U.S. patent application number 14/627651 was filed with the patent office on 2016-08-25 for low coarseness southern softwood pulps.
This patent application is currently assigned to WEYERHAEUSER NR COMPANY. The applicant listed for this patent is WEYERHAEUSER NR COMPANY. Invention is credited to Richard W. Heineman, JR., Amar N. Neogi, Hugh West.
Application Number | 20160244916 14/627651 |
Document ID | / |
Family ID | 56693607 |
Filed Date | 2016-08-25 |
United States Patent
Application |
20160244916 |
Kind Code |
A1 |
Neogi; Amar N. ; et
al. |
August 25, 2016 |
LOW COARSENESS SOUTHERN SOFTWOOD PULPS
Abstract
Pulp sheets produced from Southern pine fibers are disclosed.
Embodiments in which the fibers have a fiber length to coarseness
ratio equal to or greater than 0.11, with fiber length (LWAFL) in
mm and coarseness in mg/100 m, are found to impart stiffness
properties to tissue grade handsheets made therefrom comparable to
those achieved using of standard NBSK. Embodiments in which the
fibers have a low coarseness (of from about 16 to about 20 mg/100
m, at a fiber length (LWAFL) of from about 1.6 to about 3.0 mm) are
found to impart wicking properties to absorbent structures made
therefrom that are improved relative to those achieved using
standard high coarseness SBSK.
Inventors: |
Neogi; Amar N.; (Mountlake
Terrace, WA) ; West; Hugh; (Seattle, WA) ;
Heineman, JR.; Richard W.; (Bonney Lake, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WEYERHAEUSER NR COMPANY |
Federal Way |
WA |
US |
|
|
Assignee: |
WEYERHAEUSER NR COMPANY
Federal Way
WA
|
Family ID: |
56693607 |
Appl. No.: |
14/627651 |
Filed: |
February 20, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21H 11/20 20130101;
D21H 27/02 20130101; D21H 25/005 20130101; D21H 11/04 20130101;
D21H 15/02 20130101; D21H 27/002 20130101; D21H 27/007
20130101 |
International
Class: |
D21H 27/00 20060101
D21H027/00; D21H 11/20 20060101 D21H011/20; D21H 11/04 20060101
D21H011/04 |
Claims
1. A pulp sheet comprising Southern pine fibers that have a fiber
length to coarseness ratio from about 0.125 to 0.142, wherein fiber
length (LWAFL) is in mm, and coarseness is in mg/100 m, wherein the
length to coarseness ratio of the fibers is at a coarseness of from
about 19 to about 20 mg/100 m and a fiber length of from about 2.5
to about 2.7 mm, and wherein the content of said Southern pine
fibers is at least 20%.
2. The pulp sheet of claim 1, wherein the length to coarseness
ratio of the fibers is about 0.13.
3. The pulp sheet of claim 1, wherein the length to coarseness
ratio of the fibers is at one or more of a coarseness of from about
16 to about 25 mg/100 m, and a fiber length of from about 1.6 to
about 3.0 mm.
4-6. (canceled)
7. The pulp sheet of claim 1, wherein the fibers are bleached
Southern pine pulp fibers.
8. The pulp sheet of claim 1, wherein the fibers are kraft Southern
pine pulp fibers.
9. The pulp sheet of claim 1, wherein the fibers are SBSK pulp
fibers.
10. The pulp sheet of claim 1, wherein the fibers are one or more
of slash pine (Pinus elliottii), longleaf pine (Pinus palustris),
shortleaf pine (Pinus echinata), loblolly pine (Pinus taeda),
Virginia pine (Pinus virginiana), eastern white pine (Pinus
strobus), pitch pine (Pinus rigida), sand pine (Pinus clausa), pond
pine (Pinus serotina), and Table Mountain pine (Pinus pungens)
fibers.
11. The pulp sheet of claim 10, wherein a majority of the fibers
are loblolly pine (Pinus taeda) fibers.
12. The pulp sheet of claim 1, having a basis weight from about 500
to about 900 gsm.
13. The pulp sheet of claim 1, having a density of from about 0.5
to about 0.9 g/cc.
14. The pulp sheet of claim 1, in bale or roll form.
15. The pulp sheet of claim 1, wherein a TAPPI T-204 tissue grade
handsheet having a basis weight of 20 gsm produced therefrom and
including eucalyptus pulp in a 1:2 ratio of said Southern pine
fibers to eucalyptus pulp fibers has a tensile stiffness at a
normalized tensile index that is equal to or less than that of a
TAPPI T-204 tissue grade handsheet produced from NBSK and
eucalyptus pulp in a 1:2 ratio of NBSK fibers to eucalyptus pulp
fibers.
16. A pulp sheet comprising Southern pine fibers that have a
coarseness of from about 16 to about 20 mg/100 m and a fiber length
(LWAFL) of from about 1.6 to about 3.0 mm, wherein a composite
absorbent core having a basis weight of 500-550 gsm and a density
of 0.18-0.22 g/cc produced therefrom and including 30% of said
Southern pine fibers and 70% SAP has an inclined plane wicking rate
of at least 130 gm/500 s.
17. (canceled)
18. The pulp sheet of claim 16, comprising a blend of said Southern
pine fibers with Northern bleached softwood pulp fibers, with said
Northern bleached softwood pulp fibers having a coarseness of from
about 13 to about 18 mg/100 m and a fiber length (LWAFL) of from
about 2.0 to about 2.5 mm; wherein the pulp sheet is in roll form
with a basis weight of from about 500 to about 900 gsm and a
density of from about 0.4 to about 0.8 g/cc.
19. The pulp sheet of claim 18, wherein the blend consists of up to
25% of said Northern bleached softwood pulp fibers, with the
balance being said Southern pine fibers.
20. (canceled)
21. The pulp sheet of claim 16, wherein said Southern pine fibers
have a coarseness of from about 19 to about 20 mg/100 m and a fiber
length (LWAFL) of from about 2.5 to about 2.7 mm.
Description
TECHNICAL FIELD
[0001] This disclosure relates to pulp and pulp sheets useful for
incorporation into absorbent and/or tissue/towel products, and in
particular to pulp sheets produced using Southern pine fibers
having certain fiber length and fiber coarseness
characteristics.
