a period of not less
than four hours. Testing is conducted on a tensile testing machine
maintaining a constant rate of elongation, and the width of each
specimen tested was 3 inches. The "jaw span" or the distance
between the jaws, sometimes referred to as gauge length, is 2.0
inches (50.8 mm). The crosshead speed is 10 inches per minute (254
mm/min.) A load cell or full-scale load is chosen so that all peak
load results fall between 10 and 90 percent of the full-scale load.
In particular, the results described herein were produced on an
Instron 1122 tensile frame connected to a Sintech data acquisition
and control system utilizing IMAP software running on a "486 Class"
personal computer. This data system records at least 20 load and
elongation points per second. A total of 10 specimens per sample
are tested with the sample mean being used as the reported tensile
value. The geometric mean tensile is calculated from the following
equation:
GMT=(MD Tensile*CD Tensile).sup.1/2
[0102] To account for small variations in basis weight, GMT values
were then corrected to the 18.5 pounds/2880 ft.sup.2 target basis
weight using the following equation:
Corrected GMT=Measured GMT*(18.5/Bone Dry Basis Weight)
[0103] Caliper:
[0104] The term "caliper" as used herein is the thickness of a
single tissue sheet, and may either be measured as the thickness of
a single tissue sheet or as the thickness of a stack of ten tissue
sheets and dividing the ten tissue sheet thickness by ten, where
each sheet within the stack is placed with the same side up.
Caliper is expressed in microns. Caliper was measured in accordance
with TAPPI test methods T402 "Standard Conditioning and Testing
Atmosphere For Paper, Board, Pulp Handsheets and Related Products"
and T411 om-89 "Thickness (caliper) of Paper, Paperboard, and
Combined Board" optionally with Note 3 for stacked tissue sheets.
The micrometer used for carrying out T411 om-89 is a Bulk
Micrometer (TMI Model 49-72-00, Amityville, N.Y.) or equivalent
having an anvil diameter of 4{fraction (1/16)} inches (103.2
millimeters) and an anvil pressure of 220 grams/square inch (3.3 g
kilo Pascals).
[0105] Lint and Slough Measurement:
[0106] In order to determine the abrasion resistance, or tendency
of the fibers to be rubbed from the tissue sheet when handled, each
sample was measured by abrading the tissue specimens via the
following method. This test measures the resistance of a material
to an abrasive action when the material is subjected to a
horizontally reciprocating surface abrader. The equipment and
method used is similar to that described in U.S. Pat. No.
4,326,000, issued on Apr. 20, 1982 to Roberts, Jr. and assigned to
the Scott Paper Company, the disclosure of which is herein
incorporated by reference to the extent that it is
non-contradictory herewith. All tissue sheet samples were
conditioned at 23.degree. C..+-.1.degree. C. and 50+2% relative
humidity for a minimum of 4 hours. FIG. 8 is a schematic diagram of
the test equipment. Shown is the abrading spindle or mandrel 5, a
double arrow 6 showing the motion of the mandrel 5, a sliding clamp
7, a slough tray 8, a stationary clamp 9, a cycle speed control 10,
a counter 11, and start/stop controls 12.
[0107] The abrading spindle 5 consists of a stainless steel rod,
0.5" in diameter with the abrasive portion consisting of a 0.005"
deep diamond pattern knurl extending 4.25" in length around the
entire circumference of the rod. The abrading spindle 5 is mounted
perpendicularly to the face of the instrument 3 such that the
abrasive portion of the abrading spindle 5 extends out its entire
distance from the face of the instrument 3. On each side of the
abrading spindle 5 is located a pair of clamps 7 and 9, one movable
7 and one fixed 9, spaced 4" apart and centered about the abrading
spindle 5. The movable clamp 7 (weighing approximately 102.7 grams)
is allowed to slide freely in the vertical direction, the weight of
the movable clamp 7 providing the means for insuring a constant
tension of the tissue sheet sample over the surface of the abrading
spindle 5.
[0108] Using a JDC-3 or equivalent precision cutter, available from
Thwing-Albert Instrument Company, located at Philadelphia, Pa., the
tissue sheet sample specimens are cut into 3".+-.0.05"
wide.times.7" long strips (note: length is not critical as long as
specimen can span distance so as to be inserted into the clamps A
& B). For tissue sheet samples, the MD direction corresponds to
the longer dimension. Each tissue sheet sample is weighed to the
nearest 0.1 mg. One end of the tissue sheet sample is clamped to
the fixed clamp 9, the sample then loosely draped over the abrading
spindle or mandrel 5 and clamped into the sliding clamp 7. The
entire width of the tissue sheet sample should be in contact with
the abrading spindle 5. The sliding clamp 7 is then allowed to fall
providing constant tension across the abrading spindle 5.
[0109] The abrading spindle 5 is then moved back and forth at an
approximate 15 degree angle from the centered vertical centerline
in a reciprocal horizontal motion against the tissue sheet sample
for 20 cycles (each cycle is a back and forth stroke), at a speed
of 170 cycles per minute, removing loose fibers from the surface of
the tissue sheet sample. Additionally the spindle rotates counter
clockwise (when looking at the front of the instrument) at an
approximate speed of 5 RPMs. The tissue sheet sample is then
removed from the jaws 7 and 9 and any loose fibers on the surface
of the tissue sheet sample are removed by gently shaking the tissue
sheet sample. The tissue sheet sample is then weighed to the
nearest 0.1 mg and the weight loss calculated. Ten tissue sheet
specimen per sample are tested and the average weight loss value in
mg recorded. The result for each tissue sheet sample was compared
with a control sample containing no chemicals. Where a 2-layered
tissue sheet sample is measured, placement of the tissue sheet
sample should be such that the hardwood portion is against the
abrading surface.
