U.S. patent application number 12/104791 was filed with the patent office on 2008-10-23 for acidified polyamidoamine adhesives, method of manufacture, and use for creping and ply bond applications.
Invention is credited to Clayton J. Campbell.
Application Number | 20080257507 12/104791 |
Document ID | / |
Family ID | 39671906 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257507 |
Kind Code |
A1 |
Campbell; Clayton J. |
October 23, 2008 |
ACIDIFIED POLYAMIDOAMINE ADHESIVES, METHOD OF MANUFACTURE, AND USE
FOR CREPING AND PLY BOND APPLICATIONS
Abstract
A paper adhesive composition includes a cationic non-crosslinked
acidified solution of a polyamidoamine with the repeating units
##STR00001## wherein n.gtoreq.1; m=1 or 2; X.sup.-m is chloride,
bromide, iodide, sulfate, bisulfate, nitrate, oxalate, alkyl
carboxylate, aryl carboxylate, hydrogen phosphate, dihydrogen
phosphate, alkyl sulfonate, aryl sulfonate, or a combination
comprising at least one of the foregoing anions; R.sup.1 is a
divalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms; R.sup.2 is hydrogen or a monovalent
aliphatic, cycloaliphatic, or araliphatic group having from 1 to 24
carbon atoms; and R.sup.3 is a divalent hydrocarbon radical derived
from a dibasic carboxylic acid.
Inventors: |
Campbell; Clayton J.;
(Downingtown, PA) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Family ID: |
39671906 |
Appl. No.: |
12/104791 |
Filed: |
April 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60912225 |
Apr 17, 2007 |
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Current U.S.
Class: |
162/111 ;
162/124; 524/416; 524/606; 525/408; 525/58; 528/332 |
Current CPC
Class: |
C08G 73/0286 20130101;
D21H 27/32 20130101; C08G 73/02 20130101; D21H 27/002 20130101;
B31F 1/12 20130101; C09J 179/02 20130101; D21H 17/36 20130101; D21H
17/55 20130101 |
Class at
Publication: |
162/111 ;
162/124; 528/332; 525/408; 524/416; 524/606; 525/58 |
International
Class: |
B31F 1/12 20060101
B31F001/12; D21H 17/33 20060101 D21H017/33; C08G 59/50 20060101
C08G059/50; C08L 71/03 20060101 C08L071/03 |
Claims
1. An adhesive composition for paper manufacturing and use of the
adhesive composition for paper manufacturing, the adhesive
composition comprising an aqueous solution comprising a cationic
non-crosslinked polyamidoamine having repeating units of the
structure ##STR00007## wherein n.gtoreq.1; m=1 or 2; X.sup.-m is
chloride, bromide, iodide, sulfate, bisulfate, nitrate, oxalate,
alkyl carboxylate, aryl carboxylate, hydrogen phosphate, dihydrogen
phosphate, alkyl sulfonate, aryl sulfonate, or a combination
comprising at least one of the foregoing anions; R.sup.1 is a
divalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms; R.sup.2 is hydrogen or a monovalent
aliphatic, cycloaliphatic, or araliphatic group having from 1 to 24
carbon atoms; and R.sup.2 is a divalent hydrocarbon radical derived
from a dibasic carboxylic acid having from 1 to 24 carbon
atoms.
2. The adhesive solution of claim 1, having a pH of 1 to 6.9.
3. The adhesive of claim 1, having a weight average molecular
weight from 2 thousand to 1 million Daltons.
4. The adhesive of claim 1, wherein n=1, X.sup.-m is bisulfate,
R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3 is
butylene.
5. The adhesive of claim 1, further comprising a multivalent metal
ion.
6. The adhesive of claim 5, wherein the multivalent metal ion is
aluminum, calcium, strontium, barium, titanium, chromium,
manganese, iron, cobalt, nickel, zinc, molybdenum, tin, antimony,
niobium, vanadium, tungsten, hafnium, zirconium, or a combination
comprising at least one of the foregoing metal ions.
7. The adhesive of claim 6 wherein the multivalent metal ion is
zirconium.
8. The adhesive of claim 5, wherein n=1, X.sup.-m is bisulfate,
R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3 is
butylene.
9. The adhesive of claim 1, further comprising a crosslinked
epi-polyamide.
10. The adhesive of claim 9, wherein n=1, X.sup.-m is bisulfate,
R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3 is
butylene.
11. The adhesive of claim 9, wherein the epi-polyamide is the
product formed by the reaction of an epihalohydrin with a
condensation polymerization product of diethylenetriamine and
adipic acid.
12. The adhesive of claim 11 wherein the epihalohydrin is
epichlorohydrin.
13. The adhesive of claim 9 wherein the weight ratio of cationic
non-crosslinked polyamidoamine to crosslinked epi-polyamide is 1:99
to 99:1.
14. The adhesive of claim 9 wherein a mole ratio of epichlorohydrin
to secondary amine groups is from 0.05:1.0 to 2:1.
15. The adhesive of claim 1, further comprising monoammonium
phosphate.
16. The adhesive of claim 1, further comprising a crepe release
agent.
17. The adhesive of claim 1, further comprising a plasticizer.
18. The adhesive of claim 1, further comprising a polyvinyl
alcohol.
19. A method of creping paper, comprising: applying to a rotating
cylinder a polymer solution comprising 0.1 to 10 wt % cationic
non-crosslinked polyamidoamine in water, wherein the pH of the
polymer prior to dilution is less than 6.9, pressing the tissue
paper web against the creping cylinder to effect adhesion of the
tissue paper web to the surface of the cylinder; and dislodging the
tissue paper web from the creping cylinder by contact with a doctor
blade.
20. The method of claim 19, wherein the cationic non-crosslinked
polyamidoamine has the linear repeating units ##STR00008## wherein
n.gtoreq.1; m=1 or 2; X.sup.-m is chloride, bromide, iodide,
sulfate, bisulfate, nitrate, oxalate, alkyl carboxylate, aryl
carboxylate, hydrogen phosphate, dihydrogen phosphate, alkyl
sulfonate, aryl sulfonate, or a combination comprising at least one
of the foregoing anions; R.sup.1 is a divalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 24 carbon
atoms; R.sup.2 is hydrogen or a monovalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 24 carbon
atoms; and R.sup.3 is a divalent hydrocarbon radical derived from a
dibasic carboxylic acid.
21. The method of claim 20 wherein n=1, X.sup.-m is bisulfate,
R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3 is
butylene.
22. The method of claim 19, wherein the polymer solution further
comprises a multivalent metal ion.
23. The method of claim 22 wherein the multivalent metal ion is
aluminum, calcium, strontium, barium, titanium, chromium,
manganese, iron, cobalt, nickel, zinc, molybdenum, tin, antimony,
niobium, vanadium, tungsten, hafnium, zirconium, or a combination
comprising at least one of the foregoing.
24. The method of claim 23 wherein the multivalent metal ion is
zirconium.
25. The method of claim 19, wherein the polymer solution further
comprises a crosslinked epi-polyamide.