BACKGROUND
[0002] The pulp and paper industry in North America produces a
large volume of bleached softwood kraft pulp for use in consumer
products. Example uses of this kind of pulp include manufacturing
disposable tissues/towels (e.g. facial and bath tissue, paper
towels, etc.), and disposable absorbent products (e.g. baby
diapers, adult incontinence products, etc.), with about eight
million tons per year of such pulp used.
[0003] Tissue and towel products are usually formed using blends of
hardwood and softwood pulps, to achieve desired properties such as
softness, stiffness, and durability (e.g., tear strength, tensile
strength, etc.). Often these properties exist in a trade-off, in
which an increase in one property results in a decrease in another.
In addition, the pulp material must be able to withstand the
processes used to form the products. Tissue and towel products are
generally manufactured by either a wet process or a through-air
drying ("TAD") process. In a wet process, a low consistency
suspension (single layer, or multilayer) of a blend of softwood and
hardwood pulp fibers (typically in about a 50/50 to 30/70 ratio) is
wet laid, dewatered, and pressed, followed by creping and drying,
and finished by calendaring and forming the sheets into rolls. In a
TAD process, a wet formed sheet is through-air dried, with or
without creping, followed by converting.
[0004] Although several factors must be considered in choosing an
appropriate blend of fibers, longer fiber length is generally
preferable to shorter fiber length, and fibers of low coarseness
are generally preferable to those of high coarseness. Longer fiber
length tends to provide product durability and good machine
runnability in the aforementioned processes. Coarseness, generally
defined as weight per unit length of fiber, depends on physical
fiber attributes including fiber diameter, cell wall thickness, and
cell wall density. For example, a high coarseness value usually
indicates a thicker fiber wall, giving stiff fibers resistant to
collapse. Thin walled fibers, on the other hand, tend to result in
flexible fibers and a denser sheet. Such low coarseness features,
in tissue and towel applications, yield a better handfeel (e.g.,
tactile softness) and good tensile strength. The interplay between
these two particular fiber properties is important to achieving a
pulp that has good suitability for such applications. For example,
a good length to coarseness ratio allows high strength development
without excessive densification, to maintain high bulk and
softness, and also yields high tear strength.
[0005] The usual source of softwood kraft pulp fibers for the
aforementioned applications is Northern bleached softwood kraft
("NBSK") pulp, which in North America is produced mainly in the
Northwestern US and Canada from a wood chip furnish from softwood
trees that typically include lodgepole pine (Pinus contorta), Jack
pine (Pinus banksiana), and/or white spruce (namely, Picea
engelmannii, Picea glauca, etc.). NBSK, the fibers of which are
generally characterized by a fiber length of 2.0-3.0 mm, and a
coarseness of 13-18 mg/100 m, yielding a favorable
length-to-coarseness ratio of 0.16 or higher, is the pulp of choice
to manufacture of tissue/towel products.
[0006] With high growth of global tissue/towel consumption,
concerns over sustainability and/or constrained supply of old
growth boreal forests as well as beetle infestation of many North
American forests, many tissue/towel manufacturers have sought
effective substitutes for NBSK. Pulp from some bamboo species, with
fiber length of about 1.5 mm and a fiber-to-coarseness ratio of
about 0.12, has been considered, but has not been widely adopted,
for example due to concerns about availability, as well as cost
(such as related to adapting manufacturing processes), and so
forth. Southern bleached softwood kraft ("SBSK") pulp fibers, which
are generally characterized by high coarseness (e.g., about 20 or
higher) and low length-to-coarseness ratio (e.g., around 0.1), have
not been considered to be suitable for these applications.
[0007] However, the high coarseness of SBSK fibers has been found
to be advantageous in disposable absorbent products such as baby
diapers. Historically, such products included absorbent cores made
entirely from SBSK, at least in part because the higher coarseness
fibers were found to be easier to fiberize from roll form,
producing lower knot levels and requiring less energy, and
providing good capacity for holding body exudates. Since their
introduction, superabsorbent polymers ("SAPs") have been
increasingly used in absorbent products, generally in the absorbent
core to provide benefits of high liquid holding capacity and a
thinner product. However, effective use of SAPs has been
determined, to a great extent, by the ability of the pulp in a
composite pulp/SAP absorbent core structure to rapidly wick fluid
to the SAP. Thus, one additional role of higher coarseness SBSK
fibers in absorbent products, in addition to good pad integrity and
allowing easier processing, has come to be seen as providing
effective wicking.
SUMMARY
[0008] Various embodiments of a pulp sheet in accordance with the
present disclosure are produced using Southern pine fibers having
certain fiber length and fiber coarseness properties. In one aspect
an illustrative embodiment can be characterized as a pulp sheet in
which Southern pine fibers have a length-to-coarseness ratio equal
to or greater than about 0.11 (with fiber length, or more
specifically length weighted average fiber length or "LWAFL,"
measured in mm, and fiber coarseness measured in mg/100 m). In some
variations the length-to-coarseness ratio is at either a coarseness
of from about 16 to about 25 mg/100 m and/or a fiber length of from
about 1.6 to about 3.0 mm. In some variations the
length-to-coarseness ratio is at either a coarseness of from about
19 to about 20 mg/100 m and a fiber length of from about 2.5 to
about 2.7 mm.
[0009] As described herein, one particular property of some of the
aforementioned embodiments is in imparting tensile stiffness to
tissue grade handsheets produced therefrom, at a given tensile
strength, that is comparable or superior to that provided by use of
conventional NBSK. As tensile stiffness is one indicator of
softness, the aforementioned embodiments of pulp sheets that
include Southern pine fibers may have utility in tissue/towel
applications.
[0010] In another aspect illustrative embodiments of pulp sheets
produced in accordance with the present disclosure can be
characterized in that the Southern pine fibers have a coarseness of
from about 16 to about 20 mg/100 m and a fiber length (LWAFL) of
from about 1.6 to about 3.0 mm, irrespective of the
length-to-coarseness ratio.
[0011] As described herein, one particular property of some of
these embodiments is in imparting superior wicking properties to
composite absorbent structures produced therefrom, contrary to
expectation.
[0012] In yet another aspect an illustrative embodiment can be
characterized in that the Southern pine fibers have a coarseness of
from about 16 to about 25 mg/100 m and a fiber length (LWAFL) of
from about 1.7 to about 3.0 mm.
[0013] The aforementioned embodiments may be in roll or bale form.