[0110] Wet Out Time
[0111] The Wet Out Time of a tissue sheet treated in accordance
with the present invention is determined by cutting 20 sheets of
the tissue sheet sample into 2.5 inch squares. The number of sheets
of the tissue sheet sample used in the test is independent of the
number of plies per sheet of the tissue sheet sample. The 20 square
sheets of the tissue sheet sample are stacked together and stapled
at each corner to form a pad of the tissue sheet sample. The pad of
the tissue sheet sample is held close to the surface of a constant
temperature distilled water bath (23.degree. C..+-.2.degree. C.),
which is the appropriate size and depth to ensure the saturated pad
of the tissue sheet sample does not contact the bottom of the water
bath container and the top surface of the distilled water of the
water bath at the same time, and dropped flat onto the surface of
the distilled water, with staple points on the pad of the tissue
sheet sample facing down. The time necessary for the pad of the
tissue sheet sample to become completely saturated, measured in
seconds, is the Wet Out Time for the tissue sheet sample and
represents the absorbent rate of the tissue sheet sample. Increases
in the Wet Out Time represent a decrease in absorbent rate of the
tissue sheet sample.
[0112] Softness:
[0113] Softness of tissue sheets and/or tissue products is
determined from sensory panel testing. The testing is performed by
trained panelists who rub the formed tissue sheets and/or tissue
products and compare the softness attributes of the tissue sheets
and/or tissue products to the same softness attributes of high and
low softness control standards. After comparing these
characteristics to the standards, the panelists assign a value for
each of the tissue sheets' and/or tissue products' softness
attributes. From these values an overall softness of the tissue
sheets and/or tissue products determined on a scale from 1 (least
soft) to 16 (most soft). The higher the number, the softer the
tissue sheet and/or tissue product. In general, a difference of
less than 0.5 in the panel softness value is not statistically
significant.
EXAMPLES
Example 1
[0114] Example 1 demonstrates the preparation of a blended
(non-layered) tissue basesheet. The blended tissue basesheet was
made according to the following procedure. About 45.5 pounds (oven
dry basis) of eucalyptus hardwood kraft fiber and about 24.5 pounds
(oven dry basis) of northern softwood kraft fiber were dispersed in
a pulper for about 30 minutes at a consistency of about 3%. The
blended thick stock pulp slurry was refined for 10 minutes and then
passed to a machine chest where the thick stock pulp slurry was
diluted to a consistency of about 1%. Kymene 6500, a commercially
available PAE wet strength resin from Hercules, Inc., was added to
the pulp slurry in the machine chest at a rate of about 4 pounds of
dry chemical per ton of dry fiber. The stock pulp slurry was
further diluted to about 0.1 percent consistency prior to forming
and deposited from an unlayered headbox onto a fine forming fabric
having a velocity of about 50 feet per minute to form a 17" wide
tissue sheet. The flow rate of the stock pulp slurry in the flow
spreader was adjusted to give a target sheet basis weight of 12.7
gsm. The stock pulp slurry drained through the forming fabric,
building an embryonic tissue sheet. The embryonic tissue sheet was
transferred to a second fabric, a papermaking felt, before being
further dewatered using a vacuum box to a consistency of between
about 15 to about 25%. The tissue sheet was then transferred via a
pressure roll to a steam heated Yankee dryer operating at a
temperature of about 220.degree. F. at a steam pressure of about 17
PSI. The dried tissue sheet was then transferred to a reel
traveling at a speed about 30% slower than the Yankee dryer to
provide a crepe ratio of about 1.3:1, thereby providing the blended
tissue basesheet.
[0115] An aqueous creping composition was prepared containing about
0.317% by weight of polyvinyl alcohol (PVOH), available under the
trade designation of Celvol 523 manufactured by Celanese, Dallas,
Tex. (88% hydrolyzed and a viscosity of about 23 to about 27 cps.
for a 4% solution at 20.degree. C.); about 0.01% by weight of a PAE
resin, available under the trade designation of Kymene 6500 from
Hercules, Inc.; and, about 0.001% of a debonder/creping release
agent, available under the trade designation of Resozol 2008,
manufactured by Hercules, Inc. All weight percentages are based on
dry pounds of the chemical being discussed. The creping composition
was prepared by adding the specific amount of each chemical to 10
gallons of water and mixing well. PVOH was obtained as a 6% aqueous
solution; Kymene 557 as a 12.5% aqueous solution; and, Resozol 2008
as a 7% solution in IPA/water. The creping composition was then
applied to the Yankee dryer surface via a spray boom at a pressure
of about 60 psi at a rate of about 0.25 g solids/m.sup.2 of
product. The finished blended tissue basesheet was then converted
into a 2-ply tissue product with the dryer side of each ply facing
outward.
Example 2
[0116] Example 2 demonstrates use of a conventional wet end
debonder for preparing soft tissue products. The blended tissue
basesheet used in this example was made in general accordance with
Example 1. The Prosoft TQ-1003 was diluted to 1% solids with water
prior to addition to the machine chest. The diluted Prosoft
TQ-1003, a cationic oleylimidazoline debonder, commercially
available from Hercules, Inc. was added to the machine chest. The
machine chest was then allowed to stir for about 5 minutes prior to
start of the tissue sheet formation. The amount of debonder to
total tissue basesheet fiber on a dry weight basis was about 0.1%.
The finished blended tissue basesheet was then converted into a
2-ply facial tissue product with the dryer side of each ply facing
outward.