26. The method of claim 25 wherein n=1, X.sup.-m is bisulfate,
R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3 is
butylene.
27. The method of claim 25 wherein the epi-polyamide is the product
formed by the reaction of an epihalohydrin with a condensation
polymerization product of diethylenetriamine and adipic acid.
28. The method of claim 27 wherein the epihalohydrin is
epichlorohydrin.
29. A creped tissue produced by the process of: applying to a
rotating cylinder a polymer solution comprising 0.1 to 10 wt %
cationic non-crosslinked polyamidoamine in water, wherein the pH of
the polymer prior to dilution is less than 6.9, pressing the tissue
paper web against the creping cylinder to effect adhesion of the
tissue paper web to the surface of the cylinder; and dislodging the
tissue paper web from the creping cylinder by contact with a doctor
blade.
30. The creped tissue of claim 29, wherein the cationic
non-crosslinked polyamidoamine has the linear repeating units
##STR00009## wherein n.gtoreq.1; m=1 or 2; X.sup.-m is chloride,
bromide, iodide, sulfate, bisulfate, nitrate, oxalate, alkyl
carboxylate, aryl carboxylate, hydrogen phosphate, dihydrogen
phosphate, alkyl sulfonate, aryl sulfonate, or a combination
comprising at least one of the foregoing anions; R.sup.1 is a
divalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms; R.sup.2 is hydrogen or a monovalent
aliphatic, cycloaliphatic, or araliphatic group having from 1 to 24
carbon atoms; and R.sup.3 is a divalent hydrocarbon radical derived
from a dibasic carboxylic acid.
31. The creped tissue of claim 30 wherein n=1, X.sup.-m is
bisulfate, R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3 is
butylene.
32. The creped tissue of claim 29, further comprising a multivalent
metal ion.
33. The creped tissue of claim 32 wherein the multivalent metal ion
is aluminum, calcium, strontium, barium, titanium, chromium,
manganese, iron, cobalt, nickel, zinc, molybdenum, tin, antimony,
niobium, vanadium, tungsten, hafnium, zirconium, or a combination
comprising at least one of the foregoing.
34. The creped tissue of claim 33 wherein the multivalent metal ion
is zirconium.
35. The creped tissue of claim 29, wherein the polymer solution
further comprises a crosslinked epi-polyamide.
36. The creped tissue of claim 35 wherein the epi-polyamide is the
product formed by the reaction of an epihalohydrin with a
condensation polymerization product of diethylenetriamine and
adipic acid.
37. The creped tissue of claim 36 wherein the epihalohydrin is
epichlorohydrin.
38. A multi-ply tissue product comprising at least two plies,
wherein the plies are bonded by an aqueous polymer solution
comprising: a cationic non-crosslinked polyamidoamine with the
linear repeating units ##STR00010## wherein n.gtoreq.1; m=1 or 2;
X.sup.-m is chloride, bromide, iodide, sulfate, bisulfate, nitrate,
oxalate, alkyl carboxylate, aryl carboxylate, hydrogen phosphate,
dihydrogen phosphate, alkyl sulfonate, aryl sulfonate, or a
combination comprising at least one of the foregoing anions;
R.sup.1 is a divalent aliphatic, cycloaliphatic, or araliphatic
group having from 1 to 24 carbon atoms; R.sup.2 is hydrogen or a
monovalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms; and R.sup.3 is a divalent hydrocarbon
radical derived from a dibasic carboxylic acid.
39. The multi-ply tissue product of claim 38 further comprising a
multivalent metal ion.
40. The multi-ply tissue product of claim 39 wherein the
multivalent metal ion is aluminum, calcium, strontium, barium,
titanium, chromium, manganese, iron, cobalt, nickel, zinc,
molybdenum, tin, antimony, niobium, vanadium, tungsten, hafnium,
zirconium, or a combination comprising at least one of the
foregoing.
41. The multi-ply tissue product of claim 40 wherein the
multivalent metal ion is zirconium.
42. The multi-ply tissue product of claim 38 wherein n=1, X.sup.-m
is bisulfate, R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3
is butylene.
43. The multi-ply tissue product of claim 38, further comprising a
crosslinked epi-polyamide.
44. The multi-ply tissue product of claim 43 wherein n=1, X.sup.-m
is bisulfate, R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3
is butylene.
45. The multi-ply tissue product of claim 43, wherein the
epi-polyamide is the product formed by the reaction of an
epihalohydrin with a condensation polymerization product of
diethylenetriamine and adipic acid.
46. The multi-ply tissue product of claim 45 wherein the
epihalohydrin is epichlorohydrin.
47. The multi-ply tissue product of claim 43 wherein the weight
ratio of cationic non-crosslinked polyamidoamine to crosslinked
epi-polyamide is 1:99 to 99:1.
48. A composition, comprising the acidified, aqueous reaction
product of an aqueous solution comprising a dicarboxylic acid of
the formula HO.sub.2C--R.sup.3--CO.sub.2H wherein R.sup.3 is a
divalent hydrocarbon radical having from 1 to 24 carbon atoms; and
a polyamine of the formula ##STR00011## wherein n is 1 to 4;
R.sup.1 is a divalent aliphatic, cycloaliphatic, or araliphatic
group having from 1 to 24 carbon atoms, and R.sup.2 is hydrogen or
a monovalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms.
49. An adhesive composition, comprising the acidified, aqueous
reaction product of an aqueous solution comprising a dicarboxylic
acid of the formula HO.sub.2C--R.sup.3--CO.sub.2H wherein R.sup.3
is a divalent hydrocarbon radical having from 1 to 24 carbon atoms;
and a polyamine of the formula ##STR00012## wherein n is 1 to 4;
R.sup.1 is a divalent aliphatic, cycloaliphatic, or araliphatic
group having from 1 to 24 carbon atoms, and R.sup.2 is hydrogen or
a monovalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms.
50. The composition of claim 49, having a pH of 1 to 6.9.
51. The composition of claim 49, wherein the reaction product is
acidified with a mineral acid or an organic acid.
52. The composition of claim 49, having a weight average molecular
weight from 2 thousand to 1 million Daltons.
53. The composition of claim 49, wherein the dicarboxylic acid is
oxalic, L malonic, succinic, glutaric, adipic, pimelic, suberic,
azelaic, sebacic, maleic, fumaric, itaconic, phthalic, isophthalic,
terephthalic, or a combination comprising at least one of the
foregoing acids.
54. The composition of claim 49, wherein n=1, R.sup.2 is ethylene,
R.sup.2 is hydrogen, and R.sup.3 is butylene.
55. The composition of claim 49, wherein the adhesive composition
further comprises monoammonium phosphate, a crepe release agent,
polyvinyl alcohol, and/or a plasticizer.
56. A cationic polyamidoamine having repeating units of the
structure ##STR00013## wherein n.gtoreq.1; m=1 or 2; X.sup.-m is
chloride, bromide, iodide, sulfate, bisulfate, nitrate, oxalate,
alkyl carboxylate, aryl carboxylate, hydrogen phosphate, dihydrogen
phosphate, alkyl sulfonate, aryl sulfonate, or a combination
comprising at least one of the foregoing anions; R.sup.1 is a
divalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms; R.sup.2 is hydrogen or a monovalent
aliphatic, cycloaliphatic, or araliphatic group having from 1 to 24
carbon atoms; and R.sup.3 is a divalent hydrocarbon radical derived
from a dibasic carboxylic acid having from 1 to 24 carbon
atoms.