In some embodiments the content of the said Southern pine fibers in
the pulp sheet is at least 20%, with the balance being other pulp
fibers. In some embodiments the pulp sheet has a basis weight of
about 500-900 gsm, and/or a density of about 0.5-0.9 g/cc. In some
embodiments, a pulp sheet may include Southern pine fibers having
certain fiber length and fiber coarseness properties, such as those
listed above, blended with NBSK fibers.
[0014] The illustrative properties mentioned above and discussed in
greater detail below are not exhaustive. The concepts, features,
properties, methods, and other aspects briefly described above are
clarified with reference to the accompanying drawings and detailed
description below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 schematically represents a generalized method of
kraft pulping and bleaching appropriate for producing the pulp
sheets in accordance with the present disclosure.
[0016] FIG. 2 is a representative plot of wicking rates of example
absorbent cores made from pulp sheets of Southern pine fibers of
varying coarseness produced in accordance with the present
disclosure.
[0017] FIG. 3 is a representative plot of inclined plane wicking
rates of example composite absorbent cores that include SAP and
Southern pine fibers of varying coarseness produced in accordance
with the present disclosure.
[0018] FIG. 4 is a representative plot of pad densities of example
composite absorbent cores that include SAP and Southern pine fibers
of varying coarseness produced in accordance with the present
disclosure, as a function of press pressure in pad formation.
[0019] FIG. 5 is a representative plot of pad densities as a
function of press pressure similar to that shown in FIG. 4, but
with the example composite absorbent cores also including a
softening agent.
DETAILED DESCRIPTION
[0020] Fiber coarseness, as noted above, is defined as weight per
unit length of fiber. Herein, the term "fiber coarseness," or
simply "coarseness," refers to this measure, expressed as mg per
100 m. This particular expression is sometimes referred to as a
decigrex (dg). Coarseness of a fiber sample is determined herein
using a FQA Analyzer (OpTest Equipment Inc. Model LDA02 (HiRes
FQA), equipped with an auto sampler), which contains a flow cell
that uses hydrodynamic focusing to orient curled fibers. A sample
is soaked in water before being disintegrated, then formed into a
dry sheet on a TAPPI sheet mold, then weighed. The sample is
slurried in water to produce an approximately 0.005 wt %
suspension. Test aliquots of the dilute suspension of about 20-25
mL are drawn, recorded, and analyzed. Coarseness in mg/100 m (or
dg) is calculated from the sample mass and the average fiber length
(in mm) determined by the analysis.
[0021] Fiber length, also referred to herein as simply "length," as
used herein, refers to the length weighted average fiber length
(also referred to as "LWAFL"), as determined by a suitable length
measuring device such as the FQA Analyzer according to a process
similar to the one described above for measuring coarseness. Length
is expressed in mm.
[0022] Values for the properties of fiber coarseness and fiber
length provided herein are given in terms of the respective units
described above, even if such units are not expressly listed. For
example, the expression "a coarseness of about 18" is equivalent to
"a coarseness of about 18 mg/100 m." Likewise, values for
length-to-coarseness ratios also are given in terms of the
respective units described above, even if such units are not
expressly listed. For example, in the expression "a
length-to-coarseness ratio above about 0.16," length, or fiber
length, is in mm, and coarseness is in mg/100 m.
[0023] Wicking rate, or wick rate, refers to the rate at which
water wicks upward through an airlaid pad produced from pulp
fibers, and is measured by a standardized test method described in
detail herein. Wick rate is a characteristic that describes an
absorbent property of pulp fiber that is used to assess whether the
pulp fiber is a suitable candidate for incorporation into absorbent
products. Wicking rate is generally expressed in mm/s.
[0024] Inclined plane wicking rate refers to the rate at which
water wicks upward through a composite pulp and SAP pad placed at
an incline, along the plane of the pad, and is expressed herein as
the weight increase of the pad, representing the total amount of
liquid wicked, in a specified time period. The value is typically
given in grams per time period (e.g., g/500 s). A standardized test
method is described in detail herein. One purpose of the test is to
determine the amount of simulated urine absorbed over time by an
absorbent pad oriented to replicate that of a baby diaper being
worn.
[0025] Basis weight refers to the dry weight of a material per unit
area, and is generally expressed as grams per square meter
(g/m.sup.2 or gsm). It can be measured using a standard such as
TAPPI test method T-220. Density refers to the dry weight of a
material per unit volume.
[0026] Other properties of a pulp sheet, and/or structures made
therefrom, such as a handsheet, a tissue grade handsheet, an
airlaid pad, a composite absorbent core, and so forth, and testing
methods therefor, are described in greater detail below.
[0027] As noted above, the pulp sheets of the present disclosure
may have utility for incorporation into tissue/towel products
and/or absorbent products. "Tissue/towel products" generally refers
to various paper products, such as facial tissue, bath tissue,
paper towels, napkins, and so forth, and "absorbent products"
generally refers to baby diapers and other products adapted to
retain body exudates, such as bandages, feminine hygiene products,
adult incontinence products, and so forth.
[0028] A suitable illustrative method of producing the pulp sheets
in accordance with the present disclosure is shown at 10 in FIG. 1.
The illustrative method may be thought of as including two broad
processing areas, pulping, generally indicated at 12, and
bleaching, generally indicated at 14. The pulping process 12 is
shown as a kraft pulping process. However, other chemical pulping
processes, such as kraft/AQ pulping, soda/AQ pulping, or sulfite
pulping, may be used.
[0029] In block 100, wood chips are loaded or fed into a digester.
The wood chips used in producing the pulp sheets herein may be
obtained from Southern softwood, a designation used to describe a
group of species of coniferous trees in the genus Pinus that are
native to and/or are characteristically grown in Southern regions
of the United States. In particular, this group of species includes
slash pine (Pinus elliottii), longleaf pine (Pinus palustris),
shortleaf pine (Pinus echinata), loblolly pine (Pinus taeda),
Virginia pine (Pinus virginiana), eastern white pine (Pinus
strobus), pitch pine (Pinus rigida), sand pine (Pinus clausa), pond
pine (Pinus serotina), Table Mountain pine (Pinus pungens),
Monterey pine (Pinus radiata), and bishop pine (Pinus muricata).
