Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2000-01-20
2001-05-22
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S111000, C162S112000, C162S158000, C162S168100, C162S168300, C162S168200, C162S183000
Reexamination Certificate
active
06235155
ABSTRACT:
BACKGROUND OF THE INVENTION
In the manufacture of paper products, such as facial tissue, bath tissue, paper towels, dinner napkins and the like, a wide variety of product properties are imparted to the final product through the use of chemical additives. Examples of such additives include softeners, debonders, wet strength agents, dry strength agents, sizing agents, opacifiers and the like. In many instances, more than one chemical additive is added to the product at some point in the manufacturing process. Unfortunately, there are instances where certain chemical additives may not be compatible with each other or may be detrimental to the efficiency of the papermaking process, such as can be the case with the effect of wet end chemicals on the downstream efficiency of creping adhesives. Another limitation, which is associated with wet end chemical addition, is the limited availability of adequate bonding sites on the papermaking fibers to which the chemicals can attach themselves. Under such circumstances, more than one chemical functionality compete for the limited available bonding sites, oftentimes resulting in the insufficient retention of one or both chemicals on the fibers.
Therefore, there is a need for a means of applying more than one chemical functionality to a paper web which mitigates the limitations created by limited number of bonding sites.
SUMMARY OF THE INVENTION
In certain instances, two or more chemical functionalities can be combined into a single molecule, such that the combined molecule imparts at least two distinct product properties to the final paper product that heretofore have been imparted through the use of two or more different molecules. More specifically, polyamide epichlorohydrin (PAE) resins can be combined with polysiloxanes in a single molecule to provide several potential benefits, depending upon the specific combination employed, including: (a) wet strength resins that soften; (b) softeners that do not reduce dry or wet tensile strength; (c) wet strength with improved wet/dry tensile ratio; (d) softeners/debonders with reduced linting and sloughing; (e) wet strength aids with controlled absorbency rate; and (f) Yankee dryer additives that provide surface protection and adhesion with controlled release properties.
Hence in one aspect, the invention resides in a condensation polymer having the following structure:
where
w≧1
n≧1
p≧0
Z
1
, Z
2
, Z
3
=bridging radicals, which may be the same or different and which serve to incorporate the R
1
, R
2
, and R
3
groups into the polymer;
R
1
=a monomer unit or a block or graft copolymer containing a siloxane functionality and of the form —O—Si(R′)
2
—O—[Si(R″)
2
—O]
n
—Si(R′″)
3
where R′, R″, R′″ can be the same or different and are selected from the group consisting of: H, OH and aryl or alkyl or aliphatic hydrocarbon, C
1-40
, linear or branched, saturated or unsaturated, substituted or non-substituted, with or without ethyoxylation and/or propoxylation;
R
2
=any linear or branched, saturated or unsaturated, substituted or non-substituted aliphatic hydrocarbon containing at least one secondary amine group;
R
3
=any linear or branched, saturated or unsaturated, substituted or non-substituted aliphatic hydrocarbon of chain length 2 or higher.
In another aspect, the invention resides in a paper sheet, such as a tissue or towel sheet, comprising an amount of a condensation polymer having the following structure:
where
w≧1
q≧0
m≧1
n≧1
p≧0
Z
1
, Z
2
, Z
3
=bridging radicals, which may be the same or different and which serve to incorporate the R
1
, R
2
, and R
3
groups into the polymer;
R
1
=a monomer unit or a block or graft copolymer containing a siloxane functionality and of the form —O—Si(R′)
2
—O—[Si(R″)
2
—O]
n
—Si(R′″)
3
where R′, R″, R′″ can be the same or different and are selected from the group consisting of: H, OH and aryl or alkyl or aliphatic hydrocarbon, C
1-40
, linear or branched, saturated or unsaturated, substituted or non-substituted, with or without ethyoxylation and/or propoxylation;
R
2
=any linear or branched, saturated or unsaturated, substituted or non-substituted aliphatic hydrocarbon containing at least one secondary amine group;
R
3
=any linear or branched, saturated or unsaturated, substituted or non-substituted aliphatic hydrocarbon of chain length 2 or higher.
In another aspect, the invention resides in a method of making a paper sheet such as a tissue or towel sheet, comprising the steps of: (a) forming an aqueous suspension of papermaking fibers; (b) depositing the aqueous suspension of papermaking fibers onto a forming fabric to form a web; and (c) dewatering and drying the web to form a paper sheet, wherein a condensation polymer is added to the aqueous suspension, said condensation polymer having the following structure:
where
w≧1
q≧0
m≧1
n≧1
p≧0
Z
1
, Z
2
, Z
3
=bridging radicals, which may be the same or different and which serve to incorporate the R
1
, R
2
, and R
3
groups into the polymer;
R
1
=a monomer unit or a block or graft copolymer containing a siloxane functionality and of the form —O—Si(R′)
2
—O—[Si(R″)
2
—O]
n
—Si(R′″)
3
where R′, R″, R′″ can be the same or different and are selected from the group consisting of: H, OH and aryl or alkyl or aliphatic hydrocarbon, C
1-40
, linear or branched, saturated or unsaturated, substituted or non-substituted, with or without ethyoxylation and/or propoxylation;
R
2
=any linear or branched, saturated or unsaturated, substituted or non-substituted aliphatic hydrocarbon containing at least one secondary amine group;
R
3
=any linear or branched, saturated or unsaturated, substituted or non-substituted aliphatic hydrocarbon of chain length 2 or higher.
The amount of the condensation polymer of this invention added to the fibers can be from about 0.01 to about 2 weight percent, on a dry fiber basis, more specifically from about 0.02 to about 1.5 weight percent, and still more specifically from about 0.05 to about 1.0 weight percent. The modified condensation polymer(s) can be added to the fibers at any point in the process, particularly including the wet end of the process where the fibers are suspended in water. However, these polymers can also be added to the web during or after drying, such as during creping.
Methods of making paper products which can benefit from the various aspects of this invention are well known to those skilled in the papermaking art. Exemplary patents include U.S. Pat. No. 5,785,813 issued Jul. 28,1998 to Smith et al. entitled “Method of Treating a Papermaking Furnish For Making Soft Tissue”; U.S. Pat. No. 5,772,845 issued Jun. 30, 1998 to Farrington, Jr. et al. entitled “Soft Tissue”; U.S. Pat. No. 5,746,887 issued May 5, 1998 to Wendt et al. entitled “Method of Making Soft Tissue Products”; and U.S. Pat. No. 5,591,306 issued Jan. 7, 1997 to Kaun entitled “Method For Making Soft Tissue Using Cationic Silicones”, all of which are hereby incorporated by reference.
REFERENCES:
patent: 4447498 (1984-05-01), Fink
Clarahan Daniel Arthur
Goulet Mike Thomas
Schroeder Wen Zyo
Shannon Thomas Gerard
Chin Peter
Croft Gregory E.
Halpern Mark
Kimberly--Clark Worldwide, Inc.
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