U.S. patent application number 10/956695 was filed with the patent office on 2006-04-06 for absorbent articles comprising thermoplastic resin pretreated fibers.
Invention is credited to Lisa Ann Flugge, Michael Ralph Lostocco, Troy Michael Runge, Thomas Gerard Shannon.
Application Number | 20060070712 10/956695 |
Document ID | / |
Family ID | 35445703 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060070712 |
Kind Code |
A1 |
Runge; Troy Michael ; et
al. |
April 6, 2006 |
Absorbent articles comprising thermoplastic resin pretreated
fibers
Abstract
One embodiment of the present invention is a fibrous structure
that may comprise: cellulosic pulp fibers and pretreated cellulosic
pulp fibers. The pretreated cellulosic pulp fiber is formed by
pretreating cellulosic pulp fiber with a thermoplastic resin having
a property selected from the group consisting essentially of water
soluble, water dispersible, and combinations thereof.
Inventors: |
Runge; Troy Michael;
(Neenah, WI) ; Flugge; Lisa Ann; (Appleton,
WI) ; Lostocco; Michael Ralph; (Appleton, WI)
; Shannon; Thomas Gerard; (Neenah, WI) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
US
|
Family ID: |
35445703 |
Appl. No.: |
10/956695 |
Filed: |
October 1, 2004 |
Current U.S.
Class: |
162/141 ;
162/135; 162/158; 162/164.1; 162/168.1; 162/182 |
Current CPC
Class: |
D21H 21/20 20130101;
D21H 21/18 20130101; D21C 9/005 20130101 |
Class at
Publication: |
162/141 ;
162/158; 162/135; 162/164.1; 162/168.1; 162/182 |
International
Class: |
D21H 11/00 20060101
D21H011/00; D21F 11/00 20060101 D21F011/00 |
Claims
1. A fibrous tissue web, comprising: cellulosic pulp fibers; and,
pretreated cellulosic pulp fibers, wherein the pretreated
cellulosic pulp fiber is formed by pretreating cellulosic pulp
fiber with a thermoplastic resin having a property selected from
the group consisting essentially of water soluble, water
dispersible, and combinations thereof.
2. The fibrous tissue web of claim 1, wherein the thermoplastic
resin is present in an amount of about 0.1 wt % to about 20 wt %,
based upon the total weight of the fibrous tissue web.
3. The fibrous tissue web of claim 1, wherein the thermoplastic
resin is present in an amount of about 0.5 wt % to about 10 wt %,
based upon the total weight of the fibrous tissue web.
4. The fibrous tissue web of claim 1, wherein the cellulosic pulp
fibers comprise wood pulp fibers.
5. The fibrous tissue web of claim 1, wherein the pretreated
cellulosic pulp fibers comprise wood pulp fibers.
6. The fibrous tissue web of claim 1, wherein the thermoplastic
resin is selected from the group consisting essentially of
polyurethane, polyethylene-co-vinyl acetate, polyvinyl
acetate-co-vinyl alcohol, polyester, polyacrylate, polyvinyl ether,
polyamide, and a combination comprising at least one of the
foregoing thermoplastic resins.
7. The fibrous tissue web of claim 1, wherein the fibrous tissue
web is a wet laid fibrous structure.
8. The fibrous tissue web of claim 1, wherein the fibrous tissue
web has been hot calendared.
9. The fibrous tissue web of claim 1, wherein the thermoplastic
resin substantially fully coats the pretreated cellulosic pulp
fibers.
10. The fibrous tissue web of claim 1, wherein the thermoplastic
resin at least partially coats the pretreated cellulosic pulp
fibers.
11. The fibrous tissue web of claim 1, wherein a weight ratio of
the thermoplastic resin to the pretreated cellulosic pulp fibers is
about 1:5 to about 1:1,000.
12. A fibrous tissue web, comprising pretreated cellulosic pulp
fibers, wherein the pretreated cellulosic pulp fiber is formed by
pretreating cellulosic pulp fiber with a thermoplastic resin having
a property selected from the group consisting essentially of water
soluble, water dispersible, and combinations thereof.
13. The fibrous tissue web of claim 12, wherein the thermoplastic
resin is present in an amount of about 0.1 wt % to about 20 wt %,
based upon the total weight of the fibrous tissue web.
14. The fibrous tissue web of claim 12, wherein the thermoplastic
resin is present in an amount of about 0.5 wt % to about 10 wt %,
based upon the total weight of the fibrous tissue web.
15. The fibrous tissue web of claim 12, wherein the pretreated
cellulosic pulp fibers comprise wood pulp fibers.
16. The fibrous tissue web of claim 12, wherein the thermoplastic
resin is selected from the group consisting essentially of
polyurethane, polyethylene-co-vinyl acetate, polyvinyl
acetate-co-vinyl alcohol, polyester, polyacrylate, polyvinyl ether,
polyamide, and a combination comprising at least one of the
foregoing thermoplastic resins.
17. The fibrous tissue web of claim 12, wherein the fibrous tissue
web is a wet laid fibrous structure.
18. The fibrous tissue web of claim 12, wherein the fibrous tissue
web has been hot calendared.
19. The fibrous tissue web of claim 12, wherein the thermoplastic
resin substantially fully coats the pretreated cellulosic pulp
fibers.
20. The fibrous tissue web of claim 12, wherein the thermoplastic
resin at least partially coats the pretreated cellulosic pulp
fibers.
21. The fibrous tissue web of claim 12, wherein a weight ratio of
the thermoplastic resin to the pretreated cellulosic pulp fibers is
about 1:5 to about 1:1,000.
22. Pretreated cellulosic pulp fibers, comprising cellulosic pulp
fibers, wherein the cellulosic pulp fibers are pretreated with a
thermoplastic resin having a property selected from the group
consisting essentially of water soluble, water dispersible, and
combinations thereof, thereby forming the pretreated cellulosic
pulp fibers.
23. The pretreated cellulosic pulp fibers of claim 22, wherein the
thermoplastic resin is present in an amount of about 0.1 wt % to
about 20 wt %, based upon the total weight of the pretreated
cellulosic pulp fibers.
24. The pretreated cellulosic pulp fibers of claim 22, wherein the
thermoplastic resin is present in an amount of about 0.5 wt % to
about 10 wt %, based upon the total weight of the pretreated
cellulosic pulp fibers.
