U.S. patent application number 10/657454 was filed with the patent office on 2004-03-11 for process for the manufacture of multi-ply tissue.
This patent application is currently assigned to The Procter & Gamble Company. Invention is credited to Horner, Thomas, Loughran, Scott Thomas, Malmbak, Marianne, Werth, Anja.
Application Number | 20040045685 10/657454 |
Document ID | / |
Family ID | 31995565 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040045685 |
Kind Code |
A1 |
Horner, Thomas ; et
al. |
March 11, 2004 |
Process for the manufacture of multi-ply tissue
Abstract
The invention relates to a process for the manufacture of a
multi-ply tissue comprising at least two plies. The process
comprises steps of mechanically refining a first slurry of fibers
wherein the fibers have an average length of at least 2 mm; mixing
the refined slurry with a second slurry of fibers, providing an
embryonic web upon a foraminous surface, removing water from the
embryonic web to form a ply; and juxtaposing at least two plies to
form the multi-ply tissue.
Inventors: |
Horner, Thomas; (Hofheim,
DE) ; Loughran, Scott Thomas; (Bad Soden/Ts., DE)
; Malmbak, Marianne; (Idstein-Eschenhahn, DE) ;
Werth, Anja; (Frankfurt/M., DE) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Assignee: |
The Procter & Gamble
Company
|
Family ID: |
31995565 |
Appl. No.: |
10/657454 |
Filed: |
September 8, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10657454 |
Sep 8, 2003 |
|
|
|
09831784 |
Sep 12, 2001 |
|
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Current U.S.
Class: |
162/123 ;
162/132 |
Current CPC
Class: |
D21H 21/20 20130101;
D21F 11/006 20130101; D21F 11/14 20130101; D21H 27/30 20130101 |
Class at
Publication: |
162/123 ;
162/132 |
International
Class: |
D21H 027/30 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 24, 1998 |
EP |
98122328.2 |
Claims
What is claimed is:
1. A process for making the multi-ply tissue comprising the steps
of: mechanically refining a first slurry of fibers wherein the
fibers have an average length of at least 2 mm; mixing the refined
slurry with a second slurry of fibers, the average length of the
fibers of the second slurry being shorter than the average length
of the fibers of the first slurry; providing a embryonic web upon a
foraminous surface, the composition of fibers in the embryonic web
being substantially homogeneous throughout the thickness of the
web; removing water from the embryonic web to form a ply; and
juxtaposing at least two plies to form the multi-ply tissue.
2. A process according to claim 1 wherein a substantial proportion
of the fibers of the first slurry comprises softwood fibers, and a
substantial proportion of the fibers of the second slurry comprises
hardwood fibers.
3. A process according to claim 1 wherein the ratio of long
softwood fibers to shorter hardwood fibers is greater than 60:40,
and preferably about 70:30.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of copending U.S.
application Ser. No. 09/831,784 filed May 14, 2001.
FIELD OF INVENTION
[0002] The present invention relates to multi-ply tissue, and in
particular to facial tissue, and disposable handkerchiefs.
[0003] Paper webs or sheets, sometimes called tissue or paper
tissue webs or sheets, find extensive use in modern society. Such
items as facial and toilet tissues are staple items of commerce. It
has long been recognised that four important physical attributes of
these products are their strength, their softness, their
absorbency, including their absorbency for aqueous systems; and
their lint resistance. Research and development efforts have been
directed to the improvement of each of these attributes without
seriously affecting the others as well as to the improvement of two
or three attributes simultaneously.
[0004] Softness is the tactile sensation perceived by the consumer
as he/she holds a particular product, rubs it across his/her skin,
or crumples it within his/her hand. This tactile sensation is a
combination of several physical properties. One of the more
important physical properties related to the softness is generally
considered by those skilled in the art to be the stiffness of the
paper tissue from which the product is made. Stiffness, in turn, is
usually considered to be directly dependent on the dry tensile
strength of the web.
[0005] Strength is the ability of the product to maintain physical
integrity and to resist tearing, bursting, and shredding under use
conditions.
