U.S. patent number 3,899,387 [Application Number 05/350,004] was granted by the patent office on 1975-08-12 for process of making paper using mono-isocyanate capped poly (oxyalkylene) diols as a re-wetting and defoaming agent.
This patent grant is currently assigned to Economics Laboratory, Inc.. Invention is credited to Richard E. Freis, Larry M. Rue.
United States Patent |
3,899,387 |
Freis , et al. |
August 12, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Process of making paper using mono-isocyanate capped poly
(oxyalkylene) diols as a re-wetting and defoaming agent
Abstract
The disclosed diaryl urethanes are made by capping
poly(oxyalkylene) diols with monoisocyanates. These diurethanes are
characterized by a desirable hydrophobe/hydrophile balance
typically evidenced by low cloud points, the ability to form
micelles in aqueous media, the ability to reduce stable foam, and
the ability to be taken up and retained by paper fibers, thereby
imparting increased hydrophilic character to paper sheets made from
the fiber. The low foaming or de-foaming capability of these
compounds is particularly useful in paper re-wet compositions and
machine dishwashing detergents and additives. The
hydrophobe/hydrophile balance is typically obtained through a
combination of oxyethylene and oxypropylene units or blocks in the
oxyalkylene chain.
Inventors: |
Freis; Richard E. (Minneapolis,
MN), Rue; Larry M. (Inver Grove Heights, MN) |
Assignee: |
Economics Laboratory, Inc. (St.
Paul, MN)
|
Family
ID: |
26996441 |
Appl.
No.: |
05/350,004 |
Filed: |
April 11, 1973 |
Current U.S.
Class: |
162/158; 568/618;
568/624; 516/DIG.7; 516/131; 516/13; 516/15; 560/24; 568/620;
568/625 |
Current CPC
Class: |
C08G
18/4833 (20130101); C11D 1/50 (20130101); C08G
18/71 (20130101); D21H 17/57 (20130101); Y10S
516/07 (20130101) |
Current International
Class: |
D21H
17/00 (20060101); D21H 17/57 (20060101); C08G
18/00 (20060101); C11D 1/38 (20060101); C08G
18/48 (20060101); C08G 18/71 (20060101); C11D
1/50 (20060101); D21H 003/12 () |
Field of
Search: |
;162/164,158
;260/471C,615B ;252/351,355,357,548,89 ;117/154 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Casey, J. P., "Pulp and Paper" Vol. II, Sec. Ed., Interscience
Publishers, N.Y., N.Y., pp. 1178-1179. .
Schwartz et al., "Surface Active Agents and Detergents" Vol. II,
Interscience Publishers, Inc., N.Y., N.Y., 1958, p. 130..
|
Primary Examiner: Bashore; S. Leon
Assistant Examiner: Smith; William F.
Attorney, Agent or Firm: Meshbesher; Thomas M.
Claims
What is claimed is:
1. In a method for increasing the hydrophilic properties of a
waterlaid sheet and providing a de-foaming action during the
formation of the waterlaid sheet on a paper-making machine, said
waterlaid sheet being formed from a paper-making slurry, the
improvement which comprises the steps of:
a. treating the fibers in said paper-making slurry, and defoaming
said paper-making slurry, with an effective amount of a re-wet
composition, having de-foaming properties, the active portion of
said re-wet composition comprising at least about 25% by weight of
a diaryl urethane having a cloud point, at 1 weight percent in
water, below 45.degree.C., and having the following structural
formula:
Ar--NH--CO--O--AO).sub.n CO--NH--Ar'
wherein
Ar and Ar' are monovalent aryl groups free of --NCO radicals,
A is an alkylene group containing 2-4 carbon atoms, n is a number
greater than 3 selected such that the divalent radical (AO).sub.n
has a molecular weight less than 12,000, and
(AO).sub.n is a block copolymer containing at least one block of
oxypropylene units,
said effective amount being an amount sufficient to lower the
re-wet time of said waterlaid sheet to less than 200 seconds as
determined by the re-wet test in which a drop of water is added to
a sample of said waterlaid sheet and the time needed to absorb the
drop is noted; the defoaming action of said diaryl urethane, at
75.degree.F., being at least about equal to the defoaming action of
the compound ##SPC1##
wherein
A, n, and (AO).sub.n have the previously indicated significance;
and
b. depositing the thus-treated fibers on a foraminous surface.
2. A method according to claim 1 wherein said effective amount of
said composition is about 5 to about 120 pounds per ton of said
waterlaid sheet, and wherein at least about 25% by weight of said
composition comprises said diaryl urethane.
3. A method according to claim 1 wherein the increase in
hydrophilicity with said effective amount of said composition is
indicated by an at least 10 fold reduction in the re-wet time as
determined by said re-wet test.
4. A method according to claim 1 wherein said diaryl urethane has a
molecular weight in the range of about 700-6,500 and the following
structural formula:
.phi.--NH--CO--O--PO).sub.a (EO).sub.b (AO).sub.c (EO).sub.d
(PO).sub.e CO--NH--.phi.
wherein
.phi. represents a phenyl group,
Po represents a propyleneoxy group,
Eo represents an ethyleneoxy group,
Ao represents an alkyleneoxy group of 2-3 carbon atoms, (AO).sub.c
being a homopolymer of propyleneoxy units or a copolymer of
propyleneoxy units and ethyleneoxy units, and
a, b, c, d, and e are the same or different and are numbers
selected such that all of the following ratios,
(a+e):(a+b+c+d+e),
(b+d):(a+b+c+d+e), and
c: (a+b+c+d+e),
are in the range of 0.3 - 0.4:1.
5. A method according to claim 1 wherein said Ar and Ar' are
monocyclic.