Example 3
[0117] Example 3 demonstrates use of a conventional wet end
debonder for preparing soft tissue products. The blended tissue
basesheet used in this example was made in general accordance with
Example 1. The Prosoft TQ-1003 was diluted to about 1% solids with
water prior to addition to the machine chest. The diluted Prosoft
TQ-1003, a cationic oleylimidazoline debonder, commercially
available from Hercules, Inc. was added to the machine chest. The
machine chest was then allowed to stir for about 5 minutes prior to
start of the tissue sheet formation. The amount of debonder to
total tissue basesheet fiber on a dry weight basis was about 0.2%.
The finished blended tissue basesheet was then converted into a
2-ply facial tissue product with the dryer side of each ply facing
outward.
Example 4
[0118] Example 4 demonstrates the topical application of cationic
synthetic co-polymer of the present invention to a wet, blended
tissue basesheet prior to drying the blended tissue basesheet. The
blended tissue basesheet used in this example was prepared in
general accordance with Example 1. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer of the present
invention containing 80 mole % of n-butyl acrylate and 20 mole % of
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the tissue basesheet that
is later brought into contact with the Yankee dryer. The blended
tissue basesheet had a consistency, at this point, of between about
10% and about 20%. The aqueous dispersion was sprayed through two
nozzles (commercially available under the designation 650017 from
Spraying Systems Co., Wheaton, Ill.) at about 60 psi for a total
addition rate of about 180 mL/min. Addition levels were controlled
by adjusting the concentration of the diluted cationic synthetic
co-polymer dispersion. No changes were required to the creping
adhesive package and no felt plugging or other process issues were
encountered with application of the cationic synthetic co-polymer.
The amount of cationic synthetic co-polymer to total tissue
basesheet fiber on a dry weight basis was about 0.1%. The finished
blended tissue basesheet was then converted into a 2-ply facial
tissue product with the dryer side of each ply facing outward.
Example 5
[0119] Example 5 demonstrates the topical application of cationic
synthetic co-polymer of the present invention to a wet, blended
tissue basesheet prior to drying the blended tissue basesheet. The
blended tissue basesheet used in this example was prepared in
general accordance with Example 1. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer of the present
invention containing 80 mole % of n-butyl acrylate and 20 mole % of
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the tissue basesheet that
is later brought into contact with the Yankee dryer. The blended
tissue basesheet had a consistency, at this point, of between about
10% and about 20%. The aqueous dispersion was sprayed through two
nozzles (commercially available under the designation 650017 from
Spraying Systems Co., Wheaton, Ill.) at about 60 psi for a total
addition rate of about 180 mL/min. Addition levels were controlled
by adjusting the concentration of the diluted cationic synthetic
co-polymer dispersion. No changes were required to the creping
adhesive package and no felt plugging or other process issues were
encountered with application of the cationic synthetic co-polymer.
The amount of cationic synthetic co-polymer to total sheet fiber on
a dry weight basis was about 0.2%. The finished blended tissue
basesheet was then converted into a 2-ply facial tissue product
with the dryer side of each ply facing outward.
Example 6
[0120] Example 6 demonstrates the topical application of cationic
synthetic co-polymer of the present invention to a wet, blended
tissue basesheet prior to drying the blended tissue basesheet. The
blended tissue basesheet used in this example was prepared in
general accordance with Example 1. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer of the present
invention containing 80 mole % of n-butyl acrylate and 20 mole % of
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the tissue basesheet that
is later brought into contact with the Yankee dryer. The blended
tissue basesheet had a consistency, at this point, of between about
10% and about 20%. The aqueous dispersion was sprayed through two
nozzles (commercially available under the designation 650017 from
Spraying Systems Co., Wheaton, Ill.) at about 60 psi for a total
addition rate of about 180 mL/min. Addition levels were controlled
by adjusting the concentration of the diluted cationic synthetic
co-polymer dispersion. No changes were required to the creping
adhesive package and no felt plugging or other process issues were
encountered with application of the cationic synthetic co-polymer.
The amount of cationic synthetic co-polymer to total tissue
basesheet fiber on a dry weight basis was about 0.4%. The finished
blended tissue basesheet was then converted into a 2-ply facial
tissue product with the dryer side of each ply facing outward.
[0121] Table 1 summarizes the data for Examples 1-6. FIG. 1 shows
graphically the relationship between slough and tensile. Both Table
1 and FIG. 1 demonstrate the cationic synthetic co-polymers of the
present invention simultaneously reducing slough and strength when
applied topically to a wet, formed tissue sheet. Furthermore, the
softness data shown in Table 3 and graphically in FIG. 2 shows that
the tissue products treated with the cationic synthetic co-polymers
of the present invention follow the same strength/softness
technology curve as the standard cationic oleylimidazoline
debonder. Hence, the tissue products that have lower slough at
equivalent softness are obtained as shown in FIG. 3. Also given in
a Table 1 are wet-out times showing that the tissue products of the
present invention retain their absorbent properties.
1 TABLE 1 Amount % of Dry Example Additive Fiber Wet-out time, s
Slough, mg GMT 1 None 0 16 1.8 717 2 Prosoft TQ-1003 0.1% 3 4.8 346
3 Prosoft TQ-1003 0.2% 3 7.6 232 4 Invention 0.1% 13 2.0 496 5
Invention 0.2% 18 1.3 433 6 Invention 0.4% 18 1.2 441
Example 7
[0122] Example 7 demonstrates the preparation of a layered tissue
basesheet. About 70 pounds, oven dried basis, of eucalyptus
hardwood kraft pulp fibers were dispersed in a pulper for about 30
minutes, forming an eucalyptus hardwood pulp kraft fiber slurry
having a consistency of about 3%. The Eucalyptus pulp hardwood
kraft fiber slurry was then transferred to two machine chests and
diluted to a consistency of about 0.5 to about 1%. About 70 pounds,
oven dry basis, of LL-19 northern softwood kraft pulp fibers were
dispersed in a pulper for about 30 minutes, forming a northern
softwood kraft pulp fiber slurry having a consistency of about 3%.