[0006] Absorbency is the measure of the ability of a product to
absorb quantities of liquid, particularly aqueous solutions or
dispersions. Overall absorbency as perceived by the human consumer
is generally considered to be a combination of the total quantity
of a liquid a given mass of tissue paper will absorb at saturation
as well as the rate at which the mass absorbs the liquid.
[0007] Lint resistance is the ability of the fibrous product, and
its constituent webs, to bind together under use conditions,
including when wet. In other words, the higher the lint resistance
is, the lower the propensity of the web to lint will be.
[0008] WO95/11343, published on Apr. 27, 1995, discloses a process
for making layered paper tissues. Example 3 discloses a two-ply
facial tissue having a basis weight of about 32 g/m.sup.2 (20
lbs/3000 sq. ft.) The tissue of this example comprises 0.475% of a
wet strength resin.
[0009] U.S. Pat. No. 4,481,243, issued on Nov. 6, 1984 discloses
facial tissues which comprise multiple plies secured together by
embossing only along the margins of the tissue.
[0010] Disposable paper products having high wet burst strength are
known, for example Bounty.TM., sold by The Procter & Gamble
Company, has a wet burst strength which is greater than 200 g.
However such kitchen towels are embossed over the whole surface
which results in a surface texture which is rough and does not
provide a suitably smooth wiping surface for blowing the nose.
[0011] Facial tissues are commercially available comprising at
least two plies, the tissue having a surface area in one plane, and
a thickness orthogonal to the plane, wherein the thickness is a
caliper of at least 0.35 mm, and wherein the tissue has an
unembossed wiping surface over a major part of the surface area of
the tissue. However the rather low wet burst strength of today's
facial tissues often results in tearing or bursting which in turn
results in contamination of the user's hand with mucus or other
bodily fluids.
[0012] The object of the present invention is to provide a
multi-ply facial tissue having the at least the desired softness
and absorbency of known facial tissues, but also providing enhanced
protection against tearing or bursting when used, in particular
when used for blowing the nose.
SUMMARY OF THE INVENTION
[0013] The invention relates to a process for the manufacture of
the multi-ply tissue, wherein the process comprises the steps
of:
[0014] mechanically refining a first slurry of fibers wherein the
fibers have an average length of at least 2 mm, preferably the
first slurry comprises a substantial proportion of softwood fibers,
such as Nothern Softwood Kraft fibers;
[0015] mixing the refined slurry with a second slurry of fibers,
the average length of the fibers of the second slurry being shorter
than the average length of the fibers of the first slurry,
preferably the second slurry comprises a substantial proportion of
hardwood fibers, such as eucalyptus fibers;
[0016] providing a embryonic web upon a foraminous surface, the
composition of fibers in the embryonic web being substantially
homogeneous throughout the thickness of the web;
[0017] removing water from the embryonic web to form a ply; and
[0018] juxtaposing at least two plies to form the multi-ply
tissue.
[0019] Most preferably, the ratio of long softwood fibers to
shorter hardwood fibers is greater than 60:40, and preferably about
70:30.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention may contain, as a highly preferred
component, up to about 3.0%, preferably at least 0.5%, and more
preferably at least 0.8% by weight, on a dry fiber weight basis, of
wet strength chemical agent, such as water-soluble permanent and
temporary wet strength resin.
[0021] Wet strength resins useful herein can be of several types.
For example, Westfelt described a number of such materials and
discussed their chemistry in Cellulose Chemistry and Technology,
Volume 13, at pages 813-825 (1979).
[0022] Usually, the wet strength resins are water-soluble, cationic
materials. That is to say, the resins are water-soluble at the time
they are added to the papermaking furnish. It is quite possible,
and even to be expected, that subsequent events such as
cross-linking will render the resins insoluble in water. Further
some resins are soluble only under specific conditions, such as
over a limited pH range. Wet strength resins are generally believed
to undergo a cross-linking or other curing reactions after they
have been deposited on, within, or among the papermaking fibers.
Cross-linking or curing does not normally occur so long as
substantial amounts of water are present.
