Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2001-09-06
2003-07-15
Griffin, Steven P. (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S158000, C162S164600, C162S168200, C162S175000
Reexamination Certificate
active
06592718
ABSTRACT:
TECHNICAL FIELD
This invention concerns a method of improving retention and drainage in papermaking processes using a diallyl-N,N-disubstituted ammonium halide/acrylamide copolymer in combination with a cationic, structurally-modified polymer.
BACKGROUND OF THE INVENTION
International Patent Application No. US01/10867, published Jan. 10, 2002, describes the preparation of structurally-modified cationic polymers and their use as retention and drainage aids in papermaking processes.
The use of medium molecular weight diallyldimethylammonium chloride/acrylamide copolymers as retention and drainage aids is reviewed in Hunter et al., “
TAPPI
99
Preparing for the Next Millennium
”, vol. 3, pp. 1345-1352, TAPPI Press (1999).
U.S. Pat. No. 6,071,379 discloses the use of diallyl-N,N-disubstituted ammonium halide/acrylamide dispersion polymers as retention and drainage aids in papermaking processes.
U.S. Pat. No. 5,254,221 discloses a method of increasing retention and drainage in a papermaking process using a low to medium molecular weight diallyldimethylammonium chloride/acrylamide copolymer in combination with a high molecular weight dialkylaminoalkyl (meth)acrylate quaternary ammonium salt/acrylamide copolymer.
Nonetheless, there is a continuing need for new compositions and processes to further improve retention and drainage performance, particularly for use on the faster and bigger modern papermaking machines currently being put into use.
We have discovered that using a diallyl-N,N-disubstituted ammonium halide/acrylamide copolymer in combination with a cationic, structurally-modified polymer outperforms the dual cationic coagulant/flocculant systems such as EPI:DMA/cationic polymer that are typically used for improving retention and drainage in papermaking processes. Moreover, there is an unexpected synergistic effect with the diallyl-N,N-disubstituted ammonium halide/acrylamide copolymer—cationic, structurally-modified polymer combination of this invention that is not seen when a typical unmodified cationic flocculant of similar charge is used.
Accordingly, this invention is directed to a method of increasing retention and drainage in a papermaking furnish comprising adding to the furnish an effective amount of a diallyl-N,N-disubstituted ammonium halide/acrylamide copolymer and an effective amount of a cationic structurally-modified water soluble polymer, wherein the cationic structurally-modified water-soluble polymer is prepared by initiating polymerization of an aqueous solution of from about 95 to about 5 mole percent of an acrylamide monomer of formula
wherein R
7
, R
8
and R
9
are independently selected from H and alkyl and from about 5 to about 95 mole percent of a cationic monomer of formula
wherein A
1
is O or NH; B
1
is C
2
-C
4
alkylene or hydroxypropylene; R
1
is H or CH
3
, R
2
and R
4
are independently C
1
-C
2
alkyl; R
3
is H, C
1
-C
2
alkyl or arylalkyl; and X
1
is an anionic counterion under free radical polymerization conditions to form a polymer solution and adding at least one structural modifier to the polymer solution after at least 30% polymerization of the monomers has occurred.
DETAILED DESCRIPTION OF THE INVENTION
Definitions of Terms
As used herein, the following abbreviations and terms shall have the following meanings.
“AcAm” for acrylamide.
“DADMAC” for diallyldimethylammonium chloride.
“DMAEA.MCQ” for dimethylaminoethyl acrylate, methyl chloride quaternary salt.
“EDTA.4Na
+
” for ethylenediaminetetraacetic acid, tetrasodium salt.
“Alfonic® 1412-60” for ethoxylated linear alcohol (60% ethylene oxide) available from Vista Chemical Co., Houston, Tex.
“Span 80” for sorbitan monooleate available from ICI Specialty Chemicals, Wilmington, Del.
“Triton® N-101” for nonylphenoxy polyethoxy ethanol, available from Rohm and Haas Co., Philadelphia, Pa.
“Tween 61” for POE (4) sorbitan monostearate, available from ICI Specialty Chemicals, Wilmington, Del.