A low level of refining was applied for about 12 minutes to the
softwood kraft pulp fibers. After dispersing, the northern softwood
kraft pulp fibers to form the slurry, the northern softwood kraft
pulp fibers were passed to a machine chest and diluted to a
consistency of between about 0.5 to about 1%.
[0123] Kymene 6500, a commercially available PAE wet strength resin
from Hercules, Inc., was added to both the eucalyptus hardwood and
northern softwood kraft pulp slurries in the machine chest at a
rate of about 4 pounds of dry chemical per ton of dry fiber. The
stock pulp fiber slurries were further diluted to approximately
about 0.1 percent consistency prior to forming and deposited from a
three layered headbox onto a fine forming fabric having a velocity
of about 50 feet per minute to form a 17" wide tissue sheet. The
flow rates of the stock pulp fiber slurries into the flow spreader
were adjusted to give a target sheet basis weight of about 12.7 gsm
and a layer split of 35% Eucalyptus hardwood-kraft pulp fibers on
both outer layers and 30% LL-19 northern softwood kraft pulp fibers
in the center layer. The stock pulp fiber slurries were drained on
the forming fabric, building a layered embryonic tissue sheet. The
embryonic tissue sheet was transferred to a second fabric, a
papermaking felt, before being further dewatered with a vacuum box
to a consistency of between about 15 to about 25%. The embryonic
tissue sheet was then transferred via a pressure roll to a steam
heated Yankee dryer operating at a temperature of about 220.degree.
F. at a steam pressure of about 17 PSI. The dried tissue sheet was
then transferred to a reel traveling at a speed about 30% slower
than the Yankee dryer to provide a crepe ratio of about 1.3:1,
thereby providing the layered tissue basesheet.
[0124] An aqueous creping composition was prepared containing about
0.317% by weight of polyvinyl alcohol (PVOH), available under the
trade designation of Celvol 523 manufactured by Celanese (88%
hydrolyzed with a viscosity of about 23 to about 27 cps. for a 4%
solution at 20.degree. C.); about 0.01% by weight of a PAE resin,
available under the trade designation of Kymene 6500 from Hercules,
Inc.; and, about 0.001% of a debonder/creping release agent,
Resozol 2008, manufactured by Hercules, Inc. All weight percentages
are based on dry pounds of the chemical being discussed. The
creping composition was prepared by adding the specific amount of
each chemical to 10 gallons of water and mixing well. PVOH was
obtained as a 6% aqueous solution; Kymene 557 as a 12.5% aqueous
solution; and, Resozol 2008 as a 7% solution in IPA/water. The
creping composition was then applied to the Yankee dryer surface
via a spray boom at a pressure of about 60 psi at a rate of about
0.25 g solids/m.sup.2 of product. The finished layered basesheet
was then converted into a 2-ply tissue product with the dryer side
layer of each ply facing outward. See Table 4 showing physical
properties of blended tissue basesheets. GMT was normalized to the
basis weight of the untreated tissue sheet.
Example 8
[0125] Example 8 demonstrates use of a conventional wet end
debonder for preparing soft tissue products. The layered tissue
basesheet used in this example was made in general accordance with
Example 7. The Prosoft TQ-1003 was diluted to about 1% solids with
water prior to addition to the machine chest. The diluted Prosoft
TQ-1003, a cationic oleylimidazoline debonder, commercially
available from Hercules, Inc. was added to the machine chest
containing the eucalyptus hardwood kraft pulp fiber slurry going to
the layer that would come into contact with the dryer. The machine
chest was then allowed to stir for about 5 minutes prior to start
of the tissue sheet formation. The amount of debonder relative to
total dried fiber of the tissue basesheet was about 0.025%. The
finished layered tissue basesheets were then converted into a 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
Example 9
[0126] Example 9 demonstrates use of a conventional wet end
debonder for preparing soft tissue products. The layered tissue
basesheet used in this example was made in general accordance with
Example 7. The Prosoft TQ-1003 was diluted to about 1% solids with
water prior to addition to the machine chest. The diluted Prosoft
TQ-1003, a cationic oleylimidazoline debonder, commercially
available from Hercules, Inc. was added to the machine chest
containing the eucalyptus hardwood kraft pulp fiber slurry going to
the layer that would come into contact with the dryer. The machine
chest was then allowed to stir for about 5 minutes prior to start
of the tissue sheet formation. The amount of debonder to total
tissue basesheet fiber on a dry weight basis was about 0.05%. The
finished layered tissue basesheets were then converted into a 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
Example 10
[0127] Example 10 demonstrates the topical application of cationic
synthetic co-polymer of the present invention to a wet, layered
tissue basesheet prior to drying the layered tissue basesheet. The
layered tissue basesheet used in this example was prepared in
general accordance with Example 7. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer of the present
invention containing 80 mole % n-butyl acrylate and 20 mole % of
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the layered tissue
basesheet that is later brought into contact with the Yankee dryer.