57. The polyamidoamine of claim 56 wherein n=1, X-m is bisulfate,
R.sup.1 is ethylene, R.sup.2 is hydrogen, and R.sup.3 is
butylene.
58. An adhesive composition and use of an adhesive composition for
paper manufacturing, comprising a cationic polyamidoamine of the
formula P-1, P-2, P-3, or P-4: ##STR00014##
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims the benefit of U.S.
Provisional Patent Application Ser. No. 60/912,225 filed Apr. 17,
2007, the contents of which are hereby incorporated by reference in
their entirety.
BACKGROUND
[0002] This disclosure relates to acidified polyamidoamine adhesive
compositions, methods for their manufacture, and their use in
creping and ply bonding applications.
[0003] In the manufacture of certain wet-laid paper products, such
as facial tissue, bathroom tissue, napkins, or paper towels, the
web is conventionally subjected to a creping process in order to
give it desirable textural characteristics, such as softness
stretch and bulk. The creping process involves adhering the web to
a rotating creping cylinder, such as a Yankee dryer, and then
dislodging the adhered web with a doctor blade. The impact of the
web against the doctor blade ruptures some of the fiber-to-fiber
bonds within the web and causes the web to wrinkle or pucker
causing a formation of microfolds "crepe bars".
[0004] The severity of this creping action is dependent upon a
number of factors, including the degree of adhesion between the web
and the surface of the creping cylinder. Greater adhesion increases
softness, although generally with some loss of strength. In order
to increase adhesion, an adhesive creping aid is used to enhance
any naturally occurring adhesion that the web may have due to its
water-content. Water content can vary widely, depending on the
extent to which the web has been previously dried. Adhesive creping
aids prevent wear of the dryer surface, provide lubrication between
the doctor blade and the dryer surfaces, reduce chemical corrosion,
and control the extent of creping. The creping process can be wet
or dry.
[0005] In either the wet or dry crepe manufacturing process, crepe
adhesives can be either "soft" or "hard" polymers. Soft polymers
are typically non-crosslinked polymers. Two known soft polymer
adhesives are polyamines and polyvinyl alcohol (PVOH). Examples
include BBD 2071, a polyamine commercially available from Buckman
Laboratories International, Inc., and Airvol.RTM., a polyvinyl
alcohol sold by Air Products and Chemicals, Inc. Both materials are
non-crosslinked and provide high adhesion, and are considered
highly moisture sensitive. These are used to fabricate low sheet
moisture grade tissues such as bath tissue on TAD (Thru Air Dryer)
processes. Premium quality bath and facial tissue (<4.0% sheet
moisture) are fabricated on dry crepe processes. Disadvantages of
these adhesives are that they dissolve easily (slight to no
insolubility); they tend to associate with the sheet and the
moisture in the sheet because they are not crosslinked; they have
an uneven dryer coating profile; they have fair to poor Yankee
dryer and blade protection (low add-on due to high adhesion); and
some are corrosive, including PVOH.
[0006] Hard polymers are typically crosslinked. The level of
crosslinking in commercial hard creping adhesive products ranges
from slight to high. Useful hard creping aids include
epi-polyamides, which are thermoset resins (i.e. polymers that lose
solubility and fusibility upon crosslinking). They provide an
adhesive coating durable enough to withstand the mechanical forces
at the doctor blade under conditions of heat and/or moisture.
Epi-polyamides are derived from the crosslinking of polyamidoamines
with epihalohydrins. Polyamidoamines themselves are condensation
polymerization products formed by the reaction of a dicarboxylic
acid and a polyamine having at least two primary amines and either
a secondary or tertiary L amine. Polyamidoamines are manufactured
in an alkaline environment (pH 8.0-10.0). The pH is typically
reduced to 3.0-5.0 prior to or after the addition of the
epihalohydrin. Maintaining a low pH slows the crosslinking reaction
and maintains product viscosity. As the pH is increased the product
crosslinks, viscosity significantly increases and the product can
become unstable, resulting in gellation.
[0007] While suitable for their intended purposes, crosslinked
adhesives also have certain disadvantages. They tend to build up on
the dryer surface, which pushes the blade back and causes sheet
picking. They are ineffective on virgin fiber grades (low sheet
moisture) that require high adhesion and better rewet. They also
accumulate on dryer edges (the hottest section of the dryer),
causing uneven profile and/or sheet breaks. The harder the base
coating, the more that can build up and increase the z-directional
coating thickness. Ideally, a balanced equilibrium should be
established that the crepe chemical add-on, sheet fines and filler
that come from the sheet equals the amount of coating that is
scraped and washed off the dryer surface.
[0008] With very high coating hardness (typically on the dryer
surface edges where the dryer surface temperatures is the highest),
a bevel blade (5, 10 or 15.degree. angle) at increased blade holder
pressure is more effective in scraping off the buildup. The use of
a bevel blade on bath tissue grades, however, can also have
negative effects (such as lower bulk, bare spots on the dryer and
excessive blade and dryer wear. Changing the bevel angle and
increasing pressure can result in low sheet bulk, requiring lower
sheet moisture of 3.0 to 3.5% (much lower then desired) in order to
recover some bulk. Lower sheet moisture can require higher Yankee
steam (higher dryer surface temperature) exacerbating the problem
by further hardening the adhesive.
[0009] Some tissue machines utilize a separate cleaning blade
located after the doctor blade and before the crepe spray boom
system. The cleaning blade is typically set at a pressure from 69
to 276 megapascals (MPa) (10 to 40 pounds per square inch (psi))
and designed to remove the excess coating buildup peaks, providing
improved overall surface coating profile.
[0010] Limitations also arise in connection with use of the Yankee
dryer crepe spray boom configuration. First, the newly applied
crepe adhesive starts crosslinking and setting on the Yankee dryer
surface shortly after emerging from the spray boom. The setting
rate of the adhesive depends on the dryer type, temperature, speed,
sheet moisture, and pH. Sometimes, debunizers (steam box prior to
the vacuum pressure roll) or infrared heater are used for
additional sheet drying and can affect the coating drying rate. In
most processes, there is no available space to move the spray boom
closer to the blade holder to improve the adhesive's setting time.
If an insufficient coating base is present, an adhesive that has a
higher degree of crosslinking is used.
[0011] Second, the spray boom dilution water rewets the existing
coating base that remained on the dryer. As the coating base swells
and softens, the adhesive is retackified, allowing the sheet to
properly transfer from the vacuum pressure roll to the dryer
surface. There are occasions when a heavily crosslinked adhesive
can not be sufficiently rewetted and softened and the Z directional
coating thickness builds up causing operational problems.
