Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2001-11-15
2003-06-10
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S111000, C162S112000, C162S109000, C162S135000
Reexamination Certificate
active
06576087
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 wettability, both of which are desirable attributes for tissue, particularly bath tissue.
SUMMARY OF THE INVENTION
It has now been discovered that the wettability of a tissue can be improved with minimal negative impact on the surface feel of the tissue by treating one or both outer surfaces of the tissue with a particular group of hydrophilically-modified amino-functional polysiloxanes. More specifically, suitable polysiloxane structures have one or more pendant groups which contain an amine derivative. The general structure of the Novel polysiloxanes is as follows:
wherein
R
1
G
1
and G
2
distributed in random or block fashion;
R
1
is a C
1
to C
8
straight chain, branched, cyclic alkyl radical;
R
2
is an oxygen, a C
2
to C
10
straight chain, branched, cyclic, unsubstituted or substituted akylene diradical;
n=20 to 100,000;
m=1 to 10,000;
s=0 to 10,000;
“A” is a hydrogen, C
1
to C
8
straight chain, branched, cyclic, substituted or unsubstituted alkyl radical, a [EO]
r
R
3
, or [EO]
r
[PO]
q
R
3
radical;
R
3
is a hydrogen or a C
1
to C
6
alkyl radical;
r=1 to 10,000;
q=0 to 10,000;
G
1
is a —R
4
—[-(EO)
y
—(PO)
z
]—(NR
5
R
6
)t—N
+
R
7
R
8
R
9
X
−
, a—R
4
—[—(EO)
y
(PO)
z
]—
w
—(NR
5
R
6
)
t
—N R
10
COR
9
radical, a—R
4
—[—(EO)
y
—(PO)
z
]—
w
(NR
5
R
6
)
t
—NR
10
CON R
11
R
9
radical, a —R
4
—[—(EO)
y
—(PO)
z
]—
w
(NR
5
R
6
)
t
—NR
10
OCOR
9
radical, a —R
4
—[—(EO)
y
—(PO)
z
]—
w
(NR
5
R
6
)
t
—OOCR
9
radical, a R
4
—[—(EO)
y
—(PO)
z
]—
w
(NR
5
R
6
)
t
—OCONR
9
R
10
, or a R
4
—[—(EO)
y
—(PO)
z
]
w
—(NR
5
R
6
)
t
—N
+
(R
10
)SO
2
PhR
9
X
−
radical where Ph is a phenyl group;
t=0 or 1;
w=1 when s =0; w 0 when s>0;
y=1 to 10,000;
z=0to 10,000;
X is a halide or sulfate ion;
R
4
and R
5
are independently a C
2
to C
8
alkylene diradical;
R
10
and R
11
are independently a hydrogen or a C
1
to C
8
alkyl radical;
R
6
is a hydrogen, a, c, to c
8
alkyl radical, a COR
9
, CONR
9
R
11
, OCOR
9
, or a
+
R
10
SO
2
PhR
9
X
−
radical;
R
7
and R
8
are independently a C
1
to C
8
alkyl radical;
R
9
is a C
1
to C
30
straight chain, branched, substituted or unsubstituted alkyl radical;
G
2
is a —R
12
—(EO)
j
—(PO)
k
R
13
radical, where
R
12
is a C
2
-C
8
alkylene diradical
R
13
is a hydrogen, or a C
1
to C
8
alkyl radical
j=1 to 10,000; and
k=0 to 10,000.
Examples of specific embodiments within the scope of the general structural formula include the following structures:
The derivitized 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 0.5 to about 15 dry weight percent, based on the weight of the tissue, more specifically from about 1 to about 10 dry weight percent, still more specifically from about 1 to about 5 weight percent, still more specifically from about 2 to about 5 weight percent. The distribution of the deposits of the derivitized 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 Wet Out Time (hereinafter defined) for tissues of this invention can be about 15 seconds or less, more specifically about 10 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 8 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 derivitized 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 10 seconds or less, more specifically about 5 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.
The ratio of the Differential Wet Out Time to the add-on amount of the derivitized amino-functional polydimethylsiloxane can be about 3 seconds per weight percent or less more specifically about 1 second per weight percent or less, still more specifically about 0.5 second per weight percent or less.
Tissue sheets useful for purposes of this invention can be creped or uncreped. Such tissue sheets can be used for facial tissues, bath tissues or towels. 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 3040 grams per square meter is particularly suitable.
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Chin Peter
Croft Gregory E.
Kimberly--Clark Worldwide, Inc.
Wanzer K.
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