The layered tissue basesheet had a consistency, at this point, of
between about 10% and about 20%. The aqueous dispersion was sprayed
through two nozzles (commercially available under the designation
650017 from Spraying Systems Co., Wheaton, Ill.) at about 60 psi
for a total addition rate of about 180 mL/min. Addition levels were
controlled by adjusting the concentration of the diluted cationic
synthetic co-polymer dispersion. No changes were required to the
creping adhesive package and no felt plugging or other process
issues were encountered with application of the cationic synthetic
co-polymer. The amount of cationic synthetic co-polymer to total
tissue basesheet fiber on a dry weight basis was about 0.1%. The
finished layered tissue basesheet was then converted into a 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
Example 11
[0128] Example 11 demonstrates the topical application of cationic
synthetic co-polymer of the present invention to a wet, layered
tissue basesheet prior to drying the layered tissue basesheet. The
layered tissue basesheet used in this example was prepared in
general accordance with Example 7. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer of the present
invention containing 80 mole % n-butyl acrylate and 20 mole % of
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the layered tissue
basesheet that is later brought into contact with the Yankee dryer.
The layered tissue basesheet had a consistency, at this point, of
between about 10% and about 20%. The aqueous dispersion was sprayed
through two nozzles (commercially available under the designation
650017 from Spraying Systems Co., Wheaton, Ill.) at about 60 psi
for a total addition rate of about 180 mL/min. Addition levels were
controlled by adjusting the concentration of the diluted cationic
synthetic co-polymer dispersion. No changes were required to the
creping adhesive package and no felt plugging or other process
issues were encountered with application of the cationic synthetic
co-polymer. The amount of cationic synthetic co-polymer to total
tissue basesheet fiber on a dry weight basis was about 0.2%. The
finished layered tissue basesheet was then converted into a 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
Example 12
[0129] Example 12 demonstrates the topical application of cationic
synthetic co-polymer of the present invention to a wet, layered
tissue basesheet prior to drying the layered tissue basesheet. The
layered tissue basesheet used in this example was prepared in
general accordance with Example 7. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer of the present
invention containing 80 mole % n-butyl acrylate and 20 mole % of
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the layered tissue
basesheet that is later brought into contact with the Yankee dryer.
The layered tissue basesheet had a consistency, at this point, of
between about 10% and about 20%. The aqueous dispersion was sprayed
through two nozzles (commercially available under the designation
650017 from Spraying Systems Co., Wheaton, Ill.) at about 60 psi
for a total addition rate of about 180 mL/min. Addition levels were
controlled by adjusting the concentration of the diluted cationic
synthetic co-polymer dispersion. No changes were required to the
creping adhesive package and no felt plugging or other process
issues were encountered with application of the cationic synthetic
co-polymer. The amount of cationic synthetic co-polymer to total
tissue basesheet fiber on a dry weight basis was about 0.4%. The
finished layered tissue basesheet was then converted into a 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
Example 13
[0130] Example 13 demonstrates the topical application of cationic
synthetic co-polymer of the present invention to a wet, layered
tissue basesheet prior to drying the layered tissue basesheet. The
layered tissue basesheet used in this example was prepared in
general accordance with Example 7. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer of the present
invention containing 80 mole % n-butyl acrylate and 20 mole % of
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the layered tissue
basesheet that is later brought into contact with the Yankee dryer.
The layered tissue basesheet had a consistency, at this point, of
between about 10% and about 20%. The aqueous dispersion was sprayed
through two nozzles (commercially available under the designation
650017 from Spraying Systems Co., Wheaton, Ill.) at about 60 psi
for a total addition rate of about 180 mL/min. Addition levels were
controlled by adjusting the concentration of the diluted cationic
synthetic co-polymer dispersion. No changes were required to the
creping adhesive package and no felt plugging or other process
issues were encountered with application of the cationic synthetic
co-polymer. The amount of cationic synthetic co-polymer to total
tissue basesheet fiber on a dry weight basis was about 0.8%. The
finished layered tissue basesheet was then converted into a 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
[0131] Table 2 summarizes the data for Examples 7-12. FIG. 1 shows
graphically the relationship between slough and tensile. Both Table
2 and FIG. 1 demonstrate the cationic synthetic co-polymers of the
present invention simultaneously reducing slough and strength when
applied topically to a wet, formed tissue sheet. Furthermore, the
softness data shown in Table 3 and graphically in FIG. 2 shows that
the tissue products treated with the cationic synthetic co-polymers
of the present invention follow the same strength/softness
technology curve as the standard cationic oleylimidazoline
debonder. Hence, tissue products that have lower slough at
equivalent softness are obtained as shown in FIG. 3. Also given in
Table 2 are wet-out times showing that the tissue products of the
present invention retain their absorbent properties.
2 TABLE 2 Amount % of Total Sheet Dry Example Additive Fiber
Wet-out time, s Slough, mg GMT 7 None 0 18 2.3 753 8 Prosoft
TQ-1003 0.025% 6 6.3 594 9 Prosoft TQ-1003 0.05% 5 5.0 544 10
Invention 0.1% 18 2.2 627 11 Invention 0.2% 17 3.0 660 12 Invention
0.4% 18 2.3 652 13 Invention 0.8% 23 1.2 602
[0132] Softness testing was completed on Examples 1-13. The data is
shown in table 3 and plots of tensile vs. softness are shown
graphically in FIG. 2 for both blended and layered sheets. As seen
in FIG. 2, the cationic synthetic co-polymers of the present
invention provide equivalent softness to the standard debonders
known in the art but also provide for lower slough products. This
benefit is seen independent of the particular sheet structure
employed. Hence, as FIG. 3 shows, it is possible to make
equivalently soft tissue products that advantageously have lower
lint and slough by employing the cationic synthetic co-polymers of
the present invention. Again, this effect is independent of the
particular tissue sheet structure that may be employed.