[0012] Other drawbacks are associated with water-soluble,
thermosetting cationic epi-polyamide resins. The physical
properties of these resins, such as insolubility, rewet, adhesion,
and hardness, are in large measure controlled by the degree of
cross-linking by the epihalohydrin. It is very difficult to vary
these properties for a given creping machine. Paper makers have
recognized that the different creping machines and different wood
pulps have different properties with the contemporaneous need for
changing the properties of the creping adhesive to optimize the
creping process. Paper makers have long wanted the ability to
control and change the amount of cross-linking to achieve the
precise performance characteristics desired for a given papermaking
line to optimize the creping process. With the water-soluble,
thermosetting cationic epi-polyamide resins of the prior art, that
degree of control has been difficult to achieve because the
cross-linking of the adhesive occurs during the manufacturing
process and it is impractical to have a number of water-soluble,
thermosetting cationic epi-polyamide resins with different degrees
of cross-linking in an attempt to tailor the creping adhesive to
the creping process.
[0013] Other adhesive deficiencies relate to plied tissue products.
Laminating multiple layers, or plies, of tissue, makes various
tissue products. The plies must be bonded to prevent them from
delaminating or floating apart when they are converted into the
final product or when they are used by the consumer.
[0014] Ply bond properties vary with paper grades and machine
conditions (i.e., double layer sheets using two head boxes,
multi-cylinder machines making board and napkin/towel bonding of
two or more plies). Starch and latex polymer are typically used as
ply bonding agents. Starch is unstable and typically requires
cooking and make down dilution, and exhibits sporadic performance.
Latex can have repulpability and nozzle plugging issues.
[0015] Ply bonding of the individual tissue sheets into multi-ply
layers is usually achieved by embossing them on converting
equipment without applying adhesive. In this process, two or more
tissue webs are simultaneously unwound and fed through a nip formed
between male and female embossing rolls to emboss or crimp the webs
and thereby bond them together. Often in making such products as
napkins, the webs are embossed only around the perimeter of areas
that will be cut into the individual napkins. In a different
process, tissue plies are adhered using a chemical adhesive rather
than by embossing.
[0016] Controlling ply bonding is important and difficult.
Inadequate, excessive, or inconsistent ply bonding can jam complex,
high-speed machinery, generate high waste, and provide unacceptable
product. The strength of bonding by embossing (without adhesive)
may vary depending, among other things, on water content or dryness
of tissue webs, and on ambient air humidity. While bonding by
embossing sometimes can be improved by increasing the pressure on
the embossing rolls, such pressure can wear out the embossing rolls
more quickly, particularly the female roll, which is usually a
softer roll made of composite material onto which a pattern is
impressed by the opposing, male, engraved metal roll. In addition,
the journals and bearings of both embossing rolls can also wear out
prematurely if subjected to increased pressure over a prolonged
period.
[0017] Creping adhesives overcome some of the problems of
embossing, but they also cause problems, such as "through bonding"
or "blocking", in which adjacent laminates bond to one another,
and, prevent unwinding of the laminate product from its roll.
Non-uniformity of bonding also causes problems, such as wrinkling
of the tissue and bad printing.
[0018] Another product requirement in ply bonding is wet strength,
the resistance to tearing or pulling apart while wet, which can be
critically important to high quality paper napkins. Low wet
strength napkins may pull apart when subjected to moisture, such as
spilled liquid or a wet glass, rendering them unsatisfactory for
the high quality markets. Chemicals normally employed to impart wet
strength (e.g., urea, phenol-formaldehyde) can reduce ply
bond-strength and can make the napkin stiffer.
[0019] Floating plies at the printing stage cause jams, high waste
and machine downtime. In addition, the application of the ink
causes the top layer of the tissue to expand if the plies are not
well bonded, resulting in wrinkling, badly printed napkins, and
extremely high costs from waste.
[0020] Commonly used ply bonding adhesives are aqueous mixtures,
for example, carboxymethyl cellulose, polyvinyl alcohol, or starch.
The spraying process control described above enables the use of
higher (for example at least 13%) solids in the liquid adhesive,
which in turn results in shorter drying times. After the adhesive
is applied, the webs may be forced together by a pair of rolls
(e.g. calendar rolls) that are in contact as the two webs pass
through.
[0021] While a number of creping and ply bonding adhesives have
been disclosed and are suitable for their intended uses, no single
adhesive or adhesive blend has provided a satisfactory combination
of adhesive performance characteristics (i.e. insolubility, rewet,
adhesion and hardness) on different creping machines. Thus, a
continuing need exists for creping and ply bonding adhesives that
overcome the above deficiencies and limitations.
BRIEF DESCRIPTION
[0022] It has been discovered by the inventor hereof that acidified
polyamidoamines in various embodiments are excellent creping and
ply bond adhesives, used alone or in combination with
epi-polyamides or when crosslinked with multivalent metal ions.
Compositions are easily optimized for a range of adhesive
properties.
[0023] In one embodiment, an adhesive for use in paper
manufacturing comprises a cationic, non-crosslinked polyamidoamine
having the linear repeating units
##STR00002##
wherein n.gtoreq.1; m=1 or 2; X.sup.-m is chloride, bromide,
iodide, sulfate, bisulfate, nitrate, oxalate, alkyl carboxylate,
aryl carboxylate, hydrogen phosphate, dihydrogen phosphate, alkyl
sulfonate, aryl sulfonate, or a combination comprising at least one
of the foregoing anions; R.sup.1 is a divalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 24 carbon
atoms; R.sup.2 is hydrogen or a monovalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 24 carbon
atoms; and R.sup.3 is a divalent C.sub.2-12 hydrocarbon radical
derived from a dibasic carboxylic acid.
[0024] In another embodiment a method of creping paper comprises
applying to a rotating cylinder a polymer solution comprising 0.1
to 10 wt % of the above-described cationic non-crosslinked
polyamidoamine in water, wherein the pH of the polymer solution is
less than 6.9 prior to dilution; pressing the tissue paper web
against the creping cylinder to effect adhesion of the tissue paper
web to the surface of the cylinder; and dislodging the tissue paper
web from the creping cylinder by contact with a doctor blade.
[0025] Another embodiment is a creped tissue produced by the
process of applying to a rotating cylinder a polymer solution
comprising 0.1 to 10 wt % of the above-described cationic
non-crosslinked polyamidoamine in water, wherein the pH of the
polymer solution prior to dilution is less than 6.9; pressing the
tissue paper web against the creping cylinder to effect adhesion of
the tissue paper web to the surface of the cylinder; and dislodging
the tissue paper web from the creping cylinder by contact with a
doctor blade.
[0026] In another embodiment, a multi-ply product comprises at
least two plies, wherein the plies are bonded by an aqueous polymer
solution comprising a cationic non-crosslinked polyamidoamine with
the linear repeating units
##STR00003##
wherein n.gtoreq.1; m=1 or 2; X.sup.-m is chloride, bromide,
iodide, sulfate, bisulfate, nitrate, oxalate, alkyl carboxylate,
aryl carboxylate, hydrogen phosphate, dihydrogen phosphate, alkyl
sulfonate, aryl sulfonate, or a combination comprising at least one
of the foregoing anions; R.sup.1 is a divalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 24 carbon
atoms; R.sup.2 is hydrogen or a monovalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 24 carbon
atoms; and R.sup.3 is a divalent hydrocarbon radical derived from a
dibasic carboxylic acid. The product can be, for example, a napkin
or a corrugated media.