[0023] Of particular utility are the various
polyamide-epichlorohydrin resins. These materials are low molecular
weight polymers provided with reactive functional groups such as
amino, epoxy, and azetidinium groups. The patent literature is
replete with descriptions of processes for making such materials,
including U.S. Pat. No. 3,700,623, issued to Keim on Oct. 24, 1972,
and U.S. Pat. No. 3,772,076, issued to Keim on Nov. 13, 1973.
[0024] Polyamide-epihydrochlorin resins sold under the trademarks
Kymene 557H and Kymene LX by Hercules Inc. of Wilmington, Del., are
particularly useful in this invention. These resins are generally
described in the aforementioned patents to Keim.
[0025] Base-activated polyamide-epichlorohydrin resins useful in
the present invention are sold under the Santo Res trademark, such
as Santo Re 31, by Monsanto Company of St. Louis, Mo. These types
of materials are generally described in U.S. Pat. No. 3,855,158
issued to Petrovich on Dec. 17, 1974; U.S. Pat. No. 3,899,388
issued to Petrovich on Aug. 12, 1975; U.S. Pat. No. 4,129,528
issued to Petrovich on Dec. 12, 1978; U.S. Pat. No. 4,147,586
issued to Petrovich on Apr. 3, 1979; and U.S. Pat. No. 4,222,921
issued to Van Eenam on Sep. 16, 1980.
[0026] Other water-soluble cationic resins useful hererin are the
polyacrylamide resins such as those sold under the Parez trademark,
such as Parez 631NC, by American Cyanamid Company of Sandford,
Conn. These materials are generally described in U.S. Pat. No.
3,556,932 issued to Coscia et al on Jan. 19, 1971; and U.S. Pat.
No. 3,556,933 issued to Williams et al on Jan. 19, 1971.
[0027] Other types of water-soluble resins useful in the present
invention include acrylic emulsions and anionic styrene-butadiene
latexes. Numerous examples of these types of resins are provided in
U.S. Pat. No. 3,844,880. Meisel Jr et al, issued Oct. 29, 1974.
Still other water-soluble cationic resins finding utility in this
invention are the urea formaldehyde and melamine formaldehyde
resins. These polyfunctional, reactive polymers have molecular
weights on the order of a few thousand. The more common functional
groups include nitrogen containing groups such as amino groups and
methylol groups attached to the nitrogen. Although less preferred,
polyethylenimine type resins find utility in the present
invention.
[0028] More complete descriptions of the aforementioned
water-soluble resins, including their manufacture, can be found in
TAPPI Monograph Series No. 29, "Wet Strength in paper and
Paperboard, Technical Association of the Pulp and Paper Industry
(New York; 1965).
[0029] Temporary wet strength agents, such as modified starch may
also, optionally, be used. Combinations of permanent and temporary
wet strength agents may be used.
[0030] The present invention may contain dry strength chemical
agents, preferably at levels up to 3% by weight, more preferably at
least 0.1% by weight, on a dry fiber weight basis. A highly
preferred dry strength chemical agent is carboxymethyl cellulose.
Other suitable dry strength chemical agents include polyacrylamide
(such as combinations of Cypro.TM. 514 and Accostrength.TM. 711
produced by American Cyanamid of Wayne, N.J.); starch (such as corn
starch or potato starch); polyvinyl alcohol (such as Airvol.TM. 540
produced by Air Products Inc. of Allentown, Pa.); guar or locust
bean gums; and polyacrylate latexes. Suitable starch materials may
also include modified cationic starches such as those modified to
have nitrogen containing groups such as amino groups and methylol
groups attached to nitrogen, available from National Starch and
Chemical Company (Bridgewater, N.J.).
[0031] Chemical softening compositions, comprising chemical
debonding agents are optional components of the present invention.
U.S. Pat. No. 3,821,068, issued Jun. 28, 1974 teaches that chemical
debonding agents can be used to reduce the stiffness, and thus
enhance the softness, of a tissue paper web. U.S. Pat. No.
3,554,862, issued on Jan. 12, 1971 discloses suitable chemical
debonding agents. These chemical debonding agents include
quaternary ammonium salts.
