Note: Descriptions are shown in the official language in which they were submitted.
115600~
"
-- 1 --
The present invention relates to absorbent products and
more particularly to an improv~d absorbent structure for
use in diapers, sanitary napkins and the like.
Background of the Art
Many disposable products such as diapers, sani-
tary napkins, some tampons and some absorbent dressings
contain a layer or core of highly absorbent material~
which is wrapped or contained by other relatively less
absorbent materials. In some instances, such as in a
diaper, the absorbent Layer may be contained, at least
on one of its surfaces, by an impervious film material.
For example, a diaper may comprise a pervious upper layer,
a highly absorptive center layer, and an impervious
bottom layer. A sanitary napkin usually comprises a
highly absorptive layer wrapped in a pervious layer.
The absorptive layers used in disposable products usually
comprise a plurality of layers of creped paper tissue or,
in some instances, chemical wood pulp fibers in a fluffed
or a looso, lightly compacted configuration.
~:
B
''~
~ 1~6~0 1
-- 2 ~
For many years peat moss has been known as
possessin~ good water-absorbing characteristic~ but~ to date,
has not been successfully incorporated as a primary ingredient
in a structure suitable for use in diapers, sanitary napkins
or dressings. It is believed the reason for this may be the
intrinsic, extremely dark color of peat moss, the inability to
handle peat moss and place it in a suitable configuration for
wrappin~, or perhaps a combination of these undesirable
characteristics.
Summary of the Invention
What I have discovered is a new and improved
absorbent structure or core product. My new product may be
handled and utilized as an absorbent core in diapers, napkins
absorbent dressings and the like. By incorporating the
teachings of this invention, I have found that, unexpectedly,
my new product exhibits improved liquid-retentive properties
and is capable of maintaining its structural integrity.
The new product comprises peat moss, in combination
with finely divided mechanical wood pulp having a Canadian
Standard Freeness of from about 30 to 600 and present in
ratios, by weight of said wood pulp to peat moss of greater
than about 0.35. The term "mechanical wood pulpi' is meant to
encompass those wood pulps which have been reduced to a finely
divided state from the trunk and branches of trees after
removal of bark and dirt but without any prior~ chemical
treatment. Included in such materials are the groundwood
pulps, refiner pulps and thermo mechanical pulps.
The peat moss may be bleached to improve its white-
ness and may be bleached to a whiteness of at least about 70
as measured on the Hunter L~ninus Refleckive Scale. As ~uch,
lt will still maintain ik~ raw p~at porous structure~ i.e.,
kh~re is still a por-kion of humic acids and lignin-like
constltuen-t~ remaining in the bleached peat moss to maintain
lts open, porous, leaf-like structure~ This open structure
is believed -to he the major fac-tor in producing khe hi~hly
de~irable, absorbent properkies exhibiked by thi~ peat moss.
3 , ~ 1 S60Q ~
Unortunatel~, peat moss in this open, porous condition is
quite brittle and does not, by itse.l, withstan~ the kind of
handling absorbent products such as dLapers, napkins,
tampons and the like are subject ko. Still further, the
particles of peat moss are not self-entangliny~ such as
are lon~-Eibered absorbent material, or sel~-adherent.
In short, the peat moss, per se, has been ~ound to be
difficult to handle and incapable of being formed 1nto a
self-sustaining form having any structural integrity.
It has now been discovered that those short-
comings of the peat moss described herein can be overcome
and that an absorbent structure having both surprisingly
good absorbent properties as well as structural integrity
can be provided by including, in admixture ~ith the peat
moss, relatively fine mechanical wood pulp having a
Canadian Standard Freeness (hereinafter, CSF) of ~rom
about 30-600. Such wood pulp, which may be selected
Erom pulps such as ~roundwood pulp, refiner wood pulp
and/or thermomechanical wood pulp, generally have shorter
fiber leng~hs than the chemical pulps, e.g., the sul~it:e
or su~fate pulps usually associated with diapers~.napkins
and tampon products. The fine mechanical wood pulps are
generally characterized by their drainage and compacting
characteristics which are measured by "freeness"; i.e.,
Canadian Standard Freeness as measured by TAPPI Test
Method T-227. It has been discovered that the structural
integrity of pulp ~luff that has bee~ made by grinding.
board formed ~rom an aqueou~ ~lurry of a mix~ure ~f
peat moss and the herein prescribed ~inely divided
mechanical wood pulp i5 extremely sensitive to the rati.o
by weight,of the wood pulp to the peat moss. Spaci~iJ
cally, the mix~ure 105eS essentiall~ all i~5 cohesive-
ne~s at such ratios below 0.35~ Pre~erably such ratio
should ba maintained above 0.38.