[0027] The above described and other features are exemplified by
the following FIGURE and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a schematic of a Yankee dryer system.
DETAILED DESCRIPTION
[0029] Disclosed herein are acidic aqueous polyamidoamine
composition adhesive compositions, their method of manufacture, and
methods of use related to paper tissue manufacturing. The
compositions provide superior performance characteristics as
creping adhesives and ply bonding agents.
[0030] In the first embodiment the adhesive comprises an acidified,
cationic non-crosslinked polyamidoamine comprising repeating
backbone units of the general structure GS-1.
##STR00004##
In formula GS-1, n is greater than or equal to 1. Specifically n
has an average value of 1 to 4. Further, m=1 or 2; X.sup.-m is
chloride, bromide, iodide, sulfate, bisulfate, nitrate, oxalate,
alkyl carboxylate, aryl carboxylate, hydrogen phosphate, dihydrogen
phosphate, alkyl sulfonate, aryl sulfonate, or a combination
comprising at least one of the foregoing anions; R.sup.1 is a
divalent aliphatic, cycloaliphatic, or araliphatic group having
from 1 to 24 carbon atoms; R.sup.2 is hydrogen or a monovalent
aliphatic, cycloaliphatic, or araliphatic group having from 1 to 12
carbon atoms; and R.sup.3 is a divalent hydrocarbon radical derived
from a dibasic carboxylic acid having 2 to 24 carbon atoms.
[0031] Further in formula GS-1, R.sup.1 is divalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 24 carbon
atoms. More specifically, R.sup.1 represents a C.sub.2 to C.sub.8
alkylene group; most specifically R.sup.1 is a C.sub.2-C.sub.3
alkylene group. R.sup.2 is hydrogen or a monovalent aliphatic,
cycloaliphatic, or araliphatic group having from 1 to 12 carbon
atoms. More specifically, R.sup.2 is a C.sub.2-C.sub.3 alkyl group.
Alternatively, R.sup.1 and R.sup.2 can also together form a ring
having from 4 to 12 carbon atoms.
[0032] R.sup.3 in formula GS-1 is a divalent hydrocarbon radical
derived from a dibasic carboxylic acid having 2 to 24 carbon atoms.
More specifically R.sup.3 is an ethylene, propylene, butylene,
pentylene, or hexylene group
[0033] Further in formula GS-1, X.sup.-m represents an anion having
a charge of -1 or -2. More specifically, m is 1 or 2, and X.sup.-m
is chloride, bromide, iodide, sulfate, bisulfate, nitrate, oxalate,
alkyl carboxylate, aryl carboxylate, hydrogen phosphate, dihydrogen
phosphate, alkyl sulfonate, aryl sulfonate or a combination
comprising one or more of the foregoing anions thereof; most
specifically sulfate, bisulfate, tosylate, or combinations
thereof.
[0034] The acidic aqueous polyamidoamine composition can be formed
by reacting a dibasic carboxylic acid (or chemical equivalent
thereof) with a polyamine comprising at least two primary amines
and at least one secondary or tertiary amino group, to provide an
alkaline aqueous solution of the polyamidoamine. The mole ratio of
dibasic carboxylic acid to polyamine can vary widely. In one
embodiment, the mole ratio of dicarboxylic acid to polyamine is
from about 1:0.8 to 1:2.5, specifically from 1:0.8 to 1:1.4.
[0035] Suitable dibasic carboxylic acids include, for example,
malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic,
sebacic, maleic, fumaric, itaconic, phthalic, isophthalic, or
terephthalic acids. A combination comprising different acids can be
used. Chemical equivalents of the acids include the corresponding
C.sub.1-C.sub.6 alkyl esters of the dicarboxylic acids.
[0036] Suitable polyamines include C.sub.1-C.sub.24 aliphatic,
cycloaliphatic, or araliphatic (specifically aliphatic) polyamines.
More specifically, useful polyamines include aliphatic polyamines
of low molecular weight having the general formula GS-2
##STR00005##
wherein R.sup.1, R.sup.2, and n have the same meaning as described
above for GS-1. Such polyamines are readily formed in known manners
that do not require the use of ethyleneimine as a starting
material, as for example, by the reaction of an alpha,
omega-dihaloalkane with ammonia. More specifically, GS-2 is
diethylenetriamine or triethylenetetramine.
[0037] The alkaline aqueous polyamidoamine condensation product is
then acidified with an acid to a pH of 1 to 6.9, specifically 2.5
to 6.0, and even more specifically pH 3.5 to 4.5. In another
embodiment, the pH is adjusted to less than 5.0, specifically 3.8
to 5.0, more specifically 4.0 to 4.9. 51. Suitable acids for
acidifying the alkaline polya substituted alkyl or aryl carboxylic
acids. In one embodiment, a Lewis acid can be sued, or a mineral
acid, for example phosphoric acid, hydrochloric acid, or sulfuric
acid, or an organic acid, for example acetic acid, citric acid, or
formic acid.
[0038] Exemplary non-limiting acidic polyamidoamines include the
following:
##STR00006##
[0039] The neutral analog of P-1, designated NP-1 used in a
comparative example, is an intermediate in the commercial
manufacture of epi-polyamides.
[0040] The above-described polyamidoamines are water soluble. As
used herein, the term "water soluble" refers to materials that are
soluble in water to at least 3%, by weight at 25.degree. C. The
adhesives can accordingly be used at a wide range of solids
content, for example 1 to 99 wt % solids, specifically 8 to 75 wt %
solids.
[0041] The polyamidoamines compostions can be used with additives
known in the paper making industry, for example monoammonium
phosphate, a crepe release agent, polyvinyl alcohol, and/or a
plasticizer, for example propylene glycol, diethylene glycol,
triethylene glycol, dipropylene glycol, glycerol, or a mixture
comprising at least one of the foregoing plasticizers.
[0042] The acidic aqueous polyamidoamine compostions are further
useful because the properties of the adhesive formed from them, in
particular solubility, hardness, rewet, and tack adhesion can be
readily adjusted on-site to meet the needs of the particular
process for which they are being used.
[0043] With respect to the parameters of insolubility, hardness,
rewet, and tack adhesion, it is known that direct correlation
exists between performance and the degree of crosslinking, shown in
Table 1 for three crosslinking levels of epi-polyamide.
TABLE-US-00001 TABLE 1 Crosslinked Epi-polyamide Adhesives
Properties Property Slight Moderate Heavy Insolubility Low (25-85%)
(85-94%) (>94%) Rewet** None to low Medium/high Medium/low
Hardness* Low/medium Medium High Tack adhesion Medium/high Medium
Medium/low
[0044] For example, in the case of a slightly crosslinked adhesives
the product's performance parameters are typically reflective as
medium/high adhesion, low insolubility and low hardness.