[0032] Preferred chemical softening compositions comprise from
about 0.01% to about 3.0% of a quaternary ammonium compound,
preferably a biodegradable quaternary ammonium compound; and from
about 0.01% to about 3.0% of a polyhydroxy compound; preferably
selected from the group consisting of glycerol, sorbitols,
polyglycerols having an average molecular weight of from about 150
to about 800 and polyoxyethylene glycols and polyoxypropylene
glycols having a weight average molecular weight from about 200 to
4000. Preferably the weight ratio of the quaternary ammonium
compound to the polyhydroxy compound ranges from about 1.0:0.1 to
0.1:1.0. It has been discovered that the chemical softening
composition is more effective when the polyhydroxy compound and the
quaternary ammonium compound are first premixed together,
preferably at a temperature of at least 40.degree. C., before being
added to the papermaking furnish. Either additionally, or
alternatively, chemical softening compositions may be applied to
the substantially dry tissue paper web, for example by means of a
printing process (N.B. all percentages herein are by weight of dry
fibers, unless otherwise specified).
[0033] Examples of quaternary ammonium compounds suitable for use
in the present invention include either unmodified, or mono- or
di-ester variations of: well-known dialkyldimethylammonium salts
and alkyltrimethyl ammonium salts. Examples include the diester
variations of di(hydrogenated tallow)dimethyl ammonium
methylsulphate and di-ester variations of di(hydrogenated
tallow)dimethyl ammonium chloride. Without wishing to be bound by
theory, it is believed that the ester moity(ies) lends
biodegradability to these compounds. Commercially available
materials are available from Witco Chemical Company Inc. of Dublin,
Ohio, under the tradename "Rewoquat V3512". Details of analytical
and testing procedures are given in WO95/11343, published on Apr.
27, 1995.
[0034] Examples of polyhydroxy compounds useful in the present
invention include polyoxyethylene glycols having a weight average
molecular weight of from about 200 to about 600, especially
preferred is "PEG-400".
[0035] The tissue paper of the present invention may be made by
common methods well-known to the person skilled in the art, such as
by dewatering suitable pulp using, for example, one or more
papermakers felts and/or belts.
[0036] In one embodiment of the present invention, at least one ply
of the tissue paper has two primary regions. The first region
comprises an imprinted region which is imprinted against the
framework of the papermaking belt. The imprinted region preferably
comprises an essentially continuous network. The continuous network
of the first region of the paper is made on the essentially
continuous framework of the belt and will generally correspond
thereto in geometry and be disposed very closely thereto in
position during papermaking.
[0037] The second region of the paper comprises a plurality of
domes dispersed throughout the imprinted network region. The domes
generally correspond in geometry, and during papermaking in
position, to the deflection conduits in the belt. The domes
protrude outwardly from the essentially continuous network region
of the paper, by conforming to the deflection conduits during the
papermaking process. By conforming to the deflection conduits
during the papermaking process, the fibers in the domes are
deflected in the Z-direction between the paper facing surface of
the framework and the paper facing surface of the reinforcing
structure. Preferably the domes are discrete.
[0038] Without being bound by theory, it is believed the domes and
essentially continuous network regions of the paper may have
generally equivalent basis weights. By deflecting the domes into
the deflection conduits, the density of the domes is decreased
relative to the density of the essentially continuous network
region. Moreover, the essentially continuous network region (or
other pattern as may be selected) may later be imprinted as, for
example, against a Yankee drying drum. Such imprinting increases
the density of the essentially continuous network region relative
to that of the domes.
[0039] The paper according to the present invention may be made
according to any of commonly assigned U.S. Patents: U.S. Pat. No.
4,529,480, issued Jul. 16, 1985 to Trokhan; U.S. Pat. No.
4,637,859, issued Jan. 20, 1987 to Trokhan; U.S. Pat. No.
5,364,504, issued Nov. 15, 1994 to Smurkoski et al.; and U.S. Pat.
No. 5,529,664, issued Jun. 25, 1996 to Trokhan et al. and U.S. Pat.