“AIBN” for 2,2′-azobis(isobutyronitrile), available from E.I. du Pont de Nemours & Co. Inc.; Wilmington, Del.
“AIVN” for 2,2′-azobis(2,4-dimethylvaleronitrile), available from E.I. du Pont de Nemours & Co. Inc.; Wilmington, Del.
“POE” for polyoxyethylene.
“RSV” stands for reduced specific viscosity. Within a series of polymer homologs which are substantially linear and well solvated, “reduced specific viscosity (RSV)” measurements for dilute polymer solutions are an indication of polymer chain length and average molecular weight according to Paul J. Flory, in “
Principles of Polymer Chemistry
”, Cornell University Press, Ithaca, N.Y., ©1953, Chapter VII, “
Determination of Molecular Weights
”, pp. 266-316. The RSV is measured at a given polymer concentration and temperature and calculated as follows:
RSV
=
[
(
η
/
η
0
)
-
1
]
c
&eegr;=viscosity of polymer solution
&eegr;
o
=viscosity of solvent at the same temperature
c=concentration of polymer in solution.
The units of concentration “c” are (grams/100 ml or g/deciliter). Therefore, the units of RSV are dl/g. In this patent application, a 1.0 molar sodium nitrate solution is used for measuring RSV, unless specified. The polymer concentration in this solvent is 0.045 g/dl. The RSV is measured at 30° C. The viscosities &eegr; and &eegr;
o
are measured using a Cannon Ubbelohde semimicro dilution viscometer, size 75. The viscometer is mounted in a perfectly vertical position in a constant temperature bath adjusted to 30±0.02° C. The error inherent in the calculation of RSV is about 2 dl/g. When two polymer homologs within a series have similar RSV's that is an indication that they have similar molecular weights.
“IV” stands for intrinsic viscosity, which is RSV extrapolated to the limit of infinite dilution, infinite dilution being when the concentration of polymer is equal to zero.
“Based on formula” means the amount of reagent added based on the total formula weight.
“Based on polymer active” and “based on monomer” mean the amount of a reagent added based on the level of vinylic monomer in the formula, or the level of polymer formed after polymerization, assuming 100% conversion.
“Papermaking process” means a method of making paper products from pulp comprising forming an aqueous cellulosic papermaking furnish, draining the furnish to form a sheet and drying the sheet. The steps of forming the papermaking furnish, draining and drying may be carried out in any conventional manner generally known to those skilled in the art. Conventional microparticles, alum, cationic starch or a combination thereof may be utilized as adjuncts with the dual polymer treatment of this invention, though it must be emphasized that no adjunct is required for effective retention and drainage activity.
“Structurally modified cationic polymer” means a high molecular weight water-soluble polymer prepared by initiating polymerization of a solution of (meth)acrylamide and one or more cationic monomers under free radical polymerization conditions to form a polymer solution and adding at least one structural modifier to the polymer solution after at least 30% polymerization of the monomers has occurred. The structurally modified cationic polymer may be an emulsion polymer, dispersion polymer, solution polymer or gel polymer. The structurally modified cationic polymer preferably has a RSV of from about 12 to about 40, more preferably from about 15 to about 35 and still more preferably from about 20 to about 30 dl/g and preferably comprises from about 5 to about 30, more preferably from about 7 to about 25 and still more preferably from about 9 to about 18 mole percent cationic monomer. A preferred structurally modified cationic polymer is dimethylaminoethylacrylate methyl chloride quaternary salt/acrylamide copolymer.
“Acrylamide monomer” means a monomer of formula
wherein R
7
, R
8
and R
9
are independently selected from H and alkyl. Preferred acrylamide monomers are acrylamide and methacrylamide. Acrylamide is more preferred.
“Cationic monomer” means a monomer of formula
wherein A
1
is O or NH; B
1
is C
2
-C
4
Chen Jiwei
Gray Ross T.
Shing Jane B. Wong
Zelenev Andrei S.
Breininger Thomas M.
Griffin Steven P.
Halpern M.
Martin Michael B.
Ondeo Nalco Company
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