The term "Southern pine" is often used to refer to Southern
softwood trees; herein, the terms are synonymous. Accordingly,
"SBSK" refers to bleached pulp that is produced by the kraft
process from Southern softwood chips. In general, Southern pine
fibers suitable for pulp sheets in accordance with the present
disclosure are those having a coarseness of from about 16 to about
25 mg/100 m and/or a fiber length of from about 1.6 to about 3.0
mm. In more particular embodiments, such as those described herein
as having particular suitability for tissue/towel applications
and/or absorbent applications, Southern pine fibers having a
coarseness of from about 18 to about 20 mg/100 m, and/or a
length-to-coarseness ratio greater than about 0.11, are
appropriate.
[0030] Although SBSK fibers are generally thought of as having high
coarseness relative to NBSK fibers, the terms "low coarseness SBSK"
or "low coarseness Southern pine" herein refer to the lower portion
of the coarseness ranges typically found in SBSK and Southern pine
fibers, respectively. For example, in one aspect of the present
disclosure, low coarseness SBSK is found to impart unexpectedly
superior wicking properties to an absorbent structure made with
such SBSK, relative to the industry standard, an absorbent
structure made with high coarseness SBSK.
[0031] SBSK fibers are generally thought of as having a lower
length-to-coarseness ratio relative to NBSK fibers. As noted above,
NBSK fibers make up the pulp of choice for tissue/towel
applications. However, in another aspect of the present disclosure,
SBSK fibers having a comparatively lower length-to-coarseness ratio
are unexpectedly found to impart tensile stiffness values to tissue
handsheets incorporating such fibers that are comparable to values
achieved by use of NBSK fibers.
[0032] Coarseness of fibers, as well as fiber length, tends to vary
with tree age and also with locations within a tree. Accordingly,
representative sources of suitable fibers may be those derived from
thinnings, portions of trees of a certain age, whole trees of a
certain age, and so forth. For example, managed plantation forestry
may make trees of younger ages available, such as for conversion to
pulp, as stock is periodically thinned out to allow selected trees
to mature for eventual harvesting for lumber.
[0033] Fiber length and coarseness variation will further vary from
species to species. Table 1 is an illustrative listing of fiber
length and coarseness for pulp sheets produced from Southern pine
fibers in accordance with the present disclosure, specifically SBSK
fibers, obtained from loblolly pine (Pinus taeda) trees of various
ages, using an ODED bleaching sequence for target brightness of
90.
TABLE-US-00001 TABLE 1 Length to coarseness Description Portion of
tree Coarseness Fiber Length ratio 6 year bottom 50% 14.6 1.30
0.089 top 50% 13.3 1.32 0.099 8 year bottom 50% 16.1 1.63 0.101
middle 25% 14.7 1.59 0.108 top 25% 14.4 1.67 0.116 10 year bottom
50% 15.8 1.62 0.103 middle 25% 15.5 1.89 0.122 top 25% 14.8 1.67
0.113 10 year whole tree 16.8 1.86 0.111 12 year bottom 50% 19.1
1.97 0.103 middle 25% 18.9 2.13 0.113 top 25% 17.1 1.95 0.114 12
year whole tree 17.8 2.06 0.116 12 year, earlywood* 18 2.5 0.14 13
year, without tops 18.7 1.97 0.105 13 year, with tops 18.8 2.06
0.110 15 year whole tree 22.2 2.20 0.100 Saw mill residuals** 25.2
2.99 0.119 Topwood*** 19.3 2.53 0.131 *earlywood refers to the part
of the wood in a growth ring of a tree that is produced earlier in
the growing season. **wood chips from slab wood after extraction of
lumber from a grade log of a mature (e.g., 25 year) tree. ***the
volume of wood that exists between minimum top diameter for a fiber
log and minimum top diameter for grade logs.
[0034] Example test embodiments used selected loblolly pine wood
supplied as logs that were subsequently debarked (if necessary) and
chipped using typical mill debarkers and disc chippers, or as chips
produced by conventional chipping methods. The chips were blended,
then screened over a Black Clawson gyratory screen selected to
yield accepts of a desired size. Oversized chips and fines were
discarded, and the accepts were blended again and sub-sampled for
moisture determination and specific gravity. Charges for the
digester were made using 4.00 kg of O.D. chips. For smaller
batches, chips were screened over a Williams screen to yield
accepts of a suitable size range for baskets used for batch
cooks.
[0035] Digesters for use herein can include any digester suitable
to pulp Southern pine wood. One example of a suitable digester is a
continuous digester often referred to as a "Kamyr" digester,
so-called after the now-defunct company that designed and built
continuous digesters, currently manufactured by companies such as
Kvaerner. Such digesters have been used in the pulp and paper
industry for several decades, with modifications over the years to
improve operation. The digester system may be either a single
vessel or a two-vessel system. Kamyr digesters are typically used
in kraft or alkaline wood pulping, but may also be used in
semi-chemical pulping methods. Other continuous digesters, such as
M&D and Pandia digesters, are also suitable for use. However,
the pulp sheets may be produced using any batch or other continuous
digester.
[0036] Referring to FIG. 1, within the pulping process 12, there
are several operations, depicted schematically as blocks 100-116.
Loading, or feeding chips as discussed above, occurs at 100. The
wood chips may be pre-steamed prior to cooking, at 102. Steam at
atmospheric pressure preheats the chips and drives off air so that
liquor penetration will be enhanced. After the pre-steaming
operation is completed, cooking liquor, referred to as white
liquor, containing the pulping chemicals may be added to the chips,
at 104. The white liquor and chips are then fed into the digester.
In kraft pulping, the active chemical compounds are NaOH and
Na.sub.2S. Other chemicals may be added to influence or impart
desirable effects on the pulping process, as known to those of
skill in the art.
[0037] Impregnation, at 106, is the period during which the
chemicals are allowed to impregnate the wood material. Good liquor
penetration helps assure a uniform cooking of the chips.
[0038] Cooking, in which lignin and hemicellulose degrade into
fragments soluble in the cooking liquor, occurs at 108 and 110. The
co-current liquid contact operation, at 108, is followed by the
counter-current liquid contact operation, at 110. Cooking of the
wood material occurs during these two operations, and yields brown
stock. In either, the cooking liquor and chips can be brought to a
desired temperature.
[0039] Upon completion of the cook operation, the digester contents
are blown, at 112. Digester blowing involves releasing the wood
chips and liquor at atmospheric pressure, which generally occurs
with a sufficient amount of force to cause fiber separation. If
desired, the blow tank may be equipped with heat recovery equipment
to reduce operating expenses.