Description
FIELD OF THE INVENTION
This invention relates to polyoxyalkylene glycols capped with
monoisocyanates, the resulting diurethane compound having a
combination of properties including the ability to form micelles in
aqueous media, the ability to reduce foam, and the ability to
reduce paper re-wet times. Another aspect of this invention relates
to anti-spotting compositions, de-foaming compositions, methods for
promotion of proper and efficient use of wash water and rinse water
for articles such as dishes in a cleaning apparatus such as an
automatic or machine dishwasher, and methods for improving the
re-wet time of cellulosic waterlaid sheets such as paper while
simultaneously reducing foaming in the papermaking machine. Another
aspect of this invention relates to paper re-wet treatments wherein
a waterlaid sheet such as paper is made more water-sensitive by
treatment with an aromatic monoisocyanate-capped polyoxyalkylene
diol.
DESCRIPTION OF THE PRIOR ART
Low foaming or de-foaming non-ionic compounds and surfactants have
a variety of uses, e.g. in automatic or machine dishwashing.
Typically, these non-ionic compounds are derived from the
condensation of an alcohol or the like with ethylene oxide, and at
least some propylene oxide. Terminal hydroxyl groups remaining
after the condensation reaction may be capped, i.e. converted from
OH to an ether group, or the like. Non-ionic monohydroxy detergents
are sometimes converted to mono-urethanes. Alternatively,
hydroxyl-terminated oxyalkylene chains can be coupled together with
linking groups such as urethane "bridges" derived from
di-isocyanates. Generally speaking, some of the best paper re-wet
agents and de-foamers are aryloxy- or benzyloxy-capped oxyalkylene
glycols. Unfortunately, such compounds are more difficult to
prepare than isocyanate-capped materials and can be contaminated
with byproducts (such as NaCl) which are hard to remove.
It is a generally known technique in the art of polyurethane
chemistry to adjust the NCO/OH ratio of the urethane-forming
reactants with monoisocyanates. Thus, aromatic and aliphatic
monoisocyanates are typically used in conjunction with polyols,
particularly when a polyol mixture containing at least some triol
or tetrol is among the polyurethane-forming reactants.
In the art of spray washing (e.g. machine dishwashing or other
mechanical methods of cleaning articles involving a spray wash or
rinse step), the formation of stable foam in wash water or rinse
water can lead to serious difficulties. For example, foam formed
from the action of water on proteinaceous matter can be "stable" in
the sense that the foam height descends slowly, at best, over a
period of seconds or even several minutes. Thus, interaction of the
wash water with egg or milk food soils can produce an amount of
stable foam sufficient to clog machinery or slow down the spray arm
of the dishwashing machine. Several defoaming compounds have been
developed to counteract this foaming effect. Stable foam can be
reduced with these compounds, particularly when the wash water or
rinse water is at a temperature in excess of 140.degree.F.
(60.degree.C.). However, in the range of normal ambient
temperatures up to 140.degree.F. (60.degree.C.), the effectiveness
of the prior art de-foamers tends to decrease with decreasing
temperature. That is, the amount of stable foam tends to increase
with decreasing temperature. For reasons of safety, particularly in
home machine dishwashers, rinse or wash water temperatures in
excess of 140.degree.F. (60.degree.C.) are not preferred.
Furthermore, with long water lines and excessive demands upon the
hot water heater, the wash and rinse water can drop to a
temperature of 100.degree.F. or less. Foaming problems at these
lower temperatures are particularly acute with front-loading
washing machines and high pressure dishwashing equipment.
The formation of stable foam can also be undesirable in the art of
papermaking. Oftentimes, de-foamers or de-foaming surfactants are
added to one or more stages of the wash (e.g. the third stage or
stuff box, just before the head box), or, in some cases, to the
head box itself. One reason for adding a de-foaming agent is to
counter the foaming caused by additives such as re-wet agents. In
fact, a typical commercial practice is to sell a re-wet agent and a
de-foaming agent as a paper additive combination. ("Re-wet" agents
are an art-recognized class of chemical compositions or compounds
characterized in physicochemical terms by the ability to remain
entrapped in the fibers of a sheet of paper or the like and
increase its hydrophilic character.) A single surfactant or
micelle-forming compound with both paper re-wet and de-foaming
properties would be considered desirable in the paper industry,
particularly in the art of making wet strength paper. Wet strength
agents generally decrease the hydrophilic properties of the paper,
thus increasing the need for a re-wet treatment.
The demarcation of the class of compounds or compositions known as
paper "re-wet" agents is strictly or largely according to
performance tests, cloud point data, and the like, rather than
according to chemical composition or structure, since effective
"re-wet" agents may differ significantly in chemical structure. It
is known that re-wet agents should be hydrophilic enough to improve
the ability of the paper to take up water. It is also known that
re-wet agents should be hydrophobic enough to be rapidly taken up
by raw or treated pulp slurries and stay on the surfaces of the
paper fibers; an excessively hydrophilic agent could be taken up
too slowly or even washed off of the paper fibers during processing
on a Fourdrinier machine, a rotary paper former, or any other
machine which makes paper from a rather dilute aqueous slurry of
fibers. The ideal hydrophobe/hydrophile balance for a re-wet agent
is oftentimes an empirical determination which varies with the
nature of the hydrophobic and hydrophilic molecules or substituents
which provide this balance and the nature of the source of paper
fiber (softwood pulp, hardwood pulp, etc., which can be subjected
to various chemical pre-treatments). The characterization of
defoaming agents is based upon somewhat similar principles, but the
ideal hydrophobe/hydrophile balance for defoaming can be different
from that of a good paper re-wet agent-- hence the commercial
practice of combining the use of a re-wet agent with a
defoamer.
The hydrophobe/hydrophile balance and other properties of a paper
re-wet agent are preferably adjusted so as not to interfere with
the wet strength of the paper, the color of the paper, the
hydrolytic stability of the re-wet agent, etc.