25. The pretreated cellulosic pulp fibers of claim 22, wherein the
pretreated cellulosic pulp fibers comprise wood pulp fibers.
26. The pretreated cellulosic pulp fibers of claim 22, wherein the
thermoplastic resin is selected from the group consisting
essentially of polyurethane, polyethylene-co-vinyl acetate,
polyvinyl acetate-co-vinyl alcohol, polyester, polyacrylate,
polyvinyl ether, polyamide, and a combination comprising at least
one of the foregoing thermoplastic resins.
27. The pretreated cellulosic pulp fibers of claim 22, wherein the
thermoplastic resin substantially fully coats the pretreated
cellulosic pulp fibers.
28. The pretreated cellulosic pulp fibers of claim 22, wherein the
thermoplastic resin at least partially coats the pretreated
cellulosic pulp fibers.
29. The pretreated cellulosic pulp fibers of claim 22, wherein a
weight ratio of the thermoplastic resin to the pretreated
cellulosic pulp fibers is about 1:5 to about 1:1,000.
30. A method for making a tissue product, comprising: treating
cellulosic pulp fibers with a thermoplastic resin having a property
selected from the group consisting essentially of water soluble,
water dispersible, and combinations thereof thereby forming
pretreated cellulosic pulp fibers; forming a fibrous tissue web
comprised of the pretreated cellulosic pulp fibers; and, drying the
fibrous tissue web to form the tissue product.
31. The method of claim 31, wherein the thermoplastic resin is
present in an amount of about 0.1 wt % to about 20 wt %, based upon
the total weight of the fibrous tissue web.
32. The method of claim 31, wherein the thermoplastic resin is
present in an amount of about 0.5 wt % to about 10 wt %, based upon
the total weight of the fibrous tissue web.
33. The method of claim 31, wherein the pretreated cellulosic pulp
fibers comprise wood pulp fibers.
34. The method of claim 31, wherein the thermoplastic resin is
selected from the group consisting essentially of polyurethane,
polyethylene-co-vinyl acetate, polyvinyl acetate-co-vinyl alcohol,
polyester, polyacrylate, polyvinyl ether, polyamide, and a
combination comprising at least one of the foregoing thermoplastic
resins.
35. The method of claim 31, wherein the fibrous tissue web is a wet
laid fibrous structure.
36. The method of claim 31, wherein the fibrous tissue web has been
hot calendared.
37. The method of claim 31, wherein the thermoplastic resin
substantially fully coats the pretreated cellulosic pulp
fibers.
38. The method of claim 31, wherein the thermoplastic resin at
least partially coats the pretreated cellulosic pulp fibers.
39. The method of claim 31, wherein a weight ratio of the
thermoplastic resin to the pretreated cellulosic pulp fibers is
about 1:5 to about 1:1,000.
40. The method of claim 31, wherein the tissue product further
comprises cellulosic pulp fibers.
41. The method of claim 40, wherein the cellulosic pulp fibers
comprise wood pulp fibers.
Description
BACKGROUND
[0001] This disclosure relates to tissue products comprising
thermoplastic resin pretreated pulp fibers.
[0002] Cellulosic fibers made from wood pulp are used in a variety
of tissue products, for example, facial tissue, bath tissue, paper
towels, dinner napkins, wipes, and the like. It is known in the art
to prepare such tissue products comprising natural wood pulp
fibers, synthetic polymeric fibers, and combinations of natural
wood pulp fibers and synthetic polymeric fibers to impart high dry
and wet strength characteristics to the article.
[0003] Fibrous tissue webs having high strength and stretch are
useful for many applications as they provide the user security that
the tissue product will remain intact during use. Dry strength
additives may be used such as starches or polyarcylamides.
Unfortunately, use of these additives increase the strength of
fibrous tissue webs but do not increase the stretch of the tissue
product.
[0004] It is known that increased tensile strength generally
decreases the tactile softness of fibrous tissue webs. Generally,
the perceived stiffness of the fibrous tissue web is typically
dependent of the tensile breaking strength and the elastic modulus
of the fibrous tissue web, with high stiffness, low softness
fibrous tissue webs resulting from properties of high elastic
modulus and high tensile strength. The durability of the fibrous
tissue web is typically dependent on both the tensile strength and
stretch properties of the fibrous tissue web. In general, higher
tensile strength and stretch provide the highest durability for
fibrous tissue webs. Therefore, to maximize durability and softness
of the fibrous tissue web, it is advantageous to have the highest
stretch and lowest elastic modulus for a given tensile
strength.
[0005] Fibrous tissue webs having a high strength when they become
wet (known in the art as wet strength) are useful for many
applications. One application for such fibrous tissue webs is as
premoistened tissue products, such as wipes, often used by
travelers for cleansing the body and for surface cleaning. Such
fibrous tissue webs and their resulting tissue products must
maintain sufficient strength when stored in wet conditions for an
extended period of time to withstand wiping and rubbing actions.
Other applications for high wet strength fibrous tissue webs is in
tissue products that need to maintain integrity when wetted with
body fluids, such as nasal secretions, urine, blood, mucus, menses
and other body exudates.
[0006] In the art of papermaking, chemical additives exist for
improving the wet strength of fibrous tissue webs and ultimately,
the tissue products made from such fibrous tissue webs. These
materials are known in the art as "wet strength agents" and are
commercially available from a wide variety of sources. For example,
a polyamide epichlorohydrin resin may be used to enhance the wet
strength of the fibrous tissue web.
[0007] This cationic resin is typically added to the papermaking
pulp fiber slurry whereupon it bonds to the anionically charged
cellulose pulp fibers. During the papermaking process, the resin
crosslinks and eventually becomes insoluble in water. The wet
strength agent thus acts as a "glue" to hold the pulp fibers
together and enhances the wet strength of the fibrous tissue web.
However, one may need to use chlorine in order to remove the resin
and recycle or repulp tissue products containing pulp fibers
treated with the resin, which presents environmental problems.
"Repulping" refers to a recycling process used in the production of
the fibrous tissue web and the tissue products from scrap fibrous
tissue webs and tissue products accumulated during the production
of the fibrous tissue web and the tissue products. Since scrap
products is typically unused raw materials, a process to recycle it
for future use eliminates the inefficient disposal of a valuable
source of papermaking pulp fibers.
