DISPOSABLE ARTICLE OF IMPROVED COLOR, COMPOSITION AND METHOD FOR MAKING SAME

ARTICLES JETABLES DE TEINTE PLUS ATTRAYANTE, LEUR COMPOSITION ET LEUR FABRICATION

English Abstract

Abstract of the Disclosure
Absorbent articles and particularly such as disposable used for cap-
turing body fluids (e.g. diapers, sanitary napkins, incontinence pads, etc.)
and which are generally structured with a top sheet or sheets, a body of
absorbent material thereunder and a back sheet to restrain loss or escape of
the fluids from the article, are provided with an absorbent mass derived from
thermomechanical or mechanical pulp wherein the absorbent mass approaches or
equals the whiteness of chemical pulp products. This is obtained by treating
the pulp with minute amounts of a mixed dye system, e.g. .001% to about .05%
by weight based on the total pulp weight.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A mixed dye composition for brightening and whitening cell-
ulose material which comprises C.I. Acid Violet 47 and C.I. Acid
Violet 49 in a weight ratio of from about 10:1 to 1:10.
2. A composition as defined in claim l wherein the ratio is
from about 4:1 to 1:4.
3. A process for brightening and whitening aqueous cellulosic
pulp which comprises adding thereto a solution of a mixed dye compo-
sition for brightening and whitening cellulose material which com-
prises C.I. Acid Violet 47 and C.I. Acid Violet 49 in a weight
ratio of from about 10:1 to 1:10.
4. A process as defined in claim 3 wherein the solution is
an aqueous solution.
5. A process as defined in claim 4 wherein the dye concen-
tration in solution ranges from about 0.001% to about 0.05% by
weight.
6. A process as defined in claim 3 including the further
addition to the pulp of from about 0.01% to about 10% by weight
of titanium dioxide or barium sulfate or mixtures thereof.
7. A process as defined in claim 3 wherein the cellulosic
material is derived from thermomechanical pulp.
8. A process for producing an absorbent product suitable for
absorbing body fluids which comprises treating an aqueous cellulosic

pulp with a mixed dye, composition for brightening and whitening
cellulose material which comprises C.I. Acid Violet 47 and C.I.
Acid Violet 49 in a weight ratio of from about 10:1 to 1:10, drying
the treated pulp and thereafter forming an air-laid mass therefrom.
9. An absorbent product suitable for absorbing body fluids
comprising an air laid cellulosic fluff treated with a mixed dye
composition for brightening and whitening cellulose material which
comprises C.I. Acid Violet 47 and C.I. Acid Violet 49 in a weight
ratio of from about 10:1 to 1:10.
10. An absorbent product as defined in claim 9 wherein the
fluff is derived from thermomechanical pulp, the ratio of Dye 49
to Dye 47 ranges from about 4:1 to 1:4 and the fluff contains from
about 0.001% to about 0.05% by weight of the dye composition.
11. In a disposable product suitable for absorbing body fluids
and comprising an absorbent mass for the body fluids, a water im-
pervious backsheet and a topsheet, the improvement wherein the
absorbent mass is as defined in claim 10.