3TABLE 3 Amount % of Exam- Total Sheet Dry Slough, ple Additive
Fiber mg GMT Softness 1 None 0 1.8 717 7.7 2 Prosoft TQ-1003 0.1%
4.8 346 8.3 3 Prosoft TQ-1003 0.2% 7.6 232 8.6 4 Invention 0.1% 2.0
496 8.1 5 Invention 0.2% 1.3 433 8.2 6 Invention 0.4% 1.2 441 8.2 7
None 0 2.3 753 8.1 8 Prosoft TQ-1003 0.025% 6.3 594 8.5 9 Prosoft
TQ-1003 0.05% 5.0 544 8.4 10 Invention 0.1% 2.2 627 8.4 11
Invention 0.2% 3.0 660 8.4 12 Invention 0.4% 2.3 652 8.3 13
Invention 0.8% 1.2 602 8.3
[0133] Examples 14-19 compare the use of an anionic hydrophobically
modified acrylate polymer and the cationic synthetic co-polymers of
the present invention in a 2-layer, 2-ply facial tissue
product.
Example 14
[0134] Example 14 demonstrates the preparation of a 2-layered
tissue basesheet. The 2-layered tissue basesheet was made in
general accordance with the procedure outlined in Example 7 with
the exception that a 2-layered tissue basesheet used in this
example was formed consisting of a layer which contacted the
surface of the Yankee dryer containing 65% of the total sheet
weight of eucalyptus hardwood kraft pulp fibers and a felt (air
side) layer containing 35% total sheet weight of LL-19 northern
softwood kraft pulp fibers. The finished 2-layered tissue basesheet
was then converted into a 2-layer, 2-ply facial tissue product with
the dryer side layer of each ply facing outward.
Example 15
[0135] Example 15 demonstrates the topical application of cationic
synthetic co-polymers of the present invention to a wet, 2-layered
tissue basesheet prior to drying the 2-layered tissue basesheet.
The 2-layered tissue basesheet used in this example was prepared in
general accordance with Example 14. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer containing 80 mole %
n-butyl acrylate and 20 mole % of
[2(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the tissue basesheet that
is later brought into contact with the Yankee dryer. The 2-layered
tissue basesheet had a consistency, at this point, of between about
10% and about 20%. The aqueous dispersion was sprayed through two
nozzles (commercially available under the designation 650017 from
Spraying Systems Co., Wheaton, Ill.) at about 60 psi for a total
addition rate of about 180 mL/min. Addition levels were controlled
by adjusting the concentration of the diluted cationic synthetic
co-polymer dispersion. No changes were required to the creping
adhesive package and no felt plugging or other process issues were
encountered with application of the cationic synthetic co-polymer.
The amount of cationic synthetic co-polymer to total tissue
basesheet fiber on a dry weight basis was about 0.5%. The finished
2-layered tissue basesheet was then converted into a 2-layer, 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
Example 16
[0136] Example 16 demonstrates the topical application of cationic
synthetic co-polymers of the present invention to a wet, 2-layered
tissue basesheet prior to drying the 2-layered tissue basesheet.
The 2-layered tissue basesheet used in this example was prepared in
general accordance with Example 14. A 30% by weight aqueous
dispersion of a cationic synthetic co-polymer containing 80 mole %
n-butyl acrylate and 20 mole % of
[2(methacryloyloxy)ethyl]trimethyl ammonium chloride was diluted
with water and sprayed onto the side of the tissue basesheet that
is later brought into contact with the Yankee dryer. The 2-layered
tissue basesheet had a consistency, at this point, of between about
10% and about 20%. The aqueous dispersion was sprayed through two
nozzles (commercially available under the designation 650017 from
Spraying Systems Co., Wheaton, Ill.) at about 60 psi for a total
addition rate of about 180 mL/min. Addition levels were controlled
by adjusting the concentration of the diluted cationic synthetic
co-polymer dispersion. No changes were required to the creping
adhesive package and no felt plugging or other process issues were
encountered with application of the cationic synthetic co-polymer.
The amount of cationic synthetic co-polymer to total tissue
basesheet fiber on a dry weight basis was about 1.0%. The finished
2-layered tissue basesheet was then converted into a 2-layer, 2-ply
facial tissue product with the dryer side layer of each ply facing
outward.
Example 17
[0137] Example 17 demonstrates the topical application of a
hydrophobically modified anionic co-polymer to a wet, 2-layered
tissue basesheet prior to drying the 2-layered tissue basesheet.
The 2-layered tissue basesheet used in this example was prepared in
general accordance with Example 14. A 30% by weight aqueous
dispersion of a hydrophobically modified anionic co-polymer
containing 60 mole % acrylic acid; 24.5 mole % n-butylacrylate;
10.5 mole % 2-ethylhexylacrylate; and, 5 mole % AMPS wherein the
AMPS was converted to the sodium salt was diluted with water and
sprayed onto the side of the tissue basesheet that is later brought
into contact with the Yankee dryer. The 2-layered tissue basesheet
had a consistency, at this point, of between about 10% and about
20%. The aqueous dispersion was sprayed through two nozzles
(commercially available under the designation 650017 from Spraying
Systems Co., Wheaton, Ill.) at about 60 psi for a total addition
rate of about 180 mL/min. Addition levels were controlled by
adjusting the concentration of the diluted hydrophobically modified
anionic co-polymer dispersion. Significant issues were encountered
with crush and holes in the 2-layered tissue basesheet when using
the anionic co-polymer. The amount of anionic co-polymer to total
tissue basesheet fiber on a dry weight basis was about 0.15%. The
finished 2-layered tissue basesheet was then converted into a
2-layer, 2-ply facial tissue product with the dryer side layer of
each ply facing outward.