[0040] At 114, the pulp is sent from the blow tank to external
brown stock pulp washers. The separation of black liquor from the
pulp occurs at the brown stock washers.
[0041] Various process parameters in the aforementioned operations
may be adjusted as suitable for the wood chips, such as
impregnation time, percent alkali and sulfidity, liquor ratio,
initial, final, and interim temperatures, pH values, and so forth.
Many desired pulp properties are sensitive to variations of these
and other pulping parameters, such as fiber morphology (e.g.,
kinks, curls, fiber length), pulp viscosity (which relates, for
example, to strength and softness of downstream products that
incorporate the pulp), kappa number (which relates to lignin
content), and productivity or throughput, as desired. Thus,
although any suitable pulping method can be used, the particular
pulping method employed must be carefully calibrated to preserve
and/or achieve these and other desired pulp and fiber
properties.
[0042] For example, although not specifically represented in FIG.
1, some kraft pulping test embodiments were carried out in a batch
digester having a capacity of about 1 ft.sup.3, with liquor
recirculation ability, using a target kappa number of 25. For even
smaller batches, the digester was fitted with smaller baskets, each
having a capacity of about 150 g of O.D. chips, for cooking. The
liquor to wood ratio used in the batch digester was 6:1, effective
alkali was 19%, and at a sulfidity of 31%. The target temperature
of 170.degree. C. took approximately 60 to minutes reach, and was
maintained for 102 minutes with an H factor of 1700. After pulping
the contents were discharged to a slush maker and the excess liquor
was drained. Screening was done over an Appleton screen (10 slots).
The rejects were collected and weighed.
[0043] Chemical pulps, such as those from the kraft process or
sulfite pulping, contain much less lignin than mechanical pulps.
Bleaching is performed on chemical pulps generally to remove the
residual lignin, and thus the process is often referred to as
delignification. Following the pulping process 12, the brown stock
pulp made from the Southern pine wood chips is bleached, at 14. In
addition to lignin removal, bleaching of chemical pulps results in
a decrease in the pulp fiber length and viscosity, but does not
involve a substantial reduction to the hemicellulose content of the
pulp. Bleaching also tends to increase the brightness of the pulp,
and thus a target brightness is often used as a reference to
determine the extent to which a pulp has been bleached.
[0044] Delignification is rarely a single step process and is
frequently composed of several discrete steps, or bleaching stages.
The bleaching stages are often indicated as a sequence of a series
of letters that each represent the chemical or process used in a
bleaching stage (e.g., "C" represents chlorine, "D" represents
chlorine dioxide, "E" represents extraction with sodium hydroxide,
and so forth). Each bleaching stage is generally carried out in a
separate bleaching vessel or tower of conventional design.
Bleaching sequences that do not use elemental chlorine, for example
to avoid byproducts such as dioxins and dioxin-like compounds, are
often referred to as "ECF" (for "elemental chlorine free")
sequences. One representative ECF bleaching sequence suitable for
bleaching the brown stock pulp made according to the present
disclosure is an ODE.sub.PD sequence, with the sequence of
bleaching stages indicated in 14 as operations 116, 118, 120, and
122. Examples of various bleaching sequences are described in U.S.
Pat. Nos. 6,331,354 and 6,550,350, among others. These references
are incorporated herein in their entireties.
[0045] The first stage of bleaching is an O stage, at 116. The O
stage involves bleaching with oxygen. Oxygen bleaching is sometimes
considered to be an extension of the pulping process, but for the
sake of clarity this description treats oxygen bleaching as a first
stage in a bleaching sequence. Oxygen bleaching is the
delignification of pulps using oxygen under pressure. The oxygen is
considered to be less specific for the removal of lignin than
chlorine compounds. Oxygen bleaching takes place in an oxygen
reactor, suitable examples of which are described in U.S. Pat. Nos.
4,295,925; 4,295,926; 4,298,426; and 4,295,927, fully incorporated
herein by reference in their entirety. The reactor can operate at a
high consistency (consistency of the feedstream to the reactor is
greater than 20%) or medium consistency (feedstream consistency
ranges between 8% up to 20%). If a high consistency oxygen reactor
is used, the oxygen pressure can reach the maximum pressure rating
for the reactor, but more preferably is greater than 0 to about 85
psig. In medium consistency reactors, the oxygen can be present in
an amount ranging from greater than 0 to about 100 pounds per ton
of the pulp, but is more preferably about 50 to about 80 pounds per
ton of pulp. The temperature of the 0 stage ranges from about
100.degree. C. to about 140.degree. C.
[0046] A D stage, which involves bleaching the pulp coming from the
oxygen reactor with chlorine dioxide, is shown at 118. Chlorine
dioxide is more selective than oxygen for removing lignin. The
amount of chlorine dioxide used in this stage ranges from about 20
to about 30 lb/ton. The temperature of the D stage ranges from
about 50.degree. C. to about 85.degree. C.
[0047] An E.sub.p stage, which involves hydrogen peroxide
reinforced extraction with sodium hydroxide, is shown at 120. In
this stage, lignin is removed from the pulp using caustic in an
amount ranging from about 20 to about 50 lb/ton. The amount of
hydrogen peroxide ranges from about 20 to about 60 lb/ton. The
temperature of the E.sub.p stage ranges from about 75 to about
95.degree. C.
[0048] A second D stage, at 122, follows the E.sub.p stage, in
which the amount of chlorine dioxide used ranges from about 10 to
about 30 lb/ton. The temperature of the second D stage ranges from
about 60.degree. C. to about 90.degree. C.
[0049] A variety of bleaching sequences may be used in processes
suitable for making the pulp sheets in accordance with the present
disclosure, with the process parameters adjusted as needed. For
example, in some of the test embodiments described above, the
screened, unbleached pulp was subjected to an ODE.sub.pD sequence,
starting with oxygen delignification for which 1200 g of O.D. brown
stock at 5.5% consistency containing 180 ml of NaOH (5N) was
digested at about 90.degree. C. for 80 minutes. O.sub.2 pressure
was 100 psi at temperature for 80 minutes. The washed O.sub.2
delignified pulp (kappa number .about.13) was placed in plastic
bags, each bag containing 500 g of O.D. pulp. ClO.sub.2 addition
level at the first D stage was 1.4% and was done at 65.degree. C.
for 45 minutes. The E.sub.p stage was done with batches of 1200 g
pulp at 5.5% consistency, with 108 ml NaOH (5N) and 51 ml
H.sub.2O.sub.2 (3%) added. The material was subjected to O.sub.2
and brought to 100 psi at about 80.degree. C. over about 20
minutes, after which the O.sub.2 was stopped and the pressure held
for 20 minutes, then relieved and temperature held for 50
additional minutes. The pulp was removed from the digester, washed,
and centrifuged. The final D stage was done in bags, each bag
containing 500 g of material, and to it was added ClO.sub.2 (0.5%)
and alkali (0.25% NaOH) to reach a final pH<3. The bags were
held in a hot water bath for 3 hrs at about 80.degree. C. After
bleaching, the pulps were thoroughly washed and centrifuged to a
solids content of about 30%.
[0050] After a bleaching process such as described above and/or
schematically shown at 14, the bleached stock is typically formed
into a sheet by depositing a pulp slurry onto a machine wire,
followed by dewatering and drying. The dried pulp is then rolled,
cut, and/or baled, or otherwise prepared for shipping. The
particular form is often determined by factors such as shipping
distance or method, and/or downstream use of the pulp. For example,
tissue/towel manufacturing processes generally include machinery
adapted to use bales of pulp.
[0051] The pulp sheets produced in accordance with the present
disclosure may have any desired basis weight and density; however,
improved operational efficiency is generally achieved within a
basis weight range of about 500-900 gsm and/or a density range of
about 0.5-0.9 g/cc.
[0052] Pulp sheets can be made from a blend of one or more pulps by
mixing the pulps in the slurry, typically in a blend chest, then
diluted and formed as above. Optionally, the chip furnish for pulp
sheets can be composed of a mixture of chips selected from
different sources prior to pulping. As an illustrative example, one
test embodiment of a 100% Southern pine pulp sheet consisted of a
50:50 mixture of loblolly pine material sourced from sawmill
residuals and 11-yr whole tree. The pulp sheets of the present
disclosure include at least about 20% of the Southern pine fibers
described herein, with the balance being any other desired pulp,
such as other SBSK or other Southern softwood pulps, NBSK or other
Northern softwood pulps, hardwood pulps, and so forth. Of course,
pulp sheets may include less than 20% of the Southern pine fibers
described herein, but the beneficial effects provided by the
Southern pine fibers as discussed herein have been found to be
diluted at such concentrations. The Southern pine fibers used in a
pulp sheet may be from one species of Southern pine tree, or two or
more, or several species, in a blend. In one embodiment, a majority
of the Southern pine fibers are loblolly pine (Pinus taeda) fibers.
Further, as noted above, the Southern pine fibers used in a pulp
sheet may be from one or more portions of the same or different
Southern pine trees, with the trees being the same or different
ages, and so forth.
[0053] Strength properties of pulp, and tissues made from pulp, may
include tensile breaking properties of a handsheet such as tensile
strength, stretch or elongation, tensile energy absorption, and
tensile stiffness. Tensile stiffness is one indicator of softness
of a tissue or towel product.
[0054] For testing properties of tissue, tissue grade handsheets
were prepared according to TAPPI method T-205, "Forming handsheets
for physical tests of pulp," except using a target basis weight of
20 gsm, and eliminating the "pressing" step (TAPPI T-205 at 7.4).
The handsheets are clamped into jaws of a tensile testing
instrument (Instron 4422 R), which measures the force at a constant
rate of elongation to measure various tensile breaking properties.
Tensile strength, tensile index, and tensile stiffness were
determined according to TAPPI test method T-494, "Tensile
properties of paper and paperboard (using constant rate of
elongation apparatus)," modified to use a test span of 100 mm.
Tensile strength refers to the maximum tensile force developed in a
specimen before rupture, expressed as force per unit width of the
specimen, and indicates the potential resistance to direct stress
such as during use, and also stress during manufacturing
operations. Tensile index ("TI") is the tensile strength in N/m
divided by the basis weight of the specimen. Tensile stiffness is
the ratio of tensile force per unit width to tensile strain within
the elastic region of the tensile-strain relationship, as defined
in TAPPI T-494, and provides an indication of the response of the
sheet to converting forces. It is also one indicator of the
softness of the sheet.
[0055] Table 2 lists properties of example tissue grade sheets
prepared from two illustrative SBSK samples of the specified length
(LWAFL) and coarseness prepared in accordance with the present
disclosure, blended with eucalyptus pulp (available from Fibria
Cellulose) in a 1:2 ratio of SBSK to eucalyptus. These example
tissue grade sheets are compared with a tissue grade sheet prepared
using a blend of NBSK (LL19, available from Terrace Bay Pulp Mill)
of the specified LWAFL and coarseness, also 1:2 with eucalyptus,
which is representative of a conventional blend used for
tissue/towel products. A commercial tissue is also included in
Table 2. Tensile stiffness is reported as measured, and at tensile
index normalized to 1.
TABLE-US-00002 TABLE 2 Tensile Stiffness (MOE) LWAFL/coarseness
Tensile at normalized Sample (ratio) Index measured TI = 1 SBSK-1
2.38/21.5 (0.110) 6.88 0.295 0.043 SBSK-2 2.02/16.8 (0.120) 6.70
0.219 0.033 NBSK 2.25/13.5 (0.167) 8.20 0.332 0.040 Com'I tissue --
4.79* -- -- *GMT (geometric mean tensile strength) determined by
the square root of the product of the machine direction tensile
strength ("MD") and the cross-machine direction tensile strength
("CD")
[0056] If the normalized tensile stiffness value of the
conventional NBSK blend is considered as a target ceiling value,
the example data in Table 2 indicates that a blend using SBSK
having a length to coarseness ratio greater than about 0.110
achieves a tensile stiffness value comparable to or lower than that
of the NBSK blend. Considering that NBSK is the pulp of choice for
tissue/towel applications due to its comparatively lower coarseness
and higher fiber length, the findings that comparatively higher
coarseness Southern pine fibers impart comparable (or better, i.e.
lower) tensile stiffness is not expected. Moreover, the findings
that such tensile stiffness values are achieved by lower
length-to-coarseness ratio Southern pine fibers is also unexpected,
considering that NBSK is characterized by comparatively higher
length-to-coarseness ratio. Although not bound by theory, it is
thought that blends using SBSK produced in accordance with one
aspect of the present disclosure, that is, having a length to
coarseness ratio greater than about 0.11, achieves a tissue hand
sheet softness--at a given strength--that is comparable to or
better than that using conventional NBSK blends.
[0057] Several example tissue grade sheets were made from SBSK
samples prepared in accordance with the present disclosure, refined
to 500 PFI revolutions, and blended with eucalyptus in a 1:2 ratio.
The tissue grade sheets were made as noted above, tested for
tensile properties, and compared to a conventional NBSK/eucalyptus
blend in which the NBSK was refined to the same extent. Like Table
2, Table 3 lists tensile properties of the tissue grade sheets.
Again, tensile stiffness is reported as measured, and at tensile
index normalized to 1.
TABLE-US-00003 TABLE 3 Tensile Stiffness (MOE) LWAFL/coarseness
Tensile at normalized Sample (ratio) Index measured TI = 1 NBSK-r
2.25/13.5 (0.167) 12.1 0.453 0.037 SBSK-r1 2.53/19.3 (0.131) 8.2
0.291 0.035 SBSK-r2 1.92/18.6 (0.103) 11.1 0.478 0.043 SBSK-r3
2.99/25.2 (0.118) 9.6 0.361 0.037 SBSK-r4* 2.80/24.0 (0.116) 9.1
0.263 0.029 SBSK-r5* 2.46/22.0 (0.118) 11.2 0.361 0.032 *Mixture of
SBSK samples. LWAFL and coarseness values calculated using rule of
mixtures.
[0058] Again, a range of length-to-coarseness ratios for the SBSK
made in accordance with the present disclosure most suitable to
exhibit the desired tissue hand sheet stiffness is greater than
about 0.11. In theory, any upper limit would be that suggested by
the LWAFL/coarseness ratios found in Southern pine fibers when
pulped in accordance with the present disclosure. For example, SBSK
samples produced from loblolly pine (Pinus taeda) trees of various
ages were found to have LWAFL/coarseness ratios up to about 0.14.
Especially suitable ratio ranges may be determined by the desired
tissue properties. For example, LWAFL/coarseness ratios lower than
about 0.12 appeared to correlate well to the lowest tensile
stiffness values. However, higher LWAFL/coarseness ratios (e.g.,
around 0.13) were found to correlate well to other properties such
as tear strength, bulk, and so forth. Optionally, although it was
found that the aforementioned ratio range imparted suitable
stiffness characteristics over the available length and coarseness
ranges, a preferred coarseness range for some embodiments is from
about 16 to about 25 mg/100 m, and a preferred length range for
some embodiments is from about 1.6 to about 3.0 mm. A length and
coarseness range that imparted particularly favorable tensile
stiffness properties for some embodiments was found at a coarseness
of from about 19 to about 20 mg/100 m and a fiber length of from
about 2.5 to about 2.7 mm.
[0059] Additionally, it was found that the desired stiffness values
were exhibited by tissue hand sheets produced from blends
containing greater than about 20% of the SBSK fibers having a
length-to-coarseness ratio within the range. As noted above, the
tissue hand sheets (and other tissue products) may be produced from
blending the desired proportion of SBSK fibers (e.g., from a pulp
sheet of the Southern pine fibers) with other fibers in the
formation of the tissue item, or may be produced from a pulp sheet
that itself is a blend of SBSK fibers with other fibers (e.g., a
pulp sheet wherein the content of the Southern pine fibers is at
least 20%).
[0060] In addition to applicability in tissue and towel products,
the pulp sheets produced from Southern pine fibers in accordance
with the present disclosure may also have applicability in
absorbent products, such as baby diapers, adult incontinence
products, feminine hygiene products, bandages, and so forth. As
noted above, higher coarseness SBSK fibers (relative to NBSK
fibers) used in absorbent products, and in particular when used in
a composite pulp/SAP absorbent core in absorbent products, is
conventionally seen as providing effective wicking. In other words,
the expectation is that better wicking in such applications will
result from higher coarseness fibers. Higher coarseness fibers
generally provide increased void space and bulk, as compared to
lower coarseness fibers, and the aforementioned expectation is
based on the long-standing theory that void space and bulk in a
fibrous structure is necessary for effective fluid transfer, with
or without SAP in the fibrous structure. However, although it was
found that Southern pine fibers in accordance with the present
disclosure yields better wicking at higher coarseness in the
absence of SAP, it was unexpectedly found that such fibers, in the
presence of a large proportion of SAP, yield better wicking at
lower coarseness.
[0061] The ability of a material to wick fluid, as noted above, can
be measured in several ways. Wicking rate refers to the rate at
which water wicks upward through an airlaid pad produced from pulp
fibers. Inclined plane wicking rate refers to the ability of water
to wick upward through a composite pad made from pulp fibers and
SAP that is placed at an incline, along the plane of the pad.
[0062] Wicking rate is determined herein using the Automatic Fiber
Absorption Quality (AFAQ) Analyzer (Weyerhaeuser Co., Federal Way,
Wash.), according to the following procedure. A dry 4-gram sample
of the pulp composition is fluffed in a hammermill, then passed
through a pinmill and airlaid into a tube. The tube is then placed
in the AFAQ Analyzer. A plunger then descends on the airlaid fluff
pad at a pressure of 0.6 kPa. The pad height is measured, and the
pad bulk (or volume occupied by the sample) is determined from the
pad height. The weight is increased to achieve a pressure of 2.5
kPa and the bulk recalculated. The result is two bulk measurements
on the dry fluff pulp at two different pressures. While the dry
fluff pulp is still compressed at the higher pressure, water is
introduced into the bottom of the tube (to the bottom of the pad),
and the time required for water to wick upward through the pad and
reach the plunger is measured. From this, the wick time and wick
rate are determined. The bulk of the wet pad at 2.5 kPa is also
calculated. The plunger is then withdrawn from the tube and the wet
pad is allowed to expand for 60 seconds. In general, the more
resilient the sample, the more it will expand to reach its wet rest
state. Once expanded, this resiliency is measured by reapplying the
plunger to the wet pad at 0.6 kPa and determining the bulk. The
final bulk of the wet pad at 0.6 kPa is considered to be the "wet
bulk at 0.6 kPa" (in cm3/g, indicating volume occupied by the wet
pad, per weight of the wet pad, under the 0.6 kPa plunger load) of
the pulp composition. When the term "wet bulk" is used herein, it
refers to "wet bulk at 0.6 kPa" as determined according to this
procedure. Absorbent capacity is calculated by weighing the wet pad
after water is drained from the equipment and reported as grams
water per gram dry pulp.
[0063] Inclined plane wicking rate is determined herein using an
apparatus that includes a 30-degree incline frame with a balance
link upon which the test pad is placed, held in place with support
pins and/or clamps. The balance is tared, and the bottom edge of
the pad is brought into contact with the surface of a reservoir
charged with liquid, generally a 0.9% saline solution to simulate
urine. A timing program is started, which measures and records
liquid uptake in grams at 5-second increments. The test is
generally allowed to run for approximately 15 minutes, with the
inclined plane wicking rate reported as the weight increase of the
pad, attributable to the amount of liquid wicked, in 500 seconds.
Sample preparation for the inclined plane wicking test was done
using SAP (BASF 9400) and fluffed pulp at a 30:70 pulp to SAP
ratio, formed on a laboratory pad former at a basis weight of
500-550 gsm. 10 cm square portions were cut out for testing, with
the portions pressed on a lab Carver press to a density of
0.18-0.22 g/cc. Three portions were tested from each sample
pad.
[0064] Table 4 lists wicking rates and absorption capacity
properties of example absorbent cores made of 100% SBSK, and
inclined plane wicking rates of example absorbent cores made of 30%
SBSK and 70% SAP, using several SBSK samples produced in accordance
with the present disclosure and having different coarseness and
fiber length properties. The example absorbent cores produced from
the SBSK samples (nominally numbered 1-5) are compared against a
control in which the SBSK is a commercially available fluff pulp
available from Weyerhaeuser Company under the designation
CF416.
TABLE-US-00004 TABLE 4 Wicking Inclined plane rate, Absorp wicking
rate, Sample Coarseness LWAFL no SAP Cap. 70% SAP Control 21.6 2.35
10.99 10.18 127.2 1 17.1 1.94 9.09 11.10 139.4 2 17.8 1.99 8.72
11.35 139.4 3 18.0 2.08 7.62 11.31 138.0 4 20.0 2.52 9.49 12.00
137.0 5 25.2 2.99 10.60 12.10 124.0
[0065] FIG. 2 provides a representative plot of wicking rates of
the example 100% SBSK pulp cores listed in Table 4, and
demonstrates a correlation between higher coarseness and higher
wicking in the absence of SAP. FIG. 3, however, a representative
plot of inclined plane wicking rates of the sample composite pulp
cores listed in Table 4, demonstrates the unexpected (and
unexpectedly strong) correlation between lower coarseness fibers
and higher inclined plane wicking in the presence of a large
proportion of SAP.
[0066] Although not wishing to be bound by theory, one possible
explanation for this unexpected correlation may be related to
interaction between individual fibers and SAP particles in a
composite SAP and fiber structure. Lower coarseness generally
indicates a higher fiber population per gram. A higher fiber
population may in turn result in more fluid pathways within the
fiber structure, by obstructing SAP particles from gel-locking with
adjacent SAP particles as they swell as fluid is acquired by the
structure.
[0067] Thus, a coarseness range for SBSK pulp sheets made in
accordance with the present disclosure suitable to exhibit the
desired inclined plane wicking rate in the presence of a large
proportion of SAP appears to be about 16 to about 20 mg/100 m, over
a LWAFL range of about 1.6 to about 2.7 mm.
[0068] Based on the aforementioned observed results, the unexpected
increase in inclined plane wicking rate seen in absorbent cores in
which the pulp component is made up of low coarseness SBSK is
predicted to be preserved even when the low coarseness SBSK is
blended with up to about 25% NBSK, and in particular low coarseness
NBSK (e.g., of a coarseness of from about 13 to about 18 mg/100 m,
and of a fiber length of from about 2.0 to about 2.5 mm), such as
in an absorbent core with high levels of SAP. Accordingly, a pulp
sheet in accordance with the present disclosure includes a blend of
low coarseness (i.e., about 16-20 mg/100 m) Southern pine fibers
with NBSK. The NBSK in said pulp sheets has a coarseness of about
13-18 mg/100 m and a fiber length of about 2.0-2.5 mm. Such a
"blended" pulp sheet may be produced at a basis weight and/or
density appropriate for applications such as conversion into
absorbent products, such as a basis weight range of 500-900 gsm
and/or a density of 0.4-0.8 g/cc.
[0069] In addition to the unexpectedly increased inclined plane
wicking rate properties provided by lower coarseness pulp sheets
produced from Southern pine fibers in accordance with the present
disclosure, such lower coarseness pulps were also found to be more
easily amenable to densification, such as when incorporated into an
absorbent core for inclusion in absorbent products. Densification
can result in thinner absorbent cores, which in turn may result in
less bulky absorbent products, which are both aesthetically
preferable to more bulky alternatives, and may also result in
reduced shipping and storage costs, decreased shelf space, and so
forth. However, densification is often limited by SAP, which can be
damaged as a result of the application of pressure to a composite
structure in which it is placed. SAP particles often consist of a
highly-crosslinked polymeric shell encapsulating a less crosslinked
polymeric core. This structure helps to prevent gel-locking with
other SAP particles. If SAP particles are damaged, such as by
compromising the outer shell, the fluid acquisition properties of
the absorbent core may in turn be compromised, reducing the utility
of such absorbent products.
[0070] FIG. 4 is a representative plot of density, which relates to
thickness, against pressing pressure on a Carver press, for example
composite absorbent cores containing SBSK fibers of varying
coarseness. The absorbent cores were prepared as above, at a ratio
of 30% SBSK to 70% SAP. Lower coarseness fibers result in greater
density at the same applied pressure, or in other words, require
less pressure to achieve the same density, as compared to higher
coarseness fibers.
[0071] This effect is even more pronounced with the addition of
softening agents such as glycerin, as shown in FIG. 5, which is
also a representative plot of density against pressing pressure. An
SBSK control core (CF416, coarseness 21.6) is shown for comparison
against an SBSK core with, and without, 3% glycerin.
[0072] Although the present invention has been shown and described
with reference to the foregoing operational principles and
illustrated examples and embodiments, it will be apparent to those
skilled in the art that various changes in form and detail may be
made without departing from the spirit and scope of the invention.
The present invention is intended to embrace all such alternatives,
modifications and variances that fall within the scope of the
appended claims.
* * * * *