[0045] Insolubility is a measure of the amount of the dry crepe
adhesive remaining on the dryer surface after contact with a high
moisture sheet. The percent insolubility is determined by the
weight of an undissolved adhesive film divided by the initial dry
film weight.
[0046] Hardness is a measure of the ability to penetrate the
adhesive film using such test methods as pencil scratch test or a
Durometer Hardness tests. In creping operations, this is best
demonstrated as the sheet is creped at the blade. A fine layer of
the base coating remains on the dryer surface after the sheet has
left the dryer.
[0047] The term "rewet" has been used in the industry in two ways.
Herein, rewet is the ability of a dried film to reabsorb water,
swell, soften, reacquire increased adhesion and still maintain
minimum required insolubility for the desired creping sheet
moisture conditions. "Good rewet" refers to a film that repeatedly
rewets and can be redried. The rewet test determines the adhesive
film's water uptake and is defined by the weight of the wet film
over the weight of the dry film based at a specific time period.
Non-crosslinked water-soluble polymers are generally poor rewetters
because they rewet once and dissolve. They have none or poor
insolubility, being easily washed away.
[0048] Tack adhesion is the total coating adhesion strength for
maintaining the sheet to the dryer surface. There is an inverse
relationship between hardness and a film's percent insolubility and
adhesion. An increase in the adhesive's hardness reduces the
adhesion. An optimum adhesive chemistry provides for an effective
balance of hardness and adhesion. The degree in which the sheet
adheres to the dryer surface at the point of contact at the crepe
blade is largely based on the release to adhesive ratio.
[0049] Here, the properties of the acidic aqueous polyamidoamine
compositions can be adjusted by additives such as a crosslinking
agent, other known adhesives, and bonding agents. Such additives
are readily combinable by the end user of the compositions on site,
thereby obviating the need for maintaining an inventory of a
multiplicity of compositions designed for different use
conditions.
[0050] Thus, in a one embodiment, the composition comprises an
acidified aqueous polyamidoamine of formula GS-1 crosslinked using
a multivalent metal ion. The metal ion has at least a valence of 2
and specifically a valence of 3 or more. The multivalent metal ion
can also have a coordination number of at least two and
specifically a coordination number of four or greater. Suitable
multivalent metal ions are include, for example, Lewis acids such
as aluminum, calcium, strontium, barium, titanium, chromium,
manganese, iron, cobalt, nickel, zinc, molybdenum, tin, antimony,
niobium, vanadium, tungsten, hafnium, zirconium, and the like. A
combination comprising at least one of the foregoing ions can also
be used. A species comprising the metal ion can be used to acidify
the polyamidoamine, as well as crosslink the polyamidoamine.
[0051] The metal ion or combination of metal ions forms chelates
with the amine sites on the acidified polyamidoamine resin. The
particular metal ion and the concentration of metal ion are
adjusted to vary the properties of the resulting resin such as
insolubility, rewetability, crosslink density, hardness, and tack.
In general, as the concentration of metal ion increases, the
insolubility, rewetability, crosslink density, and hardness
increase, and the adhesive properties decrease. The ability to
control these physical properties allows the operator to precisely
control the desired properties of the creping adhesive or ply
bonding material. In effect, the operator can "dial in" the desired
creping properties by varying the metal ion concentration, without
resorting to known crosslinked epi-polyamide materials. In general,
a useful metal ion content is 0.1 to 5.0 wt % of the, more
specifically 1.0 to 4.0 wt %, based on the total weight of the
metal ion and the dry polymer.
[0052] In another embodiment, acidified aqueous polyamidoamine and
an epi-polyamide are blended together to provide for tunable
adhesion and insolubility properties.
[0053] A suitable epi-polyamide is a water-soluble, thermosetting,
cationic epi-polyamide formed by the reaction a polyamidoamine,
either acidic or neutral, with an epihalohydrin, for example
epichlorohydrin at a mole ratio of epihalohydrin to reactive amine
sites in the polyamidoamine from about 0.05 to 1 to about 2 to 1.
Acid is added before or after the epihalohydrin in order to
stabilize or retard the crosslinking reaction, thus preventing
irreversible gelation while in storage. The resulting solution
comprises a water-soluble, thermosetting, cationic epi-polyamide
resin. Exemplary methods for the preparation of the water-soluble,
thermosetting, cationic epi-polyamide resins is described by Keim
in U.S. Pat. No. 2,926,116, U.S. Pat. No. 3,058,873 and U.S. Pat.
No. 3,772,076.
[0054] Specific epi-polyamides useful herein are sold under the
tradenames OmniCrepe.TM. 681-A, OmniCrepe.TM. 681 AM, and
OmniCrepe.TM. 681 AX by Kemira. Other commercial suppliers of
epi-polyamide resins include Hercules Inc. of Wilmington, Del.,
Kemira of Birmingham, Ala., and Georgia-Pacific Corp. of Atlanta,
Ga. These resins are supplied as a concentrated solution in
water.
[0055] Thermosetting cationic epi-polyamides are compatible when
blended in any weight ratio with acidic aqueous compostions
comprising the polyamidoamines represented by GS-1, particularly
P-1. Percent insolubility and adhesion properties are tunable to
specific application requirements by varying the weight ratios in
the blend. Weight ratios of epi-polyamide to polyamidoamine can
vary from 99:1 up to 1:99.
[0056] The acidic polyamidoamine compostions are especially useful
in tissue paper and other paper making processes. As used herein,
the terms "tissue paper web, paper web, web, paper sheet and paper
product" all refer to sheets of paper made by a process comprising
the steps of forming an aqueous papermaking furnish, depositing
this furnish on a foraminous surface, such as a Fourdrinier wire,
and removing the water from the furnish as by gravity or
vacuum-assisted drainage, with or without pressing, and by
evaporation, comprising the final steps of adhering the sheet in a
semi-dry condition to the surface of a Yankee dryer, completing the
water removal by evaporation to an essentially dry state, removal
of the web from the Yankee dryer by means of a flexible creping
blade, and winding the resultant sheet onto a reel.
[0057] The terms "multi-layered tissue paper web, multi-layered
paper web, multi-layered web, multi-layered paper sheet and
multi-layered paper product" are all used interchangeably in the
art to refer to sheets of paper prepared from two or more layers of
aqueous paper making furnish which are preferably comprised of
different fiber types, the fibers typically being relatively long
softwood and relatively short hardwood fibers as used in tissue
paper making. The layers are preferably formed from the deposition
of separate streams of dilute fiber slurries upon one or more
endless foraminous surfaces. If the individual layers are initially
formed on separate foraminous surfaces, the layers can be
subsequently combined when wet to form a multi-layered tissue paper
web.
[0058] The term "single-ply tissue product" means that it is
comprised of one ply of creped tissue; the ply can be substantially
homogenous in nature or it can be a multi-layered tissue paper web.
As used herein, the term "multi-ply tissue product" means that it
is comprised of more than one ply of creped tissue. The plies of a
multi-ply tissue product can be substantially homogenous in nature
of they can be multi-layered tissue paper webs. It is to be
understood that although the description below refers to "tissue"
products, the compostions, methods, and procedures herein are also
applicable to other multi-ply products, for example corrugated
media.