Example 18
[0138] Example 18 demonstrates the topical application of a
hydrophobically modified anionic co-polymer to a wet, 2-layered
tissue basesheet prior to drying the 2-layered tissue basesheet.
The 2-layered tissue basesheet used in this example was prepared in
general accordance with Example 14. A 30% by weight aqueous
dispersion of a hydrophobically modified anionic co-polymer
containing 60 mole % acrylic acid; 24.5 mole % n-butylacrylate;
10.5 mole % 2-ethylhexylacrylate; and, 5 mole % AMPS wherein the
AMPS was converted to the sodium salt was diluted with water and
sprayed onto the side of the tissue basesheet that is later brought
into contact with the Yankee dryer. The 2-layered tissue basesheet
had a consistency, at this point, of between about 10% and about
20%. The aqueous dispersion was sprayed through two nozzles
(commercially available under the designation 650017 from Spraying
Systems Co., Wheaton, Ill.) at about 60 psi for a total addition
rate of about 180 mL/min. Addition levels were controlled by
adjusting the concentration of the diluted hydrophobically modified
anionic co-polymer dispersion. Significant issues were encountered
with crush and holes in the 2-layered tissue basesheet when using
the anionic co-polymer. The amount of anionic co-polymer to total
tissue basesheet fiber on a dry weight basis was about 0.25%. The
finished 2-layered tissue basesheet was then converted into a
2-layer, 2-ply facial tissue product with the dryer side layer of
each ply facing outward.
Example 19
[0139] Example 19 demonstrates the topical application of a
hydrophobically modified anionic co-polymer to a wet, 2-layered
tissue basesheet prior to drying the 2-layered tissue basesheet.
The 2-layered tissue basesheet used in this example was prepared in
general accordance with Example 14. A 30% by weight aqueous
dispersion of a hydrophobically modified anionic co-polymer
containing 60 mole % acrylic acid; 24.5 mole % n-butylacrylate;
10.5 mole % 2-ethylhexylacrylate; and, 5 mole % AMPS wherein the
AMPS was converted to the sodium salt was diluted with water and
sprayed onto the side of the tissue basesheet that is later brought
into contact with the Yankee dryer. The 2-layered tissue basesheet
had a consistency, at this point, of between about 10% and about
20%. The aqueous dispersion was sprayed through two nozzles
(commercially available under the designation 650017 from Spraying
Systems Co., Wheaton, Ill.) at about 60 psi for a total addition
rate of about 180 mL/min. Addition levels were controlled by
adjusting the concentration of the diluted hydrophobically modified
anionic co-polymer dispersion. Significant issues were encountered
with crush and holes in the 2-layered tissue basesheet when using
the anionic co-polymer. The amount of anionic polymer to total
sheet fiber on a dry weight basis was about 0.50%. Significant
issues with felt plugging and crush were encountered such that it
was not possible to transfer the sheet to the Yankee dryer and no
product could be obtained.
[0140] Furthermore, as Table 4 shows, the anionic co-polymer used
in Examples 17-19 did not reduce slough and tensile as did the
cationic synthetic co-polymer used in Examples 15-16. The tensile
reduction seen in Example 18 is most likely due to the large number
of holes in the sheet and not representative of a debonding effect.
The 2-layered tissue basesheet treated in accordance with Example
19 could not be transferred to the Yankee dryer and wound due to
the extremely poor quality of the tissue basesheet.
4 TABLE 4 Amount % of Dry Example Additive Fiber Wet-out time, s
Slough, mg GMT 14 None 0 4 7.2 631 15 Cationic, invention 0.5% 12
5.6 610 16 Cationic, invention 1.0% 21 4.8 550 17 Anionic 0.15% 5
11.6 661 18 Anionic 0.25% 10 7.3 577 19 Anionic 0.50% Could not
make sheet
Examples 20-28
[0141] Examples 20-28 demonstrate the applicability of the present
invention using a number of different cationic synthetic
co-polymers. Additionally, these examples demonstrate ability to
use the cationic synthetic co-polymers of the present invention in
conjunction with other cationic papermaking additives. In Examples
20-28, the layered tissue basesheets used were made in general
accordance with Examples 7-13. A cationic glyoxylated
polyacrylamide, available under the trade designation of Parez 631
NC manufactured by Bayer, Inc., Suffolk, Va., was added to the
LL-19 softwood kraft pulp fibers in the machine chest at a level of
about 5 pounds of dry solids of the chemical per ton of dry LL-19
softwood kraft pulp fibers. A commercially available cationic
polyamide epichlorohydrin wet strength resin, Kymene 6500 available
from Hercules, Inc. was added to both the northern softwood kraft
pulp fibers and the eucalyptus hardwood kraft pulp fibers in the
machine chest at a level of about 4 pounds of dry solids of the
chemical per ton of dry fiber. The cationic synthetic co-polymers
were applied as aqueous dispersions via spraying through two
nozzles (commercially available under the designation 650017 from
Spraying Systems Co., Wheaton, Ill.) at about 60 psi for a total
addition rate of about 180 mL/min. Addition levels were controlled
by adjusting the concentration of the diluted cationic synthetic
co-polymer dispersions. In each example, the layered tissue
basesheets were converted into 2-ply facial tissue products with
the dryer side layer of each ply facing outward as with all
previous examples.