3S 1'he mix~ura o~ pea~ moss and meahaniaal wood ~uLp
~ay be suppl~mented wi~h o~he~ ahsorbent In~erial~ suc~
~8 the more commonly u~ed long-~ibered wovd pulps su~h a~
~ul~ite or ~ul~a~e pulp QX rayon ~ibers or mix~ur~ o~
~e~e~ In ~oxming products ~ro~ the absorbent ~txuature
o~ this inven~ion, a core v~ the prescribed material may ~e
,
1 ~ S6~0 ~
wrapped about its entire periphery with a pervious layer
such as a non-woven fabric, as for example in a sanita.ry
napkin. Alternatively, the core may be interspersed
between a pervious layer such as a non-woven fabric and
an impervious layer such as thermoplastic film as in a
disposable diaper.
According to a further broad aspect of the
present invention -there is provided an absorbent product
comprising peat moss and mechanical wood pulp~ The wood
pulp has a Canadian Standard Freeness of from about 30-600,
and present in a ratio, by weight of the mechanical wood
pulp to the peat moss, of more than about 0.35.
Brief Description of the Drawinas
The present invention will be more fully
described when taken in conjunction with the accompanying
drawings wherein:
Figure 1 is a perspective view of a new, improved
absorbent product of the present invention.
Figure 2 is a photomicrograph at an original
en~argement of 160 times of a new and improved absorbe.nt
product of the present invention,
Figure 3 is a photomicrograph at an original
enlargement of 160 times of the bleached peat moss used
.in the absorbent products of the present invention,
Figure 4 is a perspective view, with a portion
cuk away, of a disposable diaper incorporating the
absorbent product of the present invention;
Figure 5 is a perspective view, with a portion
cut away, of a sani-tary napkin incorporating the
absorbent product of the present invention'
F'igure 6 is a perspective view of a tampon, with
a pQrtiorl cut away, which incorpora-ted the absorberlt
product o~ the preSQnt invention, and
Figure 7 i9 a graphical presentation of data
showin~ -the rela-tion~hip of the ratiol by weigh~ of
mechanical wood puLp to p~at mos~, to the structuraL
integrity of the resultin~ struct-lre.
.i ....
~ 1~600 ~
-- 5 --
Detailed De~cription of the Drawlnqs
Figures 1 and 2 show the new and improved absor-
bent product or core 10 of the present invention. This
core 10 comprises bleached peat moss 12 having a whiteness
of at least about 70, as measured on the Hunter Luminus
Reflective Scale, combinecl with finely-ground mechanical
wood pulp 14 having a Canadian Standard Freeness of from
about 30-600 and present in the ratios, by weight of wood
pulp to peat moss, of at least about 0.35. Preferably,
this ratio is at least about 0.4 and still more preferably
at least about 0.5. Also included in the core 10 are
other absorbent materials such as long-fibered chemical
wood pulp 16 and long-fibered rayon.
The peat moss 12, as can be seen more clo~ely in
the photomicrograph of Figure 3, has a leaf-like structure
with open pores 18 and maintains this structure in the
absorbent core 10. The bleached peat moss 12 has a degree
of whiteness of at least about 70, when measured on the
Hunter Color and Color Difference Scale, as set forth by
ASTM D-2244 Color Scale System "C" method.
I prefer to start with peat moss (sphagnum~ which
will hold at least 15 and preferabLy 20 times its weight
of water. I screen the peat moss between 10 and 100 rnesh
screens. The material that stays on a 10 mesh screen,
primarily roots and branches, is discarded~ The matqrial
that passes through a 100 mesh screen, namely, fines,
which add little to absorbency and are difficult to bleach,
is also discarded. Hence, my startiny peat mo~ is from
about .15 mm (100 mesh) to 1~8 mm (10 rnesh).
The peat moss is bleached by treatment with both
chlorine and calcium in the form of lime stone. The
bleaching may be carried out as a batch operation; that is,
where the peat moss i.~ dilute:d with water to a con~qntra-
tion of about 2% by wei~ht, treatecl with chlorine, Eollowed
by a calcium carbonatq treatmqn-t, eollowed by acid washe~
and wa ter washes to provicle the de~lred decJree Oe whitqne99~
0'~ 1
The bleached peat moss is dried to a degree
where it can ~e handled and ~ay actually be fonmed into
a board or sheet-type layer if desired. When formed into
a board, it is preferred tha~ it be foxmed along with the
finely-ground mechanical wood pulp 14 and optimally the
long-fibered wood pulp 16, and then this admixture
further dried together into the finished board. In
producing the absorbent core, the peat moss and mechanical
wood pulp are ground by standard wood pul~p grinding
operations, such as a ham~er mill, and laid down on a
carrier sheet, which may be the wrapping sheet or a
piece of tissue, in the desired amounts as is well known
in the art.
The finely-ground mechanica} wood pulp may be
selected from the group consisting of groundwoodpulpr th~r~
mechanical pulp and xefiner wood pulp. Groundwood pulp
is essentially trees and branches which have been debarked,
cleaned and then ground into particle mat~er. Refiner
wood pulp differs from groundwood pulp only in that the
grinding step utilizes a refiner, i.e9, a disk-like device
well known in the art and generally hav~ng metalic ribs
at the peripheral-sections thereof which last contact
the wood particles and help to separate the wood Eibers
without excessively damaging them. Thermomechanical wood
pulp is similar to re~iner pulp with the exception that
the wood particles are heated when in the refiners, usually
with steam, and this heating further aids in separating
the wood ~ibers~ ~he common characteristic o~ these
mechanical pulps ~s ~hat no attempt has be~ made to
~epa~ate the ~ibers by chemic~l me~n~ al~hou~
they m~y l~ r, a~ter being reduced to ~ine partlculate
ma~t~r, ~e subjec~ed ~o c~emical -~reatment, e.~, bleaching.
1 ~560'0 1
These mechanical pulps are commonly characterized
by the term "freeness," which is measured by the Canadian
Standard Freeness Test (TAPPI Test Method T-227). This
test essentially measures the rate of drainage of pulp andr
in e~fect, the degree of compac~ness. The preferred
Canadian Standard Freeness value for the mechanical wood
pulp materials incorporated in the absorbent cores of this
in~ention should vary between about 30-600 and preferably
from about 60-300.
The long-fibered wood pulp may comprise
approximately 5-20% by weight of the total weight o the
core and may be chosen from such chemically treated or
formed wood pulp as sulphite and sulphate wood pulp.
It is preferxed that the wood pulp selected be chosen from
soft wood materials, although hard wood fibers may also
be used. The term "long-fibered wood pulp" is meant to
describe pulps having at least 40% by weight, made up of
fibers of a length of 1/16" or more, and preferably,
about 50% by weight of the wood pulp consisting of fibers
of at least 1/16" in length.
1 ~6~0 1
In Figure 4, there is shown a disposable diaper
20 which incorporates the new and improved absorbent core
of the present invention. The diaper comprises a backing
21 which may be a thermoplastic, fluid impervious, film
material. The diaper also comprises a facing ~2 Layer
which is a material pervious to fluids and may be a non-
woven fabric of any of the standard types such as the
spunbond products, the spunlaced products, standard
carded non-woven fabrics, or in some instances, aven
pervious film materials may be used. Disposed between
the ~acing layer and backing layer, and slightly smaller
than the layers, is the new and improved absorbent
core 23 of the present invention.
In Figure 5, there is shown a sanitary napkin
24 which incorporates the absorbent core of the present
invention. In this construction the napkin may comprise
a center barrier sheet 25 which may be a thermoplastic
~ilm. On each side of this center sheet is an absorbent
core product which in this instance is ~he absorbent
core 26 of the present invention. The three-piece
laminate is wrapped about its entire periphery with a
suitable pervious material 27 such as the standard non-
woven fabrics. The wrapping extends beyond the ends o~
the absorbent core product to form tabs 28 for attaching
~he napkin.
In Figure 6 there is shown a tampon 29 which
incorporates in its centex ~he ab orbent core product 30
o~ the presen~ inven~ion~ The absorbent core i~ wrappqd
about i~ entire periphexy with ~ui~able pervious wrapping
materlal 31 such a~ the s~andard non-woven ~abxics.
The invention will be ~ur~her described i.n
conjunc~ion with the PolLowing examples. In each 0
1 ~800 1
these examples the absorbent has been;tr~ated so as to
include a wetting agent in quantities of less than 0.5
by weigh~ of dry absorbent. The wetting agent used i8
a sodium dioctyl sulfo succinate containing age~t manu-
factured by the Rohm & Haas Company and sold by themunder the tradename Triton GR-5.