[0059] A process for creping tissue paper using the above-described
compositions comprises: applying to a rotating creping cylinder an
aqueous solution comprising from about 90% to about 99.9% water and
from about 10% to about 0.1% adhesive solids, wherein said solids
comprise the acidified aqueous polyamidoamine; pressing a tissue
paper web against the creping cylinder to effect adhesion of the
web to the surface of the cylinder; and dislodging the web from the
creping cylinder by contact with a doctor blade.
[0060] The total amount of applied creping adhesive is from about
0.1 lb/ton to about 10 lb/ton based on the dry weight of the
creping adhesive and the dry weight of the paper web. The unit
lb/ton, as used herein, refers to the dry amount of creping
adhesive measured in lbs. relative to the dry amount of paper
measured in tons.
[0061] The tissue web can be comprised of various types of natural
and recycled fibers including wood pulps of chemical and mechanical
types. The fibers can comprise hardwood, softwood and cotton
fibers. The tissue web can also contain particulate fillers, fines,
ash, organic contaminates such as the cellophane from envelope
windows, adhesives such as PVA-styrene-butadiene and inks as well
as process chemicals used in the paper-making process such as
strength additives, softeners, surfactants and organic
polymers.
[0062] FIG. 1 illustrates the conventional steps in formation of a
tissue paper web. This conventional process includes the steps of
performing a fibrous web, applying a creping adhesive to the
surface of a Yankee dryer, applying the fibrous web to the surface
of the Yankee dryer having the creping adhesive on the external
surface thereof, removing the fibrous web from the Yankee dryer by
use of a creping blade and winding the dried fibrous web onto a
roll. Alternatively, the creping adhesive can be applied to the
surface of the fibrous web that will contact the dryer, before the
fibrous web is presented to the dryer.
[0063] Referring to FIG. 1, this represents one of a number of
possible configurations used in processing tissue products. In this
particular arrangement, the transfer and impression fabric
designated at 10 carries the formed, traveling web 12 around
turning roll 20 to the nip between press roll 14 and Yankee dryer
22. The fabric, web, and dryer move in the directions indicated by
the arrows. The entry of the web to the dryer is well around the
roll from creping blade 16 which, as schematically indicated,
crepes the traveling web from the Yankee dryer 22 as indicated at
24. The creped web 24 exiting from the dryer is wound into a soft
creped tissue roll 18. To adhere the traveling web 12 to the
surface of the Yankee dryer 22, a spray 26 of adhesive is applied
to the surface ahead of the nip between the press roll 14 and
Yankee dryer 22. Alternately, the spray may be applied to the
traveling web 12 directly as shown at 28.
[0064] This illustration does not incorporate all the possible
configurations used in presenting a web to a Yankee dryer. It is
used only to describe how the adhesive of the present invention can
be used to promote adhesion and thereby influence the crepe of the
product. The present invention can be used with all other known
processes that rely upon creping the web from a dryer surface. In
the same manner, the method of application of the adhesive to the
surface of the dryer or the web is not restricted to spray
applications, although these are generally the simplest method for
adhesive application.
[0065] In another embodiment, a process for creping tissue paper
comprises: applying to a rotating creping cylinder an aqueous
solution comprising from about 90% to about 99.9% water and from
about 10% to about 0.1% adhesive solids, wherein the solids
comprise a water dispersible, acidified polyamidoamine and a
multi-valent metal ion salt; pressing a tissue paper web against
the creping cylinder to effect adhesion of the web to the surface
of the cylinder; and dislodging the web from the creping cylinder
by contact with a doctor blade.
[0066] In another embodiment, a process for creping tissue paper
comprises: applying to a rotating creping cylinder an aqueous
solution comprising from about 90% to about 99.9% water and from
about 10% to about 0.1% adhesive solids, wherein said solids
comprise a water dispersible blend of cationic non-crosslinked
polyamidoamine and a epi-polyamide material; pressing a tissue
paper web against the creping cylinder to effect adhesion of the
web to the surface of the cylinder; and dislodging the web from the
creping cylinder by contact with a doctor blade.
[0067] The herein described compositions are also advantaged as ply
bond adhesives. In these embodiments, the plies can optionally have
a plurality of embossments protruding outwardly from the plane of
the ply towards an adjacent ply. The adjacent ply likewise may have
opposing protuberances protruding towards the first ply. If a three
ply paper product is desired, the central ply may have embossments
extending outwardly in both directions, although a central ply
having no embossments or unidirectional embossments may be
feasible.
[0068] Each ply may have a basis weight of about 8 to 30, and
preferably 11 to 18 pounds per 3,000 square feet, and preferably
has a composition of hardwood and/or softwood processed by any of
the means well known in the art. After the papermaking process
which forms the ply is complete, either or both plies may be
embossed. Embossing may be accomplished according to the
knob-to-knob embossing process illustrated by U.S. Pat. No.
3,414,459, issued Dec. 3, 1968 to Wells; the nested embossing
process illustrated in U.S. Pat. No. 3,556,907, issued Jan. 19,
1971 to Nystrand; or a dual ply process illustrated in U.S. Pat.
No. 5,294,475, issued Mar. 15, 1994 to McNeil.
[0069] For the embodiments described and claimed herein, the
embossments are spaced on a pitch of 0.05 to 0.70 inches and have
an area at the distal end ranging from 0.001 to 0.100 square
inches. Each embossment can be made on a roll having knobs
protruding 0 to 0.120 inches from the plane of the roll. The
embossments can be round, oval shaped, or irregularly shaped.
[0070] The plies are preferably adhesively bonded together. In one
embodiment a suitable ply bond adhesive utilizes a solution of
acidic polyamidoamine. In another embodiment a ply adhesive
comprises an acidic polyamidoamine crosslinked with a multi-valent
metal ion. In another embodiment a suitable ply bond adhesive
comprises a blend of acidic polyamidoamine and a thermosetting
cationic epi-polyamide resin. These embodiments generally utilize
compositions described herein for creping applications, tailored
specifically in % solids, viscosity, and blend ratio for specific
ply bond applications
[0071] The ply bond adhesive can be provided in a 2 to 25% aqueous
solution (i.e., 2 to 25 percent solids and 98 to 75 percent water),
specifically a 5 to 11 percent aqueous solution (i.e., 5 to 11
percent solids and 89 to 95 percent water), and specifically about
a 5 to 8 percent aqueous solution (i.e., 5 to 8 percent solids and
92 to 95 percent water). In blended compositions, at least one
percent of the total solution comprises a thermosetting cationic
epi-polyamide resin. All solution percentages are by weight.
[0072] The ply bond adhesive is applied to a ply at a total solids
quantity of 3 to 85 grams per 3,000 square feet, preferably 4 to 48
grams per 3,000 square feet, and more preferably 6 to 20 grams per
3,000 square feet. For a ply bond adhesive composition having a
constant total solids, as the amount of thermosetting cationic
epi-polyamide resin making up the constant total solids increases,
generally a lesser quantity of the ply bond adhesive composition is
applied to the ply.