Description

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The present invention relates to absorbent products which are general-
ly characterized as disposables and among such product are diapers, feminine
hygiene pads, incontinence pads and the like and in particular to improvements
in such products employing wood fluff derived from mechanical or thermomechanical
pulp. The fluff is used as the primary absorbent mass in these products and
reference is made to such recent patents as United States Patents 4,069,821;
4,066,081; 4,062,362; 4,060,085; 4,044,768; 4,029,101; 4,029,100, and 4,027,672
wherein wood fluff is employed as an absorbent mass in products of the type con-
templated herein. rhe pulp used to make the Pluff in these prior patents has
generally 6een chemical pulp and such flufP is a highly bleached product of a
whiteness of about 90 or greater. The standard of 100 ~whiteness) is based on a
magnesium carbonate surface and is accepted as the criteria for excellent white-
ness. Chemical pulp is also advantageous in that one obtains optimum fiber
lengths from tHe wood source there6y leading to absorbent pads of acceptable
structural integrity (i.e. strength and form sta6ility) which is most desirable
since the pad forming process is generally an air-laid process.
It has been found desirable and advantageous to employ thermomechanical
pulp in absorbent disposable structures due, not only to the obvious economic
advantages but also due to improvements in a6sorbency. The later results from
the semi-hydrophobic nature of thermomechanical pulp due to the presence of the
natural lignins, which give greater resiliency to the non-woven pad and concomit-
ant increased liquid holding capacity.
One of the disadvantages of thermomechanical pulp lies in the "off-
color" of the product which renders disposables made therefrom less desirable to
the consumer, particularly those consumers using disposable diapers on babies
where a very "white" product is a "must".
It has now been found that the whiteness of thermomechanical pulp and
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other off-color cellulosic pulps such as mechanical and even semi-chemical pulps
and even chemical pulps which do not meet accepted standards of whiteness can be
vastly improved in their whiteness, approaching the best of the chemical pulps
(i.e. delignified and bleached) by treating the pulp preferably in slurry form
with a mixed dye system comprising (a) CI Acid Violet 49 and (b) CI Acid Violet
47 in a weight ratio of (a) to (b) of from a~out 10:1 to 1:10, preferably 6:1 to
1:6, more preferahly 4:1 to 1:4, still more preferably 3:1 to 1:3 and most pre-
ferably 1:1 to 1:3 to provide the pulp with from about .001% to a~out 0.05%
weight of dye based on the dry pulp weight .
Accordingly the present invention provides a mixed dye com~osition for
brightening and wnitening cellulose material which comprises C.I. Acid Violet 47
and C.I. Acid Violet 49 in a weight ratio of from a~out 10:1 to 1:10.
me dye mixture is conveniently added to the aqueous pulp (usually
about 85 to 90% or more solids) as a solution preferably aqueous, but any suit-
able dye solvent (e.g. alcohol, alcohol water) may be used. While the dye sol-
ution may be of any desirable concentration, it is generally preferred to use
dilute solutions to obviate over-dyeing in localized portions of the pulp which
may result due to rapid and fairly high exhaustion values of the dye from sol-
ution onto t~e cellulosic material of the pulp.
After treatment, the pulp is handled in t~e conventional way to form
sneet products for any subsequent use and in particular the pulp may be sheeted
to form paperboard to be used in producing absorbent fluff for the disposable
products mentioned a~ove.
The following is specifically illustrative of the present invention.
EX~LE 1
To 1.5 g of an aqueous cellulose pulp ~thermcmechanical pulp - non-
delignified) of 90% cellulosic solids there are added 50 cc of a dye solution

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containing (a) 7.5 milligrams/liter of CI Acid Violet 47 and (b) 2.5 milligram/
liter of CI Acid Violet 49. After drying the pulp, subsequent to screening to
form a sheet, it is found that the Tappi brightness as conventionally measured
on a G.E. re~lectometer is 80% whereas untreated (i.e. without dye treatment)
pulp sheeted similarly has a Tappi brightness of only 65%. The dye-treated pro-
duct not only has improved brightness and whiteness but is equivalent to the
usual chemical pulp (delignified) when sheeted in a similar manner, notwithstand-
ing the presence of the lignin in the thermomechanical material.
It may also be desirable to add a small amount of titanium dioxide or
barium sulfate pigment to the aqueous pulp ~furnish) to further whiten the pro-
duct. Generally only very small quantities, from about 0.01% to about 10% by
weight and preferably 0.5% to about 3% by weight yield outstanding results as
illustrated in the following Example.
EXAMPLE II
a) Example I is repeated with the addition to the dye solution of 0.5 g/
liter of titanium dioxide.
b) Example I is repeated with the addition to the dye solution of 0.5 g/
liter of barium sulfate.
In each of the ~a) and ~b) the brightness value of the samples is 85%.
While the invention has been described with respect to a mixture of
dyes CI 47 and CI 49, it is, of course, understood that other dyes of similar
color characteristics may be used. One of the significant characteristics of
CI 47 dye (.001% in water) is a prominent absorption in the visible region of
from about 4800A to about 6000A with a flat peak at about 5100A to 5700A,
and for the CI 49 dye (.0005% in water) a broad absorption band in the region
of about 4900A to about 6300A with a sharp double peak at about 5200A to
about 6100A, and consequently other dyes of equivalent absorption characteristics

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may also be used.
CI Acid ~iolet 49 is a triphenylmethane type dye (color index no.
42640) and CI Acid Violet 47 is an anthraqulnone type.