EXAMPLE I
Approximately 28 pounds of raw peat moss is
classified using a Sweco classifier. The wet classifica-
tion re~oves the fines; that is, materials less than 100
mesh or smaller than lS0 microns in diameter. The classi-
Eication also removes the large pieces o material; that
is, materials larger ~han 10 mesh, which are the roots,
etc. The 10 to 100 mesh fraction is bleached by reac~tion
with 21 pound~ of calcium carbonate and 18.9 pounds oP
chlorine. The bleached peat is dewatered to remov~ liquid
from a 1% solids dispersion tQ-a 5% solids dispersion.
The peat is washed with tap water back to a consistency
of 1% solids and dewatered again to 5% solids. The peat
is placed in a tank and brought to 1~ co~sistency with
water and 10 pounds of 22 Baume' hydrochloric acid. The
resultant bleached peat moss has a whiteness of about
72 on the Hunter scale as pre~iously described.
The 1% bleached peat moss is held in a tank~
About 26 1/4 pounds of groundwood pulp and 5 1/4 pound~
o~ hleached ~raft woodpulp are di~persed in water to a
2~ solids consistency. Thi~ wood pulp mixture and the
acidi~ied bleached peat are mixed together to form a
misture of 0.~% solids consis~ency and containing 21 pounds
bleached peat, ~6 1/4 pounds groundwood pulp and 5 1/4
pounds of long-fibered wood pulp. The mixture is beaten
With a minox amount of agita~ion or shear so as no~ to
ab~ade ~ha peat moss leaP, and the mixture Plowed onto a
Fc~urdrlnier wire wi~h vacU~ ~o dewa~er the mixture and
~orm a board. rr~e board i~ Eorcqd air dri~d at about
' 350F and rollqd up. rrhe board is grc~und by convqn~iunal
equipm~n-k in a Hamm~r mill to produce a ~lu~ed,ab~orban-t
co~e produc~.
lo 1 ~ 5~0~ 1
As previously men-tioned, the resultant improved
absorbent product has improved capillarity compared to
chemical wood pulps or groundwood pulps per se. Furthermore,
our new product has improved liquid retention properties,
that is, holding of absorbed liquids under increased
pressure, than either the groundwood pu}ps or the
chemically formed wood pulps when used alone.
EXAMPLE 2
A plura~ity of absorbent core products are
}O made by mixing and grinding togethe~ various combinations
of chemical, long fibered, wood pulps; groundwood pulp;
unbleached peat moss; and bleached peat moss. The
absorbent core products are ormed and measured or
Liquîd Uptake, Liquid Retention After Saturationr and
Liquid Retention Under Pressure as described in the
~ollowing test methods.
Li~uid Uptake Test Method
A 7.7 cm. di~neter piece of the absorbent core`
to be tested is placed on top o~ a fritted glass filtar
plate and pressed with a con~ining pressure of 2.5 grams/
per cm. . The underside of the fritted glass plate is
in contact with liquid in the form of a column o~ liquid
extending 40 centimeters below the porous plate.
The column of liquid is in a calibrated burette and
the volume amount absorbed is me~sured a~ter a five-minute
pexiod, and a one-da~ ~eriod (reachinq essentiall~ equilib-
rium). The column is moved ~pwards to within 7 1/2
centimeters below the porous plate and allowed to come to
equilibrium and the volume amount ahsorbed measured.
The column is moved to within 1 centimeter o~ the porous
plate and again allowe~ to come to equilibrium and the
volume amount absorbed measured.
Liquid Retention After Saturation Test Method
The same piace o~ absorbent core used in the
Llquid Uptake ~est is ~ully s~turated ~nd the column m~ved
back to 1 centimetQr below t~e core leval and a volum~
me~u~emen-~ taken, and then movqd back to 4~ centirnetexs
below t~e ooXe level and a volume measureme~k ~aken~
~hi~ ~esk determin~s ~he amoun~ o~ Uld ~etained a~te~
sakuration.
1 ~L5~0 1
11
~gLui.d Retention Under Pressure Tes-t Method
Using another apparatus, a piece of absorbent
core i5 placed on top of perforated steel plate and fully
saturated with liquid. The volume amount of saturation
S is measured with no pressure on top of the absorbent
core, with a pressure of 20 grams per square centimeter
on top o~ the core, and with a pressure o~ 105 grams per
square centimeter on top of the absorbent core.
As previously mentioned, a number of cores
having the composition as shown across the top o~ the
~ollowing table I were measured for varlous absorptive
properties as shown along the lefthand side o~ the table.
o I o I c~ ~ ~n o u~ o ~ r 8
_ ~ ~
___ ~ ~ _ .
: ~
I I O O U~ O In O In O C:
~ InU~ ~ a~ u~ ~ ~
O ~ D cou cn c~ .
_l _. , ~ _ .
~5 .
u~ o~ n o oooo oo 00~
~ ~ r Oul o
_ , $
o In I ~ ~ o o O O ~ ~ ~r
:~ ,1 h , I er co r~ u7 C~ U~ ~o
. C~ _. _ Q __ .
~ ~ ~ ~ .
0~ O U~I ~ H O O O O O U~ C1 O O .
~i Z . H _I 0 1~ ~D ~~ ~r O a:~
_ ~ . E~ . .
OJ ~ l
~3 O _1 0 O o O In o O O _~ ~r r--
H . ~¢ _I _i ~ t
, C~ I 1,
~ lo o o o u~ o u~
~ ~ o I I o ~ r ~ co r~ .,
! _ . _ _ ., .
l ~ ~ ~ ,
1 rl ~1 rl
,. ,t ,, ,, ~ ~' ~ ~e ~
:~ ~ E3 Ei U ~ U :
. V~ U U U U C) C~ ~
. . ~ o O U~ o _l o .
I ~ ~ p . . ~p c:~ o u~ .
P~ I ~r~,l l l ~
_ __ , ~__ ____
' ~ ~n o . .~ '.~
. P~ ~ E~ ~
l ~ ~ rl ~ ~ :~ : ~ ~
! ~ _ ~ a~ __ ~ _
~_i ~ 9 " l~ W ; J z
._ .. , .. ~ . .. ~
l2 IIS~()o31
J
1 15~001
- 13 -
EXAMPLE 3
-
A series of fluff material is prepared by grinding,
into fluf, board formed from slurries of mixtures of peat
moss, mechanical pulp (ground wood) and chemical pulp. The
composition of each of the samples is shown in Table II
below. The samples are tested for their structural inte-
grity by placing a 5 gram sample in the pan of a RoTap*
Testing Sieve Shaker equipped with a 10 mesh Tyler screen.
This apparatus is manufactured by W. F. Tyler Inc., a
L0 subsidiary of Combustion Engineering Inc. of Ohio, U.S.A.
The pan of the Roq'ap* Shaker, which measures 8 inches in
diameter, is filled to a depth of 2 inches. The RoTap*
Sieve Shaker is operated for 25 cycles, and the quantity
of material passing through the Tyler screen during opera-
tion is collected, weighed and reported, on a weight percent
based on the original 5 gram sample, as Losses in Table II
below. Figure 7 is a graphical representation of the data
in Table II, showing the relationship between the ratio,
by weight of the finely-ground wood pulp to the peat moss,
and the structural integrity of the resulting structure as
manifested by percent Loss through the scr2en.
* ~egistered Trademark
,X
- 14 ~ 1156001
o o o
, t a~
u~ In o c: ~o
a~ co ~1 O
,~ "
U~ U~ o ~ U:~
ao ~o ~ . t
ooooo
r~ u~
. ~ n
u~ u~ ~ O ~r
~D ~ ~ _t
~,
o
U~
. u~ In 0 00
Ul U~ ~ ,
o
QO
~, o o o ~ o o
H ~
~ S:
m ,t
E~ o o o o ~ 3
~ a~ ~ ~r
-t
O O O O u~ ~a
~ a~ _t ~ o
~ .
o o o o o o
.-t o c~
_t _t
o
.
~ . ~
_.
Q ra )-J ~_
~rtU~ a ~ ~P
t
~- ~rtO S ~rt
1/~ ~ 4 ~ Ul
~ ~ ~ t ~
:E~ E~ 1~ 0 ~
f~ O ~J h O (d O
41 C~ ~
1 1 ~6QO ~
:
As Table II and Figure 7 illustrate, the
losses and, hence, the structural integrity of the
flu~f is greatly dependant upon the ratio o~ mechanical
wood pulp tu peat moss. At ratios of essentially
zero, extremely large losses result var~ing from about
40-100~. Such losses would be intolerable in absorbent
products such as diapers, napkins and ta~pons. If
material exhibiting such lossas were incorporated in
such products~ a great quantity of the peat moss would
separate from the remainder of the absorbent material
and dust out o~ the product, Additionally~ the o~f-color
of the peat moss would become evident to the user, The
separated peat moss would be ~urther broken down owing
to it~ brittleness and would lose its e~fectiveness a~
an absorbent material. Tolerable losses are encountered
only when the ratios of mechanical wood pulp approach
the value of about 0.35 and pre~erably around 0.4.
At the very high ratios, it can be seen that the losses,
are reduced to negligible levels.