[0073] A three-roll ply adhesive application system can be used to
apply the adhesive. Using this system, the ply bond adhesive is
picked up as a film on the surface of a pickup roll. The ply bond
adhesive film is then split in the nip between the pickup roll and
a metering roll. The portion of the film remaining on the metering
roll then transfers to an applicator roll where the adhesive film
is again split. The film remaining on the applicator roll is
applied to the embossments of the ply. The embossments of this ply
are then brought in contact with another ply. The plies are
adhesively bonded together in the nip of conventional marrying
rolls.
[0074] Of course, the ply bond adhesive may be applied to the
embossments in any other manner as are well known in the art and is
commonly used for nested or knob-to-knob embossing processes as
well. Suitable application systems include flexographic, spray
systems, gravure systems, as well as the three-roll system
described above.
[0075] As the spacing and size of the protuberance decreases, a
greater amount of ply bond adhesive may be applied to each
protuberance for the embodiment described. The amount of ply bond
adhesive may be increased either by using a relatively greater
solids content in the ply bond adhesive composition, or by applying
a larger quantity of the ply bond adhesive composition to the
ply.
[0076] The resulting paper product comprises a laminate of two or
more plies. The paper product has a wet ply bond strength of at
least 4.5 grams per inch, and more preferably at least 5.0 grams
per inch.
[0077] The paper product further has alkaline wet ply bond strength
of at least 4.5, and more preferably at least 5.0 grams per inch.
Alkaline wet ply bond strength provides the benefit that if the
paper product according to the present invention is used with
certain commercially available cleaning products, the plies will
remain joined together as a unitary laminate.
[0078] The resulting paper product also has a dry ply bond strength
of 4.0 to 20.0 grams per inch, and more preferably 5.0 to 15.0
grams per inch.
[0079] The creping and ply bond adhesive compositions described
herein are advantageous in a number of respects. They provide high
adhesion; they are completely water soluble and repulpable; they do
not plug the shower and are easily washed up; there are no heating
or make down dilution issues; they provide a lower cost alternative
to stocking multiple adhesive or ply bond formulations for
different applications; and they provide control of sheet
penetration (by easily adjusting solids, viscosity and %
insolubility).
[0080] The following non-limiting examples illustrate advantages of
acidic polyamidoamines set forth above. The examples are presented
for illustrative purposes only and are not intended to limit the
scope of the herein claimed compositions and processes.
EXAMPLES
Example 1
Preparation of Acidic Polyamidoamine, P-1
[0081] Polymer P-1 is produced via condensation polymerization of a
1:1 molar ratio of diethylenetriamine (DETA) and adipic acid. The
reaction is conducted neat; no diluents are initially added. The
reaction is immediate and exothermic upon addition of the adipic
acid to the DETA. Addition of the adipic acid is carried out
rapidly enough to ensure that the total charge is finished before
the exotherm reaches 100.degree. C. The reaction temperature is
raised to 180.degree. C. after the exotherm to drive the
polymerization to the desired molecular weight range, the endpoint
of which is determined by the collection of condensate water. This
material (22.85 g, 70% solids) is diluted with 77.72 g water and
acidified by slow addition of 2.17 g concentrated sulfuric acid
(H.sub.2SO.sub.4) to a final pH of 4.4, Mw 20,000 Daltons, and a
Brookfield LVT viscosity of 308 centipoise.
Example 2
Mixtures of P-1 and Epi-Polyamides of Varying Crosslink Density
[0082] The product of Example 1 was blended individually with
several epi-polyamides commercially available under the tradenames
OmniCrepe.TM. 681-A (designated XP-1), OmniCrepe.TM.-AM (designated
XP-2), and OmniCrepe.TM.-AX (designated XP-3), by Kemira North
America. These epi-polyamides are derived from the polymerization
product of adipic acid and diethylenetriamine, and subsequently
treated with epichlorohydrin and sulfuric acid. OmniCrepe.TM.
products are classified as having medium through medium-heavy
crosslinked density. OmniCrepe.TM. 681-A has the lowest crosslink
density, the highest adhesion, the lowest insolubility, and the
lowest hardness. OmniCrepe.TM.-AM has an intermediate crosslink
density level. OmniCrepe.TM.-AX has highest crosslink density, the
lowest adhesion, the highest insolubility, and highest
hardness.
[0083] Table 1 compares the advantageous properties of acidic
polyamidoamine, P-1, to its neutral analog, NP-1. P-1 is more
suitable for creping and ply bonding applications because it has
high tack (high adhesion) and is easily dissolved.
TABLE-US-00002 TABLE 1 Properties Testing Insol- ubility Rewet
Hard- Tack Dry Film Description % 5 min ness grams Appearance COMP-
NP-1 0% 0 N/A No to low 1 tack, Brittle, Chips INV-1 P-1 0% 0 20
12,500 Very tacky, no form
[0084] Table 2 illustrates the advantages of blending P-1 with
epi-polyamides XP-1 and XP-3 as a means of tuning tack (adhesion)
and insolubility. The blend P-1:XP-3 1:1, INV-2, has higher tack
than each of the individual comparison epi-polyamides alone
(COMP-2, COMP-3 and COMP-4), while providing acceptable
insolubility (43%), rewet and hardness. The blend P-1:XP-1 1:3,
INV-3, provides even higher tack and higher insolubility (91%) than
the comparison examples.
TABLE-US-00003 TABLE 2 Properties Testing Insol- ubility Rewet
Hard- Tack Dry Film Description % 5 min ness grams Appearance COMP-
XP-1 86% 3.2 1,830 Tack, form 2 COMP- XP-2 90% 2.2 62 2,260 Tack,
form 3 COMP- XP-3 90% 2.2 84 600 Slight tack, 4 form INV-2
P-1:XP-3, 43% 0.6 24 6,000 Tacky, form 1:1 INV-3 P-1:XP-1, 91% 2.3
8,823 Tacky, form 1:3
Example 3
[0085] This example demonstrates tunable rewet and % insolubility
properties using a metal ion to crosslink acidic polyamidoamine,
P-1. To a solution of P-1 was added zirconium acetate at 2, 4, 6,
and 12 wt % metal ion relative to total solids. The resulting
chelated polymer progressively increased % insolubility and rewet
properties with increasing concentration of metal ion, as shown in
Table 3.
TABLE-US-00004 TABLE 3 Metal ion, Rewet (wt %) % Insolubility (wet
wt/init. Wt) 0 0 0 2 6.6 0.10 4 10.0 0.16 6 17.0 0.25 12 39.0
0.58
[0086] The various embodiments described above provide for a
creping and ply bond adhesive compositions having tunable
combinations of insolubility, adhesion, rewet and hardness
properties.
[0087] The singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise. The
endpoints of all ranges directed to the same characteristic or
component are independently combinable and inclusive of the recited
endpoint. All patents cited herein are incorporated by reference in
their entirety.
[0088] While the invention has been described with reference to
several embodiments thereof, it will be understood by those skilled
in the art that various changes can be made and equivalents can be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications can be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiments disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *