Soft absorbent tissue treated with a chemical composition

Details Soft absorbent tissue treated with a chemical composition Soft absorbent tissue treated with a chemical composition

2002-03-14

2003-07-29

Chin, Peter (Department: 1731)

Paper making and fiber liberation

Processes and products

Non-fiber additive

C162S109000, C162S127000, C162S129000, C162S130000, C162S135000

Reexamination Certificate

active

06599394

ABSTRACT:

BACKGROUND OF THE INVENTION
In the field of soft tissues, such as facial tissue and bath tissue, it is well known that the application of polysiloxanes to the surface of the tissue can impart an improved surface feel to the tissue. However, polysiloxanes are also known to impart hydrophobicity to the treated tissue. Hence it is difficult to find a proper balance between softness and absorbency, both of which are desirable attributes for tissue, particularly bath tissue.
SUMMARY OF THE INVENTION
It has now been discovered that the softness of a tissue can be improved with minimal negative impact on the absorbency or wettability of the tissue by treating one or both outer surfaces of the tissue with a particular group of hydrophilically-modified amino-functional polydimethylsiloxanes. More specifically, suitable polysiloxane structures have one or more pendant groups which contain a terminal amine and at least one ethylene oxide moiety. The terminal amine group and the ethylene oxide moieties can be parts of the same pendant group or different pendant groups. A general structure is as follows:
wherein:
“A” is selected from the group consisting of hydroxyl, C
1
-C
8
alkyl radical, and C
1
-C
8
alkoxyl radical, which can be straight chain, branched or cyclic, unsubstituted or substituted;
R
1
, B and D are distributed in random or block fashion;
R
1
=a C
1
-C
6
alkyl radical, which can be straight chain, branched or cyclic;
m=20-100,000;
p=1-5,000;
q=1-5,000;
B=—R
3
—[(OC
2
H
4
)
r
—(OC
3
H
7
)
s
]
t
—O—(R
4
)
z
—W;
 wherein
t=0 or 1;
z=0 or 1;
r=1-50,000; and
s=0-50,000;
R
3
=a C
2
-C
8
alkylene diradical, which can be straight chain or branched, substituted or unsubstituted;
R
4
=a C
2
-C
8
alkylene diradical, which can be straight chain or branched, unsubstituted, or substituted with hydroxyl, alkoxyl, halo, organic ester, or other radicals, or an alkyl cyclic ethereal radical;
such that when z=0,
W=a hydrogen or a C
1
to C
22
alkyl radical, which can be straight chain or branched, substituted or unsubstituted;
such that when z=1,
W=a hydrogen, a —N R
5
R
6
radical, or a —N R
9
;
 wherein
R
5
and R
6
are independently a hydrogen, or a C
1
-C
8
alkyl radical, which can be straight chain or branched, unsubstituted, or substituted with hydroxyl, alkoxyl, halo, organic ester, or other radicals;
R
9
is a C
3
to C
8
alkylene diradical, unsubstituted, or substituted, which form a cyclic ring with the nitrogen;
D=—R
7
—(OC
2
H
4
)
x
—(OC
3
H
7
)
y
—O—R
8
;
 wherein
x=1-10,000;
y=0-10,000;
R
7
=a C
2
-C
8
alkylene diradical, which can be straight chain or branched, substituted or unsubstituted; and
R
8
=a hydrogen or a C
1
-C
8
alkyl radical, which can be straight chain or branched, substituted or unsubstituted.
Representative species within the foregoing general structure include the following (the values of “m”, “p”, “q”, “x” and “y” are as defined above unless otherwise specified; the terms “EO” and “PO” are shorthanded representations of “ethylene oxide” and “propylene oxide” moieties, respectively):
The hydrophilically-modified amino-functional polydimethylsiloxanes described above can be applied to the tissue web alone or in conjunction with other chemicals, such as bonders or debonders. They can be applied to the tissue web, particularly an uncreped throughdried web, by spraying or printing. Rotogravure printing of an aqueous emulsion is particularly effective. Add-on amounts can be from about 0.1 to about 10 dry weight percent, based on the weight of the tissue, more specifically from about 0.5 to about 5 dry weight percent, and still more specifically from about 1 to about 3 weight percent. The distribution of the deposits of the hydrophilically-modified amino-functional polydimethylsiloxanes is substantially uniform over the printed surface of the tissue, even though the surface of the tissue, such as in the case of uncreped throughdried tissues, may be highly textured and three-dimensional. The printing does limit the deposits to the high points of the textured tissue sheets, thereby ensuring a soft hand feel.
The Wet Out Time (hereinafter defined) for tissues of this invention can be about 10 seconds or less, more specifically about 8 seconds or less, still more specifically about 6 seconds or less, still more specifically about 5 seconds or less, still more specifically from about 4 to about 6 seconds. As used herein, “Wet Out Time” is related to absorbency and is the time it takes for a given sample to completely wet out when placed in water. More specifically, the Wet Out Time is determined by cutting 20 sheets of the tissue sample into 2.5 inch squares. The number of sheets used in the test is independent of the number of plies per sheet of product. The 20 square sheets are stacked together and stapled at each corner to form a pad. The pad is held close to the surface of a constant temperature distilled water bath (23+/−2° C.), which is the appropriate size and depth to ensure the saturated specimen does not contact the bottom of the container and the top surface of the water at the same time, and dropped flat onto the water surface, staple points down. The time taken for the pad to become completely saturated, measured in seconds, is the Wet Out Time for the sample and represents the absorbent rate of the tissue. Increases in the Wet Out Time represent a decrease in absorbent rate.
The “Differential Wet Out Time” is the difference between the Wet Out Times of a tissue sample treated with a hydrophilically-modified amino-functional polydimethylsiloxane and a control tissue sample which has not been treated. The Differential Wet Out Time, for purposes of this invention, can be about 5 seconds or less, more specifically about 4 seconds or less, still more specifically about 3 seconds or less, still more specifically about 2 seconds or less, and still more specifically about 1 second or less.
Additional ingredients can be added to the sheet, such as vitamin E and/or aloe. The amount of vitamin E in the tissue sheet can be from about 0.01 to about 5 dry weight percent. The amount of aloe in the tissue sheet can be from about 0.01 to about 5 dry weight percent.
Tissue sheets useful for purposes of this invention can be creped or uncreped. Such tissue sheets can be used for facial tissues or bath tissues. They can have one, two, three or more plies. The basis weight of the tissue product can be from about 25 to about 50 grams per square meter. If used for bath tissue, a single ply tissue having a basis weight of from about 30-40 grams per square meter is particularly suitable.


REFERENCES:
patent: 5538595 (1996-07-01), Trokhan et al.
patent: 5944273 (1999-08-01), Lin et al.
patent: 6017417 (2000-01-01), Wendt et al.
patent: 06-311943 (1994-11-01), None

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