[0142] For Examples 21-23, a standard cationic oleylimidazoline
debonder, available under the designation of Prosoft TQ-1003
manufactured by Hercules, Inc., was added to the northern softwood
kraft pulp fibers going to the layer of the tissue basesheet in
each example that is later brought into contact with the Yankee
dryer. The debonder was added to the machine chest as about 1%
aqueous emulsion and allowed to stir for about 5 minutes prior to
forming the tissue basesheet for each example.
5TABLE 5 Chemical Composition I 89.9 mole % Ethyl Acrylate, 0.1
mole % Methyl Methacrylate, 10 mole %
[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride II 89.9 mole
% Ethyl Acrylate, 0.1 mole % Methyl Methacrylate, 10 mole %
2-[(acryloyloxy)ethyl]trimethyl ammonium chloride III 74.9 mole %
Ethyl Acrylate, 0.1 mole % Methyl Methacrylate, 25 mole %
2-[(acryloyloxy)ethyl]trimethyl ammonium chloride IV 80 mole %
Butyl Acrylate, 20% mole % [2- (methacryloyloxy)ethyl]trimethyl
ammonium methosulfate
[0143] Specific chemical compositions of the cationic synthetic
co-polymers used in Examples 24-27 are shown in Table 5. The
chemical compositions I-III were prepared via an emulsion
polymerization process using a non-ionic surfactant. The chemical
compositions I-III were delivered as between about 25% to about 35%
solids aqueous emulsions. The chemical composition IV was prepared
via a solvent displacement process and was delivered as a 30%
solids aqueous dispersion containing no surfactants. The physical
test results are shown in Table 6. Example 28 is a control sample
used to determine impact of water spraying alone on the tissue
basesheet. As Example 28 demonstrates, the effects seen in the
tissue basesheet, and ultimately the facial tissue products made
from the tissue basesheets, wherein the cationic synthetic
co-polymers of the present invention was used, are related to
application of the cationic synthetic co-polymer and not a function
of the water.
6 TABLE 6 Amount % of Total Sheet Dry Wet-out Example Additive
Fiber time, s Slough, mg GMT Softness 20 None 0 6 3.5 1160 6.9 21
Prosoft TQ-1003 0.05% 5 3.9 1026 7.2 22 Prosoft TQ-1003 0.15% 3 7.8
747 7.8 23 Prosoft TQ-1003 0.20% 3 6.8 635 8.0 24 III 0.40% 10 2.0
1124 7.0 25 II 0.40% 21 2.3 842 7.6 26 I 0.40% 22 2.1 733 7.6 27 IV
0.20% 23 2.3 772 7.4 28 Water 7 4.1 1052 7.0
[0144] The data is shown graphically in FIGS. 4 and 5. As with the
previous examples, the cationic synthetic co-polymers of the
present invention show significantly less slough increase with
decreased tensile than the standard oleylimidazoline debonder. FIG.
5 shows that the facial tissue products made using the cationic
synthetic co-polymers of the present invention display lower slough
at a given level of softness.
Examples 29-34
[0145] In Examples 29-34, all examples used a layered basesheet
made in general accordance with Examples 7-13 with the exception
that no refining was done to the eucalyptus hardwood kraft pulp
fibers. A cationic glyoxylated polyacrylamide, available under the
designation of Parez 631 NC manufactured by Bayer, Inc., was added
to the LL-19 softwood kraft pulp fibers in the machine chest at a
level of about 10 pounds of dry solids of the chemical per ton of
the dry LL-19 softwood kraft pulp fibers. A cationic polyamide
epichlorohydrin wet strength resin, available under the designation
of Kymene 6500 manufactured by Hercules, Inc. was added to both the
northern softwood kraft pulp fibers and the eucalyptus hardwood
kraft pulp fibers in the machine chest at a level of about 4 pounds
of dry solids of the chemical per ton of dry kraft pulp fiber. The
cationic acrylate polymers and debonders were added to the
Eucalyptus hardwood kraft fibers in the machine chest going to the
layer of the tissue basesheets that is later brought into contact
with the Yankee dryer. Specific chemical compositions of the
cationic synthetic co-polymers used in Examples 31-34 are given in
Table 7.
7TABLE 7 Chemical Composition V 95 mole % methyl acrylate, 5 mole %
[2- (acryloyloxy)ethyl]trimethyl ammonium chloride VI 80 mole %
N-butyl acrylate, 20 mole % [2- (methacryloyloxy)ethyl]trimethyl
ammonium chloride
[0146] The slough, tensile, and softness results are shown in Table
8 and graphically presented in FIGS. 6 and 7. Relative to the
control debonders, the cationic synthetic copolymers of the present
invention show significantly less slough formation. As with the
other examples, tissue basesheets made using the cationic synthetic
co-polymers of the present invention show less slough generation at
a given tensile than the standard debonders.
8 TABLE 8 Weight % of Dry Fiber in Dryer Wet-out Example Additive
Layer time, s Slough, mg GMT Softness 29 Prosoft TQ-1003 0.10% 2.9
7.6 605 8.2 30 Prosoft TQ-1003 0.15% 2.8 8.1 495 8.3 31 V 0.25% 22
2.2 629 8.0 32 V 0.50% 50.6 4.1 548 8.1 33 VI 0.25% 38.4 5.1 581
8.1 34 VI 0.50% 103.9 5.7 459 8.3
[0147] The results show that it is possible to reduce slough at
equivalent or lower GMT by applying the cationic synthetic
co-polymers of the present invention to a fiber slurry prior to
formation of the tissue sheet.
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