SUMMARY OF THE INVENTION
It has now been discovered that the reaction product of (1) a
polyoxyalkylene diol containing at least some oxyethylene units and
(2) an aromatic mono-isocyanate, at an NCO:OH ratio of
substantially 1:1 (preferably in the presence of a suitable
catalyst) produces a diaryl polyether urethane with a useful
combination of de-foaming and/or paper re-wet properties. A
desirable aspect of the defoaming properties (i.e. the property of
resisting or reducing the formation of stable foam) is that this
property appears to be substantially independent of the water
temperature (e.g. the temperature of the wash water or rinse water
or the paper making slurry), even throughout a substantial portion
of the temperature range below about 140.degree.F. (60.degree.C.).
Improvements in low temperature de-foaming properties are generally
observed when comparing the diaryl urethane with the corresponding
uncapped diol, the dibenzyl ether analog of the diol, or even a
monourethane analog. Differences are particularly evident in the
range of about 20.degree.-40.degree.C., especially near the lower
end of this range. Preferred compounds of this invention can have a
hydrophobe/hydrophile balance which is well suited to both the
"re-wetting" of paper and the reduction of stable foam formed
during the manipulation of a papermaking slurry. Typically, this
balance is obtained by capping a diol which is a block copolymer
having at least one polyoxyethylene block and at least one
polyoxypropylene block and/or a diol which is a random
oxyethylene/oxypropylene copolymer.
In the art of spray washing (e.g. machine dishwashing), the diaryl
urethane low temperature de-foaming agents of this invention can be
included in a conventional dishwashing detergent composition or in
a rinse additive composition. Typically, a rinse additive is
provided by suspending a wax matrix containing the additive in the
dishwashing tank or by adding a liquid rinse additive to an
automatic dispenser built into the dishwashing machine.
In processes for re-wetting paper or other waterlaid sheets (e.g.
facial tissue or the like), a small amount of a compound having
carefully balanced hydrophilic properties is added during a "wash"
stage, e.g. the third wash stage, which is generally just prior to
the head box. The de-foaming property of the diaryl urethane
complements the re-wetting property and reduces the need for an
extraneous de-foaming additive. The compounds of this invention
can, if desired, be blended with other paper rewet agents (e.g. the
benzyl ether-capped analog, ethoxylated vegetable oils, or the
like) for various re-wetting effects.
DETAILED DESCRIPTION OF THE INVENTION
The diaryl urethanes of this invention can be characterized by the
following structural formula:
Ar--NH--CO--O--AO).sub.n CO--NH--Ar'
wherein
Ar and Ar' are monovalent aryl groups free of --NCO radicals,
A is an alkylene group containing 2-4 carbon atoms, at least some
of the alkylene groups being C.sub.2 alkylene, and
n is a number greater than 3 selected such that the divalent
radical --AO).sub.n has a molecular weight of less than 12,000,
preferably 500-6,000, e.g. 2,000-5,000. Various effects can be
obtained throughout the ranges. For example, de-foamers typically
have oxyalkylene chains with a molecular weight above 3,000. Good
paper re-wet properties can be more easily obtained with
oxyalkylene chains having a molecular weight above 900.
Preferably, the divalent radical --AO).sub.n is an
oxyethylene/oxypropylene block or random copolymer, e.g. a
copolymer containing at least one oxyethylene block having at least
3 units and at least one relatively larger oxypropylene block or
oxyethylene/oxypropylene block.
The starting materials and reaction conditions for producing the
diaryl urethanes of this invention will now be described in
detail.
DIOLS
As is well known in the art, polyether polyols can be made by
condensing ethylene oxide, propylene oxide, butylene oxide,
tetrahydrofuran, and the like with a mono- or polyhydroxy compound,
e.g. ethylene glycol, glycerin, trimethylolpropane,
pentaerithritol, ethanol-substituted amines, etc. Micelle-forming
and/or water soluble polymeric diols with various desired surface
active properties are typically made by condensing at least some
ethylene oxide with ethylene or propylene glycol. To obtain a
particular hydrophobe/hydrophile balance, 1,2- propylene oxide (or
some other compound capable of forming a relatively hydrophobic
repeating unit) is used with ethylene oxide as a co-monomer.
(Another technique for obtaining a desired hydrophobe/hydrophile
balance is to cap a very short poly(oxyethylene) chain with a
rather high molecular weight, hydrophobic capping group.) A wide
variety of polyoxyalkylene glycols are commercially available
throughout a broad molecular weight range up to about 12,000 or
more, the ranges most suitable for micelle-forming compounds of
this invention having been described previously in defining
--AO).sub.n of the above structural formula. Dimers, trimers, etc.
of ethylene glycol are commercially available, and some known paper
re-wet agents have as few as 3 oxyethylene units.
An extensive description of suitable polyoxyalkylene diols is
contained in the following patents:
U.S. Pat. Nos. 3,048,548 (Martin et al) issued Aug. 7, 1962;
3,036,130 (Jackson et al) issued May 22, 1962; 3,082,172 (Temple et
al) issued Mar. 19, 1963; 3,334,147 (Brunelle et al) issued Aug. 1,
1967; 3,549,543 (Kirstahler et al) issued Dec. 22, 1970.
Homopolymers of ethylene oxide are useful in this invention if the
oxyethylene chain is relatively short, e.g. less than 25 units.
As can be seen from, for example, the Martin et al., U.S. Pat. No.
3,048,548, one preferred method for obtaining a good ethylene
oxy/propyleneoxy balance for de-foaming is to use alternating
blocks of oxyethylene and oxypropylene units, although blocks or
randomly co-polymerized alkylene oxides can also be used. Thus, if
E is used to represent the oxyethylene block and P is used to
represent the oxypropylene block, typical diols used in this
invention are hydroxy-terminated E-P-E or P-E-P-E-P block
copolymers. A typical method of preparation of the diol is
described in column 4, lines 15-33 of the aforementioned U.S. Pat.
No. 3,048,548.
An example of such a block copolymer is:
HO--PO).sub.a (EO).sub.b (PO).sub.c (EO).sub.d (PO).sub.e H
wherein PO is a 1,2- propyleneoxy group (as in U.S. Pat. No.
3,334,147, column 2, lines 12-20) and EO is an ethyleneoxy group.
The numbers a, b, c, d, and e can be the same or different, but it
is preferred that a and e be the same and that b and d be the same.
The ratio of a+e or b+d or c to the sum of a through e is
preferably in the range of 0.3 to 0.4. As in the Brunelle et al
patent, the total weight of the two terminal propyleneoxy blocks
can amount to 34 to 35 percent (e.g. 34.4-34.75%) by weight of the
total molecular weight; the total of the two intermediate
ethyleneoxy blocks can amount to 32 to 33 percent (e.g. 32.2-32.6%)
by weight of the total molecular weight; and the central
propyleneoxy block can be 32.7-32.8 percent by weight of the total
molecular weight. A preferred modification of this block copolymer
diol is to form the center polymer block from propylene glycol and
a mixture of EO and PO units so that 5-7% of the weight of this
center block is EO units.
Another suitable type of diol is made from a 30-50 mole random
ethyleneoxy/propyleneoxy copolymer or propyleneoxy homopolymer as
the central block, with smaller ethyleneoxy blocks (e.g. 5-25 moles
each) on either side of the central block. Terminal blocks of 1-5
moles each of oxypropylene are preferably included in the
structure.
The hydrophobe/hydrophile balance provided by the
propyleneoxy/ethyleneoxy content of, for example, the diols used in
the de-foaming surfactants of U.S. Pat. Nos. 3,334,147 or 3,048,548
is altered somewhat by the two aryl urethane capping groups.
However, from the standpoint of low temperature defoaming and paper
re-wetting properties, the alterations appear to be generally
desirable.
AROMATIC MONO-ISOCYANATES
Aromatic mono-isocyanates generally can be used to make the
diaryl-urethanes of this invention from one or more of the
aforementioned diols. However, all aromatic isocyanates do not work
with equal effectiveness, and the monocyclic aromatic
monoisocyanates (e.g. phenyl isocyanate) are particularly preferred
for their ready availability. Polycyclic aromatic monoisocyanates,
with their additional aromatic ring or rings, can affect the
hydrophobe/hydrophile balance of the di-urethane more than, for
example, phenyl isocyanate. However, the hydrophobe/hydrophile
balance can be readjusted by using a more hydrophilic diol, e.g.
one containing a higher proportion of oxyethylene units.
Similarly, higher hydrophobic substituents on the aromatic ring on
the mono-isocyanate can also be compensated for. Such adjustments
in the hydrophobe/hydrophile balance can be avoided, however, if
the substituents on the aromatic ring do not radically alter the
properties of the aryl urethane capping group. For example, lower
alkyl groups, lower alkoxy groups, halogens, and the like have been
substituted on aromatic rings by techniques known in the art.
Higher alkyl groups (e.g. up to C.sub.18) have also been
substituted on aromatic rings. As is known in isocyanate chemistry,
aromatic compounds which can be converted to an aromatic amine and
then phosgenated can be used to make aromatic isocyanates.
Generally speaking, by "aromatic mono-isocyanate" is meant a
compound wherein the isocyanate radical is substituted directly on
a position of the aromatic ring.
CATALYSTS AND REACTION CONDITIONS
A polyoxyalkylene diol can be "capped" with an aromatic
mono-isocyanate in the manner generally known in the prior art for
making urethanes from alcohols and isocyanates. Solid starting
materials (e.g. higher molecular weight polyols) can be melted at
temperatures below 150.degree.C. and the reaction can be carried
out in the melt. If desired, solvents such as toluene, xylene, and
other organic liquids free of active hydrogen can be used to
dissolve the reactants or reduce the viscosity of the melt. Liquid
isocyanates, diols, and catalysts (e.g. tertiary amines) can be
selected for sufficient mutual compatibility to avoid or reduce the
need for solvents. The stoichiometry of the reaction mixture should
be selected so as to provide substantially complete capping of all
free hydroxyl groups without using a large excess of isocyanate.
(Excess isocyanate can be difficult to remove from the fully
reacted reaction mixture and can be an undesirable contaminant.)
Typically, about two moles of mono-isocyanate per mole of diol are
used, thus providing an equivalent weight ratio or NCO:OH ratio of
substantially 1:1. Deviations of about one or two tenths of an
equivalent from the theoretical 1:1 ratio are generally
permissible. The diarylurethane product can be sufficiently fully
reacted to have a hydroxyl number less than about 10.
The NCO/OH reaction can be spontaneous, is often exothermic and is
generally favored, both at mildly elevated temperatures (e.g.
30.degree.-150.degree.C.) and at normal ambient temperatures less
than 30.degree.C. (e.g. 20.degree.-25.degree.C.). The reaction time
can be reduced with suitable conventional catalysts for the
urethaneforming reaction. Among the conventional catalysts are the
tertiary amines and various organo-metallic compounds and
carboxylic acid salts of metals such as tin, lead, and mercury. The
liquid tertiary amines (e.g. the C.sub.1 -C.sub.6 trialkyl amines
such as triethyl or tributyl amine) are preferred for ease of
mixing with the reactants. Typically, reaction times of 0.5-5 hours
are suitable, and reaction times less than 4 hours are entirely
satisfactory in most cases. The presence and/or conversion of OH in
the reaction mixture can be conveniently monitored by infra-red
spectroscopy. The relative ease of forming the aryl urethane group
as compared to the etherification of a hydroxyl group with, for
example, a benzyl group is one of the advantageous features of the
present invention. The benzyl ether capping reaction typically
involves the use of metallic sodium, which can be hazardous,
particularly with respect to the gaseous hydrogen by product. The
sodium alcoholate/benzyl chloride reaction produces sodium
chloride, which is also an undesired byproduct.
PROPERTIES OF THE DIARYL URETHANES
The diaryl urethanes of this invention, wherein at least a portion
of the oxyalkylene chain comprises oxyethylene units, have surface
active properties, e.g. as evidenced by their ability to form
micelles in aqueous media. At low concentrations (e.g. 1 wt. %) and
at temperatures below the cloud point of these diurethanes, they
appear to form clear solutions in water. De-foaming capabilities
tend to be insufficient when the cloud point is above 45.degree.C.
A typical cloud point for a diaryl urethane of this invention at 1
wt. % concentration in water is 100.degree.F. (38.degree.C.),
preferably less than 50.degree.F. (10.degree.C.). The diaryl
urethanes with low cloud points (e.g. less than 50.degree.F.)
generally have both paper re-wet and de-foaming properties. The
molecular weight range of the diurethanes is, of course, higher
than that of the parent diols, e.g. about 700-6,500.
The significance of the paper re-wet property is that the
moisture-sensitivity of paper or other waterlaid sheets made from
cellulosic fiber or the like can be increased. One important use of
this property is in improving the water-sensitivity or wettability
of tissues, paper towels, and the like, including those paper
products which have been treated with a wet strength resin.
Oftentimes conventional wet strength resins (e.g. those of the
phenol-oldehyde type) make the paper product excessively
hydrophobic. A re-wet treatment is one method for arriving at a
proper balance of hydrophilic properties in the paper without
unduly sacrificing wet strength or other desired properties. The
effectiveness of a paper re-wet agent can be measured by placing a
drop of water on a given type of paper. If the paper was formed
without a re-wet agent, it will take a long time (e.g. 200-600
seconds) for the water to be absorbed. Paper formed with a re-wet
agent will typically need less than a tenth of that time (e.g. 3-15
seconds) to absorb about the same amount of water.
In a preferred paper re-wet process of this invention, a re-wet
composition or agent consisting of or containing a diurethane of
this invention is added to the third stage wash or stuff box of the
papermaking machine (Fourdrinier, rotary-former, or the like) just
before the head box at the rate of about 5 to about 120 pounds of
undiluted re-wet composition or agent per ton of finished paper.
The amount of re-wet material added depends upon the character of
the fiber in the papermaking slurry, e.g. upon the age, pitch
content, etc. of the wood used to make the wood pulp. The wet
strength additive is typically added just before or at about the
same time as the re-wet additive, e.g. at the second stage.
As is well known in the art, a suitable pulp or the like is made
into paper by beating it up in a large volume of water, generally
about 90-99.5 parts by weight of water to 0.5-10 parts pulp(on a
solid basis) in fact, the papermaking slurry, at some stage, may
contain only one-fourth percent (or less) by weight of solids. The
slurry goes through the aforementioned "wash" stages, and is
eventually picked up or deposited on a foraminous surface which
permits the water to drain off, leaving a sheet-like mass of
entangled fibers which becomes ordinary paper, facial tissue, paper
towel stock, or some other type of waterlaid sheet.
A particularly important property, both in paper re-wet treatment
and in mechanical dishwashing processes is the low foaming or
de-foaming action of the diaryl urethanes of this invention. It is
known that surface active agents with a cloud point less than
45.degree.C. do not produce excessive foam in water solutions and
can have the property of reducing stable foam generated by the
action of hot wash water on proteinaceous food soils. In mechanical
dishwashing, wherein the water can come in contact with milk
residue, egg residue, and other foam-producing soils, it is
preferred to provide a dishwashing composition with at least one
agent capable of de-foaming action. Compounds of the present
invention are effective de-foaming agents, both at elevated
temperatures, e.g. 40.degree.-70.degree.C., and at normal ambient
temperatures, e.g. 20.degree.-25.degree.C. Various standardized
tests have been worked out to measure de-foaming action. A
particularly realistic test is similar in concept to the test
described in column 6 of the aforementioned 3,334,147 U.S. Pat.
Instead of measuring the water pressure, however, the water
pressure can also be kept substantially constant. In this case the
height of the stable foam produced by egg soil or the like can be a
measure of the performance of the de-foaming agent.
As is known in the art, the urethane linkage can be hydrolyzed
under strongly acid or strongly basic conditions. Detergent,
de-foaming, rinse additive, and paper re-wet compositions of this
invention are nevertheless reasonably storage stable when properly
formulated and have been generally found to be sufficiently stable
under conditions of use, e.g. at normal ambient and mildly elevated
temperatures, in mildly acidic or basic papermaking slurries, and
in basic wash water having a pH in the range of, for example, 10.0
to 11.5 or 12.0. Typical acidic fibrous slurries (pH < 7) have a
pH above 5.0.
The significance of the various surface active properties of
compounds of this invention will be readily appreciated by those
skilled in the art of formulating detergent compositions and rinse
additives for mechanical or automatic dishwashing (as opposed to
hand dishwashing). The water draining from glasses, dishes,
flatware, and other utensils in the dishwasher tank is normally
treated with a rinse additive composition, which can contain a
nonionic surfactant of the de-foaming type. In institutional
mechanical dishwashers and some home dishwashers, the rinse
additive composition can be introduced or metered into the wash
tank in liquid form by a suitable automatic dispensing or metering
device. In home dishwashing machines, the rinse additives can also
be contained within a solid wax matrix which is suspended in a
suitable location in the wash tank. Sprays of rinse water washing
over the wax matrix take up small amounts of the rinse additive
composition, including the defoamer-type compound.
FORMULATIONS CONTAINING DIARYL URETHANES
Diaryl urethanes of this invention with a suitably low cloud point
(e.g. below 40.degree. or 45.degree.C. and preferably below
10.degree.C.) can be used per se as re-wet agents. All aryl
isocyanate-capped polyoxyalkylene diols do not work with equal
effectiveness, however, and the poly(oxyethylene/oxypropylene)
diols of 500-6,000 (e.g. 3,000-4,000) molecular weight capped with
phenyl isocyanate appear to be particularly preferred for their
overall combination of properties, including the ability to reduce
stable foam at normal ambient temperatures and the ability to be
taken up and retained by the paper fibers with a consequent
increase in the hydrophilic character of the paper product. The
diaryl urethanes in the preferred molecular weight range (which is
ordinarily at least about 220 higher than the diol MW) tend to be
somewhat viscous, and various viscosity-lowering additives are
preferably used in combination with these viscous re-wet agents.
Viscosity control is desirable in view of the typical methods used
in the paper industry to add the re-wet agent. For example, liquid
re-wet agents packaged in drums or other shipping or storing
containers can be provided with a pump and a small conduit or tube
leading to the stuff box, any other suitable post-beater or wash
stage, or even the head box--in short, a stage prior to the
deposition of the papermaking slurry on a foraminous surface such
as a screen or "wire." The flow rate of re-wet agent can be
adjusted empirically by occasionally sampling the paper product and
testing its re-wet time. Low viscosity re-wet compositions tend to
flow somewhat more easily from the drum to the papermaking
machine.
Solvents or diluents can be used to lower the viscosity of the
re-wet composition, and among the more common diluents is water. In
the event that the re-wet composition is less compatible with water
than might be desired, various coupling solvents and coupling
agents can be added to the water. (By "coupling" solvents or agents
is meant a material which improves the homogeneity of the
composition.) Among the commonly used coupling agents are the
anionic surfactants, e.g. alkali metal sulfonates such as sodium
xylene sulfonate. In a properly stabilized, homogeneous re-wet
composition, virtually any amount of water can be used, but
extremely large amounts of water will, of course, greatly increase
the flow rate requirements. Organic solvents or diluents can be
used in lieu of or in addition to the water or water/coupling agent
combination. To further stabilize the re-wet composition for
shipping and storage, freeze-thaw stabilizers can also be added.
Other additives will occur to those skilled in the art.
One particularly convenient means for adjusting the viscosity of
the re-wet formulation is the conbination of other, less viscous
re-wet agents with the diaryl urethanes of this invention.
Available re-wet agents with a good hydrophobe/hydrophile balance
and a relatively low molecular weight (e.g. 350-800) serve as
diluents for the diaryl urethane and also make a contribution to
the re-wetting action of the composition. Tall oil fatty acid
ethoxylates containing 2-10 (e.g. 3) oxyethylene units have been
found to be effective in thinning the diaryl urethane re-wet
compositions without interfering with the desired
hydrophobe/hydrophile balance. Other saturated or unsaturated
C.sub.12 to C.sub.20 fatty acid esters of short-chain oxyethylene
glycols will occur to those skilled in the art. Typically, about 1
to about 70% by weight of the re-wet composition can comprise a
tall oil fatty acid ethoxylate, and a 40/60-60/40 (by weight)
diaryl urethane/tall oil ethoxylate combination provides
particularly good results. In any of these contemplated re-wet
compositions, the active portion (i.e. the portion exclusive of
organic solvents, water, and anionic coupling agents or the like)
should comprise at least about 25% by weight of the diaryl urethane
re-wet component.
Other conventional re-wet agents can also be included in the active
portion of the composition in an amount ranging from 0% up to about
70% by weight. For example, the benzyl ethercapped oxyalkylene
polymers of the type described previously can be used; see the
aforementioned Brunelle et al U.S. Pat. No. 3,334,147. Another type
of re-wet agent suitable for combination with re-wet compositions
of this invention is the alkyl-aryloxy-capped poly(oxyethylene)
glycol type. This type of re-wet agent typically has the following
structural formula:
R-.phi.-O--AO).sub.x H
wherein
R is a saturated aliphatic chain containing 10-24 (preferably
12-18) carbon atoms,
.phi. represents a divalent aromatic group such as phenylene,
A is an alkylene group, preferably ethylene, and
x is a small number, typically less than 10 and greater than 3,
e.g. 6-7 (a fractional number of moles of ethylene oxide can be
used in such compounds).
In terms of re-wet properties alone (i.e. without regard to
de-foaming capability), the alkyl-phenoxy-poly(ethyleneoxy)
ethanols of this type provide a good standard for comparison in
testing re-wet compositions of this invention. Another good
standard for comparison is a combination of a benzyl ether-capped
oxyethylene/oxypropylene glycol and a tall oil fatty acid
ethoxylate.
As pointed out previously, the diaryl urethanes of this invention
can be used as low temperature de-foaming agents in rinse additives
and in mechanical dishwashing detergent compositions. Rinse
additives can be either solid or liquid. A typical type of liquid
rinse additive comprising water, a wetting agent, and a de-foaming
agent is disclosed in U.S. Pat. No. 3,082,172. Liquid rinse
additive compositions of this type contain at least one
poly(oxypropylene/oxyethylene) diol wetting agent, preferably
similar or identical to the diols used as raw materials for making
diaryl urethanes of this invention. The wetting agent helps the
wash water to drain from the utensils being washed in smooth sheets
or thin films, thereby preventing the formation of hanging drops
which form spots. The preferred diaryl urethane de-foaming agents
of this invention assist in maximizing the water pressure during
the rinse cycle and do not detract from the anti-spotting effects
of the wetting agent. However, the diaryl urethane defoaming agent
can lower the cloud point of the liquid rinse additive composition,
and, desirably, coupling agents or solvents are added to the
composition to improve its homogeneity and/or storage
stability.
In the solid rinse additive compositions, such coupling agents are
not necessary. Typically, these solid compositions comprise a
combination of wetting agent and de-foaming agent (once again, the
diaryl urethane serves as the de-foaming agent), suitable inorganic
or organic fillers, and a suitable wax matrix. All waxes do not
work with equal effectiveness, and the alkanolamide waxes are
preferred. The wetting agent/de-foaming agent combination is
ordinarily blended with a roughly equal amount of wax. The amount
of inorganic or organic filler can be slightly larger than either
the amount of de-foamer and wetting agents or wax, but is typically
less than half of the total composition. A typical formula for a
solid rinse additive is:
30 weight % de-foamer and wetting agent
30 weight % alkanol-amide wax
40 weight % inorganic or organic fillers
The low temperature de-foaming action of the diaryl urethanes of
this invention is useful in various types of mechanical dishwashing
detergent formulations including the phosphate-containing type
(see, for example, Martin et al, U.S. Pat. No. 3,048,548, and
Oberle, U.S. Pat. No. 3,306,858) and the low-phosphate or
phosphate-free detergents such as the detergent described in U.S.
Pat. No. 3,700,599 (Mizuno et al), issued Oct. 26, 1972. The diaryl
urethane can be added to either dry or liquid detergent
compositions; however, greater stability for the diaryl urethane is
observed with dry (powdered) compositions, even when the powdered
detergent is stored or aged at moderately high ambient temperatures
such as 120.degree.F. The preferred types of mechanical dishwashing
compositions generally comprise waterconditioning or softening
agents, including sequestering agents such as the alkali metal
condensed polyphosphates; pH-adjusting or buffering agents or
"builders", e.g. alkali metal carbonates, hydroxides, borates,
orthophosphates, etc.; corrosion inhibiting agents, e.g. the
metasilicates (which also function as "builders");
chlorine-releasing agents such as the hypochlorites (in liquid
detergents) or the chlorinated isocyanurates or isocyanuric
acidtype compounds (particularly in solid detergents); and other
ingredients such as de-flocculating agents, coloring agents,
fillers, etc. The water-conditioning agent normally comprises 2-70
weight percent of the composition, the pH-adjusting or buffering
agent 1-70 weight percent, and an alkali metal metasilicate 0-70
weight percent. De-foaming agents are typically included in these
compositions to the extent of 0.1-5 weight percent, though greater
percentages are permissible. The amount of chlorine-releasing agent
is also typically in this 0.1-5 weight percent range. The preferred
alkali metals are sodium and potassium, and the preferred
polyphosphates contain 2-10 (e.g. 3) phosphate units.
A typical dry powdered machine dishwashing detergent composition of
this invention is as follows:
Parts By Weight Ingredients ______________________________________
40-60 alkali metal metasilicates (e.g. sodium metasilicate) 30-50
alkali metal condensed polyphosphates (e.g. sodium
tripolyphosphate) 0-60 sodium or potassium carbonate 0.5-3 an
alkali metal salt of a chlorinated isocyanurate (e.g. sodium or
potassium dichloroisocyanurate) 0.5-3 diaryl urethane of
oxyethylene/ oxypropylene copolymer of 3,000-4,000 molecular weight
______________________________________
Detergent formulations of this general type are alkaline when
dissolved in water. For example, at 0.1-1% by weight of detergent
solids in water, the pH of the resulting solution can vary from
about 10 to about 11 for home dishwashing use, and about 11 to
about 12.5 for institutional dishwashing use. The lower end of the
pH range (below 12. and preferably below 11.0) is preferred in this
invention.
The invention is illustrated in the following nonlimiting
Examples.
EXAMPLE 1
Part A: Preparation of Diaryl Urethane
A liquid poly(oxyethylene/oxypropylene) diol was prepared generally
in accordance with the teachings of U.S. Pat. No. 3,048,548 (Martin
et al), at column 4, lines 15-33, except that the center block of
the polymer was prepared from propylene glycol and a mixture of
propylene oxide and ethylene oxide, thereby obtaining a random
copolymer center block. Of the reactants used to make this center
block, 6.7% by weight was ethylene oxide. Each homopolymeric
oxyethylene block on either side of the center block made up 16.11%
by weight of the total polymer, the total of these two blocks being
32.22 weight %. The terminal oxypropylene blocks were each 17.36%
by weight of the polymer for a total of 34.72% by weight of the
complete five-block polymer, Thus, the overall EO/PO ratio for this
diol was very similar to that of the class of diols described in
the aforementioned U.S. Pat. No. 3,048,548 patent. The molecular
weight of the diol of this Example was closer to the lower end of
the 3,000-5,000 molecular weight range than the preferred glycol
described in column 3, line 73 et seq. of the patent (in this case,
about 3,400); however, as pointed out previously, this entire
3,000-5,000 MW range is within the scope of this invention.
One mole of the liquid poly(oxyethylene/oxypropylene) diol
described previously was blended at room temperature with 2.0 moles
of phenyl isocyanate (NCO:OH ratio 1:1) by adding the liquid
isocyanate at a constant rate, with stirring. To this reaction
mixture, 0.003 mole of tri-n-butylamine was added, also at room
temperature, and the resulting reaction between the isocyanate and
the diol was exothermic. After two hours in the reaction vessel,
the resulting diaryl urethane was found to have a hydroxyl number
below 10, indicating substantial completion of the NCO/OH reaction.
The cloud point of the diaryl urethane product was found to be less
than 37.degree.F.
Part B: Standards for Comparison of De-foaming Properties
The following compounds are known to be effective defoaming
agents:
1. the benzyl ether-terminated type of compound described in U.S.
Pat. No. 3,334,147 (Brunelle et al),
2. the benzyl ether-terminated ethoxylated alkanol compound
described in Example V of U.S. Pat. No. 3,444,242.
Further comparison can be made with the following compounds:
3. the uncapped diol described in Part A of this Example,
4. the phenyl urethane-terminated analog of the compound of Example
V of U.S. Pat. No. 3,444,242, i.e. the monoaryl urethane wherein
phenyl--NH--CO-- is the capping group used in place of benzyl.
Part C: Standardized Detergent Formulation and Foam Test
This Part of this Example makes use of a standardized test
developed and used internally by Economics Laboratory, Inc. The
test is known as Q.C.T.P. 75 and is dated Apr. 8, 1971. The test
involves adding three liters of water of the required hardness to a
foam machine plastic cylinder-stainless steel beaker assembly
(Glewwe Foam Machine). A pump is operated to provide a given water
pressure, typically 6 psi, but for this Example, 10 psi was the
pressure used. The materials to be tested are added to the water,
and the temperature of the water is set at the desired level and
carefully controlled. The foam height at the completion of the test
provides an index of defoaming performance. The foam height values
obtained are significant in a relative sense, and correlate with
results obtained in end-uses.
Each of the above-described standards and the diaryl urethane
de-foamer of Part A of this Example were tested in the presence of
foam-producing soil (2 grams egg soil) and typical detergent
components, all blended with the three liters of water in the foam
test machine. The amount of de-foamer in each case (standards and
Example 1[A]) was 0.10 gram. The typical detergent components were
as follows:
5.35 grams sodium metasilicate
3.96 grams sodium tripolyphosphate
0.19 grams sodium dichloroisocyanurate
The foam height test data are reported in Table I below.
TABLE I ______________________________________ FOAM HEIGHT TEST
Foam Height in Inches at Given Water Temperature De-foamer
75.degree.F. 100.degree.F. 140.degree.F.
______________________________________ Example 1[A] (diaryl
urethane) 4.5 3.0 3.5 Standard (1) (U.S. Pat. No. 3,334,147) 6.0
3.0 5.5 Standard (2) (Ex. V, U.S. Pat. No. 3,444,242) 11.00* 7.50
5.50 Standard (3) (uncapped diol of Ex. 1[A]) 9* 6.25 5.25 Standard
(4) (monoaryl urethane) 7-9.5 6.5- 3.75- 6.75 4.50
______________________________________ *Unable to maintain 10 psi
because of excessive foam.
As will be apparent from the above Table, none of the Standards
consistently equals the Example 1[A] diaryl urethane throughout the
75.degree.-140.degree.F. range.
EXAMPLE 2
Re-Wet Compositions and Tests
Re-wet compositions were prepared from the diaryl urethane of
Example 1[A], Standard (1) of Example 1[B], and Standard (4) of
Example 1[B]. Each of these compositions consisted of 55 weight %
of the compound to be tested diluted with 45 weight % of tall oil
fatty acid ethoxylate (Emery Industry), hereinafter referred to as
"FAE."
Paper samples were made with 28-30 g. of crude wood pulp taken from
a master batch of wood pulp so that the comparisons would be
meaningful. A standard amount of the re-wet composition to be
tested was added before the papermaking slurry was laid down on the
screen on the mold. A control sample of paper was made with no
re-wet treatment. A drop of water was added to each sample and time
needed to absorb the drop was noted (i.e. the "re-wet time").
Observed re-wet times are set forth in Table II.
TABLE II ______________________________________ RE-WET TIMES Sample
Time(in Seconds) ______________________________________ Control (no
re-wet 542. treatment) Example 1[A]/FAE 3.59 Standard(1)/FAE 6.63
Standard(4)/FAE 3.9 ______________________________________
Thus, Standard (1), though better in de-foaming than Standard (4),
is less effective in re-wet properties. Neither Standard
consistently equals the Example 1[A] diurethane in overall
de-foaming/re-wet performance. The cloud point of Standard (4)
(alone, without FAE, in 1% aqueous solution) is
68.degree.-72.degree.F.
EXAMPLE 3
In this Example, the procedures of Example 1, Parts A and C and
Example 2 were substantially duplicated except that a different
diol was used in the preparation of the diaryl urethane (see Part A
of Example 1).
The diol was prepared as follows: a homopolymeric center block was
prepared from propylene glycol and 40 moles of propylene oxide;
twenty-two moles of ethylene oxide were used to make the two
intermediate poly(oxyethylene) blocks on either side of the center
block, each intermediate block being obtained from 11 moles of
ethylene oxide. The two terminal hydroxyl-terminated blocks were
obtained from 3 moles propylene oxide, resulting in an average of
1.5 moles in each terminal block. After capping with phenyl
isocyanate in the manner specified in Part A of Example 1, the
cloud point of the resulting diurethane (1 weight % aqueous
solution) was found to be less than 37.degree.F. The Example 3
diurethane was combined with the standardized detergent formulation
as in Example 1, Part C, and foam test Q.C.T.P. 75 was carried out
as described previously. The resulting foam height data is set
forth in the following Table.
Table III ______________________________________ Foam Height In
Inches For Temperature De-Foamer of Example 3
______________________________________ 70.degree.F. 6.5
100.degree.F. 4.5 140.degree.F. 4.5
______________________________________
Thus, the de-foamer of this Example had de-foaming properties at
least about equal to Standard (1) (U.S. Pat. No. 3,334,147) and
generally comparable to the diurethane of Example 1[A].
The re-wet test of Example 2 was substantially duplicated. The
control for the Example 3 re-wet test (i.e. the paper sample not
given a re-wet treatment) had a somewhat shorter re-wet time: 510.9
seconds. The re-wet time for the Standard (1)/FAE (55/45 by weight)
combination (see Example 2) was slightly shorter: 6.3 seconds.
For a 55/45 (by weight) combination of Example 3 diurethane/FAE,
the re-wet time was 4.6 seconds.
* * * * *