[0008] Cationic resins, as wet strength agents, may have other
disadvantages, such as reacting with other anionic additives which
may be added to the fibrous tissue web and, in many cases,
increasing the dry strength of the fibrous tissue web as well,
resulting in a less soft tissue product. Moreover, the
effectiveness of cationic wet strength agents may be limited by low
retention of the wet strength agent on the cellulose pulp
fiber.
[0009] Fibrous tissue webs have been disclosed containing
individualized, crosslinked pulp fibers, wherein the crosslinking
agent is selected from the group consisting of C2 to C8
dialdehydes, with glutaraldehyde being most typical. The cost
associated with producing pulp fibers crosslinked with dialdehyde
crosslinking agents, such as glutaraldehyde, may be too high to
result in commercially viable tissue products.
[0010] The use of C2 to C9 monomeric polycarboxylic acids to make
individualized, crosslinked cellulosic pulp fibers having primarily
intra-fiber crosslinking (crosslinks between cellulose units within
a single pulp fiber) and purportedly having increased absorbency,
has also been taught. Additionally, various resinous maleic
anhydride compositions have been used in conjunction with fibrous
tissue webs and tissue products. For example, fibrous tissue webs
and/or tissue products may be coated with a composition including
an amine salt of a low molecular weight C6 to C24 olefin/maleic
anhydride copolymer in combination with a bisulfite. Such fibrous
tissue webs and/or tissue products exhibit release properties. The
application of a polymeric polyacid, a phosphorous containing
accelerator, and an active hydrogen compound to a fibrous tissue
web followed by curing at 120.degree. C. to 400.degree. C. for 3
seconds to 15 minutes has also been disclosed.
[0011] The terms "pretreat" and "pretreated" as used herein, mean
treating pulp fibers and/or a fibrous sheet prior to the finishing
operation at a pulp mill with a chemical additive, completing the
finishing operation, redispersing the finished pretreated pulp
fibers at the paper mill and using the finished pretreated pulp
fibers in the production of a fibrous tissue web and/or a tissue
product.
[0012] The term "water dispersible" as used herein, means that the
synthetic copolymers, such as the thermoplastic resin of the
present invention, are either water soluble or capable of existing
as stable colloidal, self-emulsifiable or other type dispersions in
water with the presence of added emulsifiers. Added emulsifiers may
also be employed within the scope of the present invention to aid
in the polymerization of the thermoplastic resins or assist in
compatibilizing the thermoplastic resins with other chemical
additives used in the papermaking process, however, the emulsifiers
are not essential to the formation of stable dispersions or
solutions of the thermoplastic resin in water.
[0013] Water solubility and/or water dispersability of the
thermoplastic resin of the present invention enables the fibrous
tissue web and/or tissue products containing the thermoplastic
resin and/or other chemical additives to be repulpable. A
surprising aspect of the present invention is that while the
thermoplastic resins are water dispersible or water soluble, they
are capable of being retained in the wet end of the papermaking
process.
[0014] An additional disadvantage of using papermaking chemical
additives, such as wet strength agents, is that at least a portion
of the chemical additives are lost in pulping and/or repulping
operations. Thus, while the virgin tissue product may be
hydrophilic, use of an emulsion of a thermoplastic resin containing
high levels of a chemical additive may result in a finished tissue
product having unacceptable hydrophobicity due to loss of the
chemical additive. As the chemical additive may be critical to
dispersability of the thermoplastic resin, the fibrous tissue webs
and/or tissue products made with the non-water soluble or
dispersible thermoplastic resins are more likely to contain pulp
fiber bundles called nits as hereinafter described.
[0015] Such nits are described as fiber/polymer bundles that create
the appearance of white spots within the fibrous tissue web and/or
tissue product. These white spots will generally be on the order of
one square millimeter in size or greater. The nit count refers to
the number of nits counted in a 7.5 inch by 7.5 inch sample of the
fibrous tissue web and/or tissue product made from pretreated pulp
fibers. The fibrous tissue web and/or tissue product should have a
nit count of about 10 or less, more specifically about 5 or less,
and still more specifically about 3 or less.
[0016] There, however, remains a need for tissue products having
desired dry and wet strength, stretch, and modulus of elasticity
characteristics. It is also desirable to have tissue products that
may be easily dispersed to allow repulping.
BRIEF SUMMARY
[0017] Disclosed herein are fibrous tissue webs and/or tissue
products comprising cellulosic pulp fibers pretreated with water
dispersible, water soluble, or combination thereof thermoplastic
resin and methods of making such fibrous tissue webs and/or tissue
products. In one embodiment of the present invention, a fibrous
structure may comprise: a fibrous tissue web having a pair of outer
surfaces comprises greater than or equal to about 90 wt %
cellulosic pulp fibers based upon a total weight of the fibrous
tissue web, and a thermoplastic resin disposed between at least a
portion of the cellulosic pulp fibers. The thermoplastic resin may
have a property selected from the group consisting essentially of
water soluble, water dispersible, and combinations thereof.
[0018] In another embodiment of the present invention, the fibrous
structure may comprise: a fibrous tissue web having a pair of outer
surfaces comprises cellulosic pulp fibers, and a thermoplastic
resin, wherein the thermoplastic resin may have a property selected
from the group consisting essentially of water soluble, water
dispersible, and combinations thereof. The thermoplastic resin may
at least partially coat the cellulosic pulp fibers.
[0019] In one embodiment of the present invention, the pretreated
cellulosic pulp fibers may comprise: cellulosic pulp fibers and a
thermoplastic resin adhered to the cellulosic pulp fibers, wherein
a weight ratio of thermoplastic resin to the cellulosic pulp fibers
may be about 1:5 to about 1:1000. The thermoplastic resin may have
a property selected from the group consisting essentially of water
soluble, water dispersible, and combinations thereof.
[0020] The above described and other features are exemplified by
the following detailed description.
DETAILED DESCRIPTION
[0021] Disclosed herein are cellulosic pulp fibers, tissue
products, and methods of making tissue products comprising pulp
fibers pretreated with water dispersible, water soluble, or
combinations thereof thermoplastic resin. The tissue products
comprising the cellulosic pulp fibers and thermoplastic resin may
have high wet strength characteristics, high wet/dry ratio, and be
repulpable. All ranges disclosed herein are inclusive and
combinable (e.g., ranges of "about 25 wt % or less, or, more
specifically about 5 wt % to about 20 wt %" is inclusive of the
endpoints and all intermediate values of the ranges of "about 5 wt
% to about 25 wt %," etc.). The terms "first," "second," and the
like, herein do not denote any order, quantity, or importance, but
rather are used to distinguish one element from another, and the
terms "a" and "an" herein do not denote a limitation of quantity,
but rather denote the presence of at least one of the referenced
item. The modifier "about" used in connection with a quantity is
inclusive of the stated value and has the meaning dictated by the
context, (e.g., includes the degree of error associated with
measurement of the particular quantity).
[0022] The pretreated pulp fibers may be cellulosic pulp fibers, or
more specifically, natural pulp fibers, or, even more specifically,
chemical pulp fibers. The pretreated pulp fibers may comprise about
80 wt % or greater of cellulosic pulp fibers, or, more specifically
about 90 wt % or greater of cellulosic pulp fibers, and even more
specifically about 95 wt % or greater of cellulosic pulp fibers,
based upon the total weight of the tissue product. The remainder of
the pulp fibers in the tissue product may include, for example
bleached and unbleached pulp fibers, natural and synthetic pulp
fibers (such as rayon, lyocel, polyethylene, polypropylene, and the
like), and the like, as well as combinations comprising at least
one of the foregoing pulp fibers.
[0023] The specific-size and geometry of the pulp fibers, e.g.,
aspect ratio and the like, may be based upon the tissue products
into which the pulp fibers are incorporated.
[0024] Illustrative cellulosic pulp fibers include, but are not
limited to, wood pulp fibers including hardwoods and softwoods;
non-woody papermaking pulp fiber (e.g., from cotton, straw, grass
(such as rice and esparto), cane, reed (such as bagasse), bamboo,
bast fiber (such as jute, flax, kenaf, cannabis, linen, and ramie),
leaf fibers, and the like), and the like, as well as combinations
comprising at least one of the foregoing cellulosic pulp
fibers.
[0025] In one embodiment of the present invention, the cellulosic
pulp fibers may be wood pulp fibers. Suitable wood sources for wood
pulp fibers include, but are not limited to, softwood sources such
as pines, spruces, hemlocks, and firs, and hardwood sources such as
eucalyptuses, poplars, beeches, alder, oaks, and aspens. Possible
wood species include, but are not limited to, southern hardwood
kraft, eucalyptus wood kraft, northern wood kraft, and the like, as
well as combinations comprising at least one of the foregoing.
Suitable wood pulp fibers may be prepared using various methods,
which include, but are not limited to, chemical methods such as
Kraft and sulfite processes, thermomechanical methods,
chemithermomechanical methods, and combinations comprising at least
one of the foregoing methods. Useful methods of preparing pulp
fibers include dispersion to impart curl and improved drying
properties, such as disclosed in U.S. Pat. No. 5,348,620 issued to
Hermans et al.; U.S. Pat. No. 5,501,768 issued to Hermans et al.;
and, U.S. Pat. No. 5,656,132 issued to Farrington, Jr. et al.
[0026] Some or all of the cellulosic pulp fibers may be pretreated
with a thermoplastic resin (e.g., a water soluble, water
dispersible, or combination thereof thermoplastic resin) prior to,
during, or after the drying phase of the pulp fiber processing. The
term "thermoplastic resin" as used herein, refers to a crystalline
or amorphous polymer that softens when exposed to heat and returns
to its original state when cooled to ambient temperature. As used
herein, the term "water soluble" refers to solids or liquids that
will form a homogenous solution in water at a temperature of about
100.degree. C. or lower, more specifically between about 70.degree.
C. to about 100.degree. C., when the thermoplastic resin is present
in a concentration of 1% by weight or more of the total
solution.
[0027] In order to be compatible with the processing and to
facilitate formation of the pretreated cellulosic pulp fibers, the
thermoplastic resin may have a glass transition temperature of
about 50.degree. C. or less, or, more specifically about 25.degree.
C. or less, and even more specifically about -5.degree. C. or less.
The thermoplastic resin may optionally have a sufficiently high
molecular weight to enable the deposition of the thermoplastic
resin on the external surface of the cellulosic pulp fibers, or
more specifically, a sufficiently high molecular weight to enable
the deposition of about 5 wt % or less of the thermoplastic resin
within pores of the cellulosic pulp fibers, based upon the total
weight of the thermoplastic resin. For example, the thermoplastic
resin may have a weight average molecular weight (Mw) of about
1,000 atomic mass units (amu) or greater, or, more specifically
about 10,000 amu or greater, or, even more specifically about
100,000 amu or greater.
[0028] Exemplary thermoplastic resins may include, but are not
limited to water soluble, water dispersible, and combinations
thereof polyesters, polyurethanes, polyethylene-co-vinyl acetate,
polyvinyl acetate-co-vinyl alcohol, polyacrylates, polyvinyl
ethers, polyamides, and the like, as well as combinations
comprising at least one of the foregoing thermoplastic resins.
[0029] The amount of pulp fibers pretreated with the thermoplastic
resin is dependent upon the type of the tissue product to be
produced, desired structural integrity of the tissue product, and
the location of the pretreated pulp fibers in the tissue product.
In one embodiment of the present invention, the tissue product may
comprise pulp fibers selectively pretreated with a thermoplastic
resin. The term "pretreated" as used herein, means that the
thermoplastic resion is applied to the pulp fiber during pulp
manufacturing process. Examples suitable to the present invention
are described in U.S. Pat. No. 6,582,560 issued to Runge et al.
where additives are applied during the pulp sheet manufacturing
process. The pulp fibers that have been pretreated is then
transported to a different manufacturing process where it is
diluted and reslurried and made into a fibrous structure. Use of
water-soluble or water dispersible thermoplastics assists in the
reslurrying process.
[0030] Pre-treating pulp fibers with these thermoplastic resins
impart unique properties to the resulting fibrous structures as
opposed to the traditional addition of chemical additives in the
aqueous phase of the papermaking. While not being bound by theory
it is believed that the pretreatment provides improved retention of
the thermoplastic resin, by allowing the fiber to become partially
coated by the thermoplastic, which allows greater retention of the
material. The coating interferes with the natural bonding of the
cellulose fibers during drying and replaces this bonding with a
lower stiffness thermoplastic bond.
[0031] A tissue product comprising the pretreated pulp fibers
(e.g., the fibrous tissue web or the like), may comprise a weight
ratio of thermoplastic resin to cellulosic pulp fibers of about 1:5
to about 1:1,000, or, more specifically, about 1:10 to about 1:500,
or, even more specifically, about 1:25 to about 1:200.
[0032] The pulp fibers may be pretreated with the thermoplastic
resin in various fashions, such as in a wet laid process. In one
embodiment of the present invention, the process comprises mixing
pulp fibers with water to form a pulp fiber slurry. The pulp fiber
slurry may be transported to a web-forming apparatus of a
papermaking machine to form a wet fibrous tissue web. The wet
fibrous tissue web may be dewatered to a predetermined consistency,
thereby forming a dewatered fibrous tissue web. The thermoplastic
resin may be converted to a liquid form (e.g., heated, dispersed
and/or dissolved in water, and/or the like) and added to the
dewatered fibrous tissue web, thereby forming a chemically
pretreated, dewatered, fibrous tissue web containing chemically
pretreated pulp fibers. These chemically pretreated pulp fibers may
have an increased or improved level of chemical retention of the
water insoluble chemical additive through the paper making process.
In another embodiment of the present invention, the process may,
additionally or alternatively, comprise adding the thermoplastic
resin to the pulp fiber during a pulp processing stage.
[0033] Possible tissue products comprising the pretreated pulp
fibers may include, but are not limited to, bath tissue, facial
tissue, towels, wipes, dinner napkins, and the like.
[0034] In one embodiment of the present invention, the fibrous
tissue web is made into a tissue product. The tissue product may be
a single or multi-ply tissue product; e.g., the tissue product can
be a three-ply facial tissue product. Facial tissue, bath tissue,
and towel products, as used herein, are differentiated from other
paper products in terms of their bulk. The bulk of the tissue
products may be calculated as the quotient of the caliper
(hereinafter defined) in micrometers, divided by the basis weight
in grams per square meter (g/m.sup.2). The resulting bulk may be
expressed in cubic centimeters per gram (cm.sup.3/g). Writing
papers, newsprint, and other such paper products typically have
higher strength, stiffness, and density (low bulk) in comparison to
tissue products which tend to have much higher calipers for a given
basis weight. The tissue products may have a bulk of about 2
cm.sup.3/g or greater, more specifically about 2.5 cm.sup.3/g or
greater, and even more specifically about 3 cm.sup.3/g or greater.
The basis weight of the tissue product may be about 5 g/m.sup.2 to
about 200 g/m.sup.2, or, more specifically about 7 g/m.sup.2 to
about 150 g/m.sup.2, and, even more specifically, about 10
g/m.sup.2 to about 100 g/m.sup.2.
[0035] The tissue products may comprise layered and/or blended
fibrous tissue webs.
[0036] The term "blended fibrous tissue web", as used herein,
refers to the process of blending various pulp fiber types prior to
formation of the fibrous tissue web. In accordance with some
embodiments of the present invention, pretreated pulp fibers may be
blended with non-pretreated pulp fibers prior to formation of
fibrous tissue web(s). In one embodiment of the present invention,
a fibrous tissue web may comprise a cellulosic pulp fiber layer
with pulp fibers selectively pretreated with the thermoplastic
resin, e.g., the center portion of the fibrous tissue web may be
coated on one side with the thermoplastic resin. Such an
arrangement may increase the structural integrity of the fibrous
tissue web in an area generally subjected to higher stresses. In
another embodiment of the present invention, an entire area of the
fibrous tissue web may comprise pretreated pulp fibers; e.g., the
center of the fibrous tissue web. In other words, all or a portion
of a fibrous tissue web may comprise the thermoplastic resin. In
yet another embodiment of the present invention, fibrous tissue
web(s) comprising pretreated pulp fibers may be disposed adjacent
and/or between fibrous tissue web(s) of non-pretreated pulp fibers.
For example, a fibrous tissue web comprising pretreated pulp fibers
comprising about 25 wt % to about 100 wt % pretreated pulp fibers
(based upon the total weight of the fibrous tissue web) may be
disposed between fibrous tissue webs comprising about 25 wt % or
less of pretreated pulp fiber, or more specifically about 10 wt %
or less of pretreated pulp fibers, and even more specifically about
5 wt % or less of pretreated pulp fibers, based upon the total
weight of the specific fibrous tissue web. In yet another
embodiment of the present invention, a concentration gradient of
pretreated pulp fibers within a fibrous tissue web may be
established across a layer of the fibrous tissue web, where areas
of higher stress have a greater concentration. For example, a
concentration gradient may increase from an edge of a fibrous
tissue web toward a center of the fibrous tissue web.
[0037] Various tissue production methods may be employed, including
those for imprinted fibrous tissue webs and/or tissue products
(e.g., that 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), both creped and uncreped
methods of manufacture, and the like. For example, the preparation
of the fibrous tissue web and/or tissue product may be carried out
in a papermaking machine by mixing dried pretreated pulp fibers
with water to form a pretreated pulp fiber slurry. Non-pretreated
pulp fibers may optionally be added to the pretreated pulp fiber
slurry to form a blended pulp fiber slurry. The pretreated pulp
fiber slurry or blended pulp fiber slurry may then be forwarded to
a headbox, deposited onto a moving wire or belt (hereinafter belt),
dewatered, dried, and processed to form a fibrous tissue web.
[0038] Optionally, additional pulp fiber slurry(ies) comprising
non-pretreated pulp fibers may be prepared in the same manner as
the pretreated pulp fiber slurry. The pulp slurry(ies), separately
or individually, may then be directed to a stratified headbox where
they are deposited onto a moving belt to form a fibrous tissue web.
The fibrous tissue web may be is dewatered, dried, and processed to
form a dried layered fibrous tissue web. For example, as in the
wetlaid process for papermaking, the wet fibrous tissue web (formed
by depositing the aqueous pulp fiber slurry from the headbox onto
the moving belt to filter out the pulp fibers and form an embryonic
fibrous tissue web) may be dewatered using suction box(es), wet
press(es), dryer unit(s), and the like, as well as combinations
comprising at lest one of the foregoing processes. Examples of
known dewatering and other operations of the papermaking process
are set forth in U.S. Pat. No. 5,656,132 issued to Farrington, Jr.
et al.; U.S. Pat. No. 5,598,643 issue to Chuang et al.; and, U.S.
Pat. No. 4,556,450 issued to Chuang et al. Other examples of
possible drying methods include, but are not limited to, drum
drying, through air drying, steam drying (e.g., superheated steam
drying), displacement dewatering, Yankee drying, infrared drying,
microwave drying, radio frequency drying, differential gas pressure
drying, impulse drying, and the like, as well as combinations
comprising at least one of the above drying techniques. Some
exemplary paper making machines are disclosed in U.S. Pat. No.
5,230,776 issued to Andersson et al.
[0039] Optionally, the fibrous tissue webs and/or tissue products
may comprise a design, e.g., the fibrous tissue webs and/or tissue
products may be embossed with a design, and/or a design may be
applied thereto. In one embodiment of the present invention, the
pretreated pulp fibers may bond with themselves upon the
application of an externally applied stress (e.g., heat, pressure,
and/or the like) thereto (e.g., to the fibrous tissue web
comprising such pulp fibers).
[0040] The disclosure is further illustrated by the following
non-limiting examples. The following test methods were used in the
examples.
EXAMPLES
[0041] The dry tensile index or the tensile index of the handsheet
strip samples set forth in the examples was determined by
performing a dry tensile test on a handsheet strip of 1 inch wide.
The handsheet strip sample was placed into a tensile frame at a
gauge length of 5 inches. The handsheet strip sample was then
subjected to a strain of 0.5 inches per minute and the resulting
stress was recorded with an appropriate load cell. The peak load
force divided by the width of the handsheet strip sample was
recorded as the tensile index after normalization for the basis
weight of the handsheet strip sample. The tensile index is
expressed in Newton meter per gram (Nm/g). The amount of strain
that the handsheet strip sample underwent to obtain a peak load was
recorded as a stretch of the handsheet strip sample. The stretch is
expressed as a percent (%) of the test length. The slope, in
kilogram force (kgf, describes the maximum stress/strain slope
recorded by the test during the application of the first 5% of
strain. The tensile energy absorbed (TEA), in Joules per square
meter (J/m.sup.2), describes the integrated area of the stress
strain curve divided by the area of the handsheet strip sample
being tested.
[0042] The wet tensile index was determined by performing a wet
tensile test similar to the dry tensile test on a handsheet strip
sample of 1 inch where the handsheet strip sample was wetted
thoroughly, by looping the handsheet strip sample and contacting
the bottom of the loop of the handsheet strip sample in deionized
water at an ambient temperature. The loop of the handsheet strip
sample is held there until the welted area extends 1 to 1.5 inches
lengthwise and is uniform across the entire width of the handsheet
strip sample. Excess water is removed from the handsheet strip
sample by gently touching the welted area of the handsheet strip
sample once to a blotter paper. A wet tensile index, in Nm/g, was
recorded, describing a peak load force divided by the width of the
wet handsheet strip sample. The wet tensile index divided by the
dry tensile index provided a wet/dry ratio.
Example 1
[0043] This example describes a method to manufacture handsheet
strip samples.
[0044] Handsheet strip samples having a basis weight of 60 grams
per square meter (g/m.sup.2) were prepared by diluting a pulp fiber
sample in water to a consistency of 1.2 wt % in a British Pulp
Disintegrator (commercially available from Lorentzen and Wettre
located in Atlanta, Ga.). The pulp fiber sample was allowed to soak
for 5 minutes before being pulped for 5 minutes at ambient
temperature (i.e., about 25.degree. C.), diluted to 0.3 wt %
consistency, and formed into a handsheet on a 9 inch by 9 inch
Valley Handsheet Mold (commercially available from Voith Inc.
Appleton, Wis.). The handsheet was couched off the mold by hand
using a blotter paper and pressed wire-side up at 100 psi for 1
minute. The handsheet was dried, wire-side up, for 2 minutes to
absolute dryness using a Valley Steam Hotplate (commercially
available from Voith Inc. located in Appleton, Wis.) and a standard
weighted canvas cover having a weighted tube (4.75 pounds) at one
end to maintain constant tension. The resulting handsheet was then
conditioned in a humidity controlled room (at 23 degree centigrade
(.degree. C.) and 50 percent relative humidity) prior to
preparation as a handsheet strip sample and testing.
Example 2
[0045] A first set of bleached Northern softwood kraft pulp fibers
comprising 1,000 grams per square meter (g/m.sup.2) dry pulp fiber
sheet were soaked with water and allowed to dry to create a
control, hereinafter referred to as Control 1, for the handsheet
strip sample experiments. These pulp fibers were slurried and made
into standard handsheets, and ultimately handsheet strip samples,
as described in Example 1. The handsheet strip samples, Control 1,
were tested for tensile properties in accordance to the procedure
as set forth above.
Example 3
[0046] A second set of bleached Northern softwood kraft pulp fibers
were pretreated with a dispersed sulfonated polyester polymer under
the trade name Eastman AQ 38D Copolyester (commercially available
from Eastman Chemicals located in Kingsport, Tenn.). The treatment
involved soaking a 1,000 g/m.sup.2 dry pulp fiber sheet with a
solution and allowing the pulp fiber to dry. The dispersion solids
were controlled to provide a 1% treatment on a pulp fiber dry
weight basis. These pulp fibers were slurried and made into
standard handsheets, and ultimately handsheet strip samples, as
described in Example 1. The handsheet strip samples, hereinafter
referred to as Sample 1, were tested for tensile properties in
accordance to the procedure set forth above.
Example 4
[0047] Additionally a subset of the handsheet strip samples of
Sample 1 described in Example 3 were hot-calendared using a steel
to steel calendar at 100.degree. C., 120 pounds per linear inch
pressure, at a line speed of approximately 25 feet per minute
(ft/min). The hot calendared handsheet strip samples, hereinafter
referred to as Sample 2, were tested for tensile properties in
accordance to the procedure set forth above.
Example 5
[0048] A third set of bleached Northern softwood kraft pulp fibers
were pretreated with a dispersed sulfonated polyester polymer under
the trade name Eastman AQ 38D Copolyester. The treatment involved
soaking a 1,000 g/m.sup.2 dry pulp fiber sheet with a dilute
dispersion and allowing the pulp fiber to dry. The dispersion
solids were controlled to provide a 2% treatment on a pulp fiber
dry weight basis. These fibers were slurried and made into standard
handsheets, and ultimately handsheet strip samples, as described in
Example 1. The handsheet strip samples, hereinafter referred to as
Sample 3, were tested for tensile properties in accordance to the
procedure set forth above.