No. 5,679,222 issued Oct. 21, 1997 to Rasch et al., the disclosures
of which are incorporated herein by reference.
[0040] If desired, the paper may be dried and made on a through-air
drying belt not having a patterned framework. Such paper will have
discrete, high density regions and an essentially continuous low
density network. During or after drying, the paper may be subjected
to a differential vacuum to increase its caliper and dedensify
selected regions. Such paper, and the associated belt, may be made
according to the following patents: U.S. Pat. No. 3,301,746, issued
Jan. 31, 1967 to Sanford et al.; U.S. Pat. No. 3,905,863, issued
Sep. 16, 1975 to Ayers; U.S. Pat. No. 3,974,025, issued Aug. 10,
1976 to Ayers; U.S. Pat. No. 4,191,609, issued Mar. 4, 1980 to
Trokhan; U.S. Pat. No. 4,239,065, issued Dec. 16, 1980 to Trokhan;
U.S. Pat. No. 5,366,785 issued Nov. 22, 1994 to Sawdai; and U.S.
Pat. No. 5,520,778, issued May 28, 1996 to Sawdai, the disclosures
of which are incorporated herein by reference.
[0041] In yet another embodiment, the reinforcing structure may be
a felt, also referred to as a press felt as is used in conventional
papermaking without through-air drying. The framework may be
applied to the felt reinforcing structure as taught by commonly
assigned U.S. Pat. No. 5,549,790, issued Aug. 27, 1996 to Phan;
U.S. Pat. No. 5,556,509, issued Sep. 17, 1996 to Trokhan et al.;
U.S. Pat. No. 5,580,423, issued Dec. 3, 1996 to Ampulski et al.;
U.S. Pat. No. 5,609,725, issued Mar. 11, 1997 to Phan; U.S. Pat.
No. 5,629,052 issued May 13, 1997 to Trokhan et al.; U.S. Pat. No.
5,637,194, issued Jun. 10, 1997 to Ampulski et al.; U.S. Pat. No.
5,674,663, issued Oct. 7, 1997 to McFarland et al.; U.S. Pat. No.
5,693,187 issued Dec. 2, 1997 to Ampulski et al.; U.S. Pat. No.
5,709,775 issued Jan. 20, 1998 to Trokhan et al., U.S. Pat. No.
5,814,190 issued Sep. 29, 1998 to Van Phan; and U.S. Pat. No.
5,817,377 issued Oct. 6, 1998 to Trokhan et al. the disclosures of
which are incorporated herein by reference.
[0042] If desired, in place of a belt having the patterned
framework described above, a belt having a jacquard weave may be
utilized. Such a belt may be utilized as a forming wire, drying
fabric, imprinting fabric, transfer clothing etc. A jacquard weave
is reported in the literature to be particularly useful where one
does not wish to compress or imprint the paper in a nip, such as
typically occurs upon transfer to a Yankee drying drum.
Illustrative belts having a jacquard weave are found in U.S. Pat.
No. 5,429,686 issued Jul. 4, 1995 to Chiu et al. and U.S. Pat. No.
5,672,248 issued Sep. 30, 1997 to Wendt et al.
[0043] Two or more plies of tissue paper are combined to form the
multi-ply tissue. The plies may, optionally, be attached together
by means, for example, of gluing or embossing. Gluing is less
preferred because it tends to result in a stiffer, less soft
product. Indeed it is preferred that no glue is used to attach the
plies. Embossing may be used to attach the plies together, for
example, as disclosed in EP-A-0 755 212, published on Jan. 29,
1997. According to the present invention the tissue has an
unembossed wiping surface over a major part of the surface area of
the tissue. As used herein, this means that the tissue has one or
more unembossed regions and, optionally, one or more embossed
regions, and that the unembossed region is at least 50%, and as
much as 100%, of the surface area of the tissue. As used herein an
embossed region is a region of the tissue having a plurality of
embossed points. Most commonly the embossed regions lie close to
the edge of the tissue (for example along two or four edges); and
embossed regions may also be used for decorative purposes (for
example to create a pattern or to spell out a logo or brand name).
The unembossed region is the continuous region between and/or
around the embossed regions.
[0044] One or both surfaces of the tissue may, optionally, be
further treated with a lotion. The lotion may comprise
softening/debonding agents, emollients, immobilizing agents and
mixtures thereof. Suitable softening/debonding agents include
quaternary ammonium compounds, polysiloxanes, and mixtures thereof.
Suitable emollients include propylene glycol, glycerine,
triethylene glycol, spermaceti or other waxes, petrolatum, fatty
acids, fatty alcohols and fatty alcohol ethers having from 12 to 28
carbon atoms in their fatty acid chain, and mixtures thereof.
Suitable immobilizing agents include polyhydroxy fatty acid esters,
polyhydroxy fatty acid amides and mixtures thereof. Other optional
components include perfumes, antibacterial actives, antiviral
actives, disinfectants, pharmaceutical actives, film formers,
deodorants, opacifiers, astringents, solvents and the like.
Particular examples of lotion components include camphor, thymol
and menthol.
[0045] "Long fibers" as defined herein are considered to be of an
average fiber length of at least 2.0 mm. These long paper making
fibers are typically softwood fibers, preferably Northern Softwood
Kraft.
[0046] "Short fibers" as defined herein are considered to have an
average fiber length of less than 2.0 mm, preferably from 0.2 mm to
1.5 mm. These short papermaking fibers are typically hardwood
fibers, preferably Eucalyptus fibers. Alternatively low cost
sources of short fibers such as sulfite fibers, thermomechanical
pulp, Chemi-ThermoMechanical Pulp (CTMP) fibers, recycled fibers,
and mixtures thereof can also be used.
Test Methods
[0047] The wet burst strength is measured using an electronic burst
tester and the following test conditions. The burst tester is a
Thwing-Albert Burst Tester Cat. No. 177 equipped with a 2000 g load
cell. The burst tester is supplied by Thwing-Albert Instrument
Company, Philadelphia, Pa. 19154, USA.
[0048] Take eight paper tissues and stack them in pairs of two.
Using scissors, cut the samples so that they are approximately 228
mm in the machine direction and approximately 114 mm in the
cross-machine direction, each two finished product units thick.
[0049] First age the samples for one to two hours by attaching the
sample stack together with a small paper clip and "fan" the other
end of the sample stack to separate the sheets, this allows
circulation of air between them. Suspend each sample stack by a
clamp in a 107.degree. C. (.+-.3.degree. C.) forced draft oven for
5 minutes (.+-.10 seconds). After the heating period, remove the
sample stack from the oven and cool for a minimum of three minutes
before testing.
[0050] Take one sample strip, holding the sample by the narrow
cross direction edges, dipping the center of the sample into a pan
filled with about 25 mm of distilled water. Leave the sample in the
water four (4.0.+-.0.5) seconds. Remove and drain for three
(3.0.+-.0.5) seconds holding the sample so the water runs off in
the cross direction. Proceed with the test immediately after the
drain step. Place the wet sample on the lower ring of the sample
holding device with the outer surface of the product facing up, so
that the wet part of the sample completely covers the open surface
of the sample holding ring. If wrinkles are present, discard the
sample and repeat with a new sample. After the sample is properly
in place on the lower ring, turn the switch that lowers the upper
ring. The sample to be tested is now securely gripped in the sample
holding unit. Start the burst test immediately at this point by
pressing the start button. The plunger will begin to rise. At the
point when the sample tears or ruptures, report the maximum
reading. The plunger will automatically reverse and return to its
original starting position. Repeat this procedure on three more
samples for a total of four tests, i.e., 4 replicates. Report the
results, as an average of the four replicates, to the nearest
gram.
[0051] Caliper of the multi-ply tissue paper, as used herein, is
the thickness of the paper when subjected to a compressive load of
14.7 g/m.sup.2. Preferably, caliper is measured using a low load
Thwing-Albert micrometer, Model 89-11, available from the
Thwing-Albert Instrument Company of Philadelphia, Pa.
