Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-08-21
2002-04-02
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S815000, C428S311710, C428S530000, C428S533000, C428S534000, C428S535000, C162S164100, C162S164500, C162S164600, C162S168300
Reexamination Certificate
active
06365667
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 competes for the limited available bonding sites, oftentimes resulting in the insufficient retention of one or both chemicals on the fibers. For more complex chemical systems it may desirable to have two or more functional additives retained in a specified ratio and/or spatial arrangement relative to one another. Although the addition of chemicals in a pre-determined ratio is easily achieved, retention of these chemicals in a predictable ratio is difficult using wet end chemical addition because of site competition and other influencing factors. Another limitation of either wet end or topical chemical addition is the inability to predictably locate functional chemical moieties in proximity to each other on the fiber surface.
Therefore, there is a need for a means of applying more than one chemical functionality to a paper web that mitigates the limitations created by limited number of bonding sites and the unpredictable nature of chemical additive retention which limits the ability to retain functional groups in a specified ratio and/or spatial arrangement with respect to one another.
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, synthetic polymers, which are commonly used in the paper industry as dry strength resins, wet strength resins and retention aids, can be combined into a single molecule with modified aliphatic hydrocarbons, which are commonly utilized, in conjunction with cationic moieties, as softeners, debonders, lubricants and sizing agents. The resulting molecule is a synthetic polymer having hydrogen bonding capability and an aliphatic hydrocarbon moiety which can provide several potential benefits, depending on the specific combination employed, including: (a) strength aids that soften; (b) softeners that do not reduce strength; (c) wet strength with improved wet/dry strength ratio; (d) debonders with reduced linting and sloughing; (e) strength aids with controlled absorbency; and (g) retention aids that soften.
As used herein, “aliphatic hydrocarbon moieties” are functional groups derived from a broad group of organic compounds, including alkanes, alkenes, alkynes and cyclic aliphatic classifications. The aliphatic hydrocarbon moieties can be linear or branched, saturated or unsaturated, substituted or non-substituted.
The synthetic polymers as described herein, have a portion of their structure derived from the polymerization of ethylenically unsaturated compounds which contain pendant groups that can form hydrogen bonds, ionic bonds or covalent bonds with cellulose molecules in fibers, thereby increasing interfiber bonding. They include polyacrylamide, polyvinyl alcohol, polyacrylic acid, polymaleic anhydride, polymaleic acid, polyitaconic acid, cationic polyacrylamides, anionic polyacrylamides, and the like. The synthetic polymers as described herein may be water soluble, organic soluble or soluble in mixtures of water water miscible organic compounds. Preferably they are water-soluble or water dispersible but this is not a necessity of the invention. Also included within the definition are the salts of the above mentioned acidic polymers. Substances which can be combined with the acidic portion of the polymers to make the salts include the alkali metals such as K and Na usually added in form of their hydroxides, the aliphatic amines and alkanol amines, such salts and methods of preparing such salts being well known to those skilled in the art.
Depending upon the chemical and the desired impact on the paper sheet, the synthetic polymers of this invention may be applied to the paper web by any of the means known to those skilled in the art. Such means include wet end addition, spray addition on the wet web, as a creping chemical sprayed on the Yankee dryer, or as a post treatment addition, including spraying, printing or coating.
Hence in one aspect, the invention resides in a synthetic polymer having hydrogen bonding capability and containing one or more aliphatic hydrocarbon moieties, said synthetic polymer having the following structure:
where:
a, b>0;
c,d≧0 such that c+d>0;
w≧1;
Q
1
=a monomer unit or a block or graft copolymer containing a pendant group capable of forming hydrogen or covalent bonds with cellulose. Preferred pendant groups for hydrogen bonding are —CONH
2
, —COOH, —COO
−
M
+
, —OH and mixtures of said groups. Preferred pendant groups for covalent bonding are aldehydes and anhydrides. M
+
can be any suitable counter ion including Na
+
, K
+
, Ca
+2
and the like.
Q
2
=a monomer unit or a block or graft copolymer containing a C
8
or higher linear or branched, saturated or unsaturated, substituted or unsubstituted aliphatic hydrocarbon moiety. Q
2
may take the form of —Z
1
—Q
2
—Z
1
′— where Z
1
, Z
1
′ are any bridging radicals, the same or different, whose purpose is to provide incorporation into the polymer backbone and Q
2
is as defined previously;
Q
3
=a monomer unit or a block or graft copolymer containing a charge functionality. Such charge functionality is preferably cationic but may be anionic or amphoteric; and
Q
4
=a monomer unit or a block or graft copolymer containing a hydrophilic moiety, which is desirable for making the material into a form suitable for papermaking. Q
4
may take the form of —Z
2
—Q
4
—Z
2
′— where Z
2
, Z
2
′ are any bridging radicals, the same or different, whose purpose is to provide incorporation into the polymer backbone and Q
4
is as defined previously. Q
4
may be incorporated to offset the increased polymer hydrophobicity caused by introduction of the aliphatic hydrocarbon moieties. Examples of suitable Q
4
moieties are (but not limited to) the aliphatic polyether derivatives of the formula —[(CR
1
R
2
)
x
O]
y
—R
3
, wherein R
1
, R
2
is H or CH
3
, x≧2, y≧1 and R
3
is any suitable terminal group including —CH
3
, —H, —C
2
H
5
, —NH
2
.
It should be appreciated that when the Q
3
or other charged moiety is present in the synthetic polymer, that a suitable counterion will be necessary. Such counterions may or may not be represented in the formulas. Where such counterions are not represented in the formula it should be understood that such an ion will exist. The specific counterion is not critical for the invention, such counterion is only necessary for providing charge balance. For cationically charged groups the most common anions are those of the halides and alkyl sulfates. For anionically charged groups on the polymer the most common counter ions will be those of the alkali and alkaline earth metals as well as ammonia and amine derivatives.
More specifically, the invention resides in a synthetic polymer having the following structure:
where:
w≧
Clarahan Daniel Arthur
Goulet Mike Thomas
Schroeder Wen Zyo
Shannon Thomas Gerard
Croft Gregory E.
Kimberly--Clark Worldwide, Inc.
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