Example 6
[0049] Additionally a subset of the handsheet strip samples from
Example 5 were hot-calendared using a steel to steel calendar at
100.degree. C., 120 pounds per linear inch pressure, at a line
speed of approximately 25 ft/min. The hot calendared handsheet
strip samples, hereinafter referred to as Sample 4, were tested for
tensile properties in accordance to the procedure set forth
above.
[0050] The resulting properties for the Control 1 as well as
Samples 1-4 are shown in Table 1. TABLE-US-00001 TABLE 1 Pretreated
Pulp Properties Control Sample Sample Sample Sample Properties 1 1
2 3 4 Dry Tensile 21.38 20.93 26.56 23.45 38.45 Index (Nm/g)
Stretch (%) 1.56 2.35 2.17 2.88 3.13 TEA (J/m.sup.2) 15.02 21.42
23.17 24.68 35.67 slope (kgf) 456 386 274 322 254 Wet Tensile 1.23
1.84 2.54 1.95 8.32 Index (Nm/g) Wet/dry 5.8 8.8 9.6 8.3 21.6 ratio
(%)
[0051] The results as shown in Table 1 indicate an increase in
strength and stretch, and a decrease in slope on addition of the
copolyester, especially after hot calendaring, in the handsheet
strip samples, Samples 1-4. As can be seen from the Samples 1-4,
tissue products and/or fibrous tissue webs having the following
properties may be prepared using the cellulosic pulp fibers and
water soluble and/or water dispersible thermoplastic resin of the
present invention:
[0052] (i) a stretch of about 2% or greater, or, more specifically
about 2.25% or greater, and even more specifically about 2.5% or
greater;
[0053] (ii) a wet tensile index of about 1.5 Nm/g or greater, more
specifically about 1.8 Nm/g or greater, prior to hot calendaring,
while capable of attaining a wet tensile index of about 2.5 Nm/g or
greater after hot calendaring, more specifically about 5 Nm/g or
greater after hot calendaring;
[0054] (iii) a wet/dry strength ratio of about 8% or greater, more
specifically to about 9% or greater, and more specifically about
15% or greater;
[0055] (iv) a TEA of greater than or equal to about 21 J/m.sup.2 or
greater, more specifically about 23 J/m.sup.2 or greater, more
specifically about 30 J/m.sup.2 or greater; and/or,
[0056] (v) a slope of about 400 kgf or less, more specifically
about 350 kgf or less, and more specifically about 300 kgf or
less.
Example 7
[0057] A first set of bleached eucalyptus kraft pulp fibers
comprising 1,000 g/m.sup.2 dry pulpsheet were soaked with water and
allowed to dry to create a control, hereinafter referred to as
Control 2, for the handsheet strip sample experiments. These pulp
fibers were slurried and made into standard handsheets, and
ultimately handsheet strip samples, as described in Example 1. The
handsheet strip samples, Control 2, were tested for tensile
properties in accordance with the procedure set forth above.
Example 8
[0058] A second set of bleached eucalyptus kraft pulp fibers were
pretreated with a dispersed sulfonated polyester polymer (Eastman
AQ 38D Copolyester). The treatment involved soaking a 1,000
g/m.sup.2 dry pulp fiber sheet with a dilute dispersion and
allowing the pulp fibers to dry. The dispersion solids and volume
added were controlled to provide a 5% treatment on a pulp fiber dry
weight basis. The pretreated pulp fibers were slurried and made
into standard handsheets, and ultimately handsheet strip samples,
as described in Example 1. The handsheet strip samples, hereinafter
referred to as Sample 5, were tested for tensile properties in
accordance with the procedure set forth above.
Example 9
[0059] A third set of bleached eucalyptus kraft pulp fibers were
pretreated with a polyurethane polymer under the trade name Permax
120 (commercially available from Noveon located in Cleveland,
Ohio). The treatment involved soaking a 1,000 g/m.sup.2 dry pulp
fiber sheet with a dilute dispersion and allowing the pulp fibers
to dry. The dispersion solids and volume added were controlled to
provide a 5% treatment on a pulp fiber dry weight basis. The
pretreated pulp fibers were slurried and made into standard
handsheets, and ultimately handsheet strip samples, as described in
Example 1. The handsheet strip samples, hereinafter referred to as
Sample 6, were tested for tensile properties in accordance with the
procedure set forth above.
Example 10
[0060] A fourth set of bleached eucalyptus kraft pulp fibers were
pretreated with a vinyl acetate polymer under the trade name Vinac
911 (commercially available from Air Products located in Allentown,
Pa.). The treatment involved soaking a 1,000 g/m.sup.2 dry pulp
fiber sheet with a dilute dispersion and allowing the pulp fibers
to dry. The dispersion solids and volume added were controlled to
provide a 5% treatment on a pulp fiber dry weight basis. The
pretreated pulp fibers were slurried and made into standard
handsheets, and ultimately handsheet strip samples, as described in
Example 1. The handsheet strip samples, hereinafter referred to as
Sample 7, were tested for tensile properties in accordance to the
procedure as set forth above.
[0061] The resulting properties of Control 2 and Samples 5-7 are
shown in Table 2. TABLE-US-00002 TABLE 2 Handsheet Properties
Properties Control 2 Sample 5 Sample 6 Sample 7 Dry Tensile Index
13.5 19.5 13.0 16.9 (Nm/g) Stretch (%) 1.3 2.5 3.0 2.9 TEA
(J/m.sup.2) 3.5 9.5 5.9 7.9 slope (kgf) 375 254 284 301 Wet Tensile
Index 1.1 3.5 2.9 3.6 (Nm/g) Wet/dry ratio (%) 8.1 18.0 22.3
21.3
[0062] The results shown in Table 2 indicate that the handsheet
strip samples, Samples 5-7, comprising pulp fibers pretreated with
the thermoplastic resin of the present invention have a higher
stretch (e.g., about 2.00% or greater, more specifically about
2.50% or greater, versus less than about 1.35% for Control 2) and
higher wet tensile index (e.g., about 2.00 Nm/g or greater, more
specifically about 2.50 Nm/g or greater, and more specifically
about 3.25 Nm/g or greater, versus less than about 1.15 Nm/g for
Control 2), and higher wet/dry ratio (e.g.,;about 12% or greater,
more specifically about 15% or greater, and more specifically about
20% or greater, versus less than about 9% for Control 2) while
maintaining a lower slope (e.g., about 325 kgf or less, more
specifically about 300 kgf or less, and more specifically about 290
kgf or less, versus greater than about 370 kgf for Control 2).
Without being bound by theory, it has been discovered that
decreasing the slope results in a tissue product and/or fibrous
tissue web having higher strength at lower stiffness compared to
methods such as refining. This provides a more durable fibrous
tissue web and/or tissue product while allowing the fibrous tissue
web and/or tissue product to be less brittle which is particularly
advantageous for soft tissue products.
[0063] A third set of handsheet experiments were done to provide an
example of the effect of the thermoplastic addition through typical
wet-end addition of the polymer. The data for the second handsheet
experiments, Control 2, was used for this set of experiments.
Example 11
[0064] A fifth set of bleached eucalyptus kraft pulp fibers were
made with the wet-end addition of Eastman AQ polymer, hereinafter
referred to as Sample 8, for the handsheet strip sample
experiments. Handsheet strip samples having a basis weight of 60
grams per square meter (g/m.sup.2) were prepared by diluting a pulp
fiber sample in water to a consistency of 1.2 wt % in a British
Pulp Disintegrator (commercially available from Lorentzen and
Wettre located in Atlanta, Ga.). The pulp fiber sample was allowed
to soak for 5 minutes before being pulped for 5 minutes at ambient
temperature (i.e., about 25.degree. C.), and diluted to 0.3 wt %
consistency. A diluted dispersion of Eastman AQ 38D Copolyester was
added to the pulp suspension to provide a treatment of
approximately 5% on a pulp fiber dry weight basis and mixed for 5
minutes. This suspension was formed into a handsheet on a 9 inch by
9 inch Valley Handsheet Mold (commercially available from Voith
Inc. Appleton, Wis.). The handsheet was couched off the mold by
hand using a blotter paper and pressed wire-side up at 100 psi for
1 minute. The handsheet was dried, wire-side up, for 2 minutes to
absolute dryness using a Valley Steam Hotplate (commercially
available from Voith Inc. located in Appleton, Wis.) and a standard
weighted canvas cover having a weighted tube (4.75 pounds) at one
end to maintain constant tension. The handsheet strip samples,
Sample 8, were tested for tensile properties in accordance with the
procedure set forth above.
Example 12
[0065] A sixth set of bleached eucalyptus kraft pulp fibers were
made with the wet-end addition of a polyurethane polymer under the
trade name Permax 120 (commercially available from Noveon located
in Cleveland, Ohio). The treatment was identical to Example 11 with
the exception that a dispersion of Permax 120 polymer was used
instead of the Eastman AQ 38D to provide a treatment of
approximately 5% on a pulp fiber dry weight. The pulp fibers and
polymer were mixed, made into standard handsheets, and ultimately
made into handsheet strip samples, as described in Example 11. The
handsheet strip samples, hereinafter referred to as Sample 9, were
tested for tensile properties in accordance with the procedure set
forth above.
Example 13
[0066] A seventh set of bleached eucalyptus kraft pulp fibers were
made with the wet-end addition of a polyurethane polymer under the
trade name Vinac 911 (commercially available from Air Products
located in Allentown, Pa.). The treatment was identical to Example
11 with the exception that a dispersion of Permax 120 polymer was
used instead of the Eastman AQ 38D to provide a treatment of
approximately 5% on a pulp fiber dry weight. The pulp fibers and
polymer were mixed, made into standard handsheets, and ultimately
made into handsheet strip samples, as described in Example 11. The
handsheet strip samples, hereinafter referred to as Sample 10, were
tested for tensile properties in accordance with the procedure set
forth above.
[0067] The resulting properties of Control 2 and Samples 8-10 are
shown in Table 3. TABLE-US-00003 TABLE 3 Handsheet Properties
Properties Control 2 Sample 8 Sample 9 Sample 10 Dry Tensile Index
13.5 14.1 13.8 12.5 (Nm/g) Stretch (%) 1.3 1.4 1.1 1.3 TEA
(J/m.sup.2) 3.5 4.1 3.6 3.1 slope (kgf) 375 386 412 391 Wet Tensile
Index 1.1 1.0 1.1 1.0 (Nm/g) Wet/dry ratio (%) 8.1 7.1 8.0 8.0
[0068] The results shown in Table 3 indicate that the handsheet
strip samples, Samples 8-10, comprising pulp fibers treated with
the thermoplastic resin in the wet-end have properties very similar
to the control. These examples show the utility of the present
invention's pretreatment step which provides unique tensile,
stretch, and elastic moduls properties.
[0069] The cellulosic pulp fibers, tissue product, and method of
using the cellulosic fibers and water soluble and/or water
dispersible thermoplastic resin enables enhanced properties within
a fibrous tissue web and/or tissue product when compared to
cellulosic pulp fibers with either no pretreatment or treated using
a typical wet-end addition. The fibrous tissue webs and/or tissue
products comprising pretreated cellulosic pulp fibers and/or layers
of the pretreated cellulosic pulp fibers, have a dry and wet
strength that imparts durability to the fibrous tissue web and/or
tissue product comprising such pretreated cellulosic pulp fibers.
Additionally, due to the present process, the pretreated cellulosic
pulp fibers may be selectively located within the fibrous tissue
web and/or tissue product to attain the desired structural
integrity while retaining a desired texture (e.g., softness) of the
fibrous tissue web and/or tissue product. Furthermore, since the
thermoplastic resin of the present invention is water soluble
and/or water dispersible, the fibrous tissue web and/or tissue
product may be easily recycled, and, in particular repulped.
[0070] While the disclosure has been described with reference to
exemplary embodiments of the present invention, it will be
understood by those skilled in the art that various changes may be
made and equivalents may be substituted for elements thereof
without departing from the scope of the disclosure. In addition,
many modifications may be made to adapt a particular situation or
material to the teachings of the disclosure without departing from
the essential scope thereof. Therefore, it is intended that the
disclosure not be limited to the particular embodiment of the
present invention disclosed as the best mode contemplated for
carrying out this disclosure, but that the disclosure will include
all embodiments of the present invention falling within the scope
of the appended claims.
* * * * *