EXAMPLE
[0052] An aqueous slurry comprising 3% by weight of Northern
Softwood Kraft (NSK) fibers was prepared in a conventional
re-pulper. The NSK slurry was refined gently and a 2% solution of
the permanent wet strength resin (Kymene.TM. 557H) was added to the
NSK stock pipe at a rate of 1% by weight of the dry fibers. The
absorption of the permanent wet strength resin onto the NSK fibers
is enhanced by an in-line mixer. A 1% solution of the dry strength
resin (carboxymethyl cellulose) is added to the NSK stock before
the fan pump at a rate of 0.15% by weight of the dry fibers. The
NSK slurry was diluted to about 0.2% consistency at the fan
pump.
[0053] A chemical softening composition was prepared comprising
di-hard tallow diethyl ester dimethyl quaternary ammonium chloride
and polyoxyethylene glycol, having an average molecular weight of
400 (PEG-400). The PEG-400 was heated to about 66.degree. C., and
the quat was dissolved into the molten PEG-400 so that a
homogeneous mixture was formed.
[0054] An aqueous slurry comprising 3% by weight of eucalyptus
fibers was prepared in a conventional re-pulper. A 1% solution of
the chemical softening composition was added to the Eucalyptus
stock pipe at a rate of 0.15% by weight of the dry fibers. The
Eucalyptus slurry was diluted to about 0.2% consistency at the fan
pump.
[0055] The two slurries were combined so that the ratio of NSK to
eucalyptus fibers was 70:30 and the resulting slurry was deposited,
by means of a single layer headbox onto a Fourdrinier wire to form
an embryonic web. Dewatering occurred through the Fourdrinier wire
and was assisted by a deflector and vacuum boxes. The Fourdrinier
wire was a 5-shed, satin weave configuration having 3.3
machine-direction and 3.0 cross-machine direction monofilaments per
millimeter respectively.
[0056] The embryonic web was transferred from the Fourdrinier wire,
at a fiber consistency of about 20% at the point of transfer, to a
photo-polymer fabric having 0.87 Linear Idaho cells per square
millimeter (562 cells per square inch), 40% knuckle area, and 0.2
mm of photo-polymer depth. Further dewatering was accomplished by
vacuum assisted drainage until the web has a fiber consistency of
about 28%. The patterned web is predried by air blow-through to a
fiber consistency of about 65% by weight. The web was then adhered
to the surface of a Yankee dryer with a sprayed creping adhesive
comprising 0.25% aqueous solution of Polyvinyl Alcohol (PVA). The
fiber consistency was increased to an estimated 96% before dry
creping the web with a doctor blade. The doctor blade had a bevel
angle of about 25.degree. and is positioned with respect to the
Yankee dryer to provide an impact angle of about 81.degree.. The
Yankee dryer was operated at about 4 m/s and the dried paper was
formed into a roll at a reel.
[0057] The dry web comprised Kymene T at a level of 0.7%,
carboxymethyl cellulose at a level of 0.1%, chemical softening
composition at a level of 0.05%, all by weight of dry fiber.
[0058] The web is converted into a two ply tissue paper product,
having overall dimension of 210 mm square. The tissue paper product
was folded and packaged without embossing.
[0059] In a second example the same two-ply tissue paper product
was subjected to an embossing step before folding. The margin of
the tissue paper product, extending about 15 mm in from the edge
was embossed following the process described in WO95/27429,
published on Oct. 19, 1995. The major part of the surface area of
the tissue paper product (i.e. all of the surface area within the
15 mm margin) was unembossed.
[0060] In a third example the product of the previous example was
taken and decorated by embossing the brand name over a small area
of the previously unembossed area. Alternatively four decorative
leaf patterns where embossed in the previously unembossed area.
Each decorative pattern being about 30 mm square.
[0061] The process of the previous examples was repeated and the
paper was calandared either at the reel; or during combining of the
plies; or during converting; or calandared two or three times by
combination of these steps.
[0062] The two-ply tissue paper product of these examples has a
caliper of 0.45 mm, an average basis weight of 50 g/m.sup.2 and a
wet burst strength of 250 g.
[0063] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